构皮滩水电站高拱坝建基面卸荷岩体变形参数研究

 乌江构皮滩水电站高拱坝建基面开挖成型后，在建基面上进行大量的声波测试，通过不同高程、不同部位的声波测试，根据波速沿坡距综合关系曲线确定卸荷深度，并分析波速分布的规律及特征。在卸荷带内进行35点原位变形试验，其加载路径和最大压力与拱坝作用于岩体的条件相似。通过35点变形试点的动静对比试验，建立卸荷岩体变形参数与波速之间的关系，利用大范围的声波测试结果评价卸荷带岩体变形参数。结合开挖前后波速和变形参数的变化规律，分析研究该高拱坝建基面卸荷岩体变形参数的弱化程度。试验结果表明，建基面卸荷深度为6 m，卸荷带岩体平均波速降低7.0%，平均变形模量由29.1 GPa降低至16.2 GPa，平均降低43.6%。提出卸荷岩体的变形参数及取值方法。

STUDY OF UNLOADING ROCK MASS DEFORMATION PARAMETERS FOR HIGH ARCH DAM FOUNDATION BASE OF GOUPITAN HYDROPOWER STATION

After the excavation and formation of high arch dam foundation base of Gupitan hydropower station in Wujiang River，a large amount of ultrasonic wave tests have been carried out on the foundation base. Through these tests with different elevations at different places，the unloading depth is determined according to the comprehensive relationship curve between wave speed and slope distance；and the wave speed distribution pattern and characteristics are also analyzed. In-situ deformation tests are made at 35 points in the unloading zone with conditions of loading path and the maximum pressure similar to that of the arch dam acting on the rock mass. According to dynamic and static comparative tests of the 35 deformation points，the relation curve between unloading rock mass deformation parameters and wave speed is established；and the rock mass deformation parameters in the unloading zone are evaluated based on results of large-scale acoustic tests. The weakening of rock mass deformation parameters in the unloading zone on the high arch dam foundation base is analyzed and studied in combination with the regularity for change of wave speed and deformation parameters before and after excavations. It is shown by experimental study that the foundation base unloading depth is 6 m；the wave speed of the unloading rock mass declines 7.0% on average；and the average deformation modulus reduces from 29.1 GPa to 16.2 GPa，down by 43.6% on average. Finally，the unloading rock mass deformation parameters and the calculating method are put forward.