Test of Dynamic Strength Characteristics of Lishi Loess

2013 ◽  
Vol 303-306 ◽  
pp. 2902-2907 ◽  
Author(s):  
Nian Qin Wang ◽  
Xiao Ling Liu ◽  
Bo Han ◽  
Bo Tao Liu
Keyword(s):  
Stress Relaxation ◽  
Dynamic Stress ◽  
Peak Stress ◽  
Confining Pressure ◽  
Dynamic Strain ◽  
Soil Consolidation ◽  
Strength Parameters ◽  
Loading Test ◽  
Loess Slope ◽  
Effective Strength

Lishi loess is an important component of loess slope. To explore the structure and strength change characteristics of Lishi loess caused by shock (vibration) action, and to reveal the mechanism of loess slope catastrophe, the dynamic triaxial test was performed by using equivalent sine wave under strain controlling. The results show that:① There is an obvious stress relaxation phenomenon during the same cyclic loading test, the degree decreases with the increasing of dynamic strain and confining pressure. And the influence of dynamic strain variation on stress relaxation degree is less under high confining pressure than under low confining pressure;② Under a confining pressure of 40kPa, within 1% strain ranges, the needed dynamic stress to reach the specified strain is just 0.01kN, and the peak stress decreases with the augmentation of dynamic strain, when peak stress increases to 0.204kN, the sample is destructed; Under a confining pressure of 90kPa, soil radial particles are closely spaced, within 2% strain ranges also only a dynamic stress of 0.01kN is needed to reach the specified strain, and with the increase of dynamic strain, the samples are destructed when dynamic strain increases to 0.267kN. The dynamic failure stress of Lishi loess increases gradually with the increase of confining pressure, and the linear regression equation is бd=0.0011б3+0.1590, the correlation coefficient is 0.9944. ③According to Mohr-Coulomb failure criterion, the strength parameters of Lishi loess in somewhere of the north of shaanxi are C=30.33kPa，φ=14°. Under the dynamic shearing action, the dynamic effective strength parameters are obviously less than static effective strength parameters, this indicates that the soil consolidation effect reduced and the particles displaced and occluded each other.

Study on Dynamic Strength Characteristics of Malan Loess

2012 ◽  
Vol 170-173 ◽  
pp. 964-968 ◽  
Author(s):  
Nian Qin Wang ◽  
Xiao Ling Liu ◽  
Dong Hai Luo ◽  
Yong Yao
Keyword(s):  
Stress Relaxation ◽  
Dynamic Stress ◽  
Dynamic Strength ◽  
Friction Angle ◽  
Confining Pressure ◽  
Sine Wave ◽  
Dynamic Strain ◽  
Loading Test ◽  
Loess Slope ◽  
Malan Loess

Vibration effect is a major inducing factor of loess slope hazards and the basis of revealing loess slope mechanism, which often changes loess structure and decreases loess strength. Based on the GDS Lab System, the dynamic triaxial test was performed by using equivalent sine wave under strain controlling. The results are described as follows: ① there is an obvious phenomenon of stress relaxation during the cyclic loading test on Malan loess, and the degree of stress relaxation decreases with the increase of confining pressure and dynamic strain. Under the low confining pressure, Malan loess reaches certain strain only by small dynamic stress within 2% strain ranges. Under high confining pressure, Malan loess will also reach certain strain value by small dynamic stress within 1% strain ranges. At the same time, with the increase of confining pressure, the peak value of dynamic stress increases gradually. ②The dynamic failure stress of Malan loess increases linearly with the increase of confining pressure. The correlation coefficient is 0.99 and the linear regression equation is бd = 0.001б3 + 0.019. ③On the basis of Molar Coulomb failure criterion, the index of dynamic strength was c =3.36kPa, φ=16°. In comparison with the static strength, the internal friction angle decreases significantly while the cohesion slightly.

Test of Dynamic Strength Characteristics of Paleosol

2013 ◽  
Vol 690-693 ◽  
pp. 747-751
Author(s):  
Nian Qin Wang ◽  
Xiao Ling Liu ◽  
Yao Qiong Xue ◽  
Xu Peng Jiao
Keyword(s):  
Stress Relaxation ◽  
Dynamic Strength ◽  
Friction Angle ◽  
Confining Pressure ◽  
Sine Wave ◽  
Failure Stress ◽  
Strength Characteristics ◽  
Dynamic Failure ◽  
Loading Test ◽  
Deformation And Failure

Paleosol is an important factor affecting the stability of loess slope, and its mechanical properties, deformation and failure mechanism are still under in-depth exploration and research. Here based on the GDS Lab System, using equivalent sine wave progressively loading mode of strain controlling, in order to reveal the dynamic strength characteristics of Paleosol under the vibration effect. The result show that:① there is an obvious phenomenon of stress relaxation during the cyclic loading test on Paleosol; Paleosol is high-consolidated clay, when the given confining pressure less than the natural confining pressure, the degree of stress relaxation increased at first and then decreased,to the contrary first decreased and then increased.② under the 50kPa、80kPa、100kPa confining pressure, the dynamic failure stress of Paleosol is 0.176kN、0.2302kN、0.2555kN,the dynamic failure stress increases linearly with the increase of confining pressure. The correlation coefficient is 0.9009 and the linear regression equation is бd=0.001б3+0.0958.③ On the basis of Molar Coulomb failure criterion, We obtained the index of dynamic strength of Paleosol, which was C=25.63kPa and φ=14º, by Molar Circle. In comparison with the static strength, the internal friction angle and cohesion decreases significantly, show that the Paleosol have obvious characteristic of brittle.

scholarly journals The Scale Effect of Coarse-Grained Materials by Triaxial Test Simulation

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Xiaotao Ai ◽  
Guangjin Wang ◽  
Xiangyun Kong ◽  
Bo Cui ◽  
Bin Hu ◽  
...  
Keyword(s):  
Scale Effect ◽  
Triaxial Test ◽  
Failure Process ◽  
Deformation Modulus ◽  
Peak Stress ◽  
Friction Angle ◽  
Confining Pressure ◽  
Coarse Grained ◽  
Strength Parameters ◽  
And Migration

The scale effect is an unavoidable problem in the laboratory test of coarse-grained materials. By combining the self-developed cellular automaton program with laboratory experiments, a method of simulating the triaxial test of coarse-grained materials was proposed in this paper, and a triaxial test numerical specimen that can characterize the discontinuous, nonuniform, and heterogeneous characteristics of bulk geotechnical materials was established. The parallel grading method was adopted to create six grading curves for numerical simulation based on one in situ grading curve. The failure process and the scale effect on the strength and deformation of coarse-grained materials were analyzed and discussed. The results showed that under the same confining pressure, the peak stress and initial deformation modulus E i increased with the increase of the maximum particle size d max , while the degree of shear shrinkage and Poisson’s ration υ decreased. As the confining pressure increased, the scale effect of coarse-grained materials would be magnified. If particle breakage and migration were assumed to be neglected, the internal friction angle φ and d max would be roughly proportional, the cohesive force c fluctuated with the increase of d max , and the empirical relations between d max and c and φ were established, respectively, which provides a reference for estimating the actual shear strength parameters of coarse-grained materials on-site. The research results can provide a way of thinking for the study of the scale effect of coarse-grained materials and also have certain reference significance for inferring the strength parameters of the original-graded coarse-grained materials.

Influence of Replacement Rate on Triaxial Mechanical Performance of Recycled Concrete

2014 ◽  
Vol 584-586 ◽  
pp. 1531-1535 ◽  
Author(s):  
Yi Sheng Su ◽  
Er Cong Meng ◽  
Zong Ping Chen ◽  
Jun Yu Wu
Keyword(s):  
Mechanical Performance ◽  
Great Influence ◽  
Peak Stress ◽  
Confining Pressure ◽  
Recycled Concrete ◽  
Recycled Aggregate ◽  
Peak Strain ◽  
Replacement Rate ◽  
Loading Test ◽  
The Impact

Replacement rate is an important factor that affects the mechanical properties of recycled concrete. In order to study the influence of replacement rate on triaxial mechanical performance of recycled concrete, 20 recycled concrete cylinder specimens for conventional triaxial loading test with recycled aggregate replacement rate as changing parameters were designed. The results show that replacement rate has a great influence on peak stress of recycled concrete specimens under uniaxial stress, but the effects of replacement rate gradually decreased with the increase of lateral confining pressure. The influence of replacement rate on peak strain is larger than peak stress, the impact of replacement rate on peak strain gradually decreased with the increase of lateral confining pressure. The elastic modulus of recycled concrete specimens changes with different replacement rate, and the fluctuations is in the range of 20%. The results will provide reference for further theoretical study of recycled concrete.

Experimental Study on Dynamic Characteristics of Sandy Pebble Soil

2011 ◽  
Vol 250-253 ◽  
pp. 70-74
Author(s):  
Xiao Qiang Chen ◽  
Bin Jia ◽  
Yong Yao ◽  
Dai Guo Chen
Keyword(s):  
Vibration Frequency ◽  
Dynamic Stress ◽  
Dynamic Strength ◽  
Large Degree ◽  
Confining Pressure ◽  
Dynamic Strain ◽  
Soil Evolution ◽  
Evolution Law ◽  
Dynamic Triaxial Test ◽  
Consolidation Pressure

Through the laboratory dynamic triaxial test of sandy pebble soil, evolution law of influence of confining pressure and vibration frequency on dynamic strength is analyzed. Analysis indicates that dynamic stress of sandy pebble soil improves in a large degree with accretion of vibration frequency, dynamic strength of which increases significantly with confining pressure rising, and relation of dynamic stress and dynamic strain can also be symbolized with the R.L.Kondner hyperbola curve. Meanwhile, dynamic elastic modulus of sandy pebble soil decreases with growth of dynamic strain, while increases with growth of consolidation pressure.

scholarly journals New Method for Determination of Residual Strength Parameters and Critical Damage Value

2019 ◽  
Author(s):  
Qiao Jiang ◽  
Jianlin Li ◽  
Yanhai Wang ◽  
Zuosen Luo ◽  
Tao Li ◽  
...  
Keyword(s):  
Residual Strength ◽  
Confining Pressure ◽  
Stress Path ◽  
Load Test ◽  
Repeated Loading ◽  
Strength Parameters ◽  
Loading Test ◽  
Time Saving ◽  
Critical Damage

Residual strength and critical damage parameters are worthy to evaluate the stability of engineered rock masses. In this paper, new thinking, repeated load test on a single specimen was proposed to measure the residual strength of the rock. And author proposed to modify the critical damage value based on residual constitutive energy. The test results showed that: (1) the residual strength of rock is mainly controlled by the confining pressure, without a clear relationship with the confining pressure and stress path of the initial loading failure. (2) The residual strength parameters of the rock specimens under repeated loading test are consistent with the conventional triaxial test. Most importantly, the proposed method is relatively less dispersion, cheap, reliable, and time-saving. (3) The corrected critical damage value was reasonable. Relevant test methods can provide a useful reference for the determination of residual strength parameters and critical damage value.

scholarly journals Study on Dynamic Characteristics of Deep Siltstone under High Static Stress and Frequent Dynamic Disturbance

2019 ◽  
Vol 2019 ◽  
pp. 1-12 ◽  
Author(s):  
Lu-ping Cheng ◽  
Chun Wang ◽  
Li-zhong Tang ◽  
Cheng Wang ◽  
Zhu-qiang Xiong ◽  
...  
Keyword(s):  
Strain Rate ◽  
Dynamic Stress ◽  
Dynamic Deformation ◽  
Axial Stress ◽  
Tracking System ◽  
Deformation Modulus ◽  
Peak Stress ◽  
Static Stress ◽  
Dynamic Strain ◽  
Dynamic Disturbance

http://mts.hindawi.com/update/) in our Manuscript Tracking System and after you have logged in click on the ORCID link at the top of the page. This link will take you to the ORCID website where you will be able to create an account for yourself. Once you have done so, your new ORCID will be saved in our Manuscript Tracking System automatically."?>The mechanical characteristics of siltstone under high static load and frequent dynamic disturbance were investigated by the improved split Hopkinson pressure bar (SHPB), which is used to simulate the failure phenomenon of the extracted ore drift owing to high stress concentration and blasting disturbance in Dongguashan copper mine at the depth of more than 900 m. The maximum dynamic strain, dynamic stress, and dynamic deformation modulus of rock of each impact were researched to provide theoretical basis for mining production. The results show that the dynamic stress-strain curves of siltstone before the peak stress present two characteristics of linear and nonlinear variation and different degrees of resilience after the peak stress under high static stress and frequent dynamic disturbance. The strain rate rises in a linear trend with the increasing times of dynamic disturbance, but the value of the strain rate is approximately constant in the process of one impact. With the increase of the strain rate, the maximum dynamic strain rises at the same static stress, while the peak dynamic stress and dynamic deformation modulus decrease linearly. Because the inner stored elastic energy of rock determines the value of resilient strain after unloading, the elastic energy may increase with the increase of static axial stress in a certain range and then the resilient strain increases. Accumulative times of dynamic disturbance and static axial stress show the relationship that the former is obviously reduced with the increase of the later.

scholarly journals An Extension Strain Type Mohr–Coulomb Criterion

2021 ◽  
Author(s):  
Manfred Staat
Keyword(s):  
Failure Modes ◽  
Peak Stress ◽  
Fracture Initiation ◽  
Failure Surface ◽  
Confining Pressure ◽  
Biaxial Compression ◽  
Simple Extension ◽  
Strain Criterion ◽  
Shear Component ◽  
Extension Strain

AbstractExtension fractures are typical for the deformation under low or no confining pressure. They can be explained by a phenomenological extension strain failure criterion. In the past, a simple empirical criterion for fracture initiation in brittle rock has been developed. In this article, it is shown that the simple extension strain criterion makes unrealistic strength predictions in biaxial compression and tension. To overcome this major limitation, a new extension strain criterion is proposed by adding a weighted principal shear component to the simple criterion. The shear weight is chosen, such that the enriched extension strain criterion represents the same failure surface as the Mohr–Coulomb (MC) criterion. Thus, the MC criterion has been derived as an extension strain criterion predicting extension failure modes, which are unexpected in the classical understanding of the failure of cohesive-frictional materials. In progressive damage of rock, the most likely fracture direction is orthogonal to the maximum extension strain leading to dilatancy. The enriched extension strain criterion is proposed as a threshold surface for crack initiation CI and crack damage CD and as a failure surface at peak stress CP. Different from compressive loading, tensile loading requires only a limited number of critical cracks to cause failure. Therefore, for tensile stresses, the failure criteria must be modified somehow, possibly by a cut-off corresponding to the CI stress. Examples show that the enriched extension strain criterion predicts much lower volumes of damaged rock mass compared to the simple extension strain criterion.

Influence of cyclic load input on the mechanical properties of a sensitive soil from Orleans, Ontario

1980 ◽  
Vol 17 (4) ◽  
pp. 498-508 ◽  
Author(s):  
R. N. Yong ◽  
D. Taplin ◽  
G. Wiseman
Keyword(s):  
Mechanical Properties ◽  
Laboratory Test ◽  
Dynamic Loading ◽  
Cyclic Strain ◽  
Peak Stress ◽  
Confining Pressure ◽  
Constant Load ◽  
Deviatoric Stress ◽  
General Terms ◽  
Stress Levels

The importance of disturbance and remoulding to the alteration of mechanical properties of sensitive soils has been well documented in the geotechnical literature both in terms of laboratory and field behaviours. Man-made transient dynamic input such as dynamite blasting, heavy vehicles, and train movement have been suspected of being capable of causing a reduction in the in situ strength parameters of sensitive clays. A laboratory test program was undertaken to determine whether dynamic loading at peak stress levels below normal failure strength caused similar changes in the mechanical properties, and specifically to quantify the phenomena.In order to simulate highly overconsolidated conditions most of the tests were carried out under conditions of no confining pressure, although supplemental data were obtained from consolidated undrained tests. Some of the variables examined in this program were confining pressure, mean deviatoric stress, cyclic deviatoric stress, cyclic strain, number of applications, frequency, and reference strength. In order to compare the effect of dynamic input with the long-term creep phenomena, a simultaneous constant load program was undertaken.In general terms, the study indicates that under the prestated laboratory test conditions no major reduction in peak strength was found under dynamic loading, and that failure would occur at comparative stress levels under dead-load conditions, but required a greater time. In addition, examination of the sample after failure revealed that any remoulding of the sample appeared to be restricted to the area adjacent to the shear zone.

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