The selection of post grouting materials can refer to the following table.
The grouting process flow is shown in the following figure: (4) The grouting pressure should not be too high, as long as it can overcome the pipe resistance and the resistance in the backfill stone layer, because the high pressure is easy to cause lining deformation and cause engineering accidents.
1.3 The consolidated mud is developed in the cracks of surrounding rock, with serious water seepage and gushing.
2.
After the initial setting of the mortar, the grouting pipe shall be removed, and the grouting hole shall be filled and tamped with high-strength cement mortar-.
Due to the long-term leakage of water carrying a large amount of sediment, a cavity is formed behind the shaft wall, stone or brick shaft, and the mortar joint is not dense and the leakage is serious; If mud is used to reduce resistance behind the sinking shaft wall, backfill grouting is also required to replace the mud, consolidate the shaft wall, and restore the inherent force of soil on the sinking shaft wall; The over excavated holes of tunnels and tunnels, the uncompacted holes backfilled with block stones, the collapsed holes of broken surrounding rocks, or the cavities formed by the uncompacted, collapsed and long-term seepage water carrying a large amount of sediment shall be backfilled and grouted.
The slurry mix ratio and the water cement ratio of cement slurry are 3 ∶ 1 ～ 2 ∶ 1 and 1 ∶ 1 respectively.
3.
When the grouting pressure rises steadily, reaches the design pressure, and remains stable for a period of time, when the grout is not injected or the amount of grout is reduced, the grouting can be stopped and the hole sealing operation can be carried out; After the pump is stopped, the orifice valve shall be closed immediately to seal the hole, and then the pipeline shall be removed and cleaned.
Backfilling grouting materials are cement mortar, Cement clay mortar can also be used to fill large pores, and clay mortar can be used for large-area backfill grouting.
The water cement ratio of cement slurry is 6 ∶ 1, 4 ∶ 1, 3 ∶ 1, 0.8 ∶ 1, etc.
In case of serious grout bleeding or bleeding, the pump shall be turned off and the pressure shall be stopped.
Generally, the maximum grouting pressure shall not exceed 0.6MPa when grouting pump is used.
Type and characteristics of post grouting 1.1 Water blocking grouting After tunnel excavation, although the surrounding rock has been pre grouted, some parts may still leak water due to the impact of excavation, blasting and other vibrations, although the amount of water is small, if not treated, it will affect the lining quality and affect the continued construction.
(5) Key points of grouting construction Before grouting, clean the grouting hole, install the grouting pipe to ensure its smoothness, and conduct water pressure test if necessary; Grouting must be carried out continuously, otherwise it will cause precipitation of waterproof mortar, block the pipeline and affect the grouting effect; Grouting shall be carried out from the low to the high, and from the water free to the water free, so as to avoid the dilution and segregation of grout by water and achieve the effect of dense filling; During grouting, the grouting pressure must be strictly controlled to prevent the slurry from running out and the expansion of structural cracks, which may cause engineering accidents endangering the structure; When the soil layer is a compacted soil layer, the grouting that forms a waterproof layer or a dense structure outside the lining shall master the rule that the pressure stops and the low pressure slow grouting gradually increases the grouting pressure; In the process of grouting, if a small amount of grout escapes from the construction joints, concrete cracks, masonry joints of blocks or bricks, the quick setting mortar can be used to point the joints and stop the leakage before continuing grouting.
For cement clay, cement water glass double liquid grouting can be used in sections with developed rock fractures and large water leakage.
They are suitable for water leakage from small cracks caused by blasting vibration and leakage from concrete shrinkage cracks, temperature cracks, erosion cracks, etc.
After two or three days of grouting, the second grouting shall be carried out after a certain density effect is formed.
The water plugging grouting materials are superfine cement, cement water glass, acrylic cement and polyurethane acrylic cement grout, which are convenient to adjust the gelling time and have low viscosity.
Therefore, uneven hole arrangement can be adopted according to the damage of surrounding rock behind the shaft wall, the location and size of cavities, and the location and size of leakage water.
Cement mortar and water glass double liquid grout can be used to consolidate grouting material cement water glass double liquid grouting material cement mortar in places with large water leakage.
When grout flows out of the pipe, the grouting shall be stopped immediately.
If the problem cannot be solved through backfill grouting, consolidation grouting can be carried out.
Consolidation grouting is to inject grout after drilling the hole into the rock for 3~3.5m, consolidate the small cracks of surrounding rock, and reduce water leakage.
Generally, the method of air drill drilling and hand pump grouting is adopted for post grouting.
(3) Grouting equipment and process flow Backfilling grouting equipment include mixer, grouting pump, grouting pipe, rubber pipe, operation bench, etc.
Post grouting construction 3.1 Steps of backfill grouting construction (1) Grouting holes are arranged because the backfill grouting pressure is small, and the viscosity of grout used is relatively large, so it is required to densify the hole arrangement.
For tunnels in soil layer, cement clay mixed with accelerator can also be used for consolidation grouting.
The hole diameter is generally 42mm, and the hole depth is about 2m.
The applicable scope of grouting materials can be used for post grouting.
The stress on the shaft wall is relatively uniform, and the arrangement of grout holes has little influence on the structure.
The shaft is generally of circular structure.
(2) The embedded grouting pipe is mainly composed of inner pipe, outer pipe, grouting valve, return valve and grout stop plug, as shown in the figure below.
1.2 Backfill grouting Backfill grouting is applicable to the following situations: there are over excavated shafts that have not been backfilled and compacted.
Then, the steel pipe with a grout stop plug diameter of 25mm is used for grouting.
The volume ratio of cement paste to water glass is 1 ∶ 1 and 1 ∶ 0.8; The gel time is 5-10 minutes; Cement mortar can be used to inject in the sections where the cracks in the rock stratum are not very developed and there is less leakage.
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Due to small equipment, convenient movement, and no power supply, this method is suitable for underground engineering construction.
For the vertical shaft, inclined shaft or tunnel built with stone, cement mortar shall be plastered to prevent water leakage before grouting; When grouting in a certain grouting pipe, the adjacent pipes shall be opened to allow the groundwater outside the wall to flow out of the adjacent pipe, and the grouting shall be closely monitored.
