Abstract
Slurry shield tunnel construction produces a large amount of waste mud. If these engineering muds cannot be properly disposed, they probably bring environmental pollution, occupation of land and other issues, highly disturbing the normal operation of cities. The waste mud in this experiment is collected in the construction site of tunnel projects in Xiamen. In order to dispose the waste mud safely and effectively, chemical solidification technology is used to achieve the optimal curing effect through comparative tests. In these tests, different values of curing agent type, agent mixing ratio, and mud initial water content lead to different values of compressive strength, pH value, and water content of modified-curing mud samples. The optimum curing agent type, agent mixing ratio and initial water content of waste mud are obtained with the analysis of curing mechanism and related data. These tests are divided into 3 parts. The first part is curing agent types comparative test, which includes 425# ordinary Portland cement(S1), CERSM mud curing agent Ⅰ(C1), CERSM mud curing agent Ⅱ(C2) and quick lime(L1). The second part is curing agent mixing ratio comparative test, which includes 3%, 5%, 7%, 10%, 15% agent mixing ratio. The last part is mud initial water content comparative test, which includes 100%, 125%, 150%, 180% mud initial water content. Then the optimum curing agent type, mixing ratio and initial water content of slurry are obtained respectively by testing the effects of different factors(agent types, agent ratio and mud initial water content) on compressive strength, pH value, and water content of modified-curing mud samples. Based on the compressive strength, sample water content and pH value of the above three aspects, the curing effect of curing agent from high to low is ranked as CERSM mud curing agent Ⅱ(C2), 425# ordinary Portland cement(S1), CERSM mud curing agent Ⅰ(C1) and quick lime(L1) from highest to the lowest. Compressive strength increases with the increase of the curing agent ratio, sample water content decreases with the curing agent ratio increasing, and pH value increases with the increase of the curing agent ratio, decreases with age. Compressive strength decreases with the increase of mud initial water content, sample water content increases with the increase of mud initial water content, and the pH of the modified-curing mud sample has nothing to do with mud initial water content. In engineering, CERSM mud curing agent Ⅱ, 10% ratio, and 100% mud initial water content are finally chosen. The compressive strength of modified-curing mud sample after 28 d is up to 1.5 MPa, which is 4 times of the strength of ordinary cement solidified slurry sample. Moreover, as the growth of the age, the shear strength of modified-curing mud sample has a substantial increase, the cohesion of sample increases to 262 kPa, and internal friction angle increases to 38.65°, and modified-curing mud can be used as building filler. The presented technology can be used to dispose waste mud, which can not only solve the environmental pollution problem, but also help to realize the resource utilization of the waste mud.
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