圆筒试验法在岩石测试中的应用

Hollow Rock Cylinder Testing and Its Application

鉴于传统的岩石试验方法假定岩样处于均匀的应力状态,而实际地下开挖体附近的岩石一般是处于平面应变下的非均匀多轴应力状态.为了更好地模拟真实岩石的强度及变形性态,我们使用了岩石圆筒试件进行研究.本文是此系列研究报告中的一部分内容。Mohr-Coulomb强度准则是现今人们广泛引用的岩石线性强度准则,结合塑性流动法则作者建立了几种岩石圆筒的变形模式,其中包括岩石材料的弹塑性增量理论模型及弹塑性全量理论模型。同时,作者在文中还提出了应用岩石圆筒实验结果回归分析岩石材料强度及变形参数的简单方法。为了对建议的方法进行证实和评价,作者用砂岩圆筒试件进行了试验,对径向和环向应变作了测量.分析表明:在外围压力作用下的圆筒试验结果与按理想弹塑性理论考虑关联流动法则和Mohr-Coulomb线性强度条件预测的情况吻合很好。

Traditional rock tests always subject rock specimens to a presumably uniform stress and strain state whereas theroek surrounding an excavation is generally ina plane strain state and is subjected to nonuniform stresses. In view of this and in order to simulate field conditions better, the authors have carried out modelling tests of rock strength and deformation behaviour using hollow cylinder rock specimens. This paper is one of a series of research reports on this work. Using the famous Molar-Coulomb linear strength criterion of rocks in combination with the rule of plastic flow, the authors have established some deformation models for hollow rock cylinders, including models for rock materials based on the incremental and total theories of elastoplasticity. Meanwhile, the authors have also put forward a simple method for determining the strength and deformation parameters of rock materials by regression analysis using the experimental result of rock cylinders. In order to verify and assess the proposed method, the authors have carried out tests on cylindrical specimens of sandstons in which the radial and circumferential deformations are measured. Analyses show that the test result of cylinders of a soft silty sandstone under external pressure agrees agrees well with the prediction made on the basis of the theory of perfectly elastoplastic solids in combination with the rule associated flow and the Mohr-Coulomb linear strength criterion.