真三轴荷载条件下大型地质力学模型试验系统的研制及其应用

 为研究深埋、高地应力条件下地下洞群围岩稳定性，新研制大型真三轴加载地质力学模型试验系统，该系统主要由三维钢结构台架装置和液压加载控制系统组成，可实现全三轴应力状态下在侧向施加梯级荷载。在各加载面上研制和布设组合型滚珠式滑动墙，实现新型超低减摩技术。用该系统开展洞群开挖支护的模型试验，在试验技术和模型制作工艺上有了创新和重大改进：采用预制模块堆砌黏结成型的工艺方法制作模型，提高全模型在力学性能上的一致性；采用数字照相变形量测技术、基于光纤Bragg光栅的棒式位移传感器和新研制的高精度光栅尺型微型多点位移计进行围岩内变形量测；新研发施作注浆锚杆和预应力锚索的独到工艺技术；还开展大埋深条件下的超载试验，观察到围岩破坏的发展过程，试验结果还与数值分析进行对比。研究的方法技术及结果将对类似工程研究有一定的指导和借鉴意义。

DEVELOPMENT OF LARGE-SCALE GEOMECHANICAL MODEL TEST SYSTEM UNDER TRUE TRIAXIAL LOADING AND ITS APPLICATIONS

To study the stability analysis of underground cavern groups at great depth and under high geostress field,a large-scale geomechanical model test system under true triaxial loading is newly developed. The model test system mainly consists of a steel structural frame and a hydraulic loading control system,which adopts active loading on six surfaces of the model block with a true triaxial stress considering trapezoidal loading steps in two horizontal directions. Newly-developed combinational ball-type sliding walls are installed on each side of the major loading surfaces,which can significantly reduce friction. Based on the system,a large-scale geomechanical model test for an underground cavern group is carried out. Major innovations and improvements have been made in terms of experimental techniques and advanced measurement methods/techniques. Precast blocks of analog materials are piled up and bonded to enhance the consistent mechanical properties of the whole model system. Digital photogrammetric technique,fiber Bragg grating(FBG) technology-based displacement sensing bars,and a newly developed mini-extensometers are employed to measure the deformation of surrounding rock mass. A new unique technique of grouted anchor and prestressed cables are conducted. The development process and phenomenon of fracture patterns of rock surrounding are observed and analyzed during excavating and overloading tests. The test results are compared with those of numerical simulations. These achieved results would provide certain guiding significance for study of similar practical engineering projects.