基于岩体波速和Hoek-Brown准则的初始地应力场参数计算模型研究

Study on Parameter Calculation Model of Initial Ground Stress Fields Based on the Wave Velocity of a Rock Massand the Hoek-Brown Criterion

摘要:

在初始地应力场参数计算中引入岩体波速，通过基于岩体波速的Hoek-Brown准则建立初始地应力场中水平地应力σ_H的取值范围Δσ_H计算模型，并通过实测地应力数据验证了Δσ_H计算模型的合理性。在Δσ_H计算模型的基础上，推导出了σ_H/σ_V（水平地应力/垂直地应力）的取值范围Δ（σ_H/σ_V）计算模型，并通过Δ（σ_H/σ_V）计算模型从岩体稳定性的角度对σ_H/σ_V在地壳表面和深部的分布现象进行合理解释。通过Δ（σ_H/σ_V）计算模型给出的σ_H/σ_V的取值下限（σ_H/σ_V）_min和取值上限（σ_H/σ_V）_max算出侧压系数λ，并给出了侧压系数λ与深度h之间的函数关系λ=ah^b+1。

Abstract:

The wave velocity of a rock mass and the Hoek-Brown criterion are introduced to enable the building of a calculation model of the range of values of horizontal geostresses (σ_H) in an initial ground stress field. The rationality of this calculation model is evaluated by the measured geostress data. Based on the Δσ_H calculation model, a Δ(σ_H/σ_V) calculation model of the values range of the ratio of the horizontal and vertical geostresses (σ_H/σ_V) is deduced; this model is then used to provide a reasonable explanation of the σ_H/σ_V distribution of phenomenon in the surface and deep of earth's crust is given from the perspective of rock mass stability. The coefficient of horizontal pressure (λ) is calculated via the lower ((σ_H/σ_V)_min) and upper ((σ_H/σ_V)_max) limits of σ_H/σ_V, which is given by the Δ(σ_H/σ_V), and comparative analysis of the calculated and measured values of λ is performed. Results show that the calculated and measured λ present consistent characteristics in a shallow rock mass but significant differences in a deep rock mass. Thus, the Δ(σ_H/σ_V) calculation model is applicable to λ calculations in shallow rock mass engineering. The calculated λ presents obvious nonlinear variation features along the depth (h) direction, and the functional relationship λ=ah^b+1 between λ and h is given by setting up appropriate boundary conditions; this functional relationship is confirmed by curve fitting. The fitting results show a very high fitting correlation coefficient for λ=ah^b+1, which means it can describe the functional relationship between λ and h well. This functional relationship can be used for initial geostress field evaluations and provides the necessary initial geostress field conditions for simulating deformation and failure of excavated rock masses.