大面积静压群桩对邻近场地挤土变形影响试验研究

Experimental Study on Squeezing Deformation in Adjacent Site Caused by the Construction of Large-Area Jacked Pile Group

依托鲁南高铁曲阜东站并轨段路基工程,开展预应力管桩群桩成桩现场试验,研究大面积静压群桩对邻近场地挤土变形影响。结果表明:大面积静压群桩过程中,土体横向水平位移与地表隆起位移随成桩排数的增多而逐渐增大;位移发展经历快速、慢速及逐步稳定3个阶段;横向水平位移沿深度总体上呈减小趋势,其分布与土层性质有关;地表隆起位移随距试桩区水平距离的增大呈指数型衰减;该试验条件下,先成桩的微型桩对后压入的管桩挤土效应具有隔离作用,引孔深度15和20 m对横向水平位移及地表隆起位移的防控效果显著;压桩完成时,地表横向、竖向位移的影响范围分别约为88倍和30倍桩径;单排压桩新增位移量随压桩排数的增加呈先增后减趋势,表明前排压桩引发的挤土变形影响比后排压桩更大。

Based on the subgrade engineering of Qufu East Railway Station in Lunan high-speed railway, field tests on the pile forming of prestressed pipe pile(PPP) group were carried out to study the influence on soil squeezing deformation in adjacent site caused by large-area pile group construction. Results show that, in the construction process of large-area static jacked pile group, as the number of pile rows increases, both the lateral horizontal displacement of soil and the uplift displacement of ground surface increase gradually. The development of displacement experiences three stages: rapid, slow and gradually stable. The lateral horizontal displacement decreases along the buried depth, and its distribution is related to the properties of soil layers. The uplift displacement of ground surface decreases exponentially with the increase of the horizontal distance from the pile testing area. Under the test conditions, the micropiles constructed first have an isolation effect on the squeezing effect of the later PPPs. The pre-drilled holes with the depths of 15 m and 20 m have significant effects on the prevention and control of lateral horizontal displacement and the uplift displacement of ground surface. When the pile group construction is completed, the influence range of the horizontal and vertical displacement of ground surface is about 88 times and 30 times of the pile diameter respectively. The newly added displacement of single-row piles increases first and then decreases with the increase of the number of pile rows, indicating that the soil squeezing deformation caused by the construction of front row piles is larger than that of back row piles.