In Vietnam, the solution of designing and constructing deep foundation pits with the geology of sandy or clayey sand is very difficult, especially in case soil mix mud. In some deep foundation pits, the unreasonable treatment solution causes the bottom plug of the foundation pit to be pushed up to the foundation pit or not to pump a foundation pit dried. Solving those problems, this article introduces a particular case study, sealing the bottom of the foundation pit for no14 of Yen Xa drainage works with the Jet grouted bottom plug hydraulic barriers. To treat the soft soil layer, mix organic without breaking the upper soil layers, this solution uses Jet-grouting technology with a mixture of materials including cement, fly ash, blast furnace slag, lime in a reasonable proportion to ensure waterproof and not uplift the massive bottom plug hydraulic barriers when excavating soil in the pit. Results of calculation and acceptance after the foundation pit is completed show that this is a good solution, high reliability and can be applied to seal the bottom of the foundation pit in similar geological conditions.