加锚岩质边坡稳定性评价的极限分析上限法研究

基于极限分析上限法的基本原理,考虑岩石锚杆的支护效应、地震作用力和裂隙水压力的影响,提出加锚岩质边坡稳定分析计算模型。通过该岩质边坡极限分析上限法计算模型,可以将滑体按照滑裂面和侧向结构面离散为不同的滑体单元,并可构建一个机动许可的速度场。根据相关联流动法则和位移协调条件,相邻滑体单元的移动不能导致它们重叠或分离,进而可以得到应变速度场的数学表达式。应用该计算模型,不仅可以合理计算出由滑体自重、地震力、裂隙水压力和锚固力所做的外力功率,而且可以得到产生于滑体底滑裂面和侧向结构面的内能耗散。根据滑体处于极限状态时两功率相等(虚功率方程)的条件,可以推导得到加锚岩质边坡的极限分析上限法稳定系数计算公式。通过典型算例的稳定性分析计算表明,考虑裂隙水压力和地震作用力的边坡稳定系数将会减小,而合理加锚后稳定系数将会得到提高。

RESEARCH ON LIMIT ANALYSIS UPPER BOUND METHOD FOR STABILITY EVALUATION OF ANCHORED ROCK SLOPE

A new computational model for stability analysis of anchored rock slope is presented based on the theory of limit analysis upper bound method after taking the supporting effect of rock-bolts,the influences of seismic force and fissure water pressure into consideration.A kinematically admissible velocity field for the model can be obtained when the rock slope is divided into different sliding block elements along the slip surface and structural planes.According to the conditions of associated flow rule and displacement compatibility,the move of the two adjoining elements can not cause overlap or indentation.Moreover,the mathematical formulas of strain velocity field can be derived.By using the model,not only the external power done by dead weight,seismic force,fissure water pressure and anchorage force but also the internal energy dissipation produced in the slip surface and structural planes can be totally calculated.According to the condition of virtual work rate equation in limit state,the formula of stability factor for limit analysis upper bound method can be deduced.In order to evaluate the validity of the proposed method,a typical case is calculated.Results show that the stability factor of rock slope will decrease when the fissure water pressure and seismic force are considered.However,the safety factor of rock slope stability will increase after the slope is reinforced.