挤密桩在湿陷性黄土区涵洞地基处理效果研究

Study on Effect of Ground Treatment Measures of Compaction Pile of Culvert in Collapsible Loess Area

为解决湿陷性黄土地区高等级公路涵洞因地基处理不当导致的病害、沉降变形过大等问题,本文以青海东部黄土地区民和至小峡一级公路的两座涵洞为工程实例,分别采用2.5倍和3.0倍桩径桩间距的灰土挤密桩对两座涵洞进行地基处理,基于此对其实际效果和地基沉降变形特征进行研究分析。研究结果表明:经灰土挤密桩处理后,涵洞基底8 m深度内的土体湿陷系数从地基处理前的0.03～0.065减小至0.015内,基底6 m深度范围内的土体压缩模量从处理前的均值10 MPa提高到15～21.5 MPa。相对于3.0倍桩径桩间距的灰土挤密桩,2.5倍桩径桩间距的灰土挤密桩对桩间土湿陷系数的减小值略大0.003～0.005,对桩间土压缩模量的增加值略大1.5～4.5 MPa。说明不同桩间距的灰土挤密桩都能有效消除或减弱湿陷性黄土地区涵洞地基湿陷变形,桩间距越小、对消除或减弱土体湿陷性的效果越明显,对控制涵洞沉降变形更有利。经过1年后,分别采用2.5倍桩径和3.0倍桩径桩间距的灰土挤密桩处理后涵洞沉降量为40.6 mm和45.3 mm。涵洞基底土压力随施工阶段的变化呈先增大后逐渐保持平稳发展的趋势,一定程度上反映了涵洞受力状态与其沉降变形之间的内在联系。

In order to solve the problems of all kinds of disease,post-construction sedimentation and large deformation of culverts caused by poor ground treatment and design in collapsible loess area,taking the two culverts of in collapsible loess areas of Minhe to Xiaoxia I-grade highways in Qinghai province as examples,the actual effects of settlement and deformation characteristics have been analyzed based on the methods of different spacing lime-loess compaction piles in this papers,so as to provide reference for the reasonable application of ground treatment measures of different spacing lime-loess compaction piles of new highway culvert in collapsible loess area. The results show that the different spacing lime-loess compaction piles can effectively eliminate or decrease the collapsible deformation of culvert ground,the smaller the pile spacing,the more obvious in the effects of eliminating or weakening the collapsibility of loess,the more favorable to control settlement of culvert. Relative to the lime-loess compaction piles of 3.0 times the pile diameter,the amount of decreasing the coefficient of collapsibility is slightly larger 0.003 ～ 0.005 than the lime-loess compaction piles of 2.5 times the pile diameter,the added value of the compression modulus of soil is slightly superior to 1.5 ～ 4.5 MPa at the same time. The settlement of culverts of disposed by the pile spacing of2.5 and 3.0 times the pile diameter is 40.6 mm and 45.3 mm after 1 year respectively. The development trend of soil pressures of culvert basement increases in the early stage and then keeps steady gradually along with the change of construction stage,thus the results indirectly reflect the inner links between the culvert stress state and its settlement deformation to some extent.