During the process of groundwater source heat pump recharge

microbial blockage represented by Escherichia coli is one of the important causes of ground subsidence

and studying its blockage characteristics is of great practical significance. We studied the “sedimentation detachment” characteristics of Escherichia coli when the direction of seepage and fluid velocity changed using a self-developed sand layer clogging device. The experimental results showed that： 1） Escherichia coli blockage exhibited a saddle shape under three different flow rates

with concentration changes increasing first and then decreasing

and then decreasing again after a correction. Among them

the blockage of Escherichia coli at the throat has a certain degree of dependence

which affects the efficiency of reinjection; 2） After changing the direction of seepage and increasing the flow rate

the dynamic balance of “sedimentation detachment” of Escherichia coli is disrupted

and the concentration of Escherichia coli decreases. The Escherichia coli that originally deposited in the pores are driven to migrate by external forces. By monitoring the liquid sample at the outlet

it was found that there was a significant increase in concentration values. Based on engineering practice

if the method of backflushing is used to treat the wellbore blocked by Escherichia coli

excessive cleaning time may cause new blockages

which may not meet the requirements of thorough cleaning of the wellbore. Therefore

it is necessary to control the reasonable time of backflushing.