Analysis of Interaction Between Test Piles and Reaction Piles of Super-Long Large Diameter Piles in Static Loading Tests

Based on an engineering case of static load tests on super-long large-diameter cast-in-place piles by the method of reaction piles combined the stacking loads, the effect of reaction piles and stacking weight on settlement of test piles was discussed. According to test conditions, a 3D model was constructed, the influence on test piles during loading and unloading processes of cribbings and reaction piles was analyzed, involving pile-soil settlement, axial force of pile shafts, displacement of monitoring points and bearing characteristics of test piles. The results showed that during the static loading test on super-long large-diameter cast-in-place piles by reaction pile methods combined stacking loads, the uplift of reaction piles would drive soil surrounding test piles upward, and promote the development of side friction in advance. Attention should be paid to reduction in vertical displacement of test piles due to uplift of reaction piles. The space between reaction piles and test piles should be arranged large enough to satisfy the requirements of design specifications. Larger space would be expected when conditions permitted. A high precision level or total station was suggested to be used to monitor and check the vertical displacement of test piles, so that influences of reaction piles and cribbings during the loading and unloading process on displacement of reference points could be eliminated to avoid misjudgment.