关键词: 超厚细砂地层, 大直径后压浆桩, 荷载传递法, BoxLucas1模型, 增强因子, 荷载-沉降关系

Abstract: To study the deformation behavior of large-diameter grouted pile in extra-thick fine sand layer, load transfer of large-diameter grouted pile was analyzed in a case study of eight in-situ pile load tests of Shishou Yangtze River Highway Bridge. The BoxLucas1 load transfer function was used to calculate the relationship between load and settlement of the grouted pile considering the radius of the grout bulb and the thickness of cement grouting along the pile. The empirical range of enhancement factors for side friction and tip resistance in different soil deposits was also given. Then, case history was cited to demonstrate the validity of the method. Finally, according to the engineering example and calculation method of this paper, the bearing capacities of the large-diameter pile under extra-thick fine sand layer were further analyzed. The results show that the presented method can well determine the range of settlement of the grouted pile. It is suggested that the calculated lower bound can be used as an engineering design. The bearing capacity of the large-diameter pile is gradually increasing with the increase of pile diameter or pile length. When the pile diameter is constant, the increased range of bearing capacity of the large-diameter pile is decreased with the increase of pile length. The pile length reaches a certain value, the ratio of the mobilized base resistance to the total capacity is almost zero. This indicates an effective pile length problem by increasing the pile length to improve the bearing capacity of large diameter pile. Effective pile length, bearing capacity and percentage of load carried by pile tip of the large-diameter pile can be significantly improved by combined grouting of pile tip and side.

Key words: extra-thick fine sand layer, large-diameter grouted pile, load transfer method, BoxLucas1 model, improvement factor, load settlement relationship