WATER LEAKAGE REPAIR TECHNOLOGY FOR RAIL TUNNEL IN OPERATION
The Fastest And Most Effective Grouting Method For Seepage-Proofing Tunnels
1. Project Background
Water Leakage Repair : After a period of operation of the rail tunnel, water leakage occurred in some places.In order to avoid tunnel displacement caused by an increase of water flow and the serious evacuation of the outer ground stratum, emergency suppression of the water outflow was carried out by deployment of sandbags.Operations units, contractors, design units and experts in the engineering community jointly developed a project for water stop and reinforcement.
After a period of operation of the rail tunnel, water leakage occurred in some places. In order to avoid tunnel displacement caused by an increase of water flow and the serious evacuation of the outer ground stratum, emergency suppression of the water outflow was carried out by deployment of sandbags.Operations units, contractors, design units and experts in the engineering community jointly developed a project for water stop and reinforcement.
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2. Solution
Water inflow and sand emission was a continuing situation, but because the operation of rail transit could not be interrupted, the solution was limited to rush repairs only during the time period outside vehicle operation and without affecting the normal safety inspection.
The initial set up was, daily work time of about 1am to 4:30 am. Under the strict daily operation time limit, the supporting emergency repair plan developed by the professional team was divided into two categories:
(1) emergency resin leakage grouting, using light equipment and small trolley transportation. During the allowable working hours each day, enter the tunnel from the nearest station and arrive at the water leakage site at the fastest speed for leak stop treatment.
(2) fill scoured disturbed formations and block up underground water channels. Adopt a design of long-term quick-setting cement grout with water stop cistern and protective cover. Per the design goal, grouting can be stopped at any time and injection can be repeated at any time.
All equipment and materials are placed on the maintenance trolley of the railway company. During the allowable working time each day, travel was to be from the nearest dispatching station to the water leakage site for grout injection treatment.
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3. Works Design
The maintenance time of rail tunnels is limited, and the leakage points occurred are mostly concentrated in specific section blocks.
The main objectives of the construction design are:
(1) emergency plugging of water inrush
(2) permanent water stop
(3) fill the hollowed out and disturbed strata
(4) Reserve opening for future emergency repair grouting
(5) Structural repair and restoration.
Because deformation of the tunnel was related to the safety of the overall operation, and with the premise of ensuring optimum repair, a low-pressure grouting design was adopted.
After evaluation, it was decided to adopt the following works design:
(1) Use PU expansion pulp material (IP Series) for 45-degree oblique borehole grouting to seal the seepage channel at the water outflow point or crack.
(2) Use quick-setting PU non-expanding rigid resin grout (Tipor Series) for permanent blocking and repair of cracks and water seepage channels.
(3) After installation of lining or ring sheet with water stop valve, reverse-stage injection of durable quick-setting LW grout to be used to fill voids.
(4) Installation of a permanent protective cover on each grouting borehole which does not affect rail travel, and which is convenient for emergency grouting at the same location in the future.
(5) The use of high-quality resin mortar for lining surface restoration and structural repair.The location and number of grouting holes are designed.
The ground-penetrating radar detection results are matched with the water outlet and the thickness of the lining. The spacing is not greater than the thickness of the lining.
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4. Works Process
In the early stage of muddy water inrush into the tunnel first occurred, the maintenance unit used stacked sand bags to reduce the scouring phenomenon, and the location of the water outlet point was clear.
When the emergency repair work was being carried out, ground penetrating radar was first used to determine the possible hollowing out on the exterior of the lining (ring), then slanted micro-drill holes were used around the water outlet to inject expansion resin and the non-expansion rigid resin.
After the water leakage condition was alleviated, with the water outlet as the center and using the ground penetrating radar detection results, reverse grouting was performed from bottom to top to fill and reinforce the hollowed and disturbed strata.The daily construction schedule was based on the principle that the single-hole overall grouting procedure could be completed on the same day.
In the case of encountering stratum absorbing/requiring a large amount of grout, but insufficient operating time, at end of work time the water tank must be turned off and protective cover installed. When grouting was continued the next day, the already set grout material had be drilled through, and reverse grouting was performed again to ensure that the holes were completely filled.
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5. Results
Through the injection of expanding resin and non-expanding rigid resin grout, the water discharge point inrush gradually stopped.Then durable LW grout was used to fill the lining behind the hollowed out, disturbed area and the groundwater passage formed earlier.
After confirming the completion of the execution target through ground penetrating radar and water penetration tests, resin mortar was used to repair the structure and install a maintenance hole protection cover.This successfully accomplished the rail tunnel repair work.
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Water Leakage Repair Technology For Rail Tunnel In Operation
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