基坑底部土体满堂加固模型试验与数值模拟研究

为探究基坑底部土体满堂加固对基坑变形和内力的影响,采用室内模型试验方法,研究了基坑底部土体满堂加固对基坑周围地表沉降、冠梁侧向位移、桩身弯矩以及桩后土压力变化的影响。运用ABAQUS有限元软件对模型试验进行数值模拟,将试验数据与数值计算结果进行对比,并分析了加固土体的水泥掺入比和加固深度对基坑变形的影响。结果表明:满堂加固对降低基坑底部隆起效果最为明显,对降低支护结构侧向位移较为明显,对减小地表沉降不明显;通过极差分析法得出,增加加固土体的弹性模量较增加加固深度对抑制支护桩侧向位移及坑底隆起更为有效;当水泥掺入比超过一定范围后,加固效果没有显著提升,建议在含水率为20%左右的软弱土层地区,水泥掺入比一般为5%～20%;土体的加固深度超过一定范围后,控制基坑变形的效果有所提高,但不明显,建议土体加固深度取0.4～0.45倍基坑深度。

Model test and numerical simulation study of reinforcement of entire basal soil in the bottom of foundation pit

In order to study the effect of reinforcement of entire basal soil on the deformation and stress of foundation pit, the effect of the reinforcement of entire basal soil at the bottom of foundation pit on the ground surface settlement, the lateral displacement of top beam, the bending moment of pile and the earth pressure behind pile was studied by laboratory model test.The ABAQUS finite element software was used to simulate the model test and the experimental data were compared with the numerical results.The effects of cement-mixed ratio and reinforcement depth on the deformation of foundation pit were analyzed.The results show that the effect of reinforcement of entire basal soil is the most obvious to reduce the bottom heave, the lateral displacement of retaining structure is more obvious, and the ground surface settlement is not obvious.The range analysis method shows that increasing the elastic modulus of reinforced soil is more effective than increasing the reinforcement depth to restrain the lateral displacement of supporting pile and the soil heave of foundation pit.When the cement-mixed ratio exceeds a certain range, the reinforcement effect is not significantly improved.It is suggested that the cement-mixed ratio is generally 5%~20% in the soft soil area with 20% water content.When the soil reinforcement depth exceeds a certain range, the effect of controlling the deformation of foundation pit is improved but not obvious.It is suggested that the soil reinforcement depth should be 0.4~0.45 times the depth of foundation pit.