| With the extensive implementation of the "Western Development" strategy and "the Belt and Road" initiative,the number of high-fill engineering construction projects in the northwest region is increasing year by year.The rise of high fill engineering has led to the development of social economy in mountainous areas,but at the same time,a series of geotechnical engineering problems have also arisen.Judging from the post-construction operation of high-fill projects under construction or existing,there are many instances of excessive settlement and deformation or even instability,the reason is mainly due to the lack of understanding of the seepage characteristics of unsaturated soil high fill and the lack of effective collapse prevention and control measures.This paper took the seepage characteristics and collapse prevention and control of high fill foundation as the research topic,relying on a high-fill airport construction project in Northwest China,this paper adopted the research method combining field test,numerical simulation and theoretical analysis to discuss the seepage characteristics of high-fill foundation under different treatment conditions.Based on this,a comprehensive collapse prevention and control scheme was proposed,and its effectiveness was verified through engineering practice.The main research contents and research results of this paper are as follows:(1)Based on the test section of a high fill project,the post-construction flooding test was carried out,and the results showed that the infiltration law of the water body in the foundation treated by the dynamic compaction method combined with the super down-hole dynamic compaction method showed obvious periodic changes;the soil moisture content near the test pit experienced a process of transition from the natural unsaturated state to the saturated infiltration state;the growth of water content showed obvious hysteresis with the increase of depth and distance from the central axis of the test pit;after 30 days of immersion,the accumulative water injection volume of the test pit reached 80t,the high fill treatment foundation formed a closed approximately elliptical infiltration area of 2m in width and 5～6m in length,the infiltration of water body was obvious,which showed that the dynamic compaction method combined with the super down-hole dynamic compaction method is still insufficient in anti-seepage.(2)On the basis of the original treatment plan,the anti-seepage measure of the geomembrane was proposed,and the geomembrane was optimized through numerical simulation experiments,the research showed that the geomembrane arrangement can effectively cut off the infiltration of water body and reduce the subsidence of the foundation;the seepage cutoff capacity of the geomembrane is positively correlated with its arrangement width and negatively correlated with the buried depth;there is an optimal layout plan for geomembrane to achieve the optimal control effect.(3)Apply the comprehensive treatment plan to the actual project,and conduct postconstruction seepage and settlement monitoring on the treatment foundation.The monitoring results showed that the volumetric water content in the foundation after construction had little change and was almost not affected by rainfall,the anti-seepage measure of geomembrane effectively improved the reliability and safety of foundation treatment;the phenomenon of antisettlement occured in the shallow layer of the subgrade,and the theoretical analysis believed that it was the unloading rebound caused by the dynamic compaction;based on the existing settlement monitoring data,the exponential curve method was used to predict the post-construction settlement,and the calculated post-construction settlement and settlement difference both met the settlement control standards,which proves that it is reasonable and feasible to use dynamic compaction method+super down-hole dynamic compaction method+geomembrane to treat the mountainous loess high fill project. |
PDF Full Text Request