Experimental Study on Stiffness Softening of Soil‐Rock Mixture Backfill under Metro Train Cyclic Load

Abstract

Due to the thick soil layer, short backfill time, and low degree of consolidation of the soil-rock mixture backfill in Chongqing city, metro train tunnels passing through this type of strata are prone to large settlements during operation, which greatly affects the stability of the tunnel and the safety of metro train operations. In response to this problem, the dynamic triaxial test of the soil-rock mixture backfill under cyclic loading was carried out to study the dynamic characteristics of the soil-rock mixture backfill under cyclic loading. The effect of initial consolidation degree, effective consolidation confining pressure, and rock content on the stiffness softening of soil-rock mixture backfill was analyzed. The results show that the initial consolidation degree, effective consolidation confining pressure, and rock content are all important factors affecting the stiffness of soil-rock mixture backfill under cyclic loading. As the number of cycles increases, the lower the initial consolidation degree and effective consolidation confining pressure, the faster the attenuation of the softening index, and the larger the amplitude. As the rock content increases, the softening index increases and the stiffness of the backfill changes from softening to hardening. Based on the test data, the softening-hardening model of the soil-rock mixture is established, which is in good agreement with the field test results. This study can provide a reference for predicting and controlling the postconstruction settlement of the metro tunnel in the soil-rock mixture backfill.

Experimental Investigation for Shear Wave Velocity and Dynamic Characteristics of Unsaturated Sand–Clay Liners

“…The results revealed that the hysteresis loop became larger as the suction level increased. This behavior was attributed to the hardening/softening response of the tested materials under repeated loading or varying suction conditions [45][46][47]. Higher strains have developed on the extension side, indicating greater deformation compared with those on the compression side.…”

Cyclic and Post-Cyclic Behaviors of Stabilized Sand-Containing Soft Soil in Coastal Areas

“…By referencing previous research results, it is assumed that the stiffness evolution index model can be expressed by three-order In order to describe the stiffness evolution index accurately, the Yasuhara model needs to be improved. Based on the Yasuhara model, many researchers [48,49] have proposed various improved models and found that the improved model (which can be expressed by high-order polynomials) can describe the non-linear relationship between the stiffness evolution index and lgN. By referencing previous research results, it is assumed that the stiffness evolution index model can be expressed by three-order polynomials.…”

Settlement Characteristics of Urban Underground Comprehensive Pipe Gallery under Different Backfill Conditions

“…Arsyad et al [2] studied the infuence of geotextile in backfll soil on the stability of embankment by feld monitoring and numerical calculation. Zhong et al [3] carried out the dynamic triaxial test of backflling with earth-rock mixture under the cyclic load and studied the dynamic characteristics of earth-rock mixture under the cyclic load. Ardah et al [4] evaluated the performance according to the strain, lateral deformation, uplift, and lateral pressure at the intersection of approach bridge slabs.…”