Experimental Study On The Treatment Of Deep And Collapsible Loess Foundation With Drilling Immersion Water Method

The pre-immersion method is a foundation treatment method used in deep collapsible loess areas.It has the characteristics of simple construction operation,wide treatment range and effective elimination of self-weight collapsibility in the treatment range.It is especially effective for the treatment of large area immersion pits.obvious.Based on the traditional pre-immersion method,this paper makes improvements on the insufficiency of its slow infiltration process,the long time required to act on deep formations and the excessive water consumption,and proposes an improved method of immersion—drilling Pre-immersion method;The borehole pre-immersion method is to drill multiple immersion wells by drilling at the bottom of the immersion test pit.By injecting water into the multiple immersion wells at the same time,the water can act on the collapsible loess layer in the pretreatment range.This paper relies on actual engineering,using calculation model derivation,physical test and finite element software simulation verification method to evaluate the controllability of the amount of water infiltration and the treatment scope when the borehole pre-immersion method is used to treat deep and collapsible loess foundation.The main research results of the paper are as follows:(1)When the borehole pre-soaking method is used to treat the collapsible loess foundation,the volume calculation model and the required water consumption calculation model of the saturated soil saturated with the rectangular layout method are used.Through the indoor one-collapse test and the immersion-re-collapse test after pre-soakin g treatment,the effect of pre-soaking treatment on the loess under the consideration of only the gravity stress was studied.The results showed that:The ratio of the saturated self-gravity stress of the overlying soil to the initial pressure of the collapse is the dividing line.(2)The numerical simulation software was used to study the law of water infiltration and the influence range of water infiltration for single wells with different well depths,well diameters,double well spacing and infiltration time.The results of the study show that the shape of the saturated saturation area of the single well is all water drops,and the horizontal infiltration range of the saturated saturation area is stable before the vertical infiltration;The duration of water infiltration stabilization and the influence range of wetting of different well depths and diameters increase as the depth and diameter increase;When the double wells are soaked in water,the maximum effective well spacing between the wells is 7m.(1)Through the on-site test pit borehole immersion test,the water infiltration range and formation subsidence law of the collapsible loess foundation treated by the borehole pre-immersion method were studied,and the field measured parameters were substituted into the calculation model to verify the calculation model.feasibility.The research results show that the infiltration infiltration stability time of the 10m immersion well is 7d,the maximum infiltration radius affected by the wetted soil is about 3.5m,and the maximum infiltration depth is about 15.5m;the loess at different depths will produce obvious collapsible deformation,As the depth of the soil layer increases,the amount of collapsing will decrease;the deformation of the soil layer above 8m mainly occurs during the water-soaking period,and the deformation of the soil layer below 8m mainly occurs during the water-stop period.(2)Through an indoor collapsible test and residual collapsible test after pre-soaking treatment,the effect of pre-soaking treatment of loess under the condition of considering only self-weight stress is studied.The test results show that the ratio of the saturated overburden stress of the overlying soil to the initial pressure of collapsing is the dividing line.When the ratio is greater than 1,the pre-immersion method cannot completely eliminate the collapsibility of the soil layer above the dividing line;when the ratio is less than 1,with the As the depth of the layer increases,the effect of pre-soaking water to eliminate collapsibility is enhanced,and the initial pressure increment of collapsing tends to be stable.