Dynamic properties of frozen silty soils with different coarse-grained contents subjected to cyclic triaxial loading

Cyclic triaxial tests were conducted to explore the influences of dynamic axial loading on the dynamic features and fatigue of frozen silty sand, using an MTS-810 apparatus from Material Testing Systems (MTS). The temperature was −15 °C, and the cyclic axial loads with different amplitudes at 1.0 Hz were applied under confining pressures of 0.6, 1.4, and 6.0 MPa. The cyclic triaxial test results demonstrate that the residual axial strain of the frozen silty sand samples increases gradually during the initial cycles and then increases with increasing number of cycles at a constant speed until failure. The residual volumetric strain contracts during the initial loading cycles and then dilates until failure. Both the residual strain method and the residual volumetric strain method proposed here can be used to describe the degradation process in frozen silty sand samples subjected to cyclic loading. The dynamic axial stiffness of a frozen sample decreases rapidly in the initial cycles and then approaches a st...

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Fatigue and damage properties of frozen silty sand samples subjected to cyclic triaxial loading.

Dynamic shear modulus and damping ratio of thawed saturated clay under long-term cyclic loading

This paper presents a series of experimental studies for evaluating the effects of closed-system freeze–thaw (FT) cycles on the hydro-mechanical behaviours of two subgrade soils (a low plastic lean clay, SS and a lean clay with higher plasticity, HC) Investigated hydro-mechanical behaviours include the soil–water characteristic curve (SWCC) obtained from the filter paper method, resilient modulus (MR) determined from cyclic triaxial tests, unconfined compression strength (qu) and reloading tangent modulus (E1%) and stress (Su1%) at 1% strain measured from unconfined compression tests, with emphasis on the SWCC and MR Specimens compacted at the maximum dry density (ρdmax) and optimum moisture content (wopt) were firstly subjected to multiple FT cycles (number of FT cycles NFT = 0, 1, 3, 6 and 10) and then dried or wetted to different moisture contents before determining hydro-mechanical behaviours Experimental results revealed that (i) FT cycles reduce the magnitude of volumetric strain upon moisture variation for the HC but have little impact on the SS; (ii) FT cycles reduce the water retention capacity of both soils For each soil, the void ratio (e)-moisture content (w)-suction (s) relationships after different FT cycles are possibly distributed on a unique surface; (iii) Reductions in the mechanical properties (ie MR, qu, E1% and Su1%) are more significant at NFT = 1 and vary with the post-FT cycle moisture content Reductions in the MR are most serious at a threshold w level on the wet side of wopt; (iv) FT cycles reduce the sensitivity of the mechanical properties to moisture content for the HC but exert minor influence on that of the SS; (v) Relationships of the MR to the qu, E1% and Su1% are not influenced by the NFT and moisture content for both soils They are non-linear and can be well described by quadratic polynomials Soils with higher plasticity such as the HC is, in general, more vulnerable to effects of closed-system FT cycles at wopt than low plastic soils such as the SS

Characterizing hydro-mechanical behaviours of compacted subgrade soils considering effects of freeze-thaw cycles

Accumulated permanent strain and critical dynamic stress of frozen silty clay under cyclic loading

Dynamic shear modulus and damping ratio of frozen compacted sand subjected to freeze–thaw cycle under multi-stage cyclic loading

To investigate the rainfall-induce the seepage field of a high slope and effect factors, the theory of saturated-unsaturated infiltration was employed, and the numerical model of slope infiltration subjected to the rainfall are developed and programmed. The numerical results shown that, (1) With the increasing of the rainfall duration, rainfall water infiltration formed a transient saturated zone at slope surface, when the moist frontal surface reached to the groundwater level, the rainfall water would supply the groundwater. (2) Each effect factors on the seepage field play a strongest roles on the slope toe, weaker role on the middle part slope and weakest role on the top slope. (3) The longer rainfall duration, the deeper of infiltration depth. It also be deeper with the larger rainfall intensity, coefficient of permeability, the initial moisture content of the surface and the surface waterlogging depth. (4) The effect on seepage field would be faintly and could be ignored when the rainfall intensity was greater than 65.9mm/h and the surface waterlogging depth is greater than 0.3m. All above could provide technical ideas for analyzing slope seepage field under rainfall and accumulate fundamental data for early warning and preventing mud-rock flow and landslide.

Rainfall-Induce Seepage Field of a High Slope and its Effect Factors

To evaluate the influence factors of accumulative plastic strain of frozen silt clay, the dynamic cyclic triaxial tests with stress-controlled are conducted to investigate the behaviors of frozen soil induced by cyclic loading. The relationships between accumulative plastic strain and vibration numbers for frozen silt at different dynamic stress amplitudes under different temperature, vibration frequency and initial water content are obtained. The test results show that the accumulative plastic strains increase with rising tempeature, increasing the vibration numbers and dynamic stress amplitude. The accumulative plastic strain rate increases with increasing the vibration frequency. With increasing the initial water content, the accumulative plastic strain of frozen silt clay increases.

Accumulative Plastic Strain of Frozen Silt Clay under Cyclic Loading

Based on dynamic tri-axial test at low temperature, deformation behavior of ice is studied under stepped axial cyclic loading. Time history curves of residual strain of ice are investigated under different negative temperatures and frequencies. Conclusions can be drawn as follows: dynamic residual strain rate increases with the increasing of stress ratio and frequency, while decreases with the decreasing of temperature. According to test data, power function is brought forward to fit the relation between stress ratio, negative temperature, frequency and dynamic residual strain rate. Then, the effect of fitting parameters by temperature and frequency was investigated.

Qiong Lin Li

Papers

Dynamic shear modulus and damping ratio of frozen compacted sand subjected to freeze–thaw cycle under multi-stage cyclic loading

Rainfall-Induce Seepage Field of a High Slope and its Effect Factors

Accumulative Plastic Strain of Frozen Silt Clay under Cyclic Loading

Experimental Study of the Accumulation Dynamic Residual Strain of Ice under Rail Traffic Loading