天堂山水库坝区断裂构造基本特征及其活动性

野外调查与室内分析表明,影响大坝基础稳定性的北西向断裂属不活动断层;压碎岩占80％以上,强度较高,有利于坝基工程基础处理;引水隧道及峒室工程必需考虑现今构造应力场主压应力近南北向来布置,以减少构造应力对围岩稳定性带来的不利影响。

The Basic Characteristics and Activities of the Faults in the Dam-site of Tiantanshan Reservoir

A ecording to the research on fault activities, the dam-site belongs to str- ucturally stable regions. The last movement of the NW faults which have impo- rtant effects on the stability of the dam-site took place in the Early Quaternary. The thermoluminescence ages of this fault movement range from 1.5(Ma) to 0.8 (Ma). It is estimated that the moving rates of the faultblocks are about 0.0003- 0.0001 cm/a. Therefore, the faults belong to dead faults. Brittle deformation is the major type of fault deformations in this area. The cataclasite made up 80 percent of the dynamometamorphic rocks. This is favorable for the basic handling of the dam-site engineering. Neotectonic movement in this area is dominated by intervally regional uplift, without obvious differential uplift and subsidence of fault-blocks. The dam site is thought to be a "safe island"-an area without deep and great earthquakes. It should be considered that modern tectonic stress field in this area is represented by a pressure of nearly N-S while locating the pos- itions of the tunnels and caverns, so that the hamful influence of the structural stress on the stability of the surrounding rocks can be reduced.