Semi-analytical solution for drained expansion analysis of a hollow cylinder of critical state soils

The expansion of a thick-walled hollow cylinder in soil is of non-self-similar nature that the stress/deformation paths are not the same for different soil material points.As a result,this problem cannot be solved by the common self-similar-based similarity techniques.This paper proposes a novel,exact solution for rigorous drained expansion analysis of a hollow cylinder of critical state soils.Considering stress-dependent elastic moduli of soils,new analytical stress and displacement solutions for the nonself-similar problem are developed taking the small strain assumption in the elastic zone.In the plastic zone,the cavity expansion response is formulated into a set of first-order partial differential equations(PDEs)with the combination use of Eulerian and Lagrangian descriptions,and a novel solution algorithm is developed to efficiently solve this complex boundary value problem.The solution is presented in a general form and thus can be useful for a wide range of soils.With the new solution,the non-self-similar nature induced by the finite outer boundary is clearly demonstrated and highlighted,which is found to be greatly different to the behaviour of cavity expansion in infinite soil mass.The present solution may serve as a benchmark for verifying the performance of advanced numerical techniques with critical state soil models and be used to capture the finite boundary effect for pressuremeter tests in small-sized calibration chambers.

基于双曲线临界状态的改进剑桥模型及数值实现

针对传统剑桥模型不能很好反映重塑黏土力学及临界强度特性的缺陷,在试验研究的基础上,对其临界状态进行改进。不排水三轴试验发现,重塑黏土的临界状态线表现为双曲线的形态,因此,将双曲线临界状态与剑桥模型相结合,建立改进的剑桥模型,并在FLAC3D程序中进行二次开发。同时针对FLAC3D中对塑性因子算法较为繁琐的问题,引入牛顿–辛普森迭代法进行改进。最后,运用改进的剑桥模型对不同压实度土样进行三轴数值模拟试验。结果表明:改进的剑桥模型能较好地反映重塑土体的力学特性,改进后的算法计算精度较高,执行效率较好。

膨胀土临界状态强度特性及其模型拟合

针对蒙自地区膨胀土,进行了饱和重塑条件下的固结排水(CD)与固结不排水(CU)试验,系统研究了饱和土在不同固结围压σ3、初始干密度ρd、初始含水量ω0、剪切速率υ、排水条件下的应力应变特性。通过对临界状态试验结果的归一化处理,揭示了不同试验方法对同一土样抗剪强度量测差异的内在统一性,得到了重塑饱和膨胀土在固结排水与不排水条件下p'-q-ν空间内的破坏线。利用双曲线模型较好地拟合了弱硬化型应力应变曲线,用指数曲线模型拟合了弱软化型应力应变曲线,为模拟边坡在降雨条件下的抗剪强度变化及构筑物土体处于正常水位时的强度状态等工况提供了技术参数与理论支持。

含水量对非饱和重塑膨胀土抗剪强度和压实度的影响

含水量是影响膨胀土抗剪强度和压实度的重要因素。通过多组室内快剪试验,采用多元线性回归方法,分别对非饱和重塑膨胀土抗剪强度指标和压实度与其含水量的关系进行了研究。试验研究结果表明,非饱和重塑膨胀土的压实度随着含水量增加而逐渐降低,且当法向应力较低时,抗剪强度随着压实度的增加而缓慢增大,但当法向应力较大时,抗剪强度随着压实度增加而增大较快。非饱和重塑膨胀土抗剪强度指标受含水量的影响较为明显,当法向应力较低时,抗剪强度随着含水量的增加而增大,但当法向应力较大时,抗剪强度随着的含水量增加而增大的不太明显,出现含水量增加而抗剪强度基本不变的情况。