Extension of biaxial highpressure test system

该装置是对现有双轴试验系统的进一步发展和改进，使之成为真三轴压缩试验系统。根据双轴试验系统的概念，三轴试验系统中的棱柱形试件将通过六块钢板加载。众所周知，中间主应力对岩石的变形和强度特性具有决定性的影响。无论是地壳中的主应力状态，还是空洞和地下结构影响范围内的次应力状态，一般都具有很强的各向异性。因此，在实验室规模上的这些加载边界条件的实验再现是至关重要的情况下，和条件的特点是大各向异性的调查。由于在常规三轴试验（卡门型）中，两个主正应力总是相同的，因此不能用该技术研究平均主正应力的影响。无论是在TU Bergakademie弗赖贝格，还是在与之有研究合作的机构，目前都没有真正三轴压缩载荷的试验装置。因此，我们的工作组无法获得这种测试技术，也无法处理与之相关的高度热门的研究课题。选择真三轴测试设备结构类型的主要方面如下： 棱体试样的尺寸可灵活选择，边长范围为100至300 mm 实现大压应力（根据试样尺寸可达200 MPa） 所有轴上的动态载荷的可能性（例如循环载荷、地震信号或奇异冲击） 双轴测试的持续可能性，具有良好的监测可能性 通过压力板直接耦合变形测量传感器和压电陶瓷传感器 在试验箱中实现均匀的应力和变形场该设备将用于以下主题的研究项目： 当应用于结晶岩石断裂时，用于评估各向异性强度特性的扩展的流体-机械耦合Hoek-Brown破坏准则的开发和试验 花岗岩地层中深层地热威尔斯井的稳定性 三轴加载条件下裂隙岩石的力学行为 山脉形成过程/用岩石和等效材料对选定的造山过程进行实验模拟

The device applied for is a further development and improvement of an existing biaxial test system into a test system for true triaxial compressive loading. Following the concept of the biaxial test system, prismatic specimens in the triaxial test system will loaded through six steel plates. It is well known that the intermediate principal stress has a decisive influence on the deformation and strength behaviour of rocks. Both, primary stress states in the earth's crust and secondary stress states in the sphere of influence of cavities and underground structures are generally strongly anisotropic. Experimental reproduction of these loading boundary conditions on a laboratory scale is therefore of central importance when situations and conditions characterized by great anisotropy are investigated. Since in conventional triaxial tests (Karman-type) two principal normal stresses are always the same, the influence of the mean principal normal stress cannot be investigated with this technique.A testing device for true triaxial compressive loads is currently not available either at the TU Bergakademie Freiberg or at institutions with which research cooperations exist. Therefore, our working group has no access to such testing technology and cannot deal with highly topical research topics associated with it. Central aspects in the choice of the type of construction of the true triaxial testing device were the following: Flexible choice of size of prismatic specimens from 100 to 300 mm edge length Realization of large compressive stresses (up to 200 MPa depending on specimen size) Possibility of dynamic loading in all axes (e.g. cyclic loading, earthquake signal or singular impact) Continued possibility of biaxial testing with good monitoring possibilities Coupling of sensors for deformation measurement and piezoceramic sensors directly via the pressure plates Realization of a homogeneous stress and deformation field in the test specimenThe equipment will be used in research projects on the following topics: Development and testing of an extended hydro-mechanical-coupled Hoek-Brown failure criterion for the assessment of anisotropic strength behaviour when applied to fracture of crystalline rocks Stability of deep geothermal wells in granite Behaviour of fractured rock under triaxial loading Mountain formation processes / Experimental modeling of selected orogenesis processes with rocks and equivalent materials