Time-Dependent Response of a Recycled C&D Material-Geotextile Interface under Direct Shear Mode

Geosynthetic-reinforced soil structures have been used extensively in recent decades due to their significant advantages over more conventional earth retaining structures, including the cost-effectiveness, reduced construction time, and possibility of using locally-available lower quality soils and/or waste materials, such as recycled construction and demolition (C&D) wastes. The time-dependent shear behaviour at the interfaces between the geosynthetic and the backfill is an important factor affecting the overall long-term performance of such structures, and thereby should be properly understood. In this study, an innovative multistage direct shear test procedure is introduced to characterise the time-dependent response of the interface between a high-strength geotextile and a recycled C&D material. After a prescribed shear displacement is reached, the shear box is kept stationary for a specific period of time, after which the test proceeds again, at a constant displacement rate, until the peak and large-displacement shear strengths are mobilised. The shear stress-shear displacement curves from the proposed multistage tests exhibited a progressive decrease in shear stress with time (stress relaxation) during the period in which the shear box was restrained from any movement, which was more pronounced under lower normal stress values. Regardless of the prior interface shear displacement and duration of the stress relaxation stage, the peak and residual shear strength parameters of the C&D material-geotextile interface remained similar to those obtained from the conventional (benchmark) tests carried out under constant displacement rate.

Download Full-text

Experience of determining the parameters of the elastoviscoplastic soil model

E3S Web of Conferences ◽

10.1051/e3sconf/202126302051 ◽

2021 ◽

Vol 263 ◽

pp. 02051

Author(s):

Armen Ter-Martirosyan ◽

Artur Manukyan ◽

Lyubov Ermoshina

Keyword(s):

Stress Relaxation ◽

Simple Shear ◽

Experimental Studies ◽

Shear Displacement ◽

Displacement Rate ◽

Shear Stresses ◽

Shear Creep ◽

Rheological Equation ◽

Loading Mode ◽

Creep And Stress Relaxation

Rheological studies of soils were carried out by S.S. Vyalov, M.N. Gol’dshtejn, N.N. Maslov, G.I. Ter-Stepanyan, S.R. Meschyan, A.L. Gol’din, Z.G. Ter-Martirosyan and many others. On the basis of existing rheological soil models, a new universal rheological equation was proposed in Ter-Martirosyan’s dissertation, which allows describing kinematic shear, creep and stress relaxation at the same parameters. Experimental studies of the soil were carried out in a simple shear device in a kinematic loading mode at a shear displacement rate u̇= 0.05 mm/min and at two values of compaction loads (σ1 < σ2). Based on the results of the experimental studies, the parameters of the elastoviscoplastic model were determined and graphs of the dependence of shear stresses on time were plotted, which clearly show the high convergence of the experimental and theoretical curves.

Download Full-text

Experimental Study on Shear Mechanical Characteristics of Cohesionless Granular Material

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.90-93.230 ◽

2011 ◽

Vol 90-93 ◽

pp. 230-233

Author(s):

Hong Chun Xia ◽

Guo Qing Zhou ◽

Ze Chao Du

Keyword(s):

Shear Stress ◽

Normal Stress ◽

Mechanical Characteristics ◽

Stress Condition ◽

Fine Sand ◽

Shear Displacement ◽

Direct Shear ◽

Steel Particle ◽

High Normal Stress ◽

Fine Gravel

The direct shear mechanical characteristics of gravel, sand and steel particle were studied systematically using DRS-1 high normal stress direct and residual shear apparatus. The results show that the shear mechanical characteristics of gravel, sand and steel particle is different under different normal stress condition. For steel particle, the curves of shear stress-shear displacement present strain softening regardless of the magnitude of normal stress, and the shear displacement corresponding to the peak shear stress increases with the normal stress. Under low normal stress condition, the volume of fine gravel and steel particle expand, but the fine sand contracts at the beginning of direct shear and then contracts. Under high normal stress condition, the volume of steel particle contracts at the beginning of the direct shear and then contracts, but the fine sand and fine gravel contract throughout the direct shear. The particle breakage has significant effect on the shear strength of fine sand and fine gravel. Under the same high normal stress condition, the volume of fine gravel is greater than that of fine sand, which indicates that the fine gravel is easier to be crushed than the fine sand.

Download Full-text

Effect of Particle-Size Gradation on Coarse Sand-Geotextile Interface Response in Cyclic and Postcyclic Direct Shear Test

Advances in Civil Engineering ◽

10.1155/2020/1323296 ◽

2020 ◽

Vol 2020 ◽

pp. 1-11

Author(s):

Jun Wang ◽

Meng-Jie Ying ◽

Fei-Yu Liu ◽

Hong-Tao Fu ◽

Jun-Feng Ni ◽

...

Keyword(s):

Particle Size ◽

Shear Stress ◽

Shear Strength ◽

Shear Behaviour ◽

Direct Shear ◽

Interface Shear ◽

Cycle Number ◽

Cyclic Shear ◽

Stress Degradation ◽

Particle Size Gradation

In order to investigate the influence of sand particle-size gradation on cyclic and postcyclic shear strength behaviour on sand-geotextile interfaces, a series of monotonic direct shear (MDS), cyclic direct shear (CDS), and postcyclic direct shear (PCDS) tests were performed using a large-scale direct shear apparatus. The influence of cyclic shear history on the direct shear behaviour of the interface was studied. The results indicated that cyclic shear stress degradation occurred at the sand-geotextile interface. Shear volumetric contraction induced by the cyclic direct shear increased with the increase in cycle number. The lowest final contraction value was observed in discontinuously graded sand. In the MDS tests, there were great differences in interface shear strength due to the different particle-size gradations, whereas the differences between shear volumes were negligible. In the PCDS tests, the shear stress-displacement curves exhibited postpeak stress hardening behaviour for different particle-size gradations, and differences in shear volumes were detected. The well-graded sand-geotextile interface had a higher value of shear stiffness and a higher damping ratio relative to the other interfaces. Postcyclic shear stress degradation was observed for the discontinuously graded sand-geotextile interface.

Download Full-text

Experimental Study on Shear Mechanical Characteristics of Soil-Structure Interface under Different Normal Stress

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.243-249.2332 ◽

2011 ◽

Vol 243-249 ◽

pp. 2332-2337 ◽

Cited By ~ 1

Author(s):

Hong Chun Xia ◽

Guo Qing Zhou ◽

Ze Chao Du

Keyword(s):

Shear Stress ◽

Shear Strength ◽

Normal Stress ◽

Soil Structure ◽

Mechanical Characteristics ◽

Shear Displacement ◽

Interface Roughness ◽

Displacement Curve ◽

Direct Shear ◽

High Normal Stress

The direct shear mechanical characteristics of soil-structure interface under different experimental condition were studied systematically using the DRS-1 high normal stress direct and residual shear apparatus. The results show that the normal stress is an important factor which determines the mechanical characteristics of soil-structure interface. The curve of shear stress-shear displacement presents strain softening when the normal stress<3MPa, linear hardening when =3~5MPa and strain hardening when12MPa, separately. At the same time, the volume of the soil expands when <3MPa and contracts when >3MPa. But the volume of the soil expands and contracts simultaneously during the process of direct shear when =3MPa.The roughness of the interface influences not only the shape of the shear stress-shear displacement curve but also the shear strength of the interface. Under same normal stress condition，the shear strength of interface increases with the roughness but the influence degree of interface roughness reduces gradually with the increase of normal stress. The grain breakage degree is different under different normal stress. It increases evidently with the increase of normal stress.

Download Full-text

Effect of Cobble Content on the Shear Behaviour of Sand-Cobble Mixtures

Advances in Civil Engineering ◽

10.1155/2021/5554617 ◽

2021 ◽

Vol 2021 ◽

pp. 1-9

Author(s):

Chuang Wang ◽

Jinyu Dong ◽

Zhiquan Huang ◽

Jianjun Zhou ◽

Jihong Yang

Keyword(s):

Shear Stress ◽

Shear Strength ◽

Internal Friction ◽

Large Scale ◽

Shear Displacement ◽

Shear Behaviour ◽

Normal Displacement ◽

Displacement Curve ◽

Control Effect ◽

Angle Of Internal Friction

The sand and cobble stratum is a kind of mechanically unstable stratum. Shield machine often encounter problems such as difficulty in excavation, cutterhead wear, and poor slag discharge of the spiral dumper while constructing in this kind of stratum. Considering the complexly and variety of the material composition and structure of this stratum, the sand and cobble stratum in China, Chengdu Subway Line 7, Chadianzi-Yipintianxia Station, was selected to conduct indoor large-scale direct shear tests to systematically study the effects of cobble content (CC) on the shear strength and shear properties of sand and cobble soil. The test results showed that the shear strength and angle of internal friction of sand and cobble soil nonlinearly increased with CC, and the shear strength and angle of internal friction slightly increased when CC was less than 40%. The shear strength and angle of internal friction of sand and cobble soil significantly increased after CC reaching 40%. The shear stress-shear displacement curve has three stages, including the elastic deformation stage, yield stage, and hardening stage. The CC had a control effect on the strength and deformation characteristics of sand and cobble soil. The shear stress-displacement curve of sand and cobble soils with CCs of 20% and 80% can be fitted as an exponential model, while the shear stress shear displacement curves of sand and cobble soils with CCs of 40% and 60% are hyperbolic. For sand and cobble soil with same CC, the larger the vertical stress is, the larger the normal displacement is.

Download Full-text

Numerical Simulation of the Shear Behaviour of Cement Grout

Advances in Materials Science and Engineering ◽

10.1155/2021/9951193 ◽

2021 ◽

Vol 2021 ◽

pp. 1-14

Author(s):

Jianhang Chen ◽

Fan Zhang ◽

Hongbao Zhao ◽

Junwen Zhang

Keyword(s):

Shear Stress ◽

Shear Strength ◽

Stress Distribution ◽

Normal Stress ◽

Shear Failure ◽

Cement Grout ◽

Shear Stress Distribution ◽

Shear Behaviour ◽

Direct Shear ◽

Failure Plane

Cement grout is widely used in civil engineering and mining engineering. The shear behaviour of the cement grout plays an important role in determining the stability of the systems. To better understand the shear behaviour of the cement grout, numerical direct shear tests were conducted. Cylindrical cement grout samples with two different strengths were created and simulated. The numerical results were compared and validated with experimental results. It was found that, in the direct shear process, although the applied normal stress was constant, the normal stress on the contacted shear failure plane was variable. Before the shear strength point, the normal stress increased slightly. Then, it decreased gradually. Moreover, there was a nonuniform distribution of the normal stress on the contacted shear failure plane. This nonuniform distribution was more apparent when the shear displacement reached the shear strength point. Additionally, there was a shear stress distribution on the contacted shear failure plane. However, at the beginning of the direct shear test, the relative difference of the shear stresses was quite small. In this stage, the shear stress distribution can be assumed uniform on the contacted shear failure plane. However, once the shear displacement increased to around the shear strength point, the relative difference of the shear stresses was obvious. In this stage, there was an apparent nonuniform shear stress distribution on the contacted shear failure plane.

Download Full-text