Response of multilayer geosynthetic-reinforced bed resting on soft soil with stone columns

In the present study, a mechanical model has been developed to study the behavior of multilayer geosynthetic-reinforced granular fill over stone column-reinforced soft soil. The granular fill and geosynthetic reinforcement layers have been idealized by Pasternak shear layer and rough elastic membranes, respectively. The Kelvin–Voight model has been used to represent the time-dependent behavior of saturated soft soil. The stone columns are idealized by stiffer springs and assumed to be linearly elastic. The nonlinear behavior of the soft soil and granular fill is considered. The effect of consolidation of soft soil due to inclusion of the stone columns on settlement response has also been included in the model. Plane strain conditions are considered for the loading and reinforced foundation soil system. An iterative finite difference scheme is applied for obtaining the solution and results are presented in nondimensional form. It has been observed that if the soft soil is improved with stone columns, the multilayer reinforcement system is less effective as compared to single layer reinforcement to reduce the total settlement as there is considerable reduction in the total settlement due to stone column itself. Multilayer reinforcement system is effective for reducing the total settlement when stone columns are not used. However, multilayer reinforcement system is effective to transfer the stress from soil to stone column. The differential settlement is also slightly reduced due to application of multiple geosynthetic layers as compared to the single layer reinforcement system.     

双液注浆法在巨厚填土层加固施工中的应用

承德某桩基工程,在无法干成孔作业的巨厚层矿渣地层中,首先采用双液注浆法加固,然后再进行旋挖钻机干成孔。实践表明,该方法在处理松散的巨厚填土层加固是可行的,能达到良好的处理效果;控制配比和溶液的使用量是关键;加固后的土体自稳能力和承载力均有所提高。     

粗颗粒土层组合中的超深基坑复合土钉墙支护的合理性分析及探讨

对粗颗粒土层组合的超深基坑,采用了复合土钉墙支护结构形式进行设计,并对该深基坑的开挖及支护过程进行了系统监测。主要监测项目有土钉钢筋受力、锚索轴力及坡顶水平位移,通过对监测结果进行系统分析,并与传统的受力模型进行对比,分析本基坑在此方面的普遍性与特殊性,找出成功点与失败点,为今后类似工程提供借鉴。     

Analysis of A Braced Excavation In Soft Soils Considering The Consolidation Effect

The studies of excavations in soft clayey soils are normally based on undrained total stress analyses. A better approach consists of taking into account the effects of consolidation during the excavation-bracing process and after the completion of the construction by means of coupled finite element analyses in effective stresses. In this paper, the geotechnical behaviour of a braced excavation in the soft soils of San Francisco (USA) is analysed, both during and after the construction period. Numerical analyses are performed with a finite element program, which incorporates the Biot consolidation theory (coupled formulation of the water flow and equilibrium equations) and soil constitutive relations simulated by the p-q-θ critical state model. Numerical results are compared with field results.     

沧州北部地区软土物理力学指标相关性分析研究

沧州北部地区存在一层典型的滨海相沉积类型软土,其在青县西北部、大城县东南部分布稳定而广泛,工程地质条件较差。为了更好地研究该地区软土的物理力学指标,分析各指标间的相关性,结合区域内近50个钻孔及土工试验资料,系统分析了沧州北部地区软土的工程地质性质,阐述了区内软土的分布及特性等;并利用数理统计学方法,较为客观地对区内软土物理力学指标间的相关性进行了分析与探讨,给出了各指标间的最优拟合曲线。研究结果:沧州北部地区软土多属于高液限淤泥质粘土,具有含水率高、孔隙比大、压缩性高、抗剪强度低等特点;区内软土含水率与孔隙比及含水率、孔隙比与压缩系数间存在正相关的特性,大致符合多项式回归曲线形式。     

一维土层非线性地震反应分析的解析递推格式法

引入“结构动力学数值分析解析递推格式法”求解软土地基地震反应分析问题。就一维地基非线性地震反应分析问题,将解析递推格式方法与等效线性化方法在各种场地土的计算结果进行了比较,结果表明：(1) 对软土层地震反应分析时,两种方法计算结果差别较大; （2）入射波幅值较强时,两种方法计算结果差别较大;（3）对于中等硬度土层、入射波幅值较弱时,计算结果相似, 并验证了该方法的实用有效性。