节理峰值后归一化位移软化模型  

Post-peak normalized displacement softening model for discontinuous rock joint

作　　者：唐志成[1,2] 夏才初[1,2] 黄继辉[1,2] 宋英龙[1,2] 

机构地区：[1]同济大学岩土及地下工程教育部重点实验室岩石力学与工程研究中心,上海200092 [2]同济大学地下建筑与工程系,上海200092

出　　处：《岩土力学》2011年第7期2013-2016,2024,共5页Rock and Soil Mechanics

基　　金：国家自然科学基金资助项目(No.40972178)

摘　　要：切向荷载作用下贯通节理岩体峰值强度后的剪切应力、位移变形规律一般呈双曲线形式发展,即峰值后强度衰减速率逐步变小而趋于0,到达残余强度。直剪试验表明,非贯通节理岩体峰值后剪切应力、位移呈"S"型趋势发展,即强度衰减速率先是逐步增大,到达一定程度后逐步减少,最后趋于稳定达到残余强度值。贯通节理岩体峰值强度后的本构关系并不适合于描述该特征。提出一个新的非线性归一化位移软化本构模型,通过归一化剪切应力R与归一化剪切位移D的指数函数关系体现峰值后剪切应力、位移的发展趋势,即模型采用无量纲表达式。归一化剪切应力R是峰值后强度降τp-τ与峰值强度、残余强度差值τp-τr的比值;归一化位移D是峰值后剪切位移、峰值位移差值δ-δp与残余位移、峰值位移差值δr-δp的比值。对含不同起伏角的非贯通节理岩体在常法向荷载条件下的直剪试验数据进行拟合分析,模型预测结果与实测值具有相当高的吻合度,验证了模型的正确性。Usually, a negative slope of the stress-displacement curve characterizes the post-peak behavior, where the shear strength of a joint falls to a constant value that corresponds to the residual friction resistance of the joint; it means that the decay rate decreases until to ultimate strength. But for discontinuous joint, the curve follows a ＂S＂ shape; it means that strength decay rate increases at the initial stage, then decreases to zero; it means residual strength arrived. So, the constitutive model used by joints is not suitable for discontinuous joint. A new nonlinear normalized model is developed that takes a dimensionless form described by an exponential function. This function reflects the relationship between post-peak stress and displacement through normalized shear strength R and normalized displacement D. The post-peak shear strength reduction τp-τ normalized by shear reduction from the peak to residual τp-τr is called normalized shear strength R： the post-peak shear displacement δ-δp normalized by the difference from residual shear displacement to peak shear displacement δr -δp is called normalized shear displacement. At last, the model is used to fit experimental data for different types of discontinuous joints; and the high fitting accuracy shows its validity.

关 键 词：岩石力学 非贯通节理 峰值后归一化位移软化模型 归一化剪切应力 归一化位移 

分 类 号：TU458[建筑科学—岩土工程]