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The single grouting method and grouting material can not achieve an ideal grouting effect under the complex geological conditions of deep roadway surrounding rock. In order to solve this problem, a composite grouting reinforcement technology for deep roadway surrounding rock is proposed. Taking the 3210 isolated island working face of a mine in Shanxi Province as an example, this paper expounds on the principle and application of the composite grouting reinforcement technology. Firstly, combined with the geomechanical test results of the field test area and the physical and mechanical parameters of coal and rock mass, the range of each cracked zone of 3210 return air roadway is calculated. Secondly, based on the crack characteristics of surrounding rock zones, three-step grouting technology is proposed. The technology includes shallow low-pressure infiltration grouting, deep high-pressure cracking grouting and supplementary grouting. The depth of each borehole in the three-step grouting technology is determined according to the scope of each zone. Then, the corresponding grouting materials are selected according to the crack development degree and crack opening scale in each zone. The inorganic cement grouting materials should be used in high permeability zones. The ultra-fine cement grouting materials should be used in medium permeability zones. The polymer chemical grouting materials should be used for supplementary grouting in low permeability zones. Finally, according to the field grouting test, the grouting pressure parameters of different crack zones are determined. The grouting reinforcement effect of 3210 return air roadway is comprehensively judged by using three indexes. The three indexes include the anchoring force of grouting reinforcement rock mass, the uniaxial compressive strength of grouting reinforcement rock mass, and the integrity of surrounding rock mass. After adopting the composite grouting reinforcement technology, the anchoring force of the roadway side coal body is increased by 144%, reaching 230 kN. The uniaxial compressive strengths of the roof and roadway surrounding rock increase by 10.9% and 18.5% respectively, reaching 50.68 MPa and 23.37 MPa respectively. The wave velocity of the roadway side coal body increases by 15.2%, reaching 750 m/s. From the deformation rate and deformation amount of surrounding rock in grouted area and ungrouted area, the composite grouting reinforcement technology has achieved a good effect.

Corrosion and abnormal failure of rockbolts often occur in the mine water and complex environment.It is found that local corrosion such as pitting is usually the main origin of corrosion failure.Pitting process and mechanism in simulating corrosive mine water of four rockbolts were tested and analyzed with a comprehensive method including metallographic examination, electrochemical experiments and video microscope.The results showed that rockbolt steel was prone to pitting corrosion due to the inclusions.The pitting mechanism was as follows: The inclusions were preferentially dissolved, producing granular corrosion products and forming interface grooves.Local acidification in grooves accelerated the dissolution and exfoliation of matrix and inclusions, which produced etching pits.The acceleration effect of interface grooves on corrosion was verified by the comparison of polarization curves of different electrodes.

In view of problems of deep roadway with composite roof, such as easily roof falling, large deformation and difficult support, taking 53182 roadway of Chengzhuang Coal Mine of Jincheng Blue Flame Coal Industry Co., Ltd. as research object, deformation and failure characteristics of deep roadway with composite roof were analyzed. It is found that roof deformation is dominated by shallow separation layer, which mainly occurs at interface of different rock strata. Shear deformation of bolts in top corner and two sides of roof occurs mainly at coal-rock interface, and shear deformation of bolts in the middle of roof is relatively large at weakly cemented strata and interface between anchor section and free section. Roof strata experiences processes of original rock state during initial excavation of roadway, and stable state, critical instability state and instability state after roadway excavation. The numerical simulation results show that with the increase of bolt preload, plastic zone range and vertical displacement of roof decrease obviously, which indicate bolt has better inhibiting effect on roof separation and subsidence. High prestressed bolt plays an active support role and greatly improves self-bearing capacity of surrounding rock. Support countermeasures of deep roadway with composite roof with high prestressed long and short anchor cables combined with steel mesh and W steel strip were put forward, which could greatly improve support stiffness of composite roof, form constraints on roof subsidence and separation, and enhance overall stability of composite roof strata. The engineering practice shows that high prestressed support effectively controls separation and subsidence of composite roof. Shallow separation value is controlled within 30 mm, deep separation value is controlled within 10 mm, two sides displacement is controlled within 80 mm, and roof subsidence is controlled within 43 mm. The above values indicate stability and integrity of surrounding rock.

Stress of upper coal pillar is the force source of strong deformation of retaining roadway. For surrounding rock control of retaining roadway with serious deformation, traditional blasting pressure relief technology has some problems such as high safety risk, environment pollution and serious surrounding rock damage. Aiming at the above problems, pressure relief mechanism of directional hydraulic fracturing in retaining roadway was proposed, that is, through expansion of hydraulic fracture, weak structural surface is generated in roof rock, overall strength of the roof rock is reduced, and the weakened hard roof is timely broken and caved under action of mining stress, so as to reduce stress level of retaining roadway. Taking 4312 fully mechanized coal mining face of Changping Coal Mine of Shanxi Jincheng Anthracite Mining Group Co., Ltd. as test site, boreholes scheme and boreholes layout parameters of directional hydraulic fracturing were determined. The fracturing results show that transverse grooving depth is 5 mm and grooving effect is good. During fracturing step by step, pressure required for fracture expansion increases with increase of distance between fracturing site and borehole. Surface displacement and coal pillar stress of fractured and non-fractured sections of retaining roadway were monitored. The monitoring results show that deformation of retaining roadway is mainly caused by two side walls deformation, and the average displacements of two side walls and roof and floor of the fractured section are about 40.79% and 69.80% lower than those of the non-fractured section. Stress of coal pillar in the non-fractured section appears peak point when approaching working face, while stress of coal pillar in the fractured section appears peak point at about 200 m away from back of cut hole of working face, which indicates that directional hydraulic fracturing transfers stress peak position of upper coal pillar.

Compacted loess is a special collapsible unsaturated soil and is sensitive to hydraulic conditions. Understanding and modeling the coupled hydromechanical behavior of compacted loess during isotropic compression is essential for establishing a complete constitutive model for unsaturated soils, which is of significance for predicting the deformation of loess fills in engineering. In this research, a series of constant suction isotropic compression tests are conducted to study the behavior of compacted loess. The experimental results show that volume change and soil–water characteristics are mutually affected during compression and that the normal compression curves flatten out and shift downward with the decrease in suction. Based on the experimental observations, the normal compression surface is modified, and the loading–collapse yield curve is deduced for the compacted loess. An equation associated with the void ratio is used to describe the effect of the volume change on the soil–water characteristics. Furthermore, a coupled hydromechanical constitutive model for the compacted loess under isotropic compression conditions is proposed within the framework of the Barcelona basic model. Model predictions of the mechanical and hydraulic behaviors of the compacted loess for constant suction isotropic compression tests and wetting tests at constant net stresses are compared with experimental data to verify the performance and validation of the proposed model. The comparisons indicate that the proposed model can accurately reproduce the coupled hydromechanical behavior of the compacted loess under isotropic compression conditions. [ABSTRACT FROM AUTHOR]

Currently, the high -- quality fusion of SAR and optical images is a hot research topic. However, the significant radiation difference and weak gray correlation between SAR and optical images greatly reduce the fusion quality. In this regard, this study proposed a SAR and optical remote sensing image fusion algorithm that coupled non -- local self -- similarity and divergence. First, images were decomposed in the frequency domain. Then, the non -- local directional entropy and divergence were used as characteristic parameters to guide the fusion of low -- and high -- frequency components, respectively. Finally, the fusion components were reconstructed to obtain fusion images with clear structural features and rich spectral information. The comparative experiments verified the effectiveness of the proposed algorithm in fusing SAR with optical images and its superiority in maintaining structural features and reducing spectral distortion. [ABSTRACT FROM AUTHOR]