High-pressure jet grouting technology is an advanced technology that has been researched and applied in soft stratum anti-seepage in recent years. It has good water blocking effect (the wall wall permeability coefficient is only 10 -5 ～10 -7cm/s ) and the cost is low. It has the characteristics of strong adaptability, fast construction speed and easy operation. Warehouse gold mine using this technology successfully solved the problem of open-air stripping and mining operations were stripped of two problems Quaternary strata flood control sand and mud flows, access to significant economic benefits.
I. Geological overview of the deposit
The ore body and its vicinity are in the middle part of the fracture zone. The lithology is fault mud. Some of the fractured rocks in the upper and lower plates are 10~30m wide, the rock hardness is low, the fracture is developed, the fracture is loose, and the stability is very poor. It is easy to produce a collapse phenomenon.
The thickness of the Quaternary system covering the ore body is about 10m, loose and weak, and the engineering geological conditions are very poor. The weathering layer is below, the rock hardness is low, the weathering is strong, the stability is poor, and the phenomenon of Xiaopo is easy to occur.
The ore body is located in the lower part of the fracture, and the water-repellent layer of the fracture-breaking zone buried under the local erosion reference surface is well-separated and has a continuous distribution. The lower part of the fault zone contains small vein-like fissures and is the direct water-filling source of the deposit. The fissures of the upper and lower aquifers are relatively developed, but the scale is small, mostly compression-torque, and the water-conducting water-rich water is poor.
The shallow Quaternary system is rich in water and thin, distributed on and near the deposit, and is the direct water-filled rock layer of the pit.
Therefore, solving the Quaternary stratum water control is the key to the normal operation of open pit mining in Cangshang Gold Mine.
Second, high pressure jet grouting technology and its application
The use of high pressure jet grouting technology is one of the effective methods to solve the problem of soft formation anti-seepage. The main working principle of the process is: using high-pressure jet grouting of three mediums, spraying high-pressure water and compressed air simultaneously during the lifting process of the spray pipe, punching and stirring the formation, and injecting the slurry into the punching and stirring formation to form a mixed coagulation body. Under the powerful entrainment formed around the high-pressure jet, the cement slurry sent to the bottom of the pipe is wound into the punching zone in the direction of spraying, stirred, filled, and replaced, and the composition of the punched formation is improved to form the anti-seepage mortar. The body may also form a slurry solidified layer on the outer side. At the outside and at the end of the beam, although the formation cannot be punched, a compressive force is generated on the surrounding formation, so that the slurry penetrates along the pores to form an anti-seepage condensation layer.
The main processes of the construction are: measuring boreholes, wall drilling, lower jetting, pulping, spraying, lifting (orientation and oscillating), slurrying, and orifice recirculation (see Figure 1).
Figure 1 Schematic diagram of high pressure grouting equipment system
1—condensate; 2—sprinkler; 3—nozzle; 4—hole device; 5—Air Compressor;
6—high pressure water pump; 7—water; 8—lifting hoist steel rope; 9—bracket; 10—transport pump;
11—mixer; 12—water; 13—cement storage tank; 14—recycle pump; 15—return tank
(1) Main process parameters
High pressure water: pressure p≥35Mpa, displacement Q=75L/min; compressed air: pressure p=0.8Mpa, displacement Q=1.25m 3 /min; cement slurry; capacity>1.6kg/L, displacement Q=80L /min; lifting speed: fixed spray 10cm / min; pendulum spray 8cm / min; hole distance: fixed spray 2m, pendulum spray 1.8m;
Fixed spray: fold line type, the spray direction is 15° angle to the direction of the wall of the plate wall (see Figure 2); pendulum spray: (the thickness of the wall is increased in local sections to enhance the stability and compression resistance of the body) (See Figure 3), the swing angle is 30°, and the swing speed is 10°/s;
Figure 2 Schematic diagram of the direction of the fixed spray and the direction of the wall of the plate
Figure 3 Schematic diagram of the pendulum direction
The interval between the order hole and the second order hole: 3 to 6d;
Recycled recovery: 30% to 40%.
(2) Main construction process
1, jet grouting
High-pressure jet grouting construction is a continuous system operation, and all links should be coordinated and closely coordinated. Only when the process parameters of water and gas slurry reach the prescribed standards can construction work be carried out. First drill a sequence of holes, and then return to the drilled second sequence hole after the completion of the grouting. During the operation, the grouting is sprayed according to the design regulations, and the machine is lifted while swinging (spraying) or orientation (fixing spray). In order to increase the thickness of the wall during the fixed spraying, the personnel can operate the micro-swing. When jetting near the surface, first stop spraying for 1 to 2 minutes. The jet grouting tube is then raised out of the hole. In the process of jet grouting, if there is a fault, after the normal treatment, the nozzle should be inserted into the grouted section 0.5-1.0m deep, and then continue to be sprayed to ensure the continuous and complete wall.
2, rejuvenation
During the jet grouting operation, some of the sludge particles in the water, gas, slurry and punching and stirring formation in the hole are raised and emerged from the surface, flow into the returning pool, and filtered by the grit chamber. The pump recovers 30%~40% of the slurry and transports it back to the mixer for reuse to save cement. However, excessive recycling will affect the quality of the grouting wall.
3, recharge
Orifice static grouting is an important operation in the late stage of high pressure jet grouting. Before the grouting pipe stops spraying outside the lifting hole, the orifice is filled with a certain amount of slurry around the surface mud sand for static pressure grouting. As the high-injection slurry in the pores is hydrolyzed and consolidated, the orifice slurry continuously descends into the pores. Therefore, the orifice is manually refluxed once every hour for 1 hour, and each well is refilled 6-8 times until the orifice slurry no longer drops.
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