scholarly journals Effect of Moisture Content On The Time-Dependent Mechanical Characteristics of Loess

2021 ◽  
Author(s):  
Lijie Chen ◽  
Jianbing Peng ◽  
Fei Xie ◽  
Yanqiu Leng ◽  
Penghui Ma ◽  
...  
Keyword(s):  
Moisture Content ◽  
Failure Mode ◽  
Shear Failure ◽  
Time Dependent ◽  
Shanxi Province ◽  
Peak Strain ◽  
Term Strength ◽  
Creep Tests ◽  
Effect Of Moisture

Abstract It is of great significance to study the time-dependent mechanical properties of loess, as loess landslides are closely related to them. The purpose of this study is to investigate the effect of moisture content on instantaneous and time-dependent deformation, strength and failure behaviors of undisturbed loess specimens from Nangou in Yan'an City, Shanxi Province, China, via triaxial shearing tests and multi-loading triaxial creep tests under moisture contents of 5%, 10%, 17% and 22%. The results show that the time-dependent deformation of loess increase with the moisture content, while the time-dependent deformation rate decreases slowly. The soil deformation is divided into four stages based on the peak strain rate. Furthermore, the instantaneous and long-term strength of loess decrease with increasing moisture content, and the instantaneous strength decreases more than the long-term strength. The failure mode of undisturbed loess changes from shear failure to homogeneous failure with increasing moisture content; when the failure mode is shear failure, the thickness of the shear band that forms at the specimen surface over time is smaller than the corresponding thickness that forms instantaneously. Finally, the macroscopic morphology and microstructure of loess specimens were considered together to analyze the effect of moisture content on the instantaneous and long-term mechanical behavior of loess and to discuss the process of loess deformation to failure.

Experimental Study on Direct Shear Creep Characteristics and Long-Term Strength of Red Layer Sliding Zone Soil in Southern Hunan

2013 ◽  
Vol 842 ◽  
pp. 782-787 ◽  
Author(s):  
Feng Zhu ◽  
Zhong Yuan Duan ◽  
Zhen Yu Wu ◽  
Yu Qi Wu ◽  
Tian Long Li ◽  
...  
Keyword(s):  
Shear Stress ◽  
Term Strength ◽  
Direct Shear ◽  
Creep Tests ◽  
Shear Creep ◽  
Creep Characteristics ◽  
Southern Hunan ◽  
Sliding Soil ◽  
Sliding Zone

The creep characteristics of red layer sliding soil under the condition of different vertical loads and water contents were studied through a series of direct shear creep tests. Tests results showed that the water infiltrated to the sliding zone along the fissure of red layer sliding belt due to the crush of red layer sliding rock, leading to softening of sliding zone and acceleration of shear creep. When the shear stress reached the limit of long-term shear strength, sliding soil was broken suddenly with small vertical loads (50 kPa and 100kPa), while the sliding soil presented as a constant acceleration creep with enough vertical loads (200 kPa and 300 kPa). The inflection point in shear stress-shear displacement isochronous curve corresponded to the long-term strength of the soil.

scholarly journals Influence of Rib Stiffness and Limited Long-Term Junction Strength on Geogrid Performance

2019 ◽  
Vol 7 (2) ◽  
pp. 175-190
Author(s):  
Werner Müller ◽  
Andreas Wöhlecke
Keyword(s):  
Failure Mode ◽  
Failure Modes ◽  
Shear Failure ◽  
Numerical Approach ◽  
Reinforced Soil ◽  
Analytic Approach ◽  
Tensile Shear ◽  
Long Term Behavior ◽  
Longitudinal And Transverse Ribs

Abstract The description of the behavior of geogrids in reinforced soil constructions usually ignores long-term behavior and possible failure modes of junctions between longitudinal and transverse ribs. Two proposals have been made during recent years to overcome this drawback. The first analytic approach applies only to rigid geogrids and assumes a specific tensile-shear failure mode of geogrid junctions. The second numerical approach applies also for non-rigid geogrids and takes into account different modes of junction failure. This note discusses the two approaches focusing on the effects of rib stiffness and limited strength, different failure modes and degradation of junctions. It is shown that the mentioned effects should be considered in geogrid design, because they may alter significantly the long-term geogrid performance.

scholarly journals Experimental Researches on Long-Term Strength of Granite Gneiss

2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
Lin Liu ◽  
Weiya Xu
Keyword(s):  
Quantitative Methods ◽  
Strain Curve ◽  
Granite Gneiss ◽  
Term Strength ◽  
Creep Tests ◽  
New Methods ◽  
Tangent Method ◽  
Triaxial Creep ◽  
Triaxial Creep Tests

It is important to confirm the long-term strength of rock materials for the purpose of evaluating the long-term stability of rock engineering. In this study, a series of triaxial creep tests were conducted on granite gneiss under different pore pressures. Based on the test data, we proposed two new quantitative methods, tangent method and intersection method, to confirm the long-term strength of rock. Meanwhile, the isochronous stress-strain curve method was adopted to make sure of the accuracy and operability of the two new methods. It is concluded that the new methods are suitable for the study of the long-term strength of rock. The effect of pore pressure on the long-term strength of rock in triaxial creep tests is also discussed.

Time-dependent behavior of rock-like specimen containing multiple discontinuous joints under uniaxial step-loading compression

2021 ◽  
pp. 105678952098524
Author(s):  
Wendong Yang ◽  
Chunjie Bo ◽  
Xuguang Chen ◽  
Chenchen Huang ◽  
Guizhi Li
Keyword(s):  
Jointed Rock ◽  
Time Dependent ◽  
Tensile Failure ◽  
Term Strength ◽  
Test Results ◽  
Joint Plane ◽  
Discontinuous Joints ◽  
Joint Length ◽  
Rock Specimens

Rock with multiple discontinuous joints widely exists in rock engineering, and its mechanical properties are complex, which greatly increases the difficulty of engineering design and construction. Time-dependent deformation characteristics and long-term strength evaluation of jointed rock masses remain poorly understood. In this work, the creep experiments of rock-like specimens with multiple discontinuous joints under uniaxial step-loading compression are carried out to explore the influence of joint geometry (rock bridge length, joint length, joint angle, and joint spacing) on creep strain, long-term strength, and failure pattern of specimens with multiple discontinuous joints. The following conclusions are drawn from the test results: 1) The deformation of jointed rock specimens has evident time-dependent effect, and the cumulative creep deformation increases as creep load increases; 2) The strength of jointed rock specimens under loading changes with time, and the ratio of long-term strength and creep peak strength ( σ∞/ σc) of the tested specimens ranges from 41% to 96%; 3) The distribution of initial joints affects the creep fracture modes of rock-like specimens. The rupture of rock-like specimens with different joints distribution is mainly caused by the growth of wing cracks and quasi-coplanar secondary cracks. Three different failure modes are observed from these specimens: i) tensile failure with cracks across the joint plane; ii) shear failure with cracks along the joint plane; and iii) tensile failure with cracks along the joint plane. Based on the principles of damage mechanics and fracture mechanics, a theoretical mechanistic model considering both the closure stage of pre-existing open joints and time-dependent propagation stage of new cracks is established. Considering the influence of joint length, joint angle and joint density, the evolution of creep strain of rock-like specimen with multiple discontinuous joints is analyzed. The theoretical model results agree well with the experimental results, which indicates that the established model can replicate the creep failure process of jointed rock mass. These theoretical and test results help us better understand the effect of multiple joints on the long-term behavior of rock mass.

Experimental Research on Creep Laws of High-Water Material under Real Pressure Water Environment

2016 ◽  
Vol 705 ◽  
pp. 350-354
Author(s):  
Hui Xie ◽  
Ying Chen
Keyword(s):  
Experimental Research ◽  
Carrying Capacity ◽  
Water Pressure ◽  
Water Environment ◽  
High Water ◽  
Term Strength ◽  
Steady Creep ◽  
Creep Tests ◽  
Pressure Water

High-water material is a kind of new inorganic nonmetal material which mainly used in coal mine goaf filling. In order to simulate the real stress conditions of this material in goaf filling, the creep tests of high-water material in real pressure water environment were conducted and the creep laws were also researched. The results showed that water environment was conductive to maintaining and developing the strength of high-water material, and pressure water environment can improve the carrying capacity and long-term strength of high-water material. The deformation of steady creep period decreased while water pressure increased. And strain increasing caused by axial compression was less than strain increasing caused by water pressure. The time needed from starting to steady creep period was longer when water pressure was bigger.

scholarly journals An Experimental Study on the Creep Characteristics of Sandstone in the Interval of Different Critical Stresses

2021 ◽  
Vol 2021 ◽  
pp. 1-8
Author(s):  
Chao Yang ◽  
Xingchen Dong ◽  
Xuan Xu ◽  
Qiancheng Sun
Keyword(s):  
Failure Time ◽  
Strain Curve ◽  
Creep Model ◽  
Creep Process ◽  
Term Strength ◽  
Creep Tests ◽  
Critical Stresses ◽  
Brittle Sandstone ◽  
Time Required

Creep tests on brittle sandstone specimens were performed to investigate the time-dependent characteristics in the interval of different critical stresses. The results showed that failure will not occur when the loaded stress σ1 is less than the critical stress of dilation σcd, while all specimens were destroyed when σ1 is larger than σcd. In addition, the value of σcd was very close to the long-term strength obtained by the method of the isochronous stress-strain curve. Therefore, σcd can be regarded as the long-term strength of the sandstone specimens. When σ1 is larger than σcd, the time required for the failure of specimen tf decreases with the increase of σ1; the creep rate dε/dt increases with time t, and the specimen will be destroyed when it reaches a maximum value (dε/dt)max. Both relationships tf and σ1 and (dε/dt)max and σ1 can be described by the exponential function. Then, a nonlinear damage creep model considering the deformation damage and strength damage in the interval of different critical stresses was established, which can describe the whole creep process and predict the failure time of sandstone specimens.

Static fatigue of sand particles

2018 ◽  
Vol 55 (11) ◽  
pp. 1682-1687
Author(s):  
Su Liu ◽  
Jianfeng Wang
Keyword(s):  
Fatigue Test ◽  
Compressive Load ◽  
Fatigue Tests ◽  
Time Dependent ◽  
Static Fatigue ◽  
Term Strength ◽  
Short Term ◽  
Short Term Strength ◽  
Sand Particles

Static fatigue is of particular concern when studying the time-dependent mechanical behavior of brittle geomaterials. In this regard, the time-dependent strength behavior of individual particles is essential for understanding the creep behavior of sand. In this study, short-term strength tests and static fatigue tests of individual sand particles subjected to a uniaxial compressive load were carried out using a mini-loading apparatus and modified oedometer frames, respectively. The sand particles in the static fatigue test were loaded in an incremental manner, and the load at each stress level was maintained for a fixed period of time. Scatter of the strength of sand particles was described using the Weibull distribution. Long-term strength from the static fatigue test of individual sand particles is found to be less than the short-term strength.

scholarly journals Experimental Investigations on Creep Behavior of Coal under Combined Compression and Shear Loading

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Rongbin Hou ◽  
Leige Xu ◽  
Duoxin Zhang ◽  
Yanke Shi ◽  
Luyang Shi
Keyword(s):  
Inclination Angle ◽  
Creep Test ◽  
Creep Behavior ◽  
Shear Loading ◽  
Peak Strength ◽  
Term Strength ◽  
Creep Tests ◽  
Inclination Angles ◽  
Pure Compression

The creep behavior of rock has received much attention for analyzing the long-term response and stability of underground rock engineering structures. Numerous studies have been carried out on the creep properties of various rocks under pure compression conditions. However, little attention has been paid to the creep behavior of rocks in a combined compression-shear loading state. In this work, a novel combined compression and shear test (C-CAST) system was used to carry out inclined uniaxial compression tests and creep tests for various inclination angles (0°, 5°, 10°, and 15°). The results revealed that the peak strength of the coal decreased with the inclination angle of the specimen, which could provide the basis for setting up a creep test scheme. Multistage compression-shear creep tests were carried out on specimens with different inclination angles. Based on the analysis of the creep test data, the creep behavior of the coal in a combined compression-shear state was studied. It was found that the specimen inclination affected the time-dependent deformation, long-term strength (LTS), and time to failure. Compared with the specimen under pure compression, the inclination specimens tend to produce large shear strain with time, while they were more prone to shear failure. The reduction of the long-term strength was closely associated with the increase of the specimen inclination angle when the angle was more than 5°. Moreover, the ratio of the peak strength to the LTS was not affected by the specimen inclination, which is considered an inherent characteristic. We anticipate that the results obtained will assist in pillar design and long-term stability analysis.

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