基坑工程预应力锚索锚固力试验研究

基坑工程预应力锚索锚固力的影响因素很多，主要有锚固段的岩土层物理力学性质、锚索施工工艺及锚索张拉锁定过程中的预应力损失等。通过工程试验，分析锚索锁定时钢绞线不均匀受力，造成这种现象主要有两个原因：（1）千斤顶在自重作用下，千斤顶轴心偏离锚索的轴心；（2）锚杆孔的施工角度与设计角度的误差，引起锚索与锚座不垂直。通过试验分析单次张拉锁定的预应力损失、循环荷载下锁定的预应力损失，循环荷载下，锚索的锚固力增加，预应力损失减少。分析基坑开挖过程中锚索锚固力动态监测结果。讨论锚索抗拔验收试验标准存在的问题，提出锚索弹性变形简化计算方法，对锚索抗拔验收试验标准提出了改进建议，锚索抗拔验收试验应综合考虑锚头总位移、每级荷载下锚头位移量及卸荷后锚头位移的回弹率等3个指标。

TEST STUDY ON ANCHORAGE FORCE OF PRESTRESSED ANCHOR CABLES FOR FOUNDATION PIT

There are many influence factors on anchorage force of prestressed anchor cables for foundation pit.The main influence factors are physico-mechanical properties of rocks and soils in anchorage area,the construction technological process of anchor cables,and loss of prestress in locking anchors,etc..Based on engineering tests,it is analyzed that the tension force of each anchor cable is distributed unevenly.There are two causes for this phenomenon:(1) acted by the gravity,the jack axis deviates from the axis of prestressed anchors;(2) because of the error between construction angle and design angle of drilling hole,the prestressed anchor cables is not vertical to the anchorage block.The loss of prestress is discussed in single tension locking and cycle tension lockinga,nd continuous monitoring of anchorage force is described in deep excavation.The acceptance test criteria for pulling resistance are discussed,the simplified calculation method of elastic deformation of prestressed anchor cable is presented;and a revised proposal is put forward.Three indices such as total displacement,increment displacement by each grade load and percentage of rebound should be considered in the acceptance test for pulling resistance of anchor cables.