Mixture Ratio Test And Model Test Study Of Cement-bentonite Mud Cutoff Wall

The cement-bentonite mud cutoff wall has good anti-seepage performance and can effectively prevent the pollution of soil and groundwater by pollutants.At present,the mix ratio scheme of cement-bentonite anti-seepage wall and the test method of permeability coefficient are not uniform at home and abroad,therefore,the cement-bentonite slurry with a water-cement ratio of 3.85 to 5.88 and a water-bentonite ratio of 3.85 to 7.14 is set;through the laboratory test,the relationship between different permeability coefficient test methods and their laws were studied to study the effects of water-cement ratio,water-bentonite ratio and age on the mechanical properties and impermeability of cement-bentonite mud anti-seepage wall;through the model test,the influence of soil layer environment and the mixing of a small amount of silty clay on the performance parameters of cement-bentonite mud anti-seepage wall was analyzed.The following conclusions were obtained:The unconfined compressive strength of cement-bentonite slurry increases with the decrease of water-cement ratio.(1)The unconfined compressive strength of cement-bentonite anti-seepage wall has a double exponential function relationship with water-cement ratio and water-bentonite ratio;the unconfined compressive strength at 28 days is 6.8% ~169.1% higher than that at 60days;When the water-cement ratio is constant,the unconfined compressive strength of the consolidated body increases first and then decreases with the decrease of the water-bentonite ratio,and reaches its peak when the water-bentonite ratio is about 4.5;Under a certain water-bentonite ratio,the reduction of water-cement ratio can improve the deformation modulus,sensitivity and cohesion of the consolidated body,and the deformation modulus has a good linear relationship with the unconfined compressive strength.(2)The permeability coefficient of cement-bentonite anti-seepage wall has a double exponential function relationship with water-cement ratio and water-bentonite ratio;in the permeability test,under 100 kPa consolidation pressure,the permeability coefficient obtained by one-dimensional consolidation test and three-axis permeability test is close to each other,and the ratio is between 1 and 1.6 times;The results of con-ventional variable head test are10~30 times of that of triaxial permeability test under consolidation pressure of 100kPa;when the water-bentonite ratio is constant,the permeability coefficient of the mud consolidated body decreases as the water-cement ratio decreases.;the mean values of the permeability coefficient ratios at 60 d and 28 d in triaxial permeability test,one-dimensional consolidation test and variable water head test were 0.79,0.81 and 0.77,respectively,and the permeability coefficient at 28 d and 60 d presented a linear relationship.(3)The optimal mixture ratio that can meet the engineering needs is selected and used for the model box test.The test results show that the unconfined compressive strength and impermeability of the cut-off wall in the model box are improved.The unconfined compressive strength and impermeability of the cutoff wall are improved when the cement bentonite slurry is mixed with silty clay with a water-soil ratio of 10~50.