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Influence of the thermal effect on quasi-static shear characteristics of calcareous soil: an experimental study

Influence of the thermal effect on quasi-static shear characteristics of calcareous soil: an... In principle, the mechanical properties of soil particles are irreversibly changed after particles are subjected to heat- ing. Accordingly, this study performed ring-shear tests on calcareous sand samples subjected to high temperatures to qualitatively investigate the influence exerted by the degradation of the calcareous sand, caused by the thermal effect, on the large displacement shear characteristics of the samples. The effects of the shear velocity and normal stress on the quasi-static shear behavior of the calcareous sand samples were analyzed. The influence of the thermal effect on the quasi-static shear flow behavior of the samples is primarily reflected in the change in the particle mineral composition, particle hardness, and sample density. These variations result in changes in the shear strength, residual shear stress, macroscopic friction coefficient, and other shear characteristics of the calcareous sand samples. Both the shear velocity and the high temperature affect the fluctuation amplitude of the residual shear stress. The results have great theoretical and practical significance in terms of explaining the instability mechanism of a slope. Moreover, a feasible and effective technique is proposed to investigate the large-displacement shear behavior of soil subjected to the thermal effect exerted by a long-runout landslide. Keywords: Ring-shear test, Shear characteristics, High temperature, Calcareous soil Introduction its influence on particles of geotechnical materials are of Landslides can cause enormous loss of life and financial particular interest. damages. Since the 1960s, many long-runout landslides In large-displacement shear behavior, the soil has par- have occurred worldwide. In general, such landslides are tial flow characteristics. To enable the accurate predic - characterized by high-speed movement, wide disaster tion and analysis of the kinetic characteristics of the ranges, and great destructive ability  (Tika and Hutchin- shear behavior of landslides, it is important to explain son  1999; Xu et  al. 2017). Therefore, the movement and the dynamic mechanism of long-runout landslides. Mul- disaster-inducing mechanism of long-runout landslides tiple field investigations and laboratory experiments on have become a focus of researchers worldwide. The phys - landslides and debris flows have shown that Newtonian ical and chemical changes caused by the thermal effect and non-Newtonian fluid models, such as the Bingham induced by high-velocity sliding friction are among the fluid, pseudoplastic flow, expansion flow, and Coulomb main causes of long-runout landslides (Noda et al. 2011; viscous flow, can be used to describe the constitutive Pinyol et  al. 2018). The cause of the thermal effect and behavior of landslide soil (Johnson 1970; Hungr 1995; Uzuoka et  al. 1998; Wang 2006; Huang and Dai 2014). However, previous studies did not consider the influ - *Correspondence: yhuang@tongji.edu.cn ence of the thermal effect on the motion state, which Department of Geotechnical Engineering, College of Civil Engineering, is necessary for an accurate description of the dynamic Tongji University, Shanghai 200092, China characteristics. Luo et  al. (2016) summarized recent Full list of author information is available at the end of the article © The Author(s) 2022. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http:// creat iveco mmons. org/ licen ses/ by/4. 0/. Wang and Huang Geoenvironmental Disasters (2022) 9:25 Page 2 of 8 thermal-hydro-mechanical-coupled physical models of (Shimamoto et  al. 1994; Smith et  al. 2013; Ujiie et  al. long-runout landslides. Some studies have focused on 2013; Ma et al. 2014). Owing to the different characteris - the friction behavior of the sliding surface, while other tics between the rock and the soil, it is difficult to test the studies have focused on establishing thermal-hydro- soil by carrying out high-velocity friction tests at temper- mechanical-coupled physical models of long-runout atures of approximately 800 °C. Therefore, other methods landslides by introducing the depth-averaged hydrody- have been used to investigate the shear characteristics namic theory into the sliding block model. However, the of soil subjected to high temperatures. In principle, the results obtained thus far have not explained the kinetic mechanical properties of soil particles are irreversible mechanism of the thermal effect response and an accu - after heating. Accordingly, calcareous soil was first sub - rate and effective kinetic model has not yet been estab - jected to a heat treatment and then ring-shear tests were lished. Therefore, considering the thermal effect on the carried out on the samples. In this way, the influence of shear characteristics of soil is important to accurately the thermal effect on the physical and mechanical prop - describe the shear mechanism and the characteristics of erties of the soil can be investigated. Moreover, the influ - large-displacement-sheared soil. ence of this change on the shear characteristics of the soil Regarding the shear thermal effect, Hu et al. (2018) was can also be determined. the first to obtain field and experimental evidence for Based on previous studies, a ring-shear test was carried the high-temperature thermal decomposition of a long- out on calcareous sand samples subjected to high tem- runout landslide belt and accurately estimated a bottom perature using a GCTS ring-shear apparatus to examine friction temperature of 790  °C during the high-velocity the shear characteristics of calcareous sand with large- sliding process in the Jiweishan long-runout landslide. displacement shear flow. The experimental results have Hu et  al. (2019) used a thermogravimetric method to great theoretical and practical significance with respect estimate a bottom temperature of 850  °C for the sliding to explaining the flow mechanism and conducting insta - surface of the Daguangbao landslide. Using a ring-shear bility analyses. test, they obtained the microstructural variation after the thermal effect and the variation relationship between Methods and materials the friction coefficient and the shear displacement. Their Specimen preparation results revealed that friction between the particles pro- To investigate the variation in the large-displacement duces a dynamic recrystallization layer and carbon diox- shear characteristics of calcareous soil samples subjected ide, which reduces friction. These studies confirmed that to high temperature, a single mineral composition soil the thermal effect between the sliding particles is strongly sample was used in this test. The sample consisted of cal - related to the large displacement and fluidization of long- careous sand obtained from the Guangdong Province, runout landslides. China. The specific composition of the soil is presented Owing to limitations in the design of conventional geo- in Table  1, and the mechanical properties of sample is technical test equipment, the shear failure and mechani- presented in Table 2. cal behavior of soil cannot be completely obtained, particularly in studies concerned with the mechanical Test equipment and procedure properties of soil subjected to large-displacement shear. The SMF1900-50 box resistance furnace at the Uni - One such limitation is that the shearing surface of con- versity of Shanghai for Science and Technology was ventional direct shear test equipment is not sufficiently long. Therefore, the long-term shear mechanical proper - ties of soil cannot be fully monitored during a test (Hong et  al. 2009). The ring-shear test is primarily used to Table 1 Material composition investigate the post-peak stress–strain relationship and Composition Percentage (%) the shear stress variation of geotechnical materials with IL(Loss on Ignition) 43.67 large shear displacement and complex stress. The shear Al O < 0.01 flow behavior of different rocks and soil with large dis - 2 3 SiO 0.4 placement under different conditions has been investi - 3 Fe O 0.0086 gated (Skempton 1985; Kamai 1998; Agung 2004). In the 2 3 CaO 55.5 research field of coseismic faults with high-speed friction MgO 0.19 activity, a rotary-shear high-velocity friction apparatus K O 0.0085 is used to investigate high-speed friction with large dis- Na O 0.072 placement and obtain the mechanical properties of rock TiO < 0.01 under the friction heat produced by high-velocity sliding 2 W ang and Huang Geoenvironmental Disasters (2022) 9:25 Page 3 of 8 Table 2 Dry density of the samples (kg/m ) Temperature Minimum dry density Maximum dry density 20 °C 1363.8 1496.5 800 °C 826.0 882.1 Fig. 2 Appearance of the calcareous sand before (left) and after (right) heat treatment Fig. 1 Test equipment: a SMF1900-50 box resistance furnace and b GCTS SRS-150 ring-shear apparatus used to conduct a high-temperature test (Fig.  1a). The maximum temperature was 1000  °C. The heating rate and the cooling rate were set to 4 °C/min, and the tem- Fig. 3 Relationship between time and the shear stress for different perature was maintained at 800  °C for 24  h and finally shear velocities reduced to 20  °C (Zhang et  al. 2015; Chen et  al. 2017; Wang et  al. 2022a). The sample was placed in a corun - dum crucible, which was raised by a corundum gasket sand was completely converted from calcium carbonate to ensure uniform heating. to calcium oxide. The content of the remaining compo - The GCTS SRS-150 ring-shear apparatus in the key nents was negligible. laboratory of the Ministry of Geotechnical and Under- ground Engineering of Tongji University was used to Eec ff t of shear velocity on the shear strength, residual conduct the ring-shear test (Fig. 1b). In the test, the dis- shear stress, and apparent viscosity placement was continuous and the equipment automat- Under the same conditions, the mechanical behav- ically obtained the shear stress of the samples. Details ior of the calcareous sand samples sheared at differ - regarding the instrumentation and the test process are ent shear velocities was different. Figure  3 shows the provided in Wang et al. (2022b). relationship between time and the shear stress for dif- ferent shear velocities. In Fig.  3, the shear strength and the residual shear stress can be clearly observed. Results and analysis The average, maximum, and minimum residual shear Appearance of samples stresses were obtained separately, as plotted in Fig.  4. The calcareous sand was obviously different after the With shear velocities of 3°/min, 36°/min, and 180°/ high-temperature treatment (Fig.  2), and its particles min, the shear strengths of the calcareous sand samples changed from translucent gray white crystals to pure were 108.3 kPa, 110.4 kPa, and 108.9 kPa, respectively; white opaque crystals, indicating that the calcareous Wang and Huang Geoenvironmental Disasters (2022) 9:25 Page 4 of 8 Fig. 4 Relationship between the average, maximum, and minimum residual shear strains and the shear velocity the average residual shear stresses were 101.8  kPa, Fig. 5 Standard deviation of the shear stresses of the samples with 103.1  kPa, and 102.8  kPa, respectively; the maximum time residual shear stresses were 108.8  kPa, 111.8  kPa, and 114.2  kPa, respectively; and the minimum residual shear stresses were 97.5  kPa, 93.5  kPa, and 92.6  kPa, respectively. particles and clay particles with large moisture contents At lower shear velocity (3°/min), the initial peak shear (Forterre 2008). The results obtained via the ring-shear strength of the sample appeared later compared with test in this study differ from the theoretical results. Even those of samples with higher shear velocities. The fluc - though the shear flow in the ring-shear test belongs to tuation amplitude of the residual shear stress was small the quasi-static flow regime, the shear stress and shear and gentle. At higher shear velocities (36°/min and 180°/ rate are not completely independent; this is strongly min), the initial peak shear strength of the samples related to the unsteady state of the soil under large-dis- appeared faster and the residual shear stress fluctuated placement shear. significantly. In this unsteady state, the residual shear The shear rate can be calculated as follows: stress was greater than the shear strength. As the shear vD velocity increased, the residual shear stress fluctuation γ˙ = , 2h of the samples with a large displacement shear became more intense and even exceeded the shear strength. This where v is the shear velocity [°/s]; D is the average diam- is related to the shear breakage and rearrangement of eter of the ring-shear sample [mm]; h is the thickness of the soil particles in the shear box. Therefore, the resid - the ring-shear sample [mm]. ual shear stress of calcareous sand may exceed the shear The apparent viscosity η can be expressed by the rela- strength and increase with the shear velocity when the tionship between the shear stress and the shear rate: other experimental conditions remain the same. Moreo- ver, the residual shear stress of the sample with a shear τ = ηγ˙ . velocity of 180°/min kept increasing, which indicates that Accordingly, the specific value of the apparent viscosity the residual shear stress of the sample increased with the can be calculated. particle breakage. To quantify the shear stress fluctua - Because the residual shear stress fluctuated continu - tion, the standard deviation of the shear stress was used ously as the shearing progressed, the average, maximum, to measure the fluctuation amplitude of the shear stress, and minimum residual shear stresses were calculated as as shown in Fig. 5. The results indicate that a higher shear shown in Fig. 6. The approximate shear flow characteris - velocity led to an increase in the sample’s shear fluctua - tics of the calcareous sand samples were obtained under tion amplitude. The shear behavior of the calcareous sand a normal stress of 200  kPa. Here, the rheological curve exhibited the phenomenon of shear stress fluctuation, does not pass through the origin point and is concave to which is related to the continuous formation and recon- the shear rate axis. The sample has both yield characteris - struction of the force chain structure (Sun and Wang tics and pseudoplastic fluid characteristics and can there - 2008). Existing studies on dense granular flow consider fore be thought of as a yield pseudoplastic fluid. In Fig.  7, the shear stress to be independent of the shear rate; how- the curve of the average value of the apparent viscosity ever, this conclusion was reached considering simple is slightly different from the curve drawn according to W ang and Huang Geoenvironmental Disasters (2022) 9:25 Page 5 of 8 Fig. 6 Relationship between the shear rate and the residual shear stress Fig. 8 Relationship between time and the shear stress of the calcareous sand before and after heat treatment -0.988 Max value y = 110.24x -0.997 y = 102.34x -1.013 Average value y = 95.779x Min value 05 10 15 20 -1 Shear rate (s ) Fig. 7 Relationship between the shear rate and the apparent viscosity the maximum and minimum values; however, the overall Fig. 9 Relationship between time and the friction coefficient of the trends of the two are essentially identical. The apparent calcareous sand before and after heat treatment viscosity decreased as the shear rate increased; there- fore, the viscosity of the calcareous sand decreased as the shear rate increased and the relationship between the to shear failure. The average residual shear stresses shear stress and the shear rate is nonlinear, with a certain were 103.1 kPa and 110.2 kPa before and after heating, degree of shear dilution. respectively. Hence, the residual shear strength of the sample increased after the high-temperature treatment. Variation of the shear strength, residual shear stress, A comparison of the friction coefficient of the sample and friction coefficient caused by high temperature before and after heat treatment (Fig.  9) indicated that The ring-shear tests on the calcareous sand samples the average friction coefficient increased from 0.51 to before and after heat treatment were performed under 0.55. After the heat treatment at 800  °C, the friction the same normal stress and shear velocity conditions. coefficient of the sample was obviously higher com The shear characteristics of the samples were obtained pared with that prior to the heat treatment. Figure  10 before and after the heat treatment, and the shear stress shows the state of the calcareous sand sample particles curves are shown in Fig.  8. The shear strengths of the after heat treatment at different temperatures. Con - samples before and after heat treatment were 110.4 kPa sidering Fig.  10 in conjunction with the sample images and 104.1  kPa, respectively. This indicates that the captured after the ring-shear tests (Fig. 9), it was deter- shear strength of the calcareous sand decreased after mined that the variation behavior of the shear flow was the calcareous sand was subjected to high tempera primarily influenced by the change in the sand particles ture and that the calcareous sand became more prone Apparent viscocity (kPa·s) Wang and Huang Geoenvironmental Disasters (2022) 9:25 Page 6 of 8 Fig. 10 Calcareous sand samples after being subjected to different temperatures Fig. 11 Relationship between time and the shear stress under different normal stresses subjected to high temperature, after which the calcar- eous sand particles were smaller and more brittle and capable of being crushed with greater ease. After the the residual shear stress of the calcareous sand obviously heat treatment, the sand particles could more easily be increased. The average residual shear stress exceeded the destroyed and the sample became denser. This even - shear strength and was similar to that of the calcareous tually led to an increase in the friction coefficient and sand sample at high shear velocity. the residual shear strength. The calcareous sand sub - Figure 12 shows the variation in the friction coefficient jected to heat treatment had smaller particles, and its of the calcareous sand samples under different normal residual shear stress fluctuation amplitude was rela - stresses. The average friction coefficients of the samples tively reduced, which affects the stability of the soil to under normal stresses of 200  kPa, 400  kPa, and 600  kPa large-displacement flows. From the above discussion, were 0.51, 0.53, and 0.55, respectively. Therefore, the it is understood that the amplitude of the shear stress friction coefficient of the samples increased as the nor - fluctuation in the calcareous sand shear flow behavior mal stress increased. This indicates that, as the normal is related to the particle size and the particle hardness. stress increased, the friction coefficient increased and Hence, the increase in the residual shear stress and the the fluctuation amplitude of the friction coefficient obvi - decrease in the friction coefficient and residual shear ously decreased. The shear characteristics of the calcar - stress fluctuation amplitude following the high-tem - eous sand samples under different normal stresses are perature treatment were caused by the decrease in the particle size. Eec ff t of normal stress on the shear stress and friction coefficient of calcareous sand The variation in the shear characteristics of the calcare - ous sand subjected to different normal stresses is similar to that obtained in other studies. The shear stresses of the calcareous sand samples under different normal stresses are shown in Fig. 11. The shear strengths of the calcareous sand samples under normal stresses of 200 kPa, 400 kPa, and 600  kPa were 110.4  kPa, 221.8  kPa, and 323.7  kPa, respectively, and the average residual shear stresses were 199.8  kPa, 215.2  kPa, and 334.4  kPa, respectively. The shear strength and residual shear stress increased with the normal stress. The fluctuation amplitude of the resid - ual shear stress increased, particularly when the normal Fig. 12 Relationship between time and the friction coefficient under stress reached 600 kPa, and the fluctuation amplitude of different normal stresses W ang and Huang Geoenvironmental Disasters (2022) 9:25 Page 7 of 8 essentially the same as those of other sand types, such as stress will lead to decreasing shear stress and increasing quartz sand. Therefore, as the normal stress increased, sliding velocity. (2) In the process of sliding, the break- the particle breakage and the residual shear stress age of the landslide mass will have a complex impact on increased. the landslide. (3) The high temperature generated by a long-runout landslide will affect the rate of soil breakage Discussion through chemical reactions, which will then indirectly The experiment conducted in this study confirmed the affect the landslide process. irreversible reaction of minerals in calcareous sand sub- jected to high-temperature treatment, and the heat treat- ment affected the shear flow behavior of the calcareous Conclusions sand samples because of the variations in the mineral Based on the principle of the mechanical properties of composition, particle hardness, and particle size. The minerals being irreversible after heating, ring-shear tests reaction of the minerals in the calcareous sand following were conducted on calcareous sand subjected to heat heat treatment at 800 °C proceeded as treatment. The variation laws of the shear characteristics of the calcareous sand were investigated. Based on the Heating CaCO −→ CaO + CO ↑ analysis of the experimental results, the following conclu- 3 2 sions were drawn. Therefore, when investigating the influence of heating on the shear flow behavior, it is necessary to consider the (1) The calcareous sand samples exhibited obvious effect of high temperatures on changes in the mineral non-steady quasi-static shear flow characteristics, composition of the landslide soil. In this test, the hard- and the fluctuation amplitude of the shear stress ness of the calcareous sand particles after heat treatment increased with the shear velocity. In the ring-shear was lower and the particles could break more easily. test, the average residual shear stress was not According to the variation in the hardness, the shear affected by the increasing shear rate. The calcare- strength and residual shear strength of calcareous sand ous sand was identified as a yield-pseudoplastic subjected to high temperature should be lower compared fluid when subjected to large-displacement shear. with those of calcareous sand without heat treatment. The apparent viscosity decreased as the shear rate However, the test results indicate the opposite. Therefore, increased, and a certain degree of shear dilution when the results are analyzed, it is necessary to consider was observed. both the particle size variation and the sample density at which the calcareous sand was crushed. (2) The calcareous sand subjected to high temperature The calcareous sand particles were subjected to heat could be destroyed with greater ease, and the par- treatment and large displacement shear testing, and the ticles became smaller. The fluctuation amplitude of particle size partially decreased, which led to an increase the residual shear stress decreased, which affected in the sample density. In addition, the contact between the stability in the large-displacement shear behav- the particles increased, which led to an increase in the ior. The fluctuation amplitude of the shear stress macroscopic friction coefficient of the samples. Finally, in the shear behavior may be related to the parti- the shear strength and residual shear stress of the calcar- cle size and particle hardness. Moreover, the high eous sand increased. temperature directly affected the shear behavior The results obtained in this study reveal that the fluc - and induced unsteady characteristics by changing tuation amplitude of the residual shear stress increases the mineral composition of the soil. with the shear rate and that the maximum value of the (3) The friction coefficient of the calcareous sand sam- residual stress exceeds the shear strength. Therefore, ples obviously changed under different normal the frequency of the particle rearrangement and parti- stresses. As the normal stress increased, the shear cle breakage increases with the shear rate. Moreover, the strength of the calcareous sand increased while the impact force between the particles increases. It is thought friction coefficient decreased. Finally, the fluctua- that the fluctuation amplitude of a sample’s residual shear tion amplitude of the friction coefficient obviously stress is proportional to the velocity in a certain range. decreased. In long-runout landslides, the soil has similar residual shear stress fluctuations; this may be one reason for the unsteady characteristics of the soil’s shear flow behavior. This experiment resulted in multiple revelations. (1) In the process of landslide movement, decreasing overlying Wang and Huang Geoenvironmental Disasters (2022) 9:25 Page 8 of 8 Author contributions Smith SAF, Di Toro G, Kim S et al (2013) Coseismic recrystallization during shal- Conceptualization, SW; formal analysis, SW; writing: original draft preparation, low earthquake slip. Geology 41:63–66 SW; writing: review and editing, YH; supervision, YH; funding acquisition, SW Sun QC, Wang GQ (2008) Review on granular flow dynamics and its discrete and YH All authors reviewed the manuscript. element method. Adv Mech 38(1):87–100 Tika TE, Hutchinson JN (1999) Ring shear tests on soil from the Vaiont landslide. Funding Geotechnique 49(1):59–74 This study was supported by the National Natural Science Foundation of Ujiie K, Tanaka H, Saito T et al (2013) Low coseismic shear stress on the Tohoku- China (Grant Nos. 42107168, 41831291, and 42120104008). oki megathrust determined from laboratory experiments. Science 242:1211–1214 Availability of data and materials Uzuoka R, Yashima A, Kawakami T et al (1998) Fluid dynamics based predic- The datasets used and/or analyzed during the current study are available from tion of liquefaction induced lateral spreading. Comput Geotech the corresponding author on reasonable request. 22(3–4):243–282 Wang YY (2006) An approach to rheological characters of viscous debris flow and the stress constitutie. J Mt Sci 24(5):555–561 (In Chinese) Declarations Wang SR, Huang Y (2022a) Experimental study on the effect of particle size on the shear characteristics of large-displacement soil exposed to heat treat- Competing interests ment: shear fluctuation and heat degradation. Eng Geol 300:106581 The authors declare that they have no competing interests. Wang SR, Huang Y (2022b) Experimental study on the shear characteristics of quartz sand exposed to high temperatures. Acta Geotech 17:5031–5041 Author details Xu Q, Li WL, Dong XJ (2017) The Xinmocun landslide on June 24, 2017 in Department of Civil Engineering, University of Shanghai for Science Maoxian, Sichuan: characteristics and failure mechanism. Chin J Rock and Technology, 516 Jungong Road, Shanghai 200093, China. Depar tment Mech Eng 36(11):2612–2628 of Geotechnical Engineering, College of Civil Engineering, Tongji University, Shanghai 200092, China. Key Laboratory of Geotechnical and Underground Engineering of the Ministry of Education, Tongji University, Shanghai 200092, Publisher’s Note China. Springer Nature remains neutral with regard to jurisdictional claims in pub- lished maps and institutional affiliations. Received: 30 April 2022 Accepted: 18 November 2022 References Agung MW, Sassa K, Fukuoka H et al (2004) Evolution of shear-zone structure in undrained ring-shear tests. Landslide 1(1):101–112 Forterre Y (2008) Flows of dense granular media. Annu Rev Fluid Mech 40:1–24 Hong Y, Sun T, Luan MT et al (2009) Development and application of geotech- nical ring shear apparatus: an overview. Rock Soil Mech 30(3):628–634 (In Chinese) Hu W, Huang RQ, McSaveney M et al (2018) Mineral changes quantify frictional heating during a large low-friction landslide. Geology 46(3):223–226 Hu W, Huang RQ, McSaveney M et al (2019) Superheated steam, hot CO2 and dynamic recrystallization from frictional heat jointly lubricated a giant landslide: field and experimental evidence. Earth Planet Sci Lett 510:85–93 Huang Y, Dai ZL (2014) Large displacement and failure simulations for geo- disasters using smoothed particle hydrodynamics method. Eng Geol 168:86–97 Hungr O (1995) A model for the runout analysis of rapid flow slides, debris flows, and avalanches. Can Geotech J 32(4):610–623 Johnson KL (1970) The correlation of indentation experiments. J Mech Phys Solids 18(2):115–126 Kamai T (1998) Monitoring the process of ground failure in repeated landslides and associated stability assessments. Eng Geol 50(1):101–112 Luo Y, He SM, Song PF (2016) Research status and prospects of thermo-poro- mechanical analysis of long runout landslides motions. J Catastrophol 31(4):162–165 Ma SL, Shimamoto T, Yao L et al (2014) A rotary-shear low to high-velocity friction apparatus in Beijing to study rock friction at plate to seismic slip rates. Earthq Sci 27(5):469–497 Noda H, Kanagawa K, Hirose T et al (2011) Frictional experiments of dolerite at intermediate slip rates with controlled temperature: Rate weakening or temperature weakening? J Geophys Res 116:B07306 Pinyol NM, Alvarado M, Alonso EE et al (2018) Thermal effects in landslide mobility. Geotechnique 68(6):528–545 Shimamoto T, Tsutsumi A (1994) A new rotary-shear high-speed frictional test- ing machine: its basic degign and scope of research. J Tecton Res Group Jpn 39:65–78 Skempton AW (1985) Residual strength of clays in landslides, folded strata and the laboratory. Geotechnique 35(1):3–18 http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Geoenvironmental Disasters Springer Journals

Influence of the thermal effect on quasi-static shear characteristics of calcareous soil: an experimental study

Geoenvironmental Disasters , Volume 9 (1) – Nov 29, 2022

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Abstract

In principle, the mechanical properties of soil particles are irreversibly changed after particles are subjected to heat- ing. Accordingly, this study performed ring-shear tests on calcareous sand samples subjected to high temperatures to qualitatively investigate the influence exerted by the degradation of the calcareous sand, caused by the thermal effect, on the large displacement shear characteristics of the samples. The effects of the shear velocity and normal stress on the quasi-static shear behavior of the calcareous sand samples were analyzed. The influence of the thermal effect on the quasi-static shear flow behavior of the samples is primarily reflected in the change in the particle mineral composition, particle hardness, and sample density. These variations result in changes in the shear strength, residual shear stress, macroscopic friction coefficient, and other shear characteristics of the calcareous sand samples. Both the shear velocity and the high temperature affect the fluctuation amplitude of the residual shear stress. The results have great theoretical and practical significance in terms of explaining the instability mechanism of a slope. Moreover, a feasible and effective technique is proposed to investigate the large-displacement shear behavior of soil subjected to the thermal effect exerted by a long-runout landslide. Keywords: Ring-shear test, Shear characteristics, High temperature, Calcareous soil Introduction its influence on particles of geotechnical materials are of Landslides can cause enormous loss of life and financial particular interest. damages. Since the 1960s, many long-runout landslides In large-displacement shear behavior, the soil has par- have occurred worldwide. In general, such landslides are tial flow characteristics. To enable the accurate predic - characterized by high-speed movement, wide disaster tion and analysis of the kinetic characteristics of the ranges, and great destructive ability  (Tika and Hutchin- shear behavior of landslides, it is important to explain son  1999; Xu et  al. 2017). Therefore, the movement and the dynamic mechanism of long-runout landslides. Mul- disaster-inducing mechanism of long-runout landslides tiple field investigations and laboratory experiments on have become a focus of researchers worldwide. The phys - landslides and debris flows have shown that Newtonian ical and chemical changes caused by the thermal effect and non-Newtonian fluid models, such as the Bingham induced by high-velocity sliding friction are among the fluid, pseudoplastic flow, expansion flow, and Coulomb main causes of long-runout landslides (Noda et al. 2011; viscous flow, can be used to describe the constitutive Pinyol et  al. 2018). The cause of the thermal effect and behavior of landslide soil (Johnson 1970; Hungr 1995; Uzuoka et  al. 1998; Wang 2006; Huang and Dai 2014). However, previous studies did not consider the influ - *Correspondence: yhuang@tongji.edu.cn ence of the thermal effect on the motion state, which Department of Geotechnical Engineering, College of Civil Engineering, is necessary for an accurate description of the dynamic Tongji University, Shanghai 200092, China characteristics. Luo et  al. (2016) summarized recent Full list of author information is available at the end of the article © The Author(s) 2022. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http:// creat iveco mmons. org/ licen ses/ by/4. 0/. Wang and Huang Geoenvironmental Disasters (2022) 9:25 Page 2 of 8 thermal-hydro-mechanical-coupled physical models of (Shimamoto et  al. 1994; Smith et  al. 2013; Ujiie et  al. long-runout landslides. Some studies have focused on 2013; Ma et al. 2014). Owing to the different characteris - the friction behavior of the sliding surface, while other tics between the rock and the soil, it is difficult to test the studies have focused on establishing thermal-hydro- soil by carrying out high-velocity friction tests at temper- mechanical-coupled physical models of long-runout atures of approximately 800 °C. Therefore, other methods landslides by introducing the depth-averaged hydrody- have been used to investigate the shear characteristics namic theory into the sliding block model. However, the of soil subjected to high temperatures. In principle, the results obtained thus far have not explained the kinetic mechanical properties of soil particles are irreversible mechanism of the thermal effect response and an accu - after heating. Accordingly, calcareous soil was first sub - rate and effective kinetic model has not yet been estab - jected to a heat treatment and then ring-shear tests were lished. Therefore, considering the thermal effect on the carried out on the samples. In this way, the influence of shear characteristics of soil is important to accurately the thermal effect on the physical and mechanical prop - describe the shear mechanism and the characteristics of erties of the soil can be investigated. Moreover, the influ - large-displacement-sheared soil. ence of this change on the shear characteristics of the soil Regarding the shear thermal effect, Hu et al. (2018) was can also be determined. the first to obtain field and experimental evidence for Based on previous studies, a ring-shear test was carried the high-temperature thermal decomposition of a long- out on calcareous sand samples subjected to high tem- runout landslide belt and accurately estimated a bottom perature using a GCTS ring-shear apparatus to examine friction temperature of 790  °C during the high-velocity the shear characteristics of calcareous sand with large- sliding process in the Jiweishan long-runout landslide. displacement shear flow. The experimental results have Hu et  al. (2019) used a thermogravimetric method to great theoretical and practical significance with respect estimate a bottom temperature of 850  °C for the sliding to explaining the flow mechanism and conducting insta - surface of the Daguangbao landslide. Using a ring-shear bility analyses. test, they obtained the microstructural variation after the thermal effect and the variation relationship between Methods and materials the friction coefficient and the shear displacement. Their Specimen preparation results revealed that friction between the particles pro- To investigate the variation in the large-displacement duces a dynamic recrystallization layer and carbon diox- shear characteristics of calcareous soil samples subjected ide, which reduces friction. These studies confirmed that to high temperature, a single mineral composition soil the thermal effect between the sliding particles is strongly sample was used in this test. The sample consisted of cal - related to the large displacement and fluidization of long- careous sand obtained from the Guangdong Province, runout landslides. China. The specific composition of the soil is presented Owing to limitations in the design of conventional geo- in Table  1, and the mechanical properties of sample is technical test equipment, the shear failure and mechani- presented in Table 2. cal behavior of soil cannot be completely obtained, particularly in studies concerned with the mechanical Test equipment and procedure properties of soil subjected to large-displacement shear. The SMF1900-50 box resistance furnace at the Uni - One such limitation is that the shearing surface of con- versity of Shanghai for Science and Technology was ventional direct shear test equipment is not sufficiently long. Therefore, the long-term shear mechanical proper - ties of soil cannot be fully monitored during a test (Hong et  al. 2009). The ring-shear test is primarily used to Table 1 Material composition investigate the post-peak stress–strain relationship and Composition Percentage (%) the shear stress variation of geotechnical materials with IL(Loss on Ignition) 43.67 large shear displacement and complex stress. The shear Al O < 0.01 flow behavior of different rocks and soil with large dis - 2 3 SiO 0.4 placement under different conditions has been investi - 3 Fe O 0.0086 gated (Skempton 1985; Kamai 1998; Agung 2004). In the 2 3 CaO 55.5 research field of coseismic faults with high-speed friction MgO 0.19 activity, a rotary-shear high-velocity friction apparatus K O 0.0085 is used to investigate high-speed friction with large dis- Na O 0.072 placement and obtain the mechanical properties of rock TiO < 0.01 under the friction heat produced by high-velocity sliding 2 W ang and Huang Geoenvironmental Disasters (2022) 9:25 Page 3 of 8 Table 2 Dry density of the samples (kg/m ) Temperature Minimum dry density Maximum dry density 20 °C 1363.8 1496.5 800 °C 826.0 882.1 Fig. 2 Appearance of the calcareous sand before (left) and after (right) heat treatment Fig. 1 Test equipment: a SMF1900-50 box resistance furnace and b GCTS SRS-150 ring-shear apparatus used to conduct a high-temperature test (Fig.  1a). The maximum temperature was 1000  °C. The heating rate and the cooling rate were set to 4 °C/min, and the tem- Fig. 3 Relationship between time and the shear stress for different perature was maintained at 800  °C for 24  h and finally shear velocities reduced to 20  °C (Zhang et  al. 2015; Chen et  al. 2017; Wang et  al. 2022a). The sample was placed in a corun - dum crucible, which was raised by a corundum gasket sand was completely converted from calcium carbonate to ensure uniform heating. to calcium oxide. The content of the remaining compo - The GCTS SRS-150 ring-shear apparatus in the key nents was negligible. laboratory of the Ministry of Geotechnical and Under- ground Engineering of Tongji University was used to Eec ff t of shear velocity on the shear strength, residual conduct the ring-shear test (Fig. 1b). In the test, the dis- shear stress, and apparent viscosity placement was continuous and the equipment automat- Under the same conditions, the mechanical behav- ically obtained the shear stress of the samples. Details ior of the calcareous sand samples sheared at differ - regarding the instrumentation and the test process are ent shear velocities was different. Figure  3 shows the provided in Wang et al. (2022b). relationship between time and the shear stress for dif- ferent shear velocities. In Fig.  3, the shear strength and the residual shear stress can be clearly observed. Results and analysis The average, maximum, and minimum residual shear Appearance of samples stresses were obtained separately, as plotted in Fig.  4. The calcareous sand was obviously different after the With shear velocities of 3°/min, 36°/min, and 180°/ high-temperature treatment (Fig.  2), and its particles min, the shear strengths of the calcareous sand samples changed from translucent gray white crystals to pure were 108.3 kPa, 110.4 kPa, and 108.9 kPa, respectively; white opaque crystals, indicating that the calcareous Wang and Huang Geoenvironmental Disasters (2022) 9:25 Page 4 of 8 Fig. 4 Relationship between the average, maximum, and minimum residual shear strains and the shear velocity the average residual shear stresses were 101.8  kPa, Fig. 5 Standard deviation of the shear stresses of the samples with 103.1  kPa, and 102.8  kPa, respectively; the maximum time residual shear stresses were 108.8  kPa, 111.8  kPa, and 114.2  kPa, respectively; and the minimum residual shear stresses were 97.5  kPa, 93.5  kPa, and 92.6  kPa, respectively. particles and clay particles with large moisture contents At lower shear velocity (3°/min), the initial peak shear (Forterre 2008). The results obtained via the ring-shear strength of the sample appeared later compared with test in this study differ from the theoretical results. Even those of samples with higher shear velocities. The fluc - though the shear flow in the ring-shear test belongs to tuation amplitude of the residual shear stress was small the quasi-static flow regime, the shear stress and shear and gentle. At higher shear velocities (36°/min and 180°/ rate are not completely independent; this is strongly min), the initial peak shear strength of the samples related to the unsteady state of the soil under large-dis- appeared faster and the residual shear stress fluctuated placement shear. significantly. In this unsteady state, the residual shear The shear rate can be calculated as follows: stress was greater than the shear strength. As the shear vD velocity increased, the residual shear stress fluctuation γ˙ = , 2h of the samples with a large displacement shear became more intense and even exceeded the shear strength. This where v is the shear velocity [°/s]; D is the average diam- is related to the shear breakage and rearrangement of eter of the ring-shear sample [mm]; h is the thickness of the soil particles in the shear box. Therefore, the resid - the ring-shear sample [mm]. ual shear stress of calcareous sand may exceed the shear The apparent viscosity η can be expressed by the rela- strength and increase with the shear velocity when the tionship between the shear stress and the shear rate: other experimental conditions remain the same. Moreo- ver, the residual shear stress of the sample with a shear τ = ηγ˙ . velocity of 180°/min kept increasing, which indicates that Accordingly, the specific value of the apparent viscosity the residual shear stress of the sample increased with the can be calculated. particle breakage. To quantify the shear stress fluctua - Because the residual shear stress fluctuated continu - tion, the standard deviation of the shear stress was used ously as the shearing progressed, the average, maximum, to measure the fluctuation amplitude of the shear stress, and minimum residual shear stresses were calculated as as shown in Fig. 5. The results indicate that a higher shear shown in Fig. 6. The approximate shear flow characteris - velocity led to an increase in the sample’s shear fluctua - tics of the calcareous sand samples were obtained under tion amplitude. The shear behavior of the calcareous sand a normal stress of 200  kPa. Here, the rheological curve exhibited the phenomenon of shear stress fluctuation, does not pass through the origin point and is concave to which is related to the continuous formation and recon- the shear rate axis. The sample has both yield characteris - struction of the force chain structure (Sun and Wang tics and pseudoplastic fluid characteristics and can there - 2008). Existing studies on dense granular flow consider fore be thought of as a yield pseudoplastic fluid. In Fig.  7, the shear stress to be independent of the shear rate; how- the curve of the average value of the apparent viscosity ever, this conclusion was reached considering simple is slightly different from the curve drawn according to W ang and Huang Geoenvironmental Disasters (2022) 9:25 Page 5 of 8 Fig. 6 Relationship between the shear rate and the residual shear stress Fig. 8 Relationship between time and the shear stress of the calcareous sand before and after heat treatment -0.988 Max value y = 110.24x -0.997 y = 102.34x -1.013 Average value y = 95.779x Min value 05 10 15 20 -1 Shear rate (s ) Fig. 7 Relationship between the shear rate and the apparent viscosity the maximum and minimum values; however, the overall Fig. 9 Relationship between time and the friction coefficient of the trends of the two are essentially identical. The apparent calcareous sand before and after heat treatment viscosity decreased as the shear rate increased; there- fore, the viscosity of the calcareous sand decreased as the shear rate increased and the relationship between the to shear failure. The average residual shear stresses shear stress and the shear rate is nonlinear, with a certain were 103.1 kPa and 110.2 kPa before and after heating, degree of shear dilution. respectively. Hence, the residual shear strength of the sample increased after the high-temperature treatment. Variation of the shear strength, residual shear stress, A comparison of the friction coefficient of the sample and friction coefficient caused by high temperature before and after heat treatment (Fig.  9) indicated that The ring-shear tests on the calcareous sand samples the average friction coefficient increased from 0.51 to before and after heat treatment were performed under 0.55. After the heat treatment at 800  °C, the friction the same normal stress and shear velocity conditions. coefficient of the sample was obviously higher com The shear characteristics of the samples were obtained pared with that prior to the heat treatment. Figure  10 before and after the heat treatment, and the shear stress shows the state of the calcareous sand sample particles curves are shown in Fig.  8. The shear strengths of the after heat treatment at different temperatures. Con - samples before and after heat treatment were 110.4 kPa sidering Fig.  10 in conjunction with the sample images and 104.1  kPa, respectively. This indicates that the captured after the ring-shear tests (Fig. 9), it was deter- shear strength of the calcareous sand decreased after mined that the variation behavior of the shear flow was the calcareous sand was subjected to high tempera primarily influenced by the change in the sand particles ture and that the calcareous sand became more prone Apparent viscocity (kPa·s) Wang and Huang Geoenvironmental Disasters (2022) 9:25 Page 6 of 8 Fig. 10 Calcareous sand samples after being subjected to different temperatures Fig. 11 Relationship between time and the shear stress under different normal stresses subjected to high temperature, after which the calcar- eous sand particles were smaller and more brittle and capable of being crushed with greater ease. After the the residual shear stress of the calcareous sand obviously heat treatment, the sand particles could more easily be increased. The average residual shear stress exceeded the destroyed and the sample became denser. This even - shear strength and was similar to that of the calcareous tually led to an increase in the friction coefficient and sand sample at high shear velocity. the residual shear strength. The calcareous sand sub - Figure 12 shows the variation in the friction coefficient jected to heat treatment had smaller particles, and its of the calcareous sand samples under different normal residual shear stress fluctuation amplitude was rela - stresses. The average friction coefficients of the samples tively reduced, which affects the stability of the soil to under normal stresses of 200  kPa, 400  kPa, and 600  kPa large-displacement flows. From the above discussion, were 0.51, 0.53, and 0.55, respectively. Therefore, the it is understood that the amplitude of the shear stress friction coefficient of the samples increased as the nor - fluctuation in the calcareous sand shear flow behavior mal stress increased. This indicates that, as the normal is related to the particle size and the particle hardness. stress increased, the friction coefficient increased and Hence, the increase in the residual shear stress and the the fluctuation amplitude of the friction coefficient obvi - decrease in the friction coefficient and residual shear ously decreased. The shear characteristics of the calcar - stress fluctuation amplitude following the high-tem - eous sand samples under different normal stresses are perature treatment were caused by the decrease in the particle size. Eec ff t of normal stress on the shear stress and friction coefficient of calcareous sand The variation in the shear characteristics of the calcare - ous sand subjected to different normal stresses is similar to that obtained in other studies. The shear stresses of the calcareous sand samples under different normal stresses are shown in Fig. 11. The shear strengths of the calcareous sand samples under normal stresses of 200 kPa, 400 kPa, and 600  kPa were 110.4  kPa, 221.8  kPa, and 323.7  kPa, respectively, and the average residual shear stresses were 199.8  kPa, 215.2  kPa, and 334.4  kPa, respectively. The shear strength and residual shear stress increased with the normal stress. The fluctuation amplitude of the resid - ual shear stress increased, particularly when the normal Fig. 12 Relationship between time and the friction coefficient under stress reached 600 kPa, and the fluctuation amplitude of different normal stresses W ang and Huang Geoenvironmental Disasters (2022) 9:25 Page 7 of 8 essentially the same as those of other sand types, such as stress will lead to decreasing shear stress and increasing quartz sand. Therefore, as the normal stress increased, sliding velocity. (2) In the process of sliding, the break- the particle breakage and the residual shear stress age of the landslide mass will have a complex impact on increased. the landslide. (3) The high temperature generated by a long-runout landslide will affect the rate of soil breakage Discussion through chemical reactions, which will then indirectly The experiment conducted in this study confirmed the affect the landslide process. irreversible reaction of minerals in calcareous sand sub- jected to high-temperature treatment, and the heat treat- ment affected the shear flow behavior of the calcareous Conclusions sand samples because of the variations in the mineral Based on the principle of the mechanical properties of composition, particle hardness, and particle size. The minerals being irreversible after heating, ring-shear tests reaction of the minerals in the calcareous sand following were conducted on calcareous sand subjected to heat heat treatment at 800 °C proceeded as treatment. The variation laws of the shear characteristics of the calcareous sand were investigated. Based on the Heating CaCO −→ CaO + CO ↑ analysis of the experimental results, the following conclu- 3 2 sions were drawn. Therefore, when investigating the influence of heating on the shear flow behavior, it is necessary to consider the (1) The calcareous sand samples exhibited obvious effect of high temperatures on changes in the mineral non-steady quasi-static shear flow characteristics, composition of the landslide soil. In this test, the hard- and the fluctuation amplitude of the shear stress ness of the calcareous sand particles after heat treatment increased with the shear velocity. In the ring-shear was lower and the particles could break more easily. test, the average residual shear stress was not According to the variation in the hardness, the shear affected by the increasing shear rate. The calcare- strength and residual shear strength of calcareous sand ous sand was identified as a yield-pseudoplastic subjected to high temperature should be lower compared fluid when subjected to large-displacement shear. with those of calcareous sand without heat treatment. The apparent viscosity decreased as the shear rate However, the test results indicate the opposite. Therefore, increased, and a certain degree of shear dilution when the results are analyzed, it is necessary to consider was observed. both the particle size variation and the sample density at which the calcareous sand was crushed. (2) The calcareous sand subjected to high temperature The calcareous sand particles were subjected to heat could be destroyed with greater ease, and the par- treatment and large displacement shear testing, and the ticles became smaller. The fluctuation amplitude of particle size partially decreased, which led to an increase the residual shear stress decreased, which affected in the sample density. In addition, the contact between the stability in the large-displacement shear behav- the particles increased, which led to an increase in the ior. The fluctuation amplitude of the shear stress macroscopic friction coefficient of the samples. Finally, in the shear behavior may be related to the parti- the shear strength and residual shear stress of the calcar- cle size and particle hardness. Moreover, the high eous sand increased. temperature directly affected the shear behavior The results obtained in this study reveal that the fluc - and induced unsteady characteristics by changing tuation amplitude of the residual shear stress increases the mineral composition of the soil. with the shear rate and that the maximum value of the (3) The friction coefficient of the calcareous sand sam- residual stress exceeds the shear strength. Therefore, ples obviously changed under different normal the frequency of the particle rearrangement and parti- stresses. As the normal stress increased, the shear cle breakage increases with the shear rate. Moreover, the strength of the calcareous sand increased while the impact force between the particles increases. It is thought friction coefficient decreased. Finally, the fluctua- that the fluctuation amplitude of a sample’s residual shear tion amplitude of the friction coefficient obviously stress is proportional to the velocity in a certain range. decreased. In long-runout landslides, the soil has similar residual shear stress fluctuations; this may be one reason for the unsteady characteristics of the soil’s shear flow behavior. This experiment resulted in multiple revelations. (1) In the process of landslide movement, decreasing overlying Wang and Huang Geoenvironmental Disasters (2022) 9:25 Page 8 of 8 Author contributions Smith SAF, Di Toro G, Kim S et al (2013) Coseismic recrystallization during shal- Conceptualization, SW; formal analysis, SW; writing: original draft preparation, low earthquake slip. Geology 41:63–66 SW; writing: review and editing, YH; supervision, YH; funding acquisition, SW Sun QC, Wang GQ (2008) Review on granular flow dynamics and its discrete and YH All authors reviewed the manuscript. element method. Adv Mech 38(1):87–100 Tika TE, Hutchinson JN (1999) Ring shear tests on soil from the Vaiont landslide. Funding Geotechnique 49(1):59–74 This study was supported by the National Natural Science Foundation of Ujiie K, Tanaka H, Saito T et al (2013) Low coseismic shear stress on the Tohoku- China (Grant Nos. 42107168, 41831291, and 42120104008). oki megathrust determined from laboratory experiments. Science 242:1211–1214 Availability of data and materials Uzuoka R, Yashima A, Kawakami T et al (1998) Fluid dynamics based predic- The datasets used and/or analyzed during the current study are available from tion of liquefaction induced lateral spreading. Comput Geotech the corresponding author on reasonable request. 22(3–4):243–282 Wang YY (2006) An approach to rheological characters of viscous debris flow and the stress constitutie. J Mt Sci 24(5):555–561 (In Chinese) Declarations Wang SR, Huang Y (2022a) Experimental study on the effect of particle size on the shear characteristics of large-displacement soil exposed to heat treat- Competing interests ment: shear fluctuation and heat degradation. Eng Geol 300:106581 The authors declare that they have no competing interests. Wang SR, Huang Y (2022b) Experimental study on the shear characteristics of quartz sand exposed to high temperatures. Acta Geotech 17:5031–5041 Author details Xu Q, Li WL, Dong XJ (2017) The Xinmocun landslide on June 24, 2017 in Department of Civil Engineering, University of Shanghai for Science Maoxian, Sichuan: characteristics and failure mechanism. Chin J Rock and Technology, 516 Jungong Road, Shanghai 200093, China. Depar tment Mech Eng 36(11):2612–2628 of Geotechnical Engineering, College of Civil Engineering, Tongji University, Shanghai 200092, China. Key Laboratory of Geotechnical and Underground Engineering of the Ministry of Education, Tongji University, Shanghai 200092, Publisher’s Note China. Springer Nature remains neutral with regard to jurisdictional claims in pub- lished maps and institutional affiliations. Received: 30 April 2022 Accepted: 18 November 2022 References Agung MW, Sassa K, Fukuoka H et al (2004) Evolution of shear-zone structure in undrained ring-shear tests. Landslide 1(1):101–112 Forterre Y (2008) Flows of dense granular media. Annu Rev Fluid Mech 40:1–24 Hong Y, Sun T, Luan MT et al (2009) Development and application of geotech- nical ring shear apparatus: an overview. Rock Soil Mech 30(3):628–634 (In Chinese) Hu W, Huang RQ, McSaveney M et al (2018) Mineral changes quantify frictional heating during a large low-friction landslide. 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Journal

Geoenvironmental DisastersSpringer Journals

Published: Nov 29, 2022

Keywords: Ring-shear test; Shear characteristics; High temperature; Calcareous soil

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