Hoek-Brown准则中确定地质强度指标因素的量化

QUANTIFICATION OF ELEMENTS FOR GEOLOGICAL STRENGTH INDEX IN HOEK-BROWN CRITERION

追踪Hoek-Brown准则利用岩块力学参数估算岩体力学参数所采取方法的进展及各种改进措施。指出Hoek创立的最新方法——地质强度指标(GSI)法完全依赖定性描述和个人主观经验的不足,揭示决定地质强度指标的物理因素是岩体结构类型,化学因素是岩石风化状况。引入基于钻孔岩芯不同完整长度的岩体块度指数,以定量地表征岩体结构。分析岩石风化在化学上是原生矿物水解、淋失促使矿物蚀变而导致岩性改变的过程,依此提出表征岩石风化状况的定量指标——岩石绝对风化指数,同时研究推出其计算方法。将岩体块度指数、绝对风化指数在地质强度指标的区间范围概化表上有机结合起来,构成了GSI的定量确定方法。利用该方法估计一公路隧道围岩的变形模量、抗拉、抗压及抗剪强度等力学参数,并计算塌落拱高度。与实测数据对比,其最大误差在14%左右,验证方法的有效性和实用性。

The development of rock mechanical parameters estimation methods using rock mass mechanical parameters in Hoek-Brown criterion as well as measures of improvement in the process are traced to the source. However, geological strength index（GSI）, the newest method created by E. Hoek, has two deficiencies： depending on qualitative description completely and subjective experiences by individuals. By further study, it is discovered that the physical factor which determines geological strength index is the type of rock structure, and the chemical determining factor is weathering condition. Then, quantitative description of rock structure is achieved by introducing rock-mass block index based on drilled rock samples of different complete lengths. Meanwhile, absolute weathering index, which denotes rational index of weathering condition, is put forward based on the fact that rock weathering is the process of lithology changing caused by original mineral hydrolyzation and mineral alteration led by leaching out; and the calculation method is studied as well. Then, through organic combination of rock mass block index and absolute weathering index in the general sector scope table, the quantitative method of GSI is constituted. Finally, the mechanical parameters of surrounding rock in a highway tunnel are estimated, such as deformation modulus, tensile, compressive and shearing strength etc., and the pitch of cave arch is calculated as well. Relative error is around 14% compared with measured data; so the feasibility and effectiveness of the quantitative method are confirmed.