基于统一强度准则的预应力锚索极限承载力计算

CALCULATION OF ULTIMATE BEARING CAPACITY OF PRESTRESSED CABLE BASED ON UNIFIED STRENGTH CRITERION

基于统一强度理论和极限平衡原理,结合预应力锚索破裂面的形状,推导出一个能够考虑锚索破裂面形状、锚索的倾角、锚固体注浆压力、岩土体种类等因素的预应力锚索极限抗拔承载力计算公式。为验证计算公式的实用性,分别在软岩与硬岩中考虑不同的影响因素对理论计算结果与实测结果进行了比较。研究结果表明:随着加权系数的增大,锚索的极限抗拔力相应增加,但破裂面形状基本没有改变;锚索的极限抗拔力主要取决于锚索与浆体、锚固体与岩土体之间的界面强度,而破裂锥体部分岩土体所分担的抗拔力较小;在软岩中锚索的极限抗拔力和破裂锥体高度主要取决于锚固体与岩体的界面强度,受注浆压力的影响较小;在硬岩中注浆压力对锚索的极限抗拔力和破裂锥体高度都有着重要的影响,随着注浆压力的增大,极限抗拔力和破裂锥体高度相应增加。

Based on the unified strength theory, the limit equilibrium principle and the shape of rapture of surface, a formula, which takes into account the shape of rapture surface, dip angle of cable, grouting pressure, varieties of rocks, are deduced. In order to validate the practicability of the calculation formula, by taking different influential factors into account, a comparison between the theoretical and actual data is made in soft rock and hard rock. The results reveal that, with the increase of the coefficient of weight b, the ultimate bearing capacity of cable increases too, yet the shape of fracture plane doesn＇t change; the ultimate bearing capacity of cable depends much more on the boundary strength between grouting and rock, or grouting and cable than that of the fracture plane of cone. In soft rock, the ultimate bearing capacity of prestressed cable, less influenced by the grouting pressure, depends mainly on the boundary strength between rocks and grouting. In hard rock, the grouting pressure plays an important role on the ultimate bearing capacity and the height of rock cone. When the grouting pressure increases, the ultimate bearing capacity and the height of rock cone increase too. In technical application, by utilizing the intensity parameter formula of unified strength theory, the intensity parameters of soil and rocks corresponding to the coefficient of weight b which contains the contribution of the second principal stress, can be calculated.