自平衡测试技术的发展及应用现状

自平衡测试技术是从钻孔灌注桩试验发展起来的,已逐步扩展到多个领域,其试验荷载也越来越大,部分单桩承载力达万吨.荷载箱的结构形式主要有类似O-cell的开敞式、封闭圆环式和囊式.随着超长桩的应用,由于加载量或桩径的限制,荷载箱的层数由单层向多层发展.荷载箱的位置(即平衡点)是该技术的重要内容,计算其埋设位置的方法有规范经验公式法、数值模拟法及相似模拟试验法.测试数据的等效转换是该测试技术的核心,等效转换方法分为简化转换法和精确转换法.自平衡测试技术因其广泛的适应性(能满足水上和坡地等试桩要求)、测试结果的准确性和经济性,愈来愈受到重视,逐渐被纳入各国的规范.

Development and Current Application of Self-Balanced Load Test Technique

The self-balanced load test technique is developed on the basis of the testing of bored piles. The application of the technique nowadays has been extended to a number of different industrial fields and the testing load thereof has become greater and greater with the load for the bearing capacity of some of the single piles even reaching 10 000 t. The structural types of the load cells used in the technique mainly include the opening type, closed round type and capsule type similar to the O-Cell. With the application of the technique to very long piles, the arrangement layers of the load cells change from the single layer to the multiple layers to surpass the limitation of loading capacity and pile diameters. The location (point of self-balancing) of a load cell is the crux in the technique. There are empirical formula method from specifications, numerical simulation method and similarity simulation test method for calculation of the embedding location of the load cell. The equivalent conversion of the testing data is the core of the technique and the conversion method may fall into the simplified conversion method and precise conversion method. The self-balanced load test technique have attracted more and more concerns and is being included in the specifications of many countries owing to the extensive adaptability (can be used for the piles in water and slope land) and the correct and cost-saving testing results of the technique.