结构性黄土地基中挤密桩扩孔效应研究与评价

Effect of compaction pile's cavity expansion on structural loess subgrade

挤密桩扩孔效应会对黄土的结构性弱化产生重要影响,并可能影响和改变桩-土之间的相互作用。针对结构性黄土地区的挤密桩,本文首先基于小孔扩张理论分析了单桩扩孔条件下桩周土体的广义剪应变、广义剪应力的关系。然后,本文通过三轴试验得到了不同应力水平条件下的广义剪应力和应变关系。最后,将黄土结构性参数引入到单桩扩孔的分析中,研究了扩孔效应导致的黄土结构性参数的衰减变化规律。研究表明:在单桩扩孔效应作用下,距离桩轴越近,黄土的结构性参数衰减越剧烈,桩周黄土的结构性参数衰减到1.0;距离桩轴越远,黄土的结构性参数衰减越小,且在无限远处黄土的结构性参数接近原状黄土的初始结构性参数。

The cavity expansion of compaction pile should be of an important impact on the s tructural weakening of loess, and may affect the interaction between pile and soil. Firstly, aimed at the compaction pile in the area of structural loess, the relationship between generalized shear strain and shear stress of soil around the pile under the condition of single pile cavity expansion is analyzed based on the theory of cavity expansion, with the stress and strain of structural loess under different stress levels obtained by the triaxial tests. The structural parameter of loess is intro-duced into the analyses of a single pile？s cavity expansion, with the attenuation change of structural parameter of loess caused by cavity expansion effect studied. The research results show that the attenuation of structural parameter of the loess is more obvious in the cavity expansion when loess is closer to pile shaft and the structural parameter is equal to 1. 0 when loess is adjacent to pile shaft ; when the attenuation of structural parameter of the loess is smaller and when it was further from pile shaft, the structural parameter at infinity is close to the initial structural parameters of intact loess.