Research On The Strength Of Cement Mixing Saturated Loess And Bearing Characteristics Of Mixing Pile Composite Foundation

As the development of the infrastructure construction in our country, the saturated loess’ s reinforcement is getting more and more attention of scholars.Saturated loess has some characteristics such as high water content, high compressibility and rheology.Because of locating in the lower place underground or soaking under the surface water for long time,the saturated loess has no collapsibility.Therefore,when dealing with saturated loess foundation,we can regard it as soft foundation.the technique of soft foundation reinforce has been paid more and more attention. Many engineering will encounter the problem of how to deal with kinds of soft foundation in different conditions, so the technique of soft foundation reinforce has become a hot spot. This paper used the cutting ring method,the shallow plate load test, the single pile static load test and the load test of single pile composition foundation,based on soil-cement mixing piles sited in zhongchuan railway,(DK48 + 430 — DK49 + 030)segment, and analyzed the data obtained from field measurement, to study the following issues:(1)In the laboratory cement soil trail test, the unconfined compressive strength of cement soil increase with the growing of two-ash ratio. By getting the unconfined compressive strength of cement soil with different two-ash ratio to predict if the cement soil mixing pile with 12% two-ash ratio can meet engineering demand. The bearing capacity of cement soil mixing pile has close relation with the workability of cement and soil、mixing uniformity coefficient and so on.(2)The ultimate bearing capacity of cement soil mixing pile whose two-ash ratio is 20% is little bigger than 16%. At the construction site, 20% two-ash slurry is to dense to transport by the pipe, and also it is hard to mixed uniformly with the soil, causing waste of material. Cement soil mixing pile whose two-ash ratio is 16% not only can meet the construction request,but also be more economical contrast with 20%.(3)By analyzing three groups of ultimate bearing capacity of composite foundation with different two-ash ratio, the ultimate bearing capacity of composite foundation increase with the growing of two-ash ratio, but not linearity. Two-ash ratio increases 30% while its composite foundation ultimate bearing capacity increases only 10%.(4) Pile-soil stress ratio decreases with the increase of load, pile-soil stress ratio in different two-ash ratio has not obvious difference. Pile-soil stress ratio of 20% two-ash ration composite foundation is different with the former two, its scope is 1.1-2.9. From n-p curve, we can see that bearing capacity of pile-soil stress ratio has close relation with single pile quality and mixing uniformity coefficient.(5) In single pile composite foundation, the settlement of foundation increase with the increase of load. When the pile is in elastic stage, p-s curve is almost straight line; When the pile isn’t in elastic stage, p-s curve is not straight line any more.