The application of cement grouting pump in tunnel engineering is mainly reflected in advance pre-grouting, backfill grouting behind initial support, grouting behind secondary lining, tunnel water blocking grouting, and reinforcement of weak surrounding rock.
Cement Grouting Pump
Advance Pre-grouting:
1. Function: Before tunnel excavation, pre-grouting reinforcement of the stratum in front can effectively prevent unfavorable geological phenomena such as collapse and water gushing during tunnel excavation, and create safe and stable conditions for subsequent construction.
2. Operation process: First, according to geological survey data and design requirements, drill holes in the tunnel face to determine the location, depth and angle of the grouting holes. Generally speaking, the hole depth will be determined according to the range of the stratum to be reinforced, usually 3-5 meters outside the tunnel excavation contour line. Then, insert the grouting pipe into the borehole and connect the cement grouting pump and the grouting pipe. Start the cement grouting pump and inject cement slurry into the stratum according to the designed grouting pressure and grouting volume. During the grouting process, the changes in grouting pressure and grouting volume should be closely observed. When the pressure reaches the design value and the grouting volume gradually decreases, it can be considered that the grouting has achieved the expected effect.
Backfill grouting behind the initial support：
1. Function: After the initial support of the tunnel is completed, there may be some gaps between the shotcrete and the surrounding rock. These gaps can be filled by backfill grouting, so that the initial support and the surrounding rock are closely combined, jointly bear the surrounding rock pressure, and improve the stability of the support structure.
2. Operation process: During the initial support construction, grouting holes should be reserved on the surface of the shotcrete, generally one every 3-5 meters. After the shotcrete reaches a certain strength, the grouting pipe is inserted into the grouting hole and the cement grouting pump is connected for grouting. When grouting, start from the bottom of the tunnel and proceed from bottom to top to ensure that the slurry can fully fill the gap. When the slurry overflows from the adjacent grouting hole, it means that the part has been filled fully, and the grouting can be stopped and the next grouting hole can be operated.
Grouting behind the secondary lining:
1. Function: The secondary lining is an important part of the tunnel structure. Grouting behind the secondary lining can further fill the tiny gap between the lining and the initial support, improve the waterproof performance of the lining, prevent groundwater leakage, and also enhance the overall stability of the lining structure.
2. Operation process: During the construction of the secondary lining, grouting pipes should be pre-buried in the lining concrete. Generally, one pipe is set every 5-8 meters in the arch and side wall. When the secondary lining concrete reaches more than 70% of the design strength, grouting operations are started. Use a cement grouting pump to inject cement slurry or other suitable slurry into the back of the lining. The grouting pressure is generally controlled between 0.5-1.0MPa. During the grouting process, pay attention to the flow of the slurry and the changes in the lining surface to prevent problems such as slurry leakage or lining deformation.
Tunnel water blocking grouting:
1. Function: When the tunnel passes through a water-rich stratum or there is water leakage, water plugging grouting can effectively block the water flow channel, prevent groundwater from entering the tunnel, and ensure the normal use of the tunnel and structural safety.
2. Operation process: First, conduct a detailed investigation of the tunnel water leakage to determine the location, water volume and water flow direction of the leakage point. Then, drill holes around the leakage point. The drilling depth should be determined according to the leakage situation and stratum conditions. Generally, it should go deep into the leakage channel or aquifer. After inserting the grouting pipe into the borehole, use a cement grouting pump to inject slurry with good water plugging performance, such as cement-water glass double liquid slurry. When grouting, adjust the slurry mix ratio and grouting speed according to the leakage situation and the change of grouting pressure to ensure that the slurry can effectively plug the leakage channel.
Reinforcement of weak surrounding rock:
1. Function: For weak surrounding rock sections in tunnels, such as fault fracture zones, sandy soil formations, etc., cement grouting pump can inject cement slurry into the pores and cracks of the surrounding rock to cement the loose surrounding rock particles together, improve the strength and stability of the surrounding rock, and reduce deformation and settlement after tunnel excavation.
2. Operation process: According to the distribution range and characteristics of the weak surrounding rock, determine the grouting reinforcement plan, including the layout of grouting holes and the selection of grouting materials. Generally, the grouting holes are arranged in plum blossom or rectangular shapes, and the hole spacing is determined according to the surrounding rock conditions, usually 1-2 meters. After drilling with a drill, insert the grouting pipe and connect the cement grouting pump for grouting. During the grouting process, the grouting pressure and grouting volume should be adjusted in time according to the grouting absorption of the surrounding rock to ensure that the slurry can penetrate into the surrounding rock evenly and achieve a good reinforcement effect.