| Soft soil is widely distributed and grows with water.It is a fine-grained soil precipitated in the environment of slow or static water flow.It is generally distributed in the development zones of river beaches,meanders and Oxbow lakes in plain areas,as well as inland lake basins,depressions and coastal areas of inland seas.Most of the gathering points of human cities are distributed in the above areas.However,due to the special engineering characteristics of soft soil,such as high moisture content,high compressibility and low strength,its natural physical and mechanical properties are often difficult to meet the design standard of bearing capacity,and the foundation soil can only be used after certain treatment.In this paper,a new idea of soft soil foundation reinforcement-Radial preloading technology for soft soil foundation is proposed.In this paper,the drainage consolidation mechanism of soft soil foundation treated by radial preloading is analyzed.Combined with the relevant theories of seepage,consolidation and settlement,the model test of soft soil sample is carried out by using the self-developed indoor test model equipment.Through the indoor model test for nearly half a year,a large number of data are collected,and the changes of drainage and settlement between the test group and the control group are compared and analyzed,as well as the changes of parameters such as internal friction angle,cohesion,moisture content and density before and after soil sample treatment.Some suggestions are given according to the problems in the actual test.The main achievements of this paper are as follows:(1)A radial preloading model test device is successfully developed.The device uses a customized rubber air bag to pressurize and expand,and the air bag wall compresses the soil horizontally;The top of the model adopts a large capacity bucket to simulate the surcharge,and the overall test effect is good.Through two indoor model tests,the change law of soil drainage during the loading process under the action of radial preloading combined with surcharge preloading method is studied,and combined with the mechanism analysis,the feasibility and effectiveness of radial preloading to accelerate the drainage of soft soil foundation are verified: in the loading stage,the drainage of the test group is about twice that of the control group.(2)Through the comparison test and the effect of soft soil foundation treated by surcharge preloading method,it is found that the and values of corresponding soil samples treated by radial preloading combined with surcharge preloading method are basically higher than those treated by surcharge preloading method(control group): the values of different soil layers in the test group are 1.07 ～ 2.00 times higher than those in the control group,and the values of different soil layers in the test group are 0.92 ～ 3.89 times higher than those in the control group.In the vertical direction,the shear resistance of treated soil samples decreases with the deepening of depth in the vertical direction;However,the deeper the depth,the more significant the effect of radial preloading combined with surcharge preloading than surcharge preloading,and the higher the initial moisture content of soil sample,the greater the effect gap.(3)Through two model tests,the average water content of soil samples in the test group is basically twice that of the control.The higher the initial water content is,the greater the difference of soil water content per unit distance after treatment with the deepening of foundation depth;On the whole,the density of each layer of soft soil foundation decreases first and then increases with the deepening of depth.In the same loading time,the higher the moisture content before soil treatment,the greater the density increase.(4)The variation law of foundation settlement monitored by the test shows an unfavorable side: uneven settlement occurs on the foundation surface of the test group(radial preloading combined with surcharge),and even local uplift occurs. |
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