低幅值小应变振动下土体弹性刚度的非线性特征与表述方法  

Nonlinear characteristics and determinate method of elastic stiffness for soils due to low-amplitude small-strain vibrations

作　　者：贾鹏飞[1,2] 孔令伟[1] 王勇[1] 杨爱武[1] 

机构地区：[1]中国科学院武汉岩土力学研究所岩土力学与工程国家重点实验室,武汉430071 [2]西北大学地质学系大陆动力学国家重点实验室,西安710069

出　　处：《岩土力学》2013年第11期3145-3150,3158,共7页Rock and Soil Mechanics

基　　金：国家自然科学基金项目(No.51179186;No.51109208;No.41302219);湖北省自然科学基金(No.2011CDB407)

摘　　要：随着高速铁路建设的兴起,轨道以及沿线附近建筑物承受低幅值小应变振动荷载的作用。对于小应变振动下土体的有限元计算,如何确定连接应力和应变之间纽带的刚度张量E,对于建立合理的预测模型来分析高速铁路轨道以及沿线建筑物的沉降变形至关重要。低幅值小应变振动下剪切模量G和阻尼比D随剪应变幅值的变化是反映土体刚度及阻尼特征最重要的两个参数。通过共振柱试验发现,振动荷载作用下土体的剪切模量G必须通过振动应变幅值和固结围压共同来确定,即使在小应变(剪应变幅值10-6<<10-4)振动下,也会表现出明显的非线性特征。Davidenkov模型是在双曲线模型基础上为了更好地拟合剪切模量曲线G/G max-和阻尼比曲线D-的试验结果而提出的,不足之处在于Davidenkov模型的拟合参数过多,关键参数γ0的取值没有明确的物理方法。对于低幅值小应变振动情形,为了简便起见,忽略大应变振动情形下由于循环效应和速率效应引起的强度变化,在Mohr-Coulomb破坏准则的基础上,通过引入由给定应力状态下的静抗剪强度τf与最大剪切模量G max的比值来确定的参考剪应变ref来代替Davidenkov模型中的拟合参数0,尝试提出简化的两参数Davidenkov模型,并通过共(自)振柱试验验证了该方法对计算低幅值小应变振动情形下剪切模量和阻尼比的可行性。Railway track and nearby structures in the vicinity of high-speed railway are exposed to low-amplitude small-strain vibrations as high-speed railway traffic construction activities arise. In the finite element （FE） method, how to determine the stiffness tensor E is important to build a rational predicting model to analyze the settlement of track and nearby structures in the vicinity of high-speed railway. Shear modulus G and damping ratio D which will vary with shear strain amplitude are two important stiffness and damping parameters. It is found through resonant column test study that the shear modulus G of soil due to vibrations must be determined by the strain amplitude and the confining pressure, even though under small-strain （shear strain amplitude 10-6〈y〈10-4） vibrations, will still show a remarkable nonlinear characteristic. The Davidenkov model based on the classical Hardin-Dmevich model is proposed to fit the experimental tests of the curves of shear modulus G/Gma~ and damping ratio D vs. ？＇powerfully. However, the shortcoming of the Davidenkov model is that the fitting parameters are too much, and the key parameter y0 can＇t be determined through a definite physical method. This study proposes an simplified two-parameter Davidenkov model through using a reference shear strain yref which will be determined through the ratio of the shear strength rf of soil in static triaxial tests versus the maximum shear modulus Gmax at a given stress state instead of the fitting parameter y0 on the basis of Mohr-Coulomb failure criterion, and verifies the feasibility of the proposed method through tests finally.

关 键 词：两参数Davidenkov模型 共(自)振柱试验 剪切模量 阻尼比 

分 类 号：TU435[建筑科学—岩土工程]