皖中膨胀土的承载比(CBR)强度特性研究

针对皖中地区高速公路建设中遇到的膨胀土问题,选取合六叶高速公路典型土样开展了系统的承载比（CBR）特性试验研究,并在此基础上探讨了膨胀土作为路基填料的适用性。研究表明:（1）起始含水量对膨胀土CBR值影响显著,CBR最大值对应的含水量高于最佳含水量,且击实功越大,二者差值也越大;（2）CBR膨胀量随起始含水量增大而减小,起始含水量越低,CBR膨胀量就越大,路基的水稳性就越差;（3）当击实功较大时,膨胀土的最佳含水量较小,适合填筑的可变含水量范围较宽,建议现场施工控制采用重型击实标准;（4）在重型击实条件下,将弱膨胀土起始含水量控制在比最优含水量大2%⁴%范围内,能同时满足压实度和CBR值要求以用于填筑下路堤,中膨胀土作为路基填料时必须经过改性处理。研究结果对于在膨胀土地区进行公路建设具有参考意义。     

Several contributions to soil compactibility induced by cyclic loading test

To investigate the soil compactibility during the cyclic loading, three different kinds of paddy field soils were prepared so as to clarify interrelationships among stress amplitude ratio, bulk density, soil water content and pore water pressure. The presetting values of specimen include the soil water content(percent dry basis) and bulk density of 25% d.b. and 1.1 Mg/m³ respectively. The relation between the number of cyclic loading and axial strain exhibited an asymptotically increasing trend, converging toward a specific value for each experimental condition. Possible effect caused by elastic–plastic characteristics could be recognized, when axial strain for 0.5 Hz excitation becomes greater than the one of 1.0 Hz under same stress amplitude ratio. When the stress amplitude ratio took 0.1, the absolute value of axial strain of 0.5 Hz was greater than the one of 1.0 Hz, whereas its decreasing trend was recognized in the sequence of silt, clay and silty sand. The qualitative relations between pore water pressure and number of cyclic loading were also examined to scrutinize the effect of effective water pressure to the soil compactibility.     

Analysis model to simulate the cracked pipe buried in soil

This paper describes the use of the finite element method to simulate crack propagation in a pipeline in the presence of soil backfill. Since typical values for soil modulus are known, a spring element can be used to simulate the effects of backfilled soil on crack propagation. This consists of the relationship between the soil property and the stiffness of the spring element, and the effect of backfill depth on the crack propagation in the pipes. By equating crack driving force,G, in the presence of soil, to the dynamic fracture toughness of the pipeline material, a theoretical predictive capability is obtained for the first time for the gas transmission and distribution pipelines. Numerical calculations have also been carried out for the cracked pipe with backfill and without backfill.     

香港大屿山残坡积土的残余强度试验研究

粘性土的残余强度是边坡稳定性评价、桩基与土的相互作用机理研究及填土边坡设计中的重要参数。本文在综述大量文献的基础上，结合香港大屿山火山岩风化残坡积土的残余强度试验研究，分析了残余强度的测试方法和影响残余强度的因素。研究结果表明，残余强度与有效法向应力间具有明显的非线性关系；与单剪测试结果相比，多级剪测试结果明显偏高。     

Generalized Forchheimer Equation for Two-Phase Flow Based on Hybrid Mixture Theory

In this paper, we derive a Forchheimer-type equation for two-phase flow through an isotropic porous medium using hybrid mixture theory. Hybrid mixture theory consists of classical mixture theory applied to a multiphase system with volume averaged equations. It applies to media in which the characteristic length of each phase is small relative to the extent of the mixture. The derivation of a Forchheimer equation for single phase flow has been obtained elsewhere. These results are extended to include multiphase swelling materials which have nonnegligible interfacial thermodynamic properties.     

循环载荷下砂质土的本构模型

提出了一个描述砂质土循环载荷条件下主要特性的本构模型，并且采用不同围压下多种加载途径的土力学实验确定了模型中的待定材料常数，由本构模型的增量工数值积分计算所得到的理论曲线与不同应力路径下实验曲线十分接近，经实验验证这种本构模型能广泛地应用土工问题的弹－塑性有限元分析中。     

THE REFORM OF TEACHING CONTENT FOR THE COURSE OF FOUNDATION SETTLEMENT

对地基土沉降计算的课程内容提出改革思路,从讨论土体固结度的角度展开,进而引出最终沉降量的计算,最终引出不同的试验方法和压缩性指标。新的教学思路将土力学固结沉降的基本理论与实践应用进行合理的区隔,既能保证基本理论的纯粹性、合理性,也不回避实践中土体复杂 性质对理论进一步发展和丰富所提出的挑战。     

非饱和多孔介质中热-渗流-力学耦合的混合元法

提出了一个非饱和多孔介质中热-渗流-力学耦合分析的混合有限元 方法. 固相位移、应变和净应力；孔隙水和气的压力、压力空间梯度和Darcy速度；多相混 合介质的温度、温度空间梯度和热流量在单元内均为独立变量分别插值. 基于胡海 昌-Washizu 三变量广义变分原理给出的多孔介质中热-渗流-力学耦合问题控制方程的单元弱形式，导 出了单元公式. 采用共旋公式进行几何非线性分析. 数值结果证明了所提出的单元模拟以 应变局部化为特征的渐进破坏的能力     

准饱和土体中圆形衬砌对弹性波的散射

采用Vardoulakis和Beskos提出的准饱和土体的波动控制方程,根据Helmholtz矢量分解定理,得到了准饱和土中P1波(快压缩波)、P2波(慢压缩波)和S波(剪切波)的波数的势函数表达式.将准饱和土体和圆形衬砌视为各向同性的均质体,运用波函数展开法将入射波、散射波和折射波的势函数展开成Fourier-Bessel函数的级数形式,根据准饱和土体与衬砌边界处应力和位移连续及衬砌内完全自由的边界条件,得到了平面P1波入射下,准饱和土体内深埋圆形衬砌的散射系数和折射系数的理论解,通过数值计算分析了饱和度对准饱和土体和衬砌的DSCF(动应力集中因子)及准饱和土体的PPCF(孔压集中因子)的影响规律,结果表明:准饱和土体的DSCF随着饱和度的增大而减小,衬砌的DSCF基本不受饱和度的影响,而准饱和土体的PPCF则随着饱和度的增大而增大.     

横观各向同性饱和地基上中厚圆板的非轴对称振动

研究横观各向同性饱和土地基上中厚弹性圆板的非轴对称振动问题。基于横观各向同性饱和介质Biot波动方程的一般解,按混合边值问题建立了饱和地基与弹性中厚圆板非轴对称动力相互作用的对偶积分方程,并将对偶积分方程转化为易于计算的第二类Fredholm积分方程;采用数值方法求解该积分方程。数值算例结果表明,当h/a>0.05时,饱和半空间体上中厚度圆板在不同频率下的振动特性与相应频率下的刚性板的振动特性基本相同,当h/a<0.05时,板中心的位移将随h/a的减小而增大。