Experimental Study Of High-energy Humidification And Strong Ramming On Wet Sinking Loess Foundation

Since the 21 st century,western development has become an important national policy guiding the economic and social development of the western region,and in 2020 the state issued new guidelines for promoting the formation of a new pattern of western development.Under the guidance of the national policy,more and more resources from home and abroad are flowing to the west,which promotes the development of the west.In recent years,due to the topographic and spatial constraints of the western loess region,there is a shortage of land for industrial and civil construction,and a large number of field leveling projects to cut mountains and fill ditches have emerged.Wet subsidence is a unique engineering characteristic of loess,and the strong ramming method is a common foundation treatment method to eliminate wet subsidence.At present,in the treatment of low moisture content wet sinker loess foundation,there are few research and engineering application examples about high energy level wetting ramming.Therefore,combining with the current status of existing research,this paper has carried out the experimental research on high-energy level moisture-enhancing strong ramming for low moisture content wet-submerged loess foundation by using the methods of indoor test,field test and finite element analysis.The main research contents are as follows:(1)In a field leveling project in Lanzhou City,4 energy level strong ramming tests of 8000 k N-m,12000 k N-m,16000 k N-m and 25000 k N-m were carried out in the filling area and excavation area respectively,and the in-situ testing of foundation bearing capacity and basic physical parameters of soil samples were tested on the site after strong ramming,and the wet sinkability and bearing capacity of foundation soil after strong ramming were analyzed.The results show that the average moisture content of the foundation soil is within the range of 6.4%～8.8%,and the depths of the excavated area to eliminate the wetness of loess are 2m,4m,5m and 11 m respectively after the strong ramming treatment of 8000 k N-m,12000 k N-m,16000 k N-m and 25000 k N-m energy level,and the depths of the filled area to eliminate the wetness of loess are 3m,7m,8m and 12 m respectively.and 12m;the characteristic value of bearing capacity of foundation after strong ramming treatment is not less than 220 k Pa.(2)Geo Studio software was used to establish a model of foundation soil water injection and humidification,and the whole process of foundation water injection and humidification was simulated and analyzed,based on two evaluation indexes of radius of humidification influence and depth of humidification influence,the change law of soil moisture field distribution in the process of humidification was analyzed,and the effect of water injection and humidification of different depths of water injection holes was compared.The analysis shows that: the depth of humidifying influence of water injection hole can be divided into instantaneous influence depth and delayed influence depth,with the increase of water injection hole depth,the depth of humidifying influence and instantaneous humidifying influence depth are gradually increased,and the depth of humidifying influence is linearly related to the depth of water injection hole;the effect of water injection humidifying is mainly influenced by the depth of water injection hole and the time of water dissipation,and the distribution of moisture field of soil moisture content of the site is better when the moisture dissipates for 60 d.is more ideal.(3)A 25000 k N-m energy level humidification ramming test was carried out at the fill site to analyze the effects of water injection humidification,ramming frequency and moisture content of the foundation soil on the effect of ramming treatment.The test results show that: when the site has a binary structure of upper virtual fill and lower original foundation soil,it is easy to form cavities at the binary interface in the process of water injection and humidification,resulting in a locally too high or too low moisture content;according to the regression analysis of test ramming data to obtain the empirical relationship between the click ramming sinkage and the number of times,the number of rams required to achieve a certain ramming sinkage control value can be predicted;when the moisture content of the foundation soil is gradually approaching the optimal moisture content When the moisture content is controlled within ±2% of the optimum moisture content,the effective reinforcement depth of 25000 k N-m energy level ramming at the ramming point is 17～20m,which is close to the estimated value of the existing empirical formula considering rammer area,dry weight,moisture content and ramming energy level.(4)Based on the results of field tests and finite element analysis,the construction process of humidified ramming for wet sinking loess foundation is obtained,which provides a reference for the construction parameters of humidified ramming amount.