冻土非线性断裂韧度的修正因子测试方法

Correction-factor test method for nonlinear fracture toughness of frozen soil

考虑冻土的非线性断裂力学特征,基于现有J积分测试方法,提出了一种新的冻土非线性断裂韧度的测试方法——修正因子法。在传统方法中J积分可以写成如下表达:J=Je+Jp,其中Je为J积分的线弹性分量,Jp为J积分的塑性分量。Je的计算相对简单;但计算Jp相对困难,原因是其中的参数Up难于确定。为了使计算简单,可将塑性分量改写为Jp=qJe,J积分则改写为J=(1+q)Je,q称为塑性修正因子。该方法通过循环加、卸载试验得到非线性载荷-位移曲线(P-Δ曲线),并由载荷与位移的增量确定修正因子,在获得线弹性分量Je基础上,获得冻土非线性断裂韧度。采用该方法进行了冻土非线性断裂韧度测试,并将测试结果与相关文献结果进行比较,证明了该方法的合理性和有效性。

A new method for determining nonlinear fracture toughness of frozen soil is presented based on the method of J integral as well considering nonlinear behavior characteristics of frozen soil. It is well known that J integral can be expressed as J =Jr ＋Jp, in which Je represents elastic component and Jp represents plastic component. The calculation of Jc is relatively simple, but the calculation of Jp is quite difficult. Because in the process of calculating Jp, one parameter Up, which represents the plastic work of sample, is very difficult to determine. To simplify the calculation, rewriting Jp as an expression of Je, Jp =qJe, then J integral expression becomes as J=（1＋q）Je. That means when Je and factor q are determined for one kind of sample, J integral can be gotten easily. This method is named as correction-factor method. The correction factor q is obtained by increments of load and displacement according to curve of load vs. displacement （P-A curve）, in which includes two cycles of loading-unloading. Using the suggested method, nonlinear fracture toughness of frozen soil in-situ is determined; and the results in comparison with the data of related literature show its reasonableness and availability.