市政污泥真空预压模型试验研究

《城镇污水处理厂污泥处理处置技术规范》[1]执行前，市政污泥往往直接倾倒于填埋场形成污泥库，导致垃圾设计库容显著降低。为恢复填埋场库容，许多填埋场面临污泥库的原位加固处理。通过2组模型试验，探讨真空预压处理污泥的可行性。试验结果表明，真空预压后污泥含水率显著降低，强度提高至2~4 kPa；污泥排水固结系数随预压过程发展表现出非线性；排水板周围污泥含水率和渗透系数降低明显，阻碍离排水板较远处污泥排水固结，因此减少排水板间距可显著提高污泥处理效果；真空预压过程中污泥中孔压变化规律与常规淤泥质土有明显区别，特别是远离排水板的位置孔压消散幅度小，表明污泥中孔压消散规律不符合传统的太沙基固结理论；污泥真空预压过程中，间歇式通正气压会在处理初期阶段加快排水速率，但整体改善作用不明显；真空预压可作为污泥减量化的一种途径，如要满足后续堆载垃圾的要求，还需配合其他原位处理方法进一步提高强度。

Model test study of vacuum preloading on municipal sludge

Before technical guideline of sludge treatment and disposal for municipal wastewater treatment plant [1]was implemented, tons of sewage sludge was directly poured into sludge lagoon in landfill, which took up designed landfill capacity of municipal solid waste. In order to restore storage capacity of landfill, treatment of sludge lagoon was undertaken. To investigate the feasibility of using vacuum preloading technique on sludge, two model tests were conducted. The experimental results showed that after vacuum preloading water content of sludge decreased sharply and its shear strength increased to 2-4 kPa. The consolidation coefficient of sludge displayed a nonlinear behavior in preloading process. Permeability and water content of sludge around prefabricated vertical drain decreased quickly in early stage, hindering consolidation of sludge away from prefabricated vertical drain. Therefore reducing spacing of prefabricated vertical drain could enhance treatment effect significantly. Pore pressure dissipation of sludge in preloading was different from that in soft clay, especially of the sludge distant from prefabricated vertical drain, which may reveal that pore pressure dissipation in sludge could not be explained by consolidation theory of Terzaghi. In vacuum preloading of sludge, intermittent inlet of boosted air could accelerate drainage rate in early stage; but overall its improvement was limited. Vacuum preloading method can be used as a technique of sludge reduction; but for the requirements of subsequent filling of municipal solid waste on the sludge lagoon, other in situ ground improvement methods should be adopted further to increase its shear strength.