Experimental Study On Sludge Solidification In A Landfill Site In Shenzhen

With the relative shortage of urban land in China,the rational use of sludge landfills must be solved.Due to the characteristics of high moisture content in the sludge,poor permeability,strong flocculation,and high combined water content,the conventional vacuum preloading method,surcharge preloading method and other curing methods are too inefficient to meet engineering requirements.In this paper,the sludge in a sludge-filling zone in Shenzhen was used as the object,and the indoor test was conducted by electroosmosis and in-situ solidification methods.The curing laws of the two curing methods were explored,and a systematic and quantitative comparison of the two curing methods was conducted.Provide reference and reference for the actual project.The main work and research results are as follows:(1)An indoor electro-osmotic drainage consolidation test was designed.Through the various indexes in the experiment and the unconfined compressive strength of the soil before and after the experiment,the water content changes.It studies the effect of load and drainage on the electro-osmotic drainage test and the electro-osmotic drainage consolidation rule of different electrode spacing under electric potential gradient.The effect of the load,drainage pattern and electrode spacing on the electro-osmotic test was evaluated by means of the strength of solidified sludge,moisture content and electro-osmosis rate,electro-osmosis efficiency and economy.The experimental results show that reasonable drainage pattern,stacking and shortening of electrode spacing can increase the strength of solidified sludge by 1.1 times,1.6 times,2.8 times,and reduce the moisture content by 19.8%,25.5%,55.6%?At the same time,the soil interface resistance grows faster than the soil resistance,and at the end of the electro-osmosis it can reach more than three times than the soil resistance(2)In mass stabilization test,The solidification rules of cement,gypsum and dry soil were studied by parallel experiment and orthogonal experiment.In parallel experiments,the amount of cement,the amount of gypsum,the amount of dry soil and the age were used as independent variables,the change rule of strength,sensitivity and moisture content of solidified soil was studied by controlled variable method.In the orthogonal experiment,the influence degree of cement content,gypsum content and dry soil content on strength and moisture content was determined by designing proper orthogonal test.At the same time,the optimal scheme is obtained by combining the rules obtained in parallel experiments: Cement content accounts for 8% of sludge quality,Gypsum content is 30% of cement content,The amount of dry soil is four times that of cement.Using this scheme,the sludge can be maintained for 28 days,which can increase the strength by 9.9 times and reduce the moisture content by 57.1%(3)The strength of solidified sludge can meet the standard requirement in the optimal solution of electro-osmosis test and in mass stabilization test.But mass stabilization has better curing effect,and its strength is about 2.3 times of the strength of the electro-osmosis test.However,the treatment speed of electro-osmosis is faster than that of mass stabilization and the mass stabilization is about 9-14 times of the electro-osmotic method.