| Expansive soil is a kind of clay with obvious expansion and contraction in the process of drying and wetting and is obviously affected by the environment.It is widely distributed in China and even the world.With the large-scale construction of infrastructure construction,the engineering structure is becoming more and more complex,and the engineering problems caused by expansive soil are becoming more and more serious.The application of expansive soil has important engineering significance for expansive soil area.At present,the treatment method of expansive soil is to improve it,and the improvement effects of different types of expansive soil will also be different.In this study,aiming at the expansive soil in Nanning,Guangxi,the deficiency of the improvement effect of cement and CMA(Changing the Montmoriuonite’s Absorbent)modifiers on the expansive soil is obtained through the test,which verifies the feasibility of cement CMA composite improvement.At the same time,the fluid solidified soil based on expansive soil is studied,and the experimental research is carried out from four aspects:expansibility,fluidity,unconfined compressive strength and durability.The main conclusions of this paper are as follows:(1)In terms of plasticity index,standard hygroscopic moisture content and expansion rate,both cement and CMA modifier can play a role in reducing,but they can not modify the soil sample from medium expansive soil to non expansive soil,especially cement,which has a poor improvement effect in terms of expansion rate.Under the joint action of the two modifiers,the properties of expansive soil can be better improved in the composite improvement of cement montmorillonite neutralizer;Cement has little effect on the compaction test results.CMA can slightly increase the maximum dry density and reduce the optimal water content.(2)Through the unconfined compressive strength test,the saturated and unsaturated unconfined compressive strength of the improved soil with different improvement methods and different curing time were studied.The conclusion is that the expanded soil with cement improvement still dissolves directly in case of water.CMA can obviously improve the water stability of the soil sample,but the saturation strength is low.Composite improvement not only improves the water resistance of soil samples,but also significantly improves the saturation strength.When the cement content is increased to 3%,the unconfined compressive strength can meet the requirements of the specification.(3)Taking the free expansion rate as the evaluation index,the expansibility of fluid soil based on expansive soil is tested,and the influence law of standard sand and initial water content on the free expansion rate of expansion rate is further studied.The conclusion is that the reduction effect of sand on the free expansion rate is approximately proportional to the content of sand,and the free expansion rate of cement improved expansive soil decreases and then increases with the increase of initial water content,The minimum point is related to the cement content.(4)The initial moisture content is the most critical factor affecting the fluidity,which can significantly improve the fluidity,but at the same time,the increase of the initial moisture content will also reduce the strength of the fluid solidified soil,which should be comprehensively considered according to the needs in the application process.The addition of standard sand can also improve the fluidity of the mixture,and the improvement effect of fluidity and unconfined compressive strength decreases when the content exceeds 10%.The cement content has little effect on the fluidity,but has a direct effect on the growth rate of strength.The addition of sand and cement will affect the bonding ability between soil particles.The increase of sand content will reduce the ability of soil to resist dry wet cycle,and cement will improve this ability. |
