| The base material of this study was municipal sludge,construction waste particles and other solid waste,which also had a small amount of Ca-bentonite.The study tried to develop a capillary barrier material covering the landfill.In order to evaluate the engineering performance of the covering material,the mechanical properties of the covering material were observed by volume shrinkage test,unconfined compressive strength test,consolidation test and triaxial compression test.The permeability and capillary effect of the covering material were analyzed by permeability test and SWCC test.SEM,laser particle size analyzer and T2 nuclear magnetic resonance analyzer were used to test the particle connection mode,microscopic particle size composition and pore structure of the covering material.By using indoor and outdoor rainfall model tests,the water seepage characteristics of capillary barrier system under different rainfall conditions were obtained.The following conclusions were reached:（1）A capillary barrier material was prepared,which was composed of municipal sludge（30%～45%）,construction waste particles（40%～70%）and Ca-bentonite（3%～9%）.After 15 days of indoor drying,the mass moisture content of the material is 0.4%～2.3%,the volume shrinkage is 0.36%～6.57%,and there is no big crack on the test block’s surface.The first influencing factor of volume shrinkage is municipal sludge content,the second is ca-bentonite.The material ratio of minimum volume shrinkage is municipal sludge:construction waste:ca-bentonite=5:10:1.The proportion of small pores in the pore distribution of the material is more than 90%,the surface microstructure is compact,and the gaps between the construction waste particles are filled with compactness.（2）The unconfined compressive strength,consolidation coefficient and shear strength parameters（c,φ）of the composite were observed.The unconfined compressive strength is158.57～371.15 k Pa,the consolidation coefficient is 9.738×10-6～1.176×10-5 at 100～200k Pa,the cohesion is 10～150 k Pa,and the internal friction angle is 11.86～36.87°.（3）The permeability coefficient and capillary effect were obtained.The saturated permeability coefficient of the material is 2.06×10-6～1.41×10-4.There is obvious hydraulic hysteresis in the SWCC of the material,which is in accordance with Van Genuchten model,the model parameters are obtained,too.The capillary performance of the material is better than the sand.Ca-bentonite can effectively reduce the saturated permeability of the material and improve its capillary effect.（4）The water seepage characteristics of the capillary barrier system was tested.After4 hours of rainstorm and heavy rain,the upper 50cm thick capillary layer near the bottom of the slope was broken by rain water,and the middle 10cm building waste drainage layer played a good drainage effect,the lower 30cm thick capillary layer has not been broken by rain.The experiment result shows that the capillary barrier system has a strong ability to resist the impact of heavy rainfall. |
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