Abstract
A new soluble polymer foaming (PF) grouting material was developed by using hydrophilic amino resin as the base material and adding other cross-linking, foam, foam stabilizing, toughening, and coupling agents. The PF material exhibited low viscosity, excellent adhesion, and strong penetration. The grouting reinforcement effect of the proposed PF material on broken coal masses was investigated and compared with that of traditional superfine cement (SC) through simulation experiments. Results showed that after grouting, fractures, joints, and other failure planes inside raw coal were filled and bonded, and the mechanical strength of the grout-coal concretion improved relative to the residual strength of raw coal. The average uniaxial compressive strength of SC specimens was 6.16 MPa, whereas that of PF specimens was 10.85 MPa. Moreover, the PF specimens presented an obvious characteristic of plastic strengthening. Analyzing the reinforcement effect of the grouting materials on the basis of single structural plane theory revealed that at the critical state, the average σ3 value of SC specimens was 1.43 MPa, whereas that of PF specimens was 3.09 MPa. In addition, coordination between the lateral and axial deformations of the PF specimens during compression promoted the formation of a bearing structure that can adapt to deformation. This structure is crucial for the safe operation of coal mines.
Highlights
Fractures and joints develop in coal and rock masses under the action of extended geological evolution and engineering disturbance. e development of these fractures and joints results in the destruction of the integrity and continuity of coal and rock masses
Ordinary cement blocks grouting channels during grouting and hinders the achievement of the ideal reinforcement effect, given its long solidification time and low early strength, as well as its high content of inorganic particles with average particle sizes of 60∼100 μm [7, 8]. e application range of Advances in Civil Engineering ordinary cement can be extended by grinding cement into superfine particles with sizes of 5∼20 μm; the largescale application of superfine cement (SC) is hampered by its high reactivity, short storage period, and tendency to cake in moist environments [9, 10]. e use of organic grouting materials has expanded with their continuous development and improvement
Fracture evolution, extension, and connection are the root causes of coal destruction. These fractures and joints are the channels through which grouting materials can be injected to provide reinforcement
Summary
Fractures and joints develop in coal and rock masses under the action of extended geological evolution and engineering disturbance. e development of these fractures and joints results in the destruction of the integrity and continuity of coal and rock masses. Fractures and joints develop in coal and rock masses under the action of extended geological evolution and engineering disturbance. E development of these fractures and joints results in the destruction of the integrity and continuity of coal and rock masses. Polyurethane, a representative of organic materials, is produced by reacting polyester polyol with polyisocyanate It is widely used because of its short curing time and high foaming coefficient; its high foaming speed and viscosity prevent its full diffusion in strata [11,12,13]. Other organic materials, such as epoxy and phenolic resins, have high mechanical strength and strong thermal stability, they are insoluble in water and must be diluted with specific diluents before use; this requirement increases their cost [14,15,16]. E grouting reinforcement effects of the two materials on broken coal masses were compared, and the reinforcement mechanism of the PF material was analyzed from the perspectives of micromorphology and micromechanics. e results of this study are expected to provide a reference for the popularization and application of PF materials
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