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This study focused on investigating the damage development mode and strength prediction model of layered cemented paste backfill (LCPB) using digital image correlation (DIC) and ultrasonic pulse velocity (UPV). The results indicated that the damage mode was associated with the cement-to-tailings (c/t) ratio and the height (h/H) ratio of the middle layer of LCPB. The damage mode of LCPB was mainly tensile damage for a small h/H ratio while increasing the h/H ratio to 0.8 resulted in LCPB exhibiting macroscopic shear damage. With the reduction of the c/t ratio, the damage area of LCPB gradually shifted from the upper layer to the middle layer. The UPV tended to decrease exponentially with both the decrease of the c/t ratio and the increase of the h/H ratio. Comparing the predicted and experimental values, the maximum error of the predicted values was only 0.299, and the value of the a20-index was 0.9792, indicating that the predictive model was reliable. The findings could provide guidance for the design of LCPB. [ABSTRACT FROM AUTHOR]

In order to investigate the influence of Linglong cementitious material on the consolidation of tailings under different conditions,a series of backfill blocks at different ratios,different densities and different curing ages are designed with ordinary Portland cement control and their uniaxial compressive strength is measured through strength test.Then the phase composition and the micro-morphology of the tailings backfill are discussed by such measuring and testing techniques as XRD and SEM.The results show that the hydration reaction of the cementitious material produces ettringite and C-S-H gel,and promotes the consolidation of the tailings backfill;the age and the ratio of cementitious material to tailings will affect the development of the content and morphology of ettringite and C-S-H gel in the hydration products,and the content of hydration products will increase with the increase of age and the ratio of cementitious material to tailings.The content of the products increases and overlaps to form a dense network structure,which is macroscopically expressed as an increase in strength;the mass concentration affects the pores in the test block,thereby affecting the strength.

To effectively control the underground goaf and realize the construction goal of no tailings, the stability analysis and treatment of the multi-stage left goaf group in Linglong mining area were carried out.Firstly, the stability of the roof was analyzed by using the fixed beam theory, the simply supported beam theory and the load transfer intersection line theory, and the stability of the pillar was analyzed according to the area bearing theory and pillar strength formula.Then, the distribution of the stress and displacement of surrounding rock in goaf were studied by using FLAC3D software.Finally, according to the theoretical analysis and numerical simulation results, the remaining space groups were divided into three grades of stability, relatively stability and instability, and the whole tailings cementation filling test was carried out in goaf G16, vein No.47, vein No.50 and vein No.47-1 abandoned roadway.The result of research shows that goaf G9, G17 and G26 are in stable state, while seventeen goafs such as G1, G2 and G3 are in a relatively stable state.Six goafs such as G6, G7 and G10 are in an instable state.The results of cemented filling test show that the backfill has good consolidation effect,and realize the underground safe disposal of tailings in mineral processing. It is useful to can design reasonable management plan according to the analysis result of goaf stability.

In order to study the stability analysis method and parameter optimization for the upward drift stope, several indexes representing the engineering quality of rock mass in mines were acquired by the survey of engineering geology, digital photographic, the ore-bearing rock mechanics experiments etc in Jiuzhanggou gold mine.The 3D digital measurement system(ShapeMetrix3D) is employed to survey and collect the digital information of the plane parameters of rockmass structures that including rock mass occurrence, joint spacing, joint set numbers, volume density of structural plane for 100 m stope at Jiuzhanggou gold mine.Based on the digital joint structure characteristics, the RMR system and Q-system are employed to analyze and classify the stability of stope rockmass, incorperating with drilling peep results and rock mechanics parameters.According to the acquired indexes, the current span of the testing stope is optimized by using the Mathews stability graph method.It is concluded that the span of the stope should be strictly controlled below 7.5 m in order to ensure the stability of stope.