Aiming at the extremely low bearing capacity of hydraulic fill foundation, the twice vacuum pre-loading reinforcing method, firstly preloading cushion layer without sand and then preloading cushion layer containing sand, was adopted to strength-en the silt foundation. By in-situ test, the vacuum degree and foundation settlement in the two preloading process were meas-ured. The results showed that the first preloading could effectively solve the problem of unable-to -construction caused by the extremely low foundation bearing capacity;the second preloading could improve transmission effect of vacuum pressure and fur-ther upgrade the foundation bearing capacity.%针对吹填淤泥地基承载力几乎为零的特点，采用二次(一次无砂垫层，二次有砂垫层)真空预压法对大面积吹填淤泥进行处理。通过现场试验，分别对两次真空预压中的真空度、地基沉降等进行了观测。结果表明，对超软淤泥地基采用无砂垫层进行一次预压处理，能有效解决因地基承载力过低而无法施工的问题；进而采用有砂垫层的二次预压提高了真空压力的传递效果，可以进一步提高地基承载力。
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