基于微震监测与数值模拟的大岗山右岸边坡抗剪洞加固效果分析

摘要

大岗山水电站坝址区右岸边坡高、陡,地应力较高,发育有辉绿岩脉、卸荷裂隙密集带及中倾坡外的断层等不利组合体,使边坡岩体的性状急剧下降,在边坡开挖过程中曾出现若干条宏观裂缝,对施工期边坡稳定性构成极大威胁.将实际微震监测技术与符合岩石类准脆性材料本构关系的RFPA3D数值模拟相结合,对抗剪洞加固前、后的边坡稳定性进行分析.指出边坡开挖过程中岩体空间损伤劣化的微震活动规律和可能发生坡体失稳的潜在滑动面位置.研究结果证实抗剪洞加固措施的合理性,发现经抗剪洞回填混凝土置换处理后的结构体抗剪阻滑力大幅增加,加固后单月发生的微震事件数减少66.4％,边坡安全系数也较加固前增大了51.2％.但由于复杂的坡体结构,使得在边坡开挖过程中仍然存在局部失稳的可能,建议应随着施工作业对剪出口进行锁固,并在后期大坝浇筑过程中对抗剪洞未贯通区域的岩体微破裂情况和卸荷裂隙带XL-316与f231断层交界处的岩体变形情况进行重点监测.%The right bank slope ofDagangshan hydropower station is steep and high,characterized by high in-situ stress.The geological defects in this project include diabase dikes,dense belts of unloading fissures and faults moderately dipping outside slope,which attribute to the poor rock mass quality.In addition,several sets of macrocracks were observed during excavation,which greatly threatened the slope stability unexpectedly.In this paper,the microseismic monitoring technology is employed in combination of numerical simulations,i.e.the sottware RFPA3D.The RFPA3D can consider the constitutive relationship of quasi-brittle materials such as rocks.Consequently,slope stabilities with and without anti-shear gallery are conducted.Also,the potential sliding surface of slope failure is determined by microseismic events of rock mass spatial damages during slope excavation.The results confirm the rationality of anti-shear gallery.It is found that the shear resistance against sliding of the structured rock mass increases significantly after concrete replacement in anti-shear gallery.The monthly microseismic events were reduced by 66.4％ after application of anti-shear gallery,and the factor of safety of slope increases by 51.2％.However,owing to the complex slope structures,the possibility of local instability still exists in the process of slope excavation.Therefore,it is suggested to lockup shearing outlet in the construction progress,and to monitor the microfracturing of rock mass where the anti-shear gallery did not pass through.The rock deformation at the junction between the unloading fissure XL-316 and fault f231 should be observed in the later stage when pouring concrete is performed on the dam.