增压法和加热法真空预压新工艺的机理和加固效果探讨

真空预压是一种应用广泛的软土地基处理工艺。针对增压法真空预压、加热法真空预压两种新工艺,结合现场试验及工程实例对其进行分析和探讨。结果表明,增压法真空预压在地基内充入高压气体不能改变土体的饱和状态,同时高压气体会降低真空预压的真空度并可能阻碍真空度沿塑料排水板向深层传递;增压法真空预压的加固效果存在较大差异,在实际工程施工前应做好试施工验证其加固效果;加热法真空预压法通过升高土体温度提高渗透系数、缩短固结时间,同时增大固结沉降量,尤其适用于低渗透性的软黏土或淤泥;针对加热法真空预压现场应用难题提出了新型加热型塑料排水板和闷晒式太阳能加热循环水等改进方法,分别较好地解决了加热塑料排水板的制作加工、加热成本高的难题。

Discussion on mechanism and treatment effect of new techniques of overpressure and thermal vacuum preloading

Vacuum preloading is a widely used soft soil foundation treatment technique.Aiming at two new processes including overpressure vacuum preloading and thermal consolidation vacuum preloading,the two new processes are analyzed and discussed based on field test and engineering cases.The results show that the high pressure gas filled into the foundation by overpressure vacuum preloading cannot change the soil saturation state,but may reduce vacuum degree and prevent vacuum degree from transferring to the deeper layer along the prefabricated vertical drains (PVD).The reinforcement effect of overpressure vacuum preloading is quite different,the trial construction should be done to verify the reinforcement effect before practical engineering application.The thermal consolidation vacuum preloading increases the soil temperature,which can improve the permeability coefficient,shorten the consolidation time and increase the consolidation settlement,so it is especially suitable for soft clay or sludge.Focusing on the difficulty in the field application of thermal vacuum preloading,the new advances such as new kind of thermal PVD and integral solar heater for circulating water are invented to solve manufacturing difficulty and high heating cost respectively.