Study On The Solidification Effect And Strength Properties Of Common Solidification Agents For Engineering Muck

Muck refers to the waste soil generated during the construction process of the project,and the main disposal method in China is still landfill.With the rapid development of subway project construction,the output of waste soil has increased sharply.Due to the limited capacity of landfills,traditional landfilling methods will become expensive and occupy land resources,so it will become very important to carry out research on the recycling of waste soil.The solidification of waste soil is one of the methods for resource utilization.The commonly used solidification agents include cement,lime,fly ash,and waste soil.After the solidification process,they can be used as a new geotechnical engineering material.Based on this background,this paper conducted a study on the solidification effect and unconfined compressive strength performance of commonly used solidification agents on engineering waste soil,and achieved the following main results:(1)Using three commonly used solidification agents in engineering,cement,lime,and fly ash,four types of slag soil were tested.The four types of residue are white powdery kaolin,red and yellow sandy clay,and black muddy soil(hereinafter referred to as kaolin,red soil,loess,and black soil).By conducting unconfined compression tests on solidified waste soil,the effect of solidification agents on the solidification strength of waste soil was studied.The results show that under the condition of cement solidification,the strength of solidified waste soil increases with the decrease of water cement ratio,while the effect of cement solidification on waste soil with high organic content is not ideal;Under lime solidification conditions,the increase of lime content and the decrease of water content lead to a downward trend in the strength of solidified soil.The strength change rule of fly ash stabilized soil is basically consistent with that of cement,but the overall solidification strength effect is not as good as that of cement.At the same time,the solidification effects of the three solidification agents on the four test soils were compared.The finer particle size of kaolin cement was about=lime>fly ash,the higher sand content of loess and laterite cement was>lime=fly ash,and the higher organic content of black soil lime was>cement=fly ash.(2)The analysis of solidification mechanism of solidified soil was explained using scanning electron microscope results.The results showed that the microstructure of solidified soil with high cement content produced more flocculent and rod-shaped hydrated calcium silicate products than that with low cement content;The scanning electron micrograph of lime solidified residue soil shows that the addition of lime reduces macropores and extra-large pores in the soil,reducing the unstable overhead structures in the soil;In the scanning electron microscope of fly ash solidified slag soil,the analysis of fly ash particles produces a large number of gel,and these gel form a dense network to fill the soil voids.These products and phenomena all increase the strength of the waste soil to a certain extent,and explain the strength change rule of the solidified waste soil.(3)Based on a large number of cement stabilized residue soil tests,two indoor cement soil sample preparation methods are summarized: dry soil sample preparation method and wet soil sample preparation method.The dry soil sample preparation method is more widely used,but the drying process is more complex and may damage the soil structure;The wet soil sample preparation method retains the structure and properties of the undisturbed soil,but when the initial moisture content of the soil is higher than the target moisture content,sample preparation cannot be performed.At the same time,two sample preparation methods were used to cement solidify the same kind of residue.By comparing the unconfined compressive strength results,the two sample preparation methods did not show significant differences,so the two methods are similar.(4)Sorting out and summarizing the strength prediction formulas for cement stabilized soil proposed by predecessors,analyzing the applicable conditions and limitations of these formulas,and through comparison,it is found that the strength prediction formula proposed by Erika Yamashita is most suitable for the scenario of slag soil solidification.By substituting the data in this article into this formula,it is found that the error between the predicted value and the actual value is within an acceptable range,which proves that this formula can be applied to the engineering scenario of cement solidification of Chinese slag soil.