高拱坝坝肩软弱结构面HM耦合效应试验研究

Experimental Study on HM Coupling Effect of Weak Structural Planes for High Arch Dam Abutment

为定量揭示高拱坝工程蓄水运行后,坝肩岩体中软弱结构面在HM(Hydro-Mechanical)耦合作用下的弱化效应,结合锦屏一级高拱坝工程,现场采集该拱坝坝肩主要断层的原样,用重塑试样方法制备试件,在MTS岩石力学试验系统上开展不同水压(0,1,2,3,4 MPa)情况下的系列三轴压缩试验。结果表明:断层物质的强度参数具有显著的水压弱化效应,其中强度参数f随水压的升高弱化不大,各断层的平均弱化率不超过7%;强度参数c随水压的升高急剧减小,最大弱化率可达100%;考虑两者的综合效应抗剪强度τ,在3 MPa水压与10MPa正应力的工程条件下,各断层抗剪强度的平均弱化率约为25%。同时,建立了不同渗透水压力条件下结构面强度参数预测模型,并采用有效应力原理对结构面抗剪强度的弱化规律和机理进行初步分析。试验成果已应用于锦屏一级拱坝坝肩稳定性研究,研究方法可供多场耦合作用下软弱结构面的力学性能研究参考。

In order to quantitatively reveal the hydro-mechanical（HM） coupling effect of the weak structural planes in the dam abutment after a high arch dam project put into operation, the dam abutment rock samples of main faults of Jinping I high arch dam were collected, and the speci mens were prepared by using remolding method, then a series of triaxial compression tests were performed on the replica specimens under hydrostatic pressures of 0,1,2,3 and 4 MPa in the MTS Rock Mechanics Testing System. The results show that the strength parameters of Jinping I arch dam abutment faults material have significant hydraulic pressure weakening effect, the friction coefficient f changes a little when the water pressure increases, the average weakening rate is less than 7 %, while the cohesion c significantly decreases when the water pressure increa- ses and the maximum weakening rate is up to 100 %. Considering the combined effect of strength parameters f and c,the average weakening rate of the anti-shear strength r of the main faults is a-round 25~ under engineering condition of 3MPa water pressure and10 MPa normal stress. A prediction model of structural plane strength parameters under different water osmotic pressures was established, and according to the effective stress principle, the weakening rule and mecha- nism of shear strength of structural plane were analyzed preliminarily. The test results have been applied in the dam abutment stability study of the Jinping I high arch dam, and the research methods can provide the reference for the research of the mechanical properties of weak structure plane under multi-field coupling condition.