基于强度折减法的重力坝深层抗滑加固措施研究

对于重力坝坝基存在软弱结构面的抗滑稳定处理,工程实践中常采用混凝土硐塞置换或预应力锚索方案。为分析比较两种方案的处理效果,采用有限元方法,建立包含基岩内软弱结构面的三维模型,采用Drucker-Prager强度准则,考虑自重荷载、水荷载、扬压力、坝前淤沙压力,研究某水电站工程溢流坝段坝基深层抗滑稳定问题。在采用重力坝设计规范计算抗滑处理后安全系数相同的条件下,采用有限元通过强度折减的方法可计算得到不处理、硐塞置换方案与锚索方案3种不同工况下的破坏形态,采用等效塑性应变超过某一幅值作为判断材料是否进入塑性状态的指标,结合坝体位移随强度折减系数的变化曲线,判断坝基是否出现滑动,分析结果表明硐塞置换方案较锚索方案的安全裕度更大。

Study on Anti-slide Effects of Gravity Dam Reinforcement Based on Strength Reduction FEM

When there are nature faults or weak zones in the foundation, the prestressed anchor or concrete replacement method was often used to deal with it and reinforce the foundation, both methods were recommended by the design specification of concrete gravity dams. In order to study and compare the anti-slide effects of these two methods, this paper builds up a concrete gravity dam’s three dimension model which contains the nature faults and weak zones, and applies the finite element method to compute and analyze the deep foundation’s sliding stability.By applying the Drucker Prager Strength Criterion, this paper analyzes the displacement and stress behavior of the dam’s foundation when it’s loaded by gravity load, hydrostatic load, uplift pressure and silt load,and gets the form of the foundation’s destruction and the displacement-reduction factor curve of the prestressed anchor and concrete replacement method, then judges the safety factor of the dam’s foundation’s stability by analyzing the displacement-reduction factor curve. Meanwhile, this paper applies the PEEQ parameter to judge whether the material is coming into plastic state, by which we can easily judge whether the dam’s foundation is coming into sliding state and the level of destruction. The result shows that the concrete replacement method is safer than the other method, as its safety factor is larger than the concrete replacement method’s, while they are the same if they are computed by using the design specification of concrete gravity dams.