Experimental Study On Damage Rule Under Freezing-thawing Failure And Cretaceous Rock Formation Groutability

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, lithological soft, ordinary sinking method is hard to break through, freezing method combining face pregrouting or common construction is generally used.Part of the freezing method produce flow water phenomenon in shaft and ingate after freezing wall thawed, consequently,the wellbore construction period is long, water treatment cost is high.It is hard to use common grout injection for the most of the Jurassic and Cretaceous strata water is pore fissure water, porosity rock, and the effect of grouting waterproof permeability is poor, commonly used method that combining working face pregrouting construction is difficult to implement.Under the action of another due to freezing and thawing soft rock, the lack of physical and mechanical properties research, especially in soft rock, the lack of physical and mechanical parameters of frozen thawed, wellbore wall design of freezing method construction in western region lack of scientific nature.The problems above have become the influence for the western region of mine safety, scientific construction and technical problems needed to be resolved.According to the engineering problem, in the engineering background of XinZhuang coal mine wind shaft lining construction, on the basis of indoor test, we analyzed the coarse grained sandstone, medium grained sandstone, mudstone before freezing, frozen and thawed after the physical and mechanical properties changed, tested parameters such as pore size distribution, pore specific surface area, entrance for the coarse grained sandstone and medium grained sandstone before and after freezing and freeze-thaw action. Also conducted pore fissure sandstone under different grouting materials, groutability under grouting pressure.Disscusion on the water problem of the wall of freezing and and puts forward the reasonable suggestions on the wall back grouting. The main research conclusions are as follows:(1) Uniaxial compression test for coarse grain in sandstone and sandstone and mudstone int three kinds of condition: normal temperature and freezing(-30℃) and thawing. The experiment indicates that:(1)The effective displacement curve shape for three kinds of saturated rocks under three states is consistent. Each experienced four phases : compaction stage, elastic stage of growth, the plastic yield and destruction, which damage form is mainly within the rock tensile failure.(2)In these kinds of condition, rock strength has a different degree of change, frozen strength is the biggest, normal temperature strength is smaller, thawed strength is the minimum. The impact on the thick sandstone under uniaxial compressive strength after a freezing and thawing cycle is huge, on powder sand and mudstone is very small.(3)After a freezing and thawing cycle, the three kinds of rock elastic modulus are decreased, the level of different rocks decreases too.(4)Thick sandstone and mudstone of saturated water absorption is sensitive to a freezing and thawing cycle, its internal structure caused by the freezing and thawing damage, the powder sandstone saturated water absorption effect is not big, big influence on its internal structural damage.(2) Testing of thick sandstone and sandstone in the microstructure before and after freezing and thawing and sample surface microscopic scanning analysis indicates that: Saturated coarse sandstone and sandstone in a microstructure changed significantly before and after freezing and thawing, grit specific surface area and entrance has increased, but the average pore diameter decreased; medium grained sandstone specific surface area decreases and average pore diameter are increased, and the bibulous rate of two kinds of rock, size, porosity, increase rate is not the same.(3) Using the independent design and processing of rock permeability testing and grouting experiment device, superfine cement and two kinds of serum urea formaldehyde resin, through repeated grouting and the permeability of rock specimen after each grouting measurement and comparative analysis, we researched coarse grained sandstone under different grouting materials and groutability under grouting pressure. The experiment indicates that:(1)The initial time of urea-formaldehyde resin chemical grout decreases as the oxalic acid solution concentration increased and decrease rate reduced with oxalic acid solution concentration increased.(2)The permeability coefficient decreases with the increasing number of grouting, grouting effect.(3)Chemical grout can play a good role to the particle types which material can’t injection pore fissure sandstone.