高地应力下硬岩的本构模型研究

传统的本构模型在模拟高地应力下硬岩破坏的范围和深度方面并不理想。针对高应力下的拉西瓦花岗岩，通过真三轴压缩试验模拟了开挖时应力路径的演化。在摩尔-库仑强度准则、格里菲斯强度准则、德鲁克-普拉格准则、双剪统一强度理论和霍克-布朗强度准则的基础上，考虑十二面单元体主剪面上主剪应力、正应力和静水压力的共同作用，提出了一个有关高应力下硬岩的三剪强度准则。根据试验结果，利用遗传算法全局寻优的功能，搜索出了三剪强度准则的参数。预测样本和与摩尔-库仑强度准则、德鲁克-普拉格准则、双剪统一强度理论的比较表明，该三剪强度准则与试验结果吻合，适用于高地应力下的硬岩。根据试验得到的应力-应变关系曲线，建立了基于三剪强度准则和应变软化的弹-脆-塑性本构模型，并用FLAC3D提供的基于C++的用户自定义模型工具UDM，创建了用户自定义模型的动态链接库，嵌入了FLAC3D软件。采用遗传算法-FLAC方法，搜索得到了基于岩石试样和岩体的本构模型参数。计算结果与实测情况吻合，表明建立的本构模型适用于高地应力下的硬岩，为高地应力下硬岩地下工程的安全性和稳定性分析奠定了基础。

Study on constitutive model for hard rock under high geostresses

Conventional constitutive model is not good at simulating the failure range and depth for hard rock under high geostress.The complicated evolvement of stress load,which produced by excavating underground engineering under high geostress in Laxiwa,is simulated through true triaxial experiment.Based on analysis of Mohr-Coulomb strength criterion,Griffith strength criterion,Drucker-Prager strength criterion,twin shear theory and Hoek-Brown strength criterion,a new three shear strength criterion is proposed for hard rock.The effect of three principal shear stress and three normal stress acting on the dodecahedral element and average principal stress are taken into account in the establishment of strength criterion.Based on the experimental result about Laxiwa new granite,the parameters of three shear strength criterion are searched using the global optimum features of genetic algorithm.The results of predicting samples and comparing with Mohr-Coulomb strength criterion,Drucker-Prager strength criterion,twin shear theory show that three shear strength criterion agrees with the experiment and is the same with hard rock.Based on the stress-strain relation curve obtained by experiment,three shear strength criterion and strain softening law,the elastic-brittle-plastic constitutive model is established,which is implanted in FLAC3D through UDM.The parameters of elastic-brittle-plastic constitutive model are searched using genetic algorithm-FLAC method.Calculating results agree with the fact and show that the elastic-brittle-plastic constitutive model can be used in the safety and stability analysis of hard rock underground engineering under high geostresses.