水泥搅拌饱和黄土复合地基桩土荷载分担研究

兰州至中川机场城际铁路工程沿线大多地段属于饱和黄土地基,承载力低,压缩性大,无法满足设计要求,采取水泥土搅拌桩复合地基进行加固,通过现场实测路堤荷载及刚性承载板下水泥土搅拌桩复合地基中桩土荷载分担情况。结果表明:随着路堤填筑高度及时间的增加,桩体、桩间土的应力都增大,桩体的应力大于桩间土的应力;相同的路堤填土荷载下,二灰掺量16%的复合地基中最大桩顶应力272.5 kPa,对应桩间土应力45.5 kPa;二灰掺量12%的最大桩顶应力166.3 kPa,对应桩间土应力为69.3 kPa。随着二灰掺入量的增加,路堤荷载下水泥土搅拌桩复合地基桩土应力比增大,二灰掺量16%时的最大桩土应力比为5.57,是二灰掺量为12%的2.34倍;刚性基础下桩土应力比随荷载的变化呈现出凸单峰曲线。复合地基中桩体应力集中系数的值随着荷载的增加而逐渐增大,桩间土应力减小系数随着荷载的增加而减小。

Research on Load Share among Piles and Soil of Cement-soil Mixed Saturated Loess Composite Foundation

Most sections along the Lanzhou-Zhongchuan Intercity Railway are located in saturated loess with low bearing capacity and high compressibility,which can hardly meet the design requirements. Soilcement mixed pile composite foundation is applied and site tests are carried out to measure the embankment load and the stress of the pile and soil in soil-cement mixing pile composite foundation under the rigid load plate and to analyze the situation of load share among piles and soil. The results show that:with the increase of embankment filling height and time,the stress of pile and soil between piles increases,the stress of the pile is greater than that of the soil between them; under the same embankment fill load,the maximum pile stress of the composite foundation is 272. 5 k Pa with 16% admixture of two ashes and 45. 5 k Pa corresponding soil stress between piles; the maximum pile top stress of the composite foundation is 166. 3 k Pa with 12% admixture of two ashes and 69. 3 k Pa corresponding soil stress between piles. With the increase of two ashes,the pile soil stress ratio of soil-cement mixed pile composite foundation under the embankment load increases,when the two ashes admixture reaches 16%,the maximum pile-soil stress ratio is 5. 57,which is 2. 34 times of 12% two ashes admixture. Pile-soil stress ratio under rigid foundation presents a convex unimodal curve along with the change of load. The value of the pile stress concentration factor of the composite foundation increases with the increase of load,and the soil stress( between piles) reduction coefficient decreases with the increase of load.