ABSTRACT

This study presents the results of a systematic investigation on enhancing the shear strength and bearing capacity of subgrade fill by blending the completely weathered phyllite (CWP) with locally won red clay at varying blending ratios. Many CWP soil samples were prepared at varying bended ratios for carrying out a compaction test, micro-penetration test and direct shear test. The effects of the red clay blending ratio, moisture content (w) and compaction coefficient (K) on the shear strength of CWP clay were also been investigated. Micro-penetration test results show that there are three types of micro-penetration strength growth patterns. It is found that, at a given set level of moisture content and compact coefficient, an increase of red clay in the blending ratio result in a higher shear strength and the ultimate bearing capacity. Cubic polynomial function models were developed to predict the ultimate bearing capacity and cohesion of the CWP blended soils with the red clay at varying blending ratios. The observed three stages of strength growth can be predicted, and the mechanism of this phenomenon has been analyzed using the results from soil micro-structure analysis. It has been found that the addition of red clay increases clay content within the soil mass and enhances iron cementation among the soil particles. At a given blending ratio, the ultimate bearing capacity increases linearly with the compaction coefficient and decreases linearly with moisture content. The ultimate bearing capacity calculation model of blended subgrade fill was developed based on the Bzz-100 load standard, and the optimum schemes of blending soils were proposed to meet the requirement of urban road bearing capacity. Field trials and applications show that the optimum scheme proposed in this paper can not only improve the bearing capacity of CWP, but also reduce the cracking potential of red clay.

摘要

本研究展示了通过将完全风化的千枚岩 (CWP) 与当地获得的红粘土以不同的混合比例混合来提高路基填料的抗剪强度和承载力的系统研究结果。许多 CWP 土壤样品以不同的弯曲比制备，用于进行压实试验、微渗透试验和直剪试验。红粘土掺混比、含水量（w）和压实系数（K ）的影响) 对 CWP 粘土剪切强度的影响也进行了研究。微渗透测试结果表明，微渗透强度增长模式存在三种类型。研究发现，在给定的含水量和压实系数的设定水平下，混合比中红粘土的增加导致更高的剪切强度和极限承载力。开发了三次多项式函数模型来预测 CWP 混合土壤与红粘土在不同混合比例下的极限承载力和凝聚力。可以预测观察到的强度增长的三个阶段，并利用土壤微观结构分析的结果分析了这种现象的机制。已经发现，添加红粘土增加了土壤团块中的粘土含量并增强了土壤颗粒之间的铁胶结。在给定的混合比下，极限承载力随压实系数线性增加，随含水量线性降低。基于Bzz-100荷载标准，建立了混合路基填料极限承载力计算模型，提出了满足城市道路承载力要求的混合土优化方案。现场试验和应用表明，本文提出的优化方案不仅可以提高CWP的承载力，还可以降低红土的开裂潜力。极限承载力随压实系数线性增加，随含水量线性降低。基于Bzz-100荷载标准，建立了混合路基填料极限承载力计算模型，提出了满足城市道路承载力要求的混合土优化方案。现场试验和应用表明，本文提出的优化方案不仅可以提高CWP的承载力，还可以降低红土的开裂潜力。极限承载力随压实系数线性增加，随含水量线性降低。基于Bzz-100荷载标准，建立了混合路基填料极限承载力计算模型，提出了满足城市道路承载力要求的混合土优化方案。现场试验和应用表明，本文提出的优化方案不仅可以提高CWP的承载力，还可以降低红土的开裂潜力。