考虑扰动影响的土体小应变硬化模型参数试验研究及其在基坑工程中的应用

Experimental study on HS-small model parameters of soil considering disturbance and its application in foundation pit engineering

天然结构性土体容易受到各类施工扰动,导致土体物理力学性质改变,进而影响工程稳定、变形以及邻近环境。针对宁波两种典型土体,分别对原状土和轻、重扰动土以及重塑土开展了三轴试验及一维压缩试验,分析了扰动度对小应变硬化模型(HS-small model,简称HSS模型)主要参数的影响规律,并将其应用于宁波某基坑工程,利用Plaxis3D分析了考虑周边土体扰动影响的坑后土体水平位移变化。研究结果表明,扰动会使土体的强度及刚度参数降低。对于淤泥质黏土,轻扰动试样的参考切线模量E_(oed)^(ref)、参考割线模量E50ref及参考加卸载模量Eurref值分别降低14%、10%、2%,重扰动试样三参数分别降低43%、14%、15%,粉质黏土三参数也呈现相似降低趋势。在考虑土体扰动影响的情况下,基坑周边两个测斜孔的最大水平位移值分别增大13%、15%,更加接近实测值。研究结果可为小应变硬化模型的参数取值以及考虑扰动影响的基坑工程分析计算提供指导。

Natural structural soil is susceptible to various types of construction disturbance.The disturbance results in the change of the physical and mechanical properties of soil,which in turn the engineering stability,deformation and adjacent environment.In this paper,triaxial tests and one-dimensional compression tests were carried out on undisturbed soil,lightly disturbed soil,heavily disturbed soil and remolded soil of two typical soils in Ningbo.The influence of disturbance degree on the main parameters of HSS model was analyzed,the influence laws were applied to a foundation pit project in Ningbo City.The horizontal displacement of the foundation pit was analyzed with Plaxis3D considering the influence of surrounding soil disturbance.The results show that disturbance has adverse effects on the strength and stiffness of soil.For mucky clay,the reference tangent modulusE_(oed)^(ref),reference secant modulusE50refand reference loading/unloading modulusEurrefof lightly disturbed samples are respectively reduced by 14%,10%and 2%,the above parameters of the heavily disturbed sample are reduced by 43%,14%and 15%respectively,and similar decreasing laws can also observed in silty clay.Considering the influence of soil disturbance,the maximum calculated horizontal displacement of the two inclined holes around the foundation pit increases by 13%and 15%respectively,which is closer to the measured values.The research results can provide a guidance for HSS model parameter selection and foundation pit engineering analysis and calculation considering disturbance effect.