基于应力及尺度耦合因素的典型形貌特征结构面抗剪强度应力效应机理研究

It is usually considered that shear strength parameters　of rock joint basically don't change with the normal stress. but the　preliminary results of direct shear test obtained by applicant showed shear　strength parameters of simulation rock joint reduced with increasing of the normal stress and its stress effect of large-scale and rough-undulating surface rock joint became more obvious. Because shear strength parameters obtained by direct shear test was constant, engineering evaluation by use of shear strength parameters inevitably led to large errors. The methods of multi-scale model samples of rock joint invented by the research group overcame the difficulty of situ sampling and achieved the repeatability and systematization of multi-scale direct shear test. The load and multi-scale transforming system invented by the research group solved the difficulties of testing investment and achieved the series scales direct shear testing on the same machine. In this project, firstly, based on four typical rough-undulating surface, the stress effect mechanism will be studied to establish the stress effect model by the direct shear test of multi-scale and whole stress model structure surface. Secondly, according to comparion with numerical simulation and test of natural rock structure surface the shear strength stress effect model of rock joint can be improved. Thirdly, stress effect model will be tested by the application of typical engineering. Finally, based on low-stress shear strength of rock joint, the high-stress shear strength evaluation method of rock joint was established. This study will have great theoretical significance and bright prospect of engineering application.

普遍认为岩石结构面抗剪强度参数基本上不随法向应力变化，申请人对岩石模型结构面直剪试验的初步结果却表明抗剪强度参数随法向应力的增大而降低，且该应力效应特征对于大尺度粗糙起伏结构面更加明显，因此，由现行规程直剪试验方法获得的不随应力变化的抗剪强度参数应用于工程评价势必会造成较大误差。课题组研制的多尺度结构面模型试样制作克服了现场取样困难，可实现不同尺寸结构面直剪试验的重复性和系统化；荷载和尺度转换系统解决了试验技术和投资的困难，可实现在同一台试验机上进行全应力多尺度模型结构面直剪试验。本项目通过四类具有典型粗糙起伏程度的全应力系列尺度模型结构面直剪试验研究抗剪强度应力效应机理，建立抗剪强度应力效应模型；并通过三轴数值试验、原岩结构面试验对比及典型工程应用，检验结构面抗剪强度应力效应准则的普适性，建立基于低应力结构面抗剪强度评价高应力工程岩体结构面抗剪强度的方法，具有重大理论意义和工程应用价值。

普遍认为岩石结构面抗剪强度参数基本上不随法向应力变化，申请人对岩石模型结构面直剪试验的初步结果却表明抗剪强度参数随法向应力的增大而降低，由现行规程直剪试验方法获得的不随应力变化的抗剪强度参数应用于工程评价势必会造成较大误差。本项目通过3D激光扫描技术和3D打印技术获得原岩结构面天然表面形态，利用研制的吻合岩体结构面一体化制作模具可实现不同尺寸结构面直剪试验的重复性和系统化。通过荷载和尺度转换系统解决了试验技术和投资的困难，自主研发了可用于测试速率效应、应力效应以及尺寸效应的多功能岩土体接触破损测试系统，可实现在同一台试验机上进行全应力多尺度模型结构面直剪试验。通过平直、锯齿、台阶、天然形貌等四类具有典型粗糙起伏程度的全应力岩体结构面直剪试验研究抗剪强度应力效应机理和建立抗剪强度应力效应模型，获取基于低应力结构面抗剪强度评价高应力工程岩体结构面抗剪强度的方法。研究结果表明：平直结构面抗剪强度随法向应力的增大呈线性增长，应力效应不显著；齿型结构面的破坏模式与法向应力和锯齿参数相关，其抗剪强度存在应力效应，表现为随着法向应力增加，峰值抗剪强度呈现出先增加然后趋于稳定的趋势；台阶型岩体结构面破坏模式主要有压切破坏和剪断破坏两类，主要由台阶高长比、剪切速率以及法向应力控制，其抗剪强度随法向应力的增大呈非线性增长，且增长速率逐渐降低，具有明显的应力效应特征；天然形态结构面在低法向应力下主要发生爬坡和爬坡啃断破坏，在中高法向应力下主要以啃断、完全啃断破坏为主，结构面峰值剪切强度存在应力效应。项目研究成果能突破对结构面抗剪强度应力效应机理的认识，使工程岩体结构面抗剪强度参数可靠性明显提高，设计更加精确，可大幅节省工程投资，提高工程评价安全性，应用前景十分广阔。