疏排桩-土钉墙组合支护结构排桩荷载分担比试验研究

对10个疏排桩-土钉墙组合支护结构进行离心机模型试验。基于试验结果，提出排桩荷载分担比的计算模型，探讨排桩荷载分担比的变化规律以及影响因素，并提出简化计算式。研究结果表明：当基坑挖深较小时，支护结构的荷载主要由土钉墙承担，排桩承担的荷载较小，随着开挖深度的增加，土拱效应将支护结构范围内的土压力不断传递给桩身，排桩承担的荷载越来越多，最多可达到总荷载的90%以上；增加土钉长度、减小土钉间距既可有效减少排桩分担的荷载，同时还能明显提高整个支护结构的整体稳定性；当桩间距在一定范围内时，增加桩间距能减小排桩荷载分担比，但是桩间距过大会明显降低整个支护结构的稳定性；土钉竖向间距对排桩荷载分担比的影响比土钉水平间距更为明显。

Experimental study on pile load sharing ratio of composite structure with scattered piles and soil nailing

Based on the results of ten groups centrifuge model tests for composite structure with scatlered piles and soil nailing, a calculation model of load sharing ratio for piles was proposed. In addition, the variation rules and influencing factors of pile load sharing ratio were analyzed and the simplified load sharing ratio calculation formula was given. The results of centrifuge tests show that when the excavation depths of pit is small, the load on supporting structure is mainly resisted by soil nailing and the bearing force of piles is small. With increase of excavation depths, piles bear more and more load up to more than 90% of the total load, since the soil arching effect passes the soil pressure within supporting structure to piles continuously. Increasing nail length and reducing nail spacing can reduce the bearing force of piles effectively, and improve the stability of the whole supporting structure significantly. Increasing pile spacing can reduce the load bearing ratio of piles, but too large pile spacing will reduce the stability of the entire supporting structure significantly. Effect of the vertical nail spacing on load sharing ration of piles is more obvious than the horizontal nail spacing.