Geostress measurement was conducted in the south of Himalayas for the first time. 3D hydraulic fracturing method was adopted to measure the geostress at Upper Tamakoshi hydropower station in Nepal. The results are reliable in comparison with the related overseas study. The major principal stress σ1 in this field is 17.00 MPa, approximately in NS direction, and small dip angle means its orientation of action is almost horizontal. The intermediate principal stress σ2 is 13.39 MPa, approximately in EW direction. The minor principal stress σ3 is 8.07 MPa, its azimuth and dip angle indicate that the trend of σ3 points down. All of these results prove the combined action of crustal stress and rock gravity. The conclusion of medium-high stress state in this field was drawn according to the ratio of rock mass strength to stresses. The stress tensor characteristics parameter was calculated, which indicates that the geostress field has the characteristics of compression-shear. The larger shear action is one of the main factors that induce frequent tectonic movements. The work is helpful for full understanding of stress state in this field. Furthermore, all these data are greatly important for analysis of fault activity and crustal movement in south of Himalayas mountain%采用三维水压致裂技术对尼泊尔上塔马克西水电站站址地应力进行细致的测试.与国外同期同一区域的测试数据对比,该测试结果更为准确,测试方法更有效.测点处最大主应力σ1=17.00 MPa,方向近NS向,倾角较小,近似水平作用;中间主应力σ2=13.39 MPa,近EW向,倾角小,呈水平作用；最小主应力σ3=8.07 MPa,其作用趋势向下,体现出地壳应力和自重应力共同作用的结果.按照强度应力比评定标准可知,该工程区域为中等偏高应力状态;根据测试结果计算应力张量特征参数,结果显示该区域地应力场呈现压剪特征,且较大的剪切作用是该区域地质构造活动频繁的主要原因之一.测试工作有助于准确把握工程区域应力状态,同时也为研究喜马拉雅山脉南麓的地壳运动及断层活动性提供极为重要的科学依据.
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