Understanding frictional anisotropy,which refers to the variation in frictional resistance based on the shear direction,is crucial for optimizing the friction angle between a bio-inspired structure and the surrounding...Understanding frictional anisotropy,which refers to the variation in frictional resistance based on the shear direction,is crucial for optimizing the friction angle between a bio-inspired structure and the surrounding soil.Previous studies focused on estimating the interface frictional anisotropy mobilized by snakeskin-inspired textured surfaces and sand under monotonic shear loading conditions.However,there is a need to estimate interface frictional anisotropy under repetitive shear loads.In this study,a series of repetitive direct shear(DS)tests are performed with snakeskin-inspired textured surfaces under a constant vertical stress and two shear directions(cranial first half→caudal second half or caudal first half→cranial second half).The results show that(1)mobilized shear stress increases with the number of shearing cycles,(2)cranial shearing(shearing against the scales)consistently produces a higher shear resistance and less contractive behavior than caudal shearing(shearing along the scales),and(3)a higher scale height or smaller scale length of the surface yields a higher interface friction angle across all shearing cycles.Further analysis reveals that the gap between the cranial and caudal shear zones of the interface friction angle as a function of L/H(i.e.the ratio of scale length L to scale height H)continues to decrease as the number of shearing cycles approaches asymptotic values.The directional frictional resistance(DFR)decreases as the number of shearing cycles increases.Furthermore,the discussion covers the impact of initial relative density,vertical stress,and the number of shearing cycles on interface frictional anisotropy.展开更多
Several groups of direct shear tests of Nanning expansive soil samples were carded out by improved direct shear apparatus. The results of the characteristics of the ultimate shear stress and residual shear stress at t...Several groups of direct shear tests of Nanning expansive soil samples were carded out by improved direct shear apparatus. The results of the characteristics of the ultimate shear stress and residual shear stress at the interface of expansive soil-structure are presented as follows： linear relation can approximately reflect changes between the both shear stress and the three factors： vertical load, water content and dry density, just different degrees from each other; increasing the vertical load from 25 kPa to 100 kPa （up by 300%） can cause the average increase of ultimate shear stress from 58% （for samples with 1.61 g/cm^3） to 80% （for samples with 1.76 g/cm^3）, and an close average increase of 180% for the residual shear stress; increasing the water content from 14.1% to 20.8% （up by 47.5%） can cause the average decrease of the ultimate shear stress from 40% （for samples with 25 kPa） to 80% （for samples with 100 kPa）, and the average decrease from 25% （for samples with 25 kPa） to 30% （for samples with 100 kPa） for the residual shear stress; increasing the dry density from 1.61 g/cm^3 to 1.76 g/cm^3 （up by 9.3%） can cause the average increase of ultimate shear stress from 92% （for samples with 25 kPa） to 138% （for samples with 100 kPa）, and an average increase of 4% for the residual shear stress. Sensitive analysis was further made to explain reasons causing the differences of the both shear stress induced by the three factors.展开更多
基金the funding supported from the National Research Foundation of Korea(NRF)grant funded by the Korea Government MSIT(No.2021R1C1C1006003).
文摘Understanding frictional anisotropy,which refers to the variation in frictional resistance based on the shear direction,is crucial for optimizing the friction angle between a bio-inspired structure and the surrounding soil.Previous studies focused on estimating the interface frictional anisotropy mobilized by snakeskin-inspired textured surfaces and sand under monotonic shear loading conditions.However,there is a need to estimate interface frictional anisotropy under repetitive shear loads.In this study,a series of repetitive direct shear(DS)tests are performed with snakeskin-inspired textured surfaces under a constant vertical stress and two shear directions(cranial first half→caudal second half or caudal first half→cranial second half).The results show that(1)mobilized shear stress increases with the number of shearing cycles,(2)cranial shearing(shearing against the scales)consistently produces a higher shear resistance and less contractive behavior than caudal shearing(shearing along the scales),and(3)a higher scale height or smaller scale length of the surface yields a higher interface friction angle across all shearing cycles.Further analysis reveals that the gap between the cranial and caudal shear zones of the interface friction angle as a function of L/H(i.e.the ratio of scale length L to scale height H)continues to decrease as the number of shearing cycles approaches asymptotic values.The directional frictional resistance(DFR)decreases as the number of shearing cycles increases.Furthermore,the discussion covers the impact of initial relative density,vertical stress,and the number of shearing cycles on interface frictional anisotropy.
基金Projects(50378097 50678177) supported by the National Natural Science Foundation of ChinaProject (01JJY3043) supported by the Natural Science Foundation of Hunan Province, China
文摘Several groups of direct shear tests of Nanning expansive soil samples were carded out by improved direct shear apparatus. The results of the characteristics of the ultimate shear stress and residual shear stress at the interface of expansive soil-structure are presented as follows： linear relation can approximately reflect changes between the both shear stress and the three factors： vertical load, water content and dry density, just different degrees from each other; increasing the vertical load from 25 kPa to 100 kPa （up by 300%） can cause the average increase of ultimate shear stress from 58% （for samples with 1.61 g/cm^3） to 80% （for samples with 1.76 g/cm^3）, and an close average increase of 180% for the residual shear stress; increasing the water content from 14.1% to 20.8% （up by 47.5%） can cause the average decrease of the ultimate shear stress from 40% （for samples with 25 kPa） to 80% （for samples with 100 kPa）, and the average decrease from 25% （for samples with 25 kPa） to 30% （for samples with 100 kPa） for the residual shear stress; increasing the dry density from 1.61 g/cm^3 to 1.76 g/cm^3 （up by 9.3%） can cause the average increase of ultimate shear stress from 92% （for samples with 25 kPa） to 138% （for samples with 100 kPa）, and an average increase of 4% for the residual shear stress. Sensitive analysis was further made to explain reasons causing the differences of the both shear stress induced by the three factors.
