【Daily Discussion】Utilities - Civil Engineering - 20210327

Error analysis: The functions of slurry during hole formation are to protect the wall, carry away debris, cool, and lubricate; among these, the function of protecting the wall is the most important. Mud has a certain density; if the level of the mud in the hole is above the groundwater level by a certain amount, a certain hydrostatic pressure is generated within the hole. This pressure acts as a kind of liquid support that helps to stabilize the soil walls and prevent the hole from collapsing. Furthermore, the mud can also fill and compact the voids in different soil layers within the borehole, forming a dense layer with low water permeability. This prevents water from leaking out of the inner walls of the borehole and helps maintain a certain water pressure inside it, thereby contributing to the stability of the borehole walls. The mud also has high viscosity; by circulating it, the soil and rock debris resulting from cutting can be suspended and carried out of the hole along with the mud, thus serving to transport the debris and remove soil. At the same time, since the mud is used as a flushing fluid, it cools and lubricates the drill bit, reducing its wear.