Study On Compressibility And Settlement Of Landfill For Municipal Solid Waste

Municipal Solid Waste (MSW) is rubbish that generated by people in the activity of daily life or service for the everyday life. Recent years, the management for MSW is the hot topic of geo-environmental engineering. It had been studied about the subject in the half of sixty years of twenty centuries, but in ninety years of twenty centuries in China by the geo-technical engineering method.In this paper, the basic geo-parameters such as natural density, specific gravity, moisture content, porosity ratio, the content of organic substance, cohesive force, internal friction angle and its regularity of distribution has been studied by domestic traditional geo-apparatus. The results can be draw as (1) The natural density is range 0.9-1.2t/m~3. (2) The moisture content is range 40%-100%. (3) The specific gravity is range 2.0-2.4, and its value is dependence of the content of organic substance.(4) The content of organic substance is range 20%-40%. (5)The relationship between porosity ratio and the depth is linear. The relationship between self-weight stress and porosity ratio is been studied based on the relationship between natural density and the depth. The range of compression modulus and compression ratio is been obtained. The between stress and strain is belong to the hyperbolic model by the results of unconsolidated-undrained and consolidated-undrained triaxial test.The big-high pressure MSW compression apparatus (BHMSW-2035) has been developed. The apparatus has the structure of worm and gear. The maximum stroke is 30cm. The maximum bear pressure is 1600kPa. The height of the compression barrel is 35cm. The inner diameter is 19cm. It has two steel bands around the surface of the barrel. It has four drain holes in the bottom of the barrel, then the water(generated by MSW) can be drain out.The compressibility and its regularity had been studied for MSW by the compression apparatus. The results can be draw as: (1) The cumulative decrement of MSW grows by the time elapsed, but The primary compression and secondcompression of the MSW can be not separated. ? The decrement of first 24h is about 90% of the total decrement of three months. ?The steady standard of 24hours is developed. @The relationship between t and tie is linear, and the relationship between t and e is belong to hyperbolic model. ?If the compression time is to be infinitely large quantity, then the compression strain is to be ultimate compression strain. ?The ultimate compression strain can be instead of the compression strain of 24hours. ?If the pressure is over 50kPa, then the relationship between ultimate compression strain and logarithm pressure is linear. ?The mechanical compression mechanism of MSW has been further explanted based on the results of the compression test. The steady-state standard of 24h has been developed. The method of the compression test is been suggested for MSW.The parameters of Duncan-Chang model has been studied based on the results of the large-scale triaxial test. The simplified calculating method of Duncan-Chang model has been put out by the results of the axial direction compression test and shearing test. The relationship between the model parameter K and initial void ratio e0 is linear. The model parameter n is about 1.05. The model parameter G is range 0.3-0.4. The model parameter F is range 0-0.1, and can be draw as linear.The law of the organic matter degradation of MSW has been studied by soil mechanics theory and laboratory and in-situ testing consequence. The results can be draw as: ? The relationship between the content of organic matter and time is e exponent reduced. The degradation parameter is 0.095/yr. ? Based on the dry density is not changed in the process of organic matter degradation of MS W, the new settlement model of organic matter degradation is developed by applied the primary theory of soil mechanics. The model is only relevant of content of organic matter. ? The design method of storage capacity of MSW landfill is developed by considering the organic matter degradation.The calculating method of one-dimension mechanics compression has been presented according to the reclaiming features of MSW. The law of two-dimension mechanical compression has been studied for MSW by the finite element program worked out by professor Lin dao-sheng about Duncan-Chang model. The predict method of capacity of MSW landfill has been presented by compare and analysis the results of the one-dimension and two-dimension.