1. water pump grouting method
water pump grouting method is the most commonly used method, which pumps cement slurry into the leaking or collapsed rock stratum through the drill pipe to achieve the purpose of blocking protection. This method is suitable for cement grouting with large grouting quantity and is not limited by drilling depth. It can also be used in the middle of the borehole as long as it is bridged. Pressurized perfusion can also be realized by this method. The water pump grouting method is simple in construction, without special equipment and tools, but it requires good fluidity and easy pumping of cement slurry. Figure 12-12 Schematic Diagram of Cement Grouting The operation process of water pump grouting method is: when plugging, when the drilling tool is lowered to a predetermined depth of about .3～.5m from the bottom of the hole, clean water is pumped first to check that the inside of the drill pipe is really unblocked, and then the prepared cement slurry can be pumped. Put the water pump shower head into the cement slurry bucket to pump the cement slurry. Regardless of plugging or protecting the wall, when starting the pump, the return pipe of the pump should be turned on first, and the clear water in the suction pipe and the pump should be discharged. After shotcreting, the tee joint should be opened to send the cement slurry into the hole. After the process of pumping slurry is finished, immediately put the shower head into the prepared slurry replacement bucket and start the pump to replace slurry. In order to make the backflow at the bottom of the hole uniform, the drilling tool can be rotated slowly when replacing slurry. The pressure of slurry displacement should be based on the water level in the hole and the principle of achieving the pressure balance of the liquid column in the hole. It can be estimated and calculated according to the following formula: (12-23), in which:-the water pressure required for slurry displacement, kg; L-drill string length, m; L-hole static water level from the orifice height, m; Q-internal product of drill pipe per meter, l; -ground pipeline and pump volume; K-water pressure coefficient, .9 for shallow holes and .95 for deep holes.
according to the above formula, when there is no water in the hole or the water level is very low, when the water pressure reaches the drill pipe on the machine (about 6 ~ 8l), the pump should be stopped, and then the drill pipe on the machine should be disassembled, and the cement slurry will continue to descend along the drill pipe by the pressure difference between the internal and external liquid columns of the drill pipe, and return out of the drill pipe from the bottom of the drilling tool until the internal and external pressures of the drill pipe reach a balance.
when the water level is very high or the water return hole, the water pressure is close to the internal volume of the drilling tool and the volume of the ground pipeline multiplied by the water pressure coefficient, which can ensure that the water does not press out of the bottom of the drilling tool. At this time, the height of the cement slurry outside the drill pipe will be higher than that of the drilling tool. When lifting the drill, it will flow back into the drill pipe or fill the space at the bottom of the hole, and the cement slurry will not be diluted.
after slurry replacement, the drilling tool can be lifted, and the drilling tool should be lifted off the cement surface for more than 1 ~ 15m (1 ~ 2 stands) before washing it. The drilling speed must be slow. If it is too fast, suction will easily occur and the grouting work will fail. In order to ensure the pressure balance in the hole, we should also consider recharging the hole with clean water.
after the drill pipe on the machine is unloaded, the pump should be started to clean the residual slurry in the water pump, high-pressure pipeline and drill pipe on the machine to ensure smooth circulation.
To sum up, the technical regulations that should be followed by the water pump grouting method are as follows:
(1) When plugging, stick to punching; When protecting the wall, insist on sweeping the hole to the end, ensure the removal of cuttings in the hole and check the smoothness of drilling tools.
(2) Run the drilling tool .3～.5m away from the bottom of the hole or at the bridge to reduce the dilution of cement slurry. Fig. 7-13 schematic diagram of cement grouting
(3) After the grouting process or grouting is completed, the drilling tool can be rotated but not lifted, and the drilling tool can be lifted only after the slurry is replaced.
(4) all the slurry should be poured at one time, and the pump should not be stopped halfway to prevent the slurry from being disconnected or diluted by water.
(5) Open the return pipe before pumping slurry, and the discharged clean water shall not be injected into the hole.
(6) The water level in the hole should be considered to accurately calculate the water pressure for slurry replacement.
(7) After slurry replacement and drilling, it is necessary to leave the cement surface for 1 ~ 15m before cleaning the drilling tools.
(8) The drilling speed should be slow, so as to prevent the suction effect and timely recharge clean water at the orifice.
(9) Reduce the water-cement ratio as much as possible, and use cement water reducer to ensure the good pumpability of the slurry.
(1) Insist on detecting the cement surface strength and reasonably determine the waiting time.
The water pump grouting method can also be used in the following special situations:
(1) Pressurized grouting method
In order to ensure that the cement slurry can better enter the blocked stratum, form sufficient seepage radius and effectively reinforce the rock on the hole wall, a sealing device can be adopted on the upper part of the orifice pipe, or a drilling packer can be added on the drill pipe to seal the upper part of the lost stratum, so that high pressure will be generated in the hole during grouting, forcing the cement slurry to enter the stratum.
(2) segmental grouting method
When encountering a thick fractured zone, such as a hard and brittle loose stratum, the incubating gravels with different sizes often encounter the phenomena of blockage, sticking or collapse after drilling, so the segmental grouting method can be adopted at this time.
(3) Filling grouting method
When the cracks are large or meet with small caves, it is best to put a certain amount of inert materials before grouting to play the role of blocking, bridging and filling. After putting into operation, run the drilling tool for extrusion, and then pour. This can not only reduce the loss, but also improve the plugging effect.
(4) mesh bag grouting method
When encountering a large cave, in order to reduce the loss of cement slurry, it is best to use mesh bag grouting to control the diffusion and loss range of cement slurry (Figure 12-13). Fig. 12-13 schematic diagram of mesh bag grouting cement slurry
1- drilling; 2- drill pipe; 3- positive and negative connectors; 4- cloth bag; 5- drill pipe with holes
; 6- Cave; 7- cement slurry; 8- blockage 2. Injector injection method
When plugging large cracks or caves, in order to reduce the loss of cement slurry, cement slurry with small water-cement ratio (.3 ~ .35) and high concentration or quick-acting mixed liquid is often used for injection. At this time, the water pump can't suck in and pump, so the perfusion method can be used. Sometimes this method can be used for timely treatment when the closed hole section is short, the amount of slurry is not much, or multiple layers of intermittent leakage are encountered during drilling. The advantage of this method is that it is not limited by hole depth, slurry performance is not limited by fluidity, and the slurry is diluted less, but it needs a special injector, and the requirements for grouting are quite strict.
There are many types of pourers. At present, most of them are hydraulic piston pourers. Its working principle is: when grouting, the cement slurry is put into the slurry container, and then the drill pipe for the pourer is lowered to the leakage layer. After starting the water pump, the pressure water enters the pourer through the drill pipe to push the cement slurry, and the upper piston opens the slurry discharge valve of the pourer, so that the cement slurry is squeezed out and enters the leakage layer. Figure 7-14 shows a hydraulic piston injector. It is simple in structure and convenient to operate. When working, under the action of water pressure, the cement slurry in the slurry holding pipe 4 is squeezed downward by the piston 6, the pin 9 is cut off, and the valve 8 is opened, so that the cement slurry can be discharged out of the pipe and enter the position to be blocked. Fig. 12-14: Piston Pounder
1- Gland; 2- Sliding joint; 3- drill pipe; 4- slurry tube;
5- water diversion joint; 6- piston; 7- connector; 8- Valve; 9- Pin At present, in order to increase the pouring amount, different sizes of core pipes are used as slurry holding pipes to manufacture simple core pipe pourers, which has achieved good technical and economic benefits.
3. orifice grouting method
when the hole is shallow, the crack is wide and the water level in the hole is very low, the cement slurry with high concentration can be poured directly from the orifice, and the potential energy generated by the liquid level difference between the orifice and the hole can be used to press the cement slurry into the blocked layer. In order to make the orifice perfusion smooth, small-sized casing can also be inserted into the orifice to the perfusion hole section, and then cement slurry can be poured from the casing, which can be lowered by its own weight.
4. Dry material throwing method
Pack the cement in plastic bags, send it into the hole alone or with the drilling tool, then stir it with the drilling tool, and use the water in the drilling hole to stir and tamp it, so that the slurry can enter the crack and stop the leakage.
5. Cement ball throwing method
Mix cement with a small amount of water to form cement balls or specially made cement balls with appropriate setting time and strength. After throwing them into the hole, run a drilling tool to impact and squeeze them into the leakage layer.