圆弧型墙背下的主动土压力研究

基于平面滑裂面假设,采用水平层分析法计算墙背为圆弧型情况下的挡土墙主动土压力及其分布情况,分析了挡土墙与墙后填土的各参数对主动土压力大小及分布的影响。计算结果表明,随着挡土墙倾斜角的减小,土压力分布曲线由凸曲线变成凹曲线。最后通过算例将圆弧型墙背下主动土压力及分布的计算结果与平面墙背下的进行分析对比,结果表明当墙背倾斜...     

土体主动滑动场及主动土压力的计算

将边坡临界滑动场方法进行推广与改进,提出挡土结构中的土体主动滑动场的数值模拟方法,并得到相应的主动土压力分布。数值计算结果表明,本文方法精度高,与现有的解析解一致;且可方便地考虑挡墙面的摩擦作用、土体的不均匀分布以及复杂的外载组合,值得推广应用于工程设计。     

库伦主动土压力作用点高度确定方法的改进

库伦主动土压力作用点位置高度确定为墙高的1/3 处,分析表明这一结论及其推求过程不尽合理.为解决此问题,针对墙后滑动土楔体的受力情况,根据三力汇交原理,考虑墙背土压力的分布与土楔体对其下稳定土体的压力分布的相关关系,采取几何推导方法,得出了主动土压力作用点位置高度表达式;进一步分析了作用点高度对影响因素的敏感性,结果表明其敏感性从大至小的排序为：墙背倾角、内摩擦角、外摩擦角、填土坡角.     

Upper bound limit analysis of active earth pressure with different fracture surface and nonlinear yield criterion

Conventional calculations of static and seismic active earth pressures of soils on a retaining wall are formulated assuming the soils obeying a linear Mohr–Coulomb yield criterion. However, experimental evidences show that the strength envelopes of almost all geomaterials are nonlinear in nature over a wide range of normal stresses. In this paper, the strength envelope of the backfill behind a retaining wall is considered to follow a nonlinear yield criterion. A simple method is proposed for calculating the static and seismic active earth pressures acting against a retaining wall using a nonlinear yield criterion. This method is based on the upper bound theorem of limit analysis. Both translational and rotational fracture surfaces are employed in the formulation for calculating active earth pressures. Quasi-static representation of earthquake effects using a seismic coefficient concept is adopted for seismic active earth pressure calculations. Instead of using directly the actual nonlinear yield criterion, a linear Mohr–Coulomb yield criterion, which is tangential to the nonlinear yield criterion, is used to formulate the active earth pressure problem as a classical nonlinear programming problem. A nonlinear sequential quadratic programming algorithm is used to search for the maximum solution. In order to assess the validity of the proposed method, values of active earth pressures for different values of seismic coefficients and nonlinear parameters in the yield criterion are calculated and compared with solutions obtained using an extended Rankine’s active earth pressure theory. For the case of static active earth pressure, the upper bound solutions using the present method with a translational fracture surface are equal to the extended Rankine’s theoretical solutions and are slightly smaller than those obtained using the present method with a rotational fracture surface. For the case of seismic active earth pressure, numerical results obtained using the present method with a rotational fracture surface is very close to the extended Rankine’s theoretical solutions. A study is conducted to investigate the effects of the parameters in the nonlinear yield criterion on the active earth pressures.     

临近既有地下室平动模式挡土墙主动土压力研究

对于挡土墙距既有地下室很近,挡土墙与既有地下室外墙之间的填土宽度有限的情形,采用经典的库伦、郎肯土压力理论计算挡墙主动土压力是不合适的,设计偏于保守.本文基于库伦滑动土楔假定,考虑地面超载以及墙土之间的摩擦作用,推导出了临近既有地下室的挡土墙主动极限状态下滑裂面倾角和主动土压力系数的解析公式.分析结果表明滑裂面倾角、主动土压力系数与填土宽高比、土内摩擦角、墙土摩擦角以及地面超载等因素有关.并与经典土压力理论及前人研究成果进行对比,所得结论对实际工程有参考价值.     

储氢高压容器钢壁中氢的浓度分布规律研究

储氢高压容器中的氢通过渗透会进入容器钢壁并在钢壁中扩散,最终透过容器外表面进入容器存放环境中.在容器钢壁中的氢会引起材料力学性能变化,从而引起容器承载能力变化.要认识这些变化,首先就要了解氢在钢壁中的渗透、扩散规律和浓度的瞬态分布规律.针对球形高压容器外表面满足一般传质边界条件的情况,建立求解容器壁中氢浓度的解析理论模型,导出了容器壁中瞬态氢浓度和渗透到环境中的氢累积量的理论公式.通过解析计算,给出了器壁中氢浓度和氢在环境中的累积渗透量随时间的变化曲线,分析了相应的变化规律.这些公式和规律性认识为后续的容器壁材料力学性能分析和容器承载能力评估提供了前提.