Poly[(glycidyl methacrylate)-co-(glycerol monomethacrylate)]-grafted magnetic microspheres were prepared by graft random copolymerization via ATRP from polymer microspheres with dispersed Fe(3)O(4) nanoparticles. Penicillin G acylase (PGA) was immobilized onto the polymer brush-grafted magnetic microspheres. The immobilized PGA prepared with initial glycidyl methacrylate/glycerol monomethacrylate ratios of 40/60 to 60/40 possessed higher catalytic activity than that prepared with higher proportions of glycidyl methacrylate in the initial monomer mixture. The immobilized PGA showed high thermal stability and enhanced tolerability to the pH variance.

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Drift-sand layer is a common weak stratum in mine construction. e construction of the shaft passing over the drift-sand layer is very difficult. Traditional construction method faces many problems such as long construction period, high construction cost, poor working environment, and uncontrollability of the support effect. In view of the loose and fragile rock mass with great deformation of sinking and driving engineering penetrating drift-sand layers in coal mine, the reaction mechanism and shortcomings of conventional chemical grouting materials were analyzed. New-type polymer grouting materials were prepared with catalysts and vinyl epoxy resin, which was made from epoxy resin. A comprehensive chemical grouting construction technology was proposed, which comprises initiative closing, concentrated bypass flow, water plugging priority, and secondary sand curing for the inclined shaft passing over the drift-sand layer. Results show that new-type polymer sand-cured materials have lower viscosity, better grout ability, and fire resistance, and the solidified material has stronger bonding strength and better deformation resistance compared with traditional chemical grouting materials.e engineering application effect is very prominent in controlling water burst and leakage at the drift-sand layer; thus the on-site comprehensive construction progress and safety are guaranteed.

The back-filling body in the gob-side entry retaining is subject to continuous disturbance due to repeated mining. In this study, uniaxial and cyclical loading tests of back-filling concrete samples were carried out under laboratory conditions to study damage evolution characteristics with respect to microscopic hydration, deformation properties, and energy evolution. The results showed that, due to the difference in the gradation of coarse and fine aggregates, the cemented structure was relatively loose, and the primary failure modes under cyclical loading were tensile and shearing failure, which significantly decreased its strength. With an increasing number of loadings, a hysteresis loop appeared for the axial strain, and the area showed a pattern of decrease–stabilization–increase. This trend, to a certain extent, reflected the evolution of the cracks in the back-filling concrete samples. The axial, radial, and volumetric plastic strain curves of the back-filling concrete samples showed a “U” shape. The plastic strain changed in three stages, i.e., a rapid decrease, stabilization, and a rapid increase. A damage parameter was defined according to the plastic strain increment to accurately characterize the staged failure of the samples. The plastic strain and energy dissipation of the samples were precursors to sample failure. Prior to the failure of the back-filling samples, the amount and speed of change of both the plastic strain and energy parameters increased significantly. Understanding the characteristics of plastic strain, damage evolution, and energy dissipation rate of the back-filling samples are of great reference value for realizing real-time monitoring of back-filling concrete in the gob-side entry retaining and providing early warning of failure.