Evaluation Of Compaction Effect Of The Reinforcement For Old Subgrade In High Water Content Using The Technical Measures Of Lime Pile

Fujian province is located in hot and humid areas. The subgrade moisture continued to rise and has greatly exceeded its original optimum moisture content after several years of road operation,it due to the affected of rainfall and groundwater witch led to the decrease of subgrade strength and stiffnessand and induce disease of pavement.Thus, how to effectively restore the performance of both the old subgrade has plagued engineers. Compared to ground treatment, the reinforcement of old roadbed with high water content exists peculiarities:the mainly quality control standards for ground treatment is carrying capacity but roadbed is compaction degree; old subgrade with high water content is difficult to be compacted,and is difficult to exclude the non-free water around the soil by using the general drainage methods and dynamic reinforcement methods.In view of this,by using the performance of lime swelling when absorbing water,the paper explores the compaction mechanism of high moisture content of old subgrade reforced with lime piles in the means of the theoretical derivation, the indoor model test and numerical simulation technology.The main work and conclusions are as follows:First, through the indoor model test, the different old subgrade soil with different lime-sand pile diameter of pile in different depths of pile diameter expansion amount determined; radial pile surrounding soil of different depth and different radial radius variation of stress. The results show that:the final expansion rate of lime-sand pile diameter decreases with the initial diameter of pile and pile depth increases; the cement-sand ratio of lime sand pile prepared by 1:1, about 80 percent its expansion completed within 5 hours, pile diameter expansion peaked in about 2 days, decreaseed slightly after the peak; the initial pile diameter is smaller and the larger the pile of soil moisture, early expansion rate of the pile larger; cement-sand ratio of 1:1 in the preparation of lime-sand pile soil around the pile into a pile of soft-core critical initial expansion of the pile diameter is 20cm.Secord, simplify the stress-strain model of consolidated soil and over-conso lidated soil around the lime pile into elastic-plastic model or trilinear model so ftening model.Based on the generalized SMP criterion, plasticity non-associated shear expansion, plane strain assumption,this paper deduces the analytical soluti ons of stress field, strain field and displacement field suitable for the plastic p erformance of the soil around the pile compacted and reaming of lime of nor mally consolidated soil and over-consolidated soil respectively.Again, in lime pile calculations, the numerical solution is greater than the measured value of 7.6%, elastic-plastic model analytical solution of 5.3% small er than the measured value, all of these can basically meet the engineering cal culation accuracy. The larger the pile soil strength, the greater the radius of th e plastic and radial stress; Plastic radius increases with increasing initial pile di ameter, and increasing the initial pile diameter can enhance the effect of comp action. The top and bottom of the pile with varying degrees axial expansion pi ercing, and the radial stress along the radial direction has been reduced, to so me extent these can weaken the effect of radial consolidation of soil around th e pile. In the project, the end of pile should be taken to with a smaller amou nt of ratio of lime to reduce its vertical expansion amount.Finally, in lime pile group, the analytical solution of elastic-plastic model and the nalytical solution of linear softening model are smaller than the num erical solution of 6.7% and 14.56% respectively, elastic-plastic model is more r easonable. Linear softening model is not suitable for calculating the normally c onsolidated clay. Under the same conditions, lime pile group has greater range of plastic reinforced radius than the pile, the pile group is more practical. Wh en using square pile, increasing the initial pile diameter, the greater the subgra de soil strength, the soil around pile of plastic strain and plastic penetration le ngth is larger. When the pile spacing and pile diameter ratio is consistent, the initial pile diameter is smaller, the better effect of soil compaction; the effect o f Square pile is better than quincunx effect.