三峡船闸边坡岩体拉剪试验及强度准则研究

IN-SITU TENSION-SHEAR TESTS AND STRENGTH CRITERION STUDIES ON TGP SHIPLOCK SLOPE ROCKMASS

三峡永久船闸边坡开挖后,卸荷和应力重分布使得岩体出现较大范围的拉应力区,且该区岩体多呈拉剪应力状态。为研究受拉区岩体拉剪强度准则,进行了室内岩石拉剪试验,但采用现场试验进行岩体拉剪强度准则研究则较为少见。通过在船闸区开展拉剪面尺寸为50 cm×50 cm的现场岩体拉剪试验,获得了不同拉应力时的岩体拉剪强度,岩体拉剪强度与拉应力关系呈明显的曲线特征。岩体拉剪强度准则研究结果表明:三峡花岗岩岩体拉剪强度准则宜采用莫尔强度准则的二次抛物线型来描述,其次为双曲线型,而双直线型偏差较大。进行边坡变形稳定分析时,对于拉剪应力区岩体则不宜采用直线型强度准则,更不能简单地采用压剪试验取得的直线型关系向拉应力区延伸方法确定岩体拉剪强度。

After the excavation of the Three Gorges Project（TGP） shiplock slope, a larger tension stress area is seen because of unloading and stress redistribution, where the rockmass is shown on a tension-shear stress state. The laboratory rock tension-shear tests are carried out to study the strength criterion of the tension stress area. However, the in-situ rockmass test to analyze the criterion is seldom seen. Based on the in-situ tension-shear test with the size of 50 cm×50 cm in the TGP shiplock slope rockmass, the test results show that the tension-shear strength of rockmass is reduced continually as the tension stress increases; and the relationship between τ and cr has a obvious curve characteristic. The achieved conclusion of tension-shear strength criterion can be drawn that the rockmass tension-shear strength criterion should adopt the second-degree parabola model best; and the next preferable choice of criterion is hyperbola model. However, the beeline model applied to the tests will cause a considerably larger discrepancy. Consequently, when carrying on the deformation stability analysis to side slope, the strength criterion of beeline model to analyze the rockmass of tension-shear stress area should be avoided; and the beeline model relationship, which is obtained from the laboratory press-shear test of rock, can not be used to determinate the tension stress zone.