Experimental Study On Freezing Shaft Water Burst Mechanism And Control Technology In Water-Abundant Bedrock

Currently, in the construction of northwest mines, most wellbore need to break through the thick rock formation of Jurassic and Cretaceous. In accord with a high water content and soft lithological rock property, ordinary sinking method is hard to break through, freezing sinking method is generally been used.Most of the freezing method will produce a flow water phenomenon inshaft and ingate after freezing sinking method, the consequence is a long period of wellbore construction and a high cost of water treatment.At present, most used water treatment is backfill grouting method. The effect of this treatment is not as expected, the safety in production is debased.Focusing on this issue, this paper developed an experimental study on cretaceous rock formation freezing shaft water spray and control technology, which has an important engineering application value and theoretical significance. According to the engineering problem, on the basis of indoor test and the engineering background of XinZhuang mining construction, this paper bring out the freezing and thawing effects of cretaceous soft rock microstructure and a physical simulation of shaft freezing water burst mechanism. And then discussed the changing law of soft rock, soft rock and concrete condensation penetrating properties with a simulation of wellbore specimen grouting permeability experiment. The main conclusion is as followed:(1)By testing the porosity data, we made the conclusuion that after a freezing and thawing, the coefficient of permeability of coarse, medium and fine sandstone in increased as 50.8%、25.5%、28.5%; after twice of freezing and thawing, the coefficient of permeability of coarse, medium and fine sandstone in increased as 134.9%、76.8%、64.2%. The scanning electron microscopy(sem) test indicates that after a freezing and thawing, the rock particles are loosed and departed, the pore is increased. After a twice freezing and thawing, pore fissure continue developed with a longer fracture and a well through pore. It means that after a freezing and thawing, the cretaceous soft rock porosity is increased, well through pore formed a watercourse.(2)To provide the basis of the microstructure analysis of freezing and thawing freeze-thaw cycle effect on the structure of the soft sandstone, we did a test of low-temperature nitrogen adsorption experiments before and after freezing and thawing with both thick sandstone, sandstone and fine sandstone.It indicates that after freezing and thawing cycle, thick sandstone pore volume increase is mainly by macro-porous increase; increment after a once freezing and thawing is 9.8% and 15.0% after a twice freezing and thawing. Medium sandstone pore volume increase is mainly by macro-porous increase and medium-porous increase; increment after a once freezing and thawing is 9.4% and 13.9% after a twice freezing and thawing. Fine sandstone pore volume increase is mainly by medium-porous increase; increment after a once freezing and thawing is 7.6% and 14.2% after a twice freezing and thawing.(3)This paper designed and processed a simulation shaft freezing experiment device, using indoor test verified the freeze-thaw cycle of rock and concrete wall interface, a watercourse formed between the rock and concrete interface. The result is rock and concrete combining water penetration ability is enhanced.(4)Used three kinds of serum urea formaldehyde resin, ordinary portland cement and superfine cement to simulate the re-grouting of freezing and thawing wellbore simulator. By measuring the permeability coefficient of rock specimens before and after grouting, we studied the water treatment effect of soft rock and soft rock and concrete combination in different grouting material and grouting pressure.The result is: The permeability coefficient decreased with the increase of grouting time; for the same kind of slurry permeability coefficient slow down with the increase of grouting time; for the particle type cement, the way to improve grout injectablity is to increase the water cement ratio and grouting pressure; superfine cement grout injection is better than portland cement. The best way of water treatment is the chemical grouting, chemical grout can be injected into the pore fissure which water grouting can not do.