李家峡拱坝复杂地基处理效果和反馈分析

REINFORCEMENT EFFECTS OF LIJIAXIA ARCH DAM ON COMPLICATED ROCK FOUNDATIONS AND ITS BACK ANALYSIS

李家峡大坝复杂地基的处理措施涉及到坝肩沿断层的深部混凝土网格置换、地基内高压固结灌浆、大吨位深孔预应力锚索加固、两岸坝肩设置完善的排水系统等。结合现场10 a的监测数据反馈分析,针对加固措施采用基于Drucker-Prager(D-P)准则非线性本构模型,并运用此模型开展有限元反馈计算,然后评价了李家峡拱坝复杂地基的处理效果。反分析计算和原型观测资料的结果显示:(1)大坝河床建基面经加固处理后,安全度有明显提高,大坝的荷载主要转移到两岸,两岸整体承受荷载和点安全度较对称。(2)上游坝踵拉裂安全度:K1=2.0P0(P0为正常工况下水压);K2=3.5P0;大坝开始丧失正常工作荷载:K3=(5～7)P0。(3)左岸"金三角"在正常荷载下,无论是现场监测数据还是反演计算都表明大坝基本是稳定的。(4)李家峡大坝的基础处理经过10 a的运行,证明其基础处理是有效的,且基础安全稳定,可以满足大坝正常水位的运行。

The reinforcement effects of Lijiaxia arch dam on complicated rock foundation are studied. The reinforcement measures include concrete grid replacement in faults, cement grouting in weak rocks, water drainage and huge-ton reinforcement of anchorages with high performance tendons, etc.. A nonlinear constitutive model that is based on Drucker-Prager（D-P） criterion with damage elasto-plasticity finite elements is proposed to study its stability evaluation with the monitoring results of ten-year dam prototype monitoring. A back analysis of stress-strain distribution of Lijiaxia arch dam is also conducted. The stresses, strain and stability between numerical analysis and prototype observations of the dam show good coincidence. It is concluded that： （1） The factors of safety and the load-bearing capacity of both abutments are increased with reinforcement of rock foundation. The loading of the dam will be transferred to both abutments of the river, and the whole loading and point safety are evenly distributed. （2） The opening cracks appear in dam heel at the 2nd-stage water load with K1= 2.0P0（P0 denotes normal water load）; K2 = 3.5P0; and the ultimate bearing capacity of dam nonlinear deformation appears in downstream surface at K3 = （5 - 7）P0, and the limit loading （7.0 - 8.5）P0. （3） The gold triangle of rock mass of left abutment is stable under normal water load; which is proven with numerical calculation and in-situ data. （4） The dam worked normally in the last ten years.