Abstract: Xiaojiang fault is an important geological boundary in southwest China, which exerts certain influence on the long-term stability of Baihetan hydropower reservoir. It is necessary to study the influence characteristics of the creep deformation of the active fault. Based on the geodetic monitoring results of Xiaojiang active fault and its adjacent areas, considering the strike-slip and thrust characteristics of the fault, a three-dimensional numerical generalized model is established to simulate and analyze the temporal and spatial evolution characteristics of the stress field around the fault zone under the long-term creep movement of 10 mm/a. The calculation shows that with the long-term creep of Xiaojiang fault, the surrounding geostress field presents an approximate linear and gentle increasing trend. The maximum principal stress increment of the rock mass near the fault zone in 200 years is about 0.35~0.55 MPa, and the stress increment in 1 000 years is about 1.1~3.3 MPa. After the reservoir impoundment, the influence area of reservoir water is limited to the periphery of the valley, and the direct influence on the geostress field in large area is not obvious. The relevant research results can provide certain reference for the long-term stability evaluation of the project.

Key words: Xiaojiang fault, active fault, creep deformation, geostress field, numerical simulation

摘要： 小江断裂是西南地区一条重要地质界线，对白鹤滩水电站库区工程长期稳定有一定影响，研究该活动断裂长期蠕滑变形的影响特征十分必要。基于小江活动断裂及其邻近地区的大地运动监测结果，考虑断裂的走滑与逆冲运动特征，建立三维数值概化模型，对该断裂带在10 mm/a级长期蠕滑运动下的周边应力场的时空演化特征进行模拟分析。计算显示，随着小江断裂长期蠕滑，周边地应力场呈近似线性、平缓的增长势态。在工程百年寿命期或短暂的地质时间尺度内，并不会对周边地应力场造成明显影响，断裂带附近岩体在200年内的最大主应力增量约0.35~0.55 MPa，1 000年内的应力增量约1.1~3.3 MPa。水库蓄水后，库水影响区仅限于河谷周边，对大区域地应力场的直接影响不显著。相关研究成果可为工程长期稳定性评估提供一定参考。

关键词: 小江断裂, 活动性断裂, 蠕滑变形, 地应力场, 数值模拟