Experimental study on uneven load phenomenon of tendons of tensile anchors

Under integral tensioning of anchors, the results of 65 tensile anchor tests in 3 foundation pit projects with different tensile methods such as synchronous tension, separate tension and integral tension show that: (1) The real tensile resistance or ultimate bonding resistance is low if the number of tendons is less or the bonding length between tendon and grouting is short, and they are the important reasons for uneven loads on tendons. (2) The serious uneven load phenomenon of tendons is general under the serviceability limit state and ultimate limit state, and the ultimate load capacity of the anchor is reduced obviously. The variable coefficient 0.15, relative range 30% and deviation degree 20% can be used as the quantitative indice for estimating the severity. (3) The stiffness coefficient of tendons has much randomness and uncertainty, and it decreases along with the free length of tendons and increases along with the loads on tendons in general. (4) The degree of uneven load increases but serious degree decreases along with the loads on tendons in general. (5) The more the number of anchors, the more the uniform loads. (6) The ultimate tensile resistance of tendons can get 0.8 times the characteristic value. (7) Pretensioning and high pretension loads can not improve the unevenness degree of the tendons, while the synchronous tension method can improve it.