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Water level monitoring points are buried
Groundwater level monitoring should be carried out by means of setting a water level pipe in the borehole. The diving water level pipe should be set before the precipitation of the foundation pit, the bore diameter should not be less than 110mm, the diameter of the water level pipe should be 50~70mm, the spacing between monitoring points should be 20~50m, and the burial depth should be controlled 3~5m below the groundwater level. Above the filter section of the water level pipe, the bentonite ball should be sealed to the orifice, and the water level pipe mouth should be covered and protected to prevent surface water and debris from entering people.
Before the installation of the pressurized water level pipe, the depth of the pressure water layer must be found, and after the water level pipe is placed in the drill hole, the water level pipe filter head must be in the pressure water layer. The filter pipe section and the borehole wall should be filled with sand, effective water insulation measures should be taken between the measured aquifer and other aquifers, the above parts of the aquifer should be bentonite balls or grout sealing holes, and the water level pipe nozzle should be covered and protected. As shown in the following figure:
After the water level pipe is buried, the water level should be continuously observed day by day using a water level meter, and the stable value of at least 3 days should be taken as the initial value. The amount of change in the groundwater table is the difference between the monitored value and the initial value. When observing, attention should be paid to the distortion of observations caused by the obstruction of the water level pipe or the measured water level due to communication with other aquifers.
Water level measurement
Before precipitation begins, all precipitation wells, observations and unified time joint measurement of static water levels, unified number measurement of the reference water level. By measuring the level of the orifice elevation h, the probe is slowly lowered along the water level tube, when the probe touches the water surface, the electric water level meter buzzer sounds, then read the ruler reading ai, then the groundwater level elevation hi = h-ai, the difference between the groundwater level elevation and the last measured groundwater level elevation is the rise and fall change value of the water level.
Starting from precipitation, the observation interval of observation and hole is 30min, lh, 2h, 4h, 8h and 12h respectively, and then every 12h until the end of the precipitation project. During the observation process, the water level change curve with time and the water level change curve with the construction process are plotted according to the water level change value.