Decompression device for slurry pump of engineering investigation drilling machine

The engineering investigation drilling machine slurry pump pressure reducing device comprises a drilling mechanism, the bottom of the drilling mechanism is provided with a plurality of drill rods connected through a connecting mechanism, the bottom of each drill rod is provided with a drill bit fixedly connected with the drill rod, and the periphery of each drill bit is provided with a first annular pipe detachably connected with the drill bit; the surface of the drill bit is provided with a plurality of first channels, the first channels extend to the top of the drill rod, the tops of the first channels are provided with slurry pumps communicated with the first channels, and the drilling device further comprises a fixing mechanism used for being fixed to the ground. The device can ensure that the pressure in the hole always adapts to and keeps balance with the hole wall side pressure generated by continuous increase of the drilling depth, the hole wall is kept complete and does not collapse, the device can b