Abstract
Obtaining the optimal gradation of aggregate particles is beneficial for improving the strength of cemented paste backfill (CPB). Consequently, the uniaxial compression tests with acoustic emission (AE) monitoring were performed on CPB, for which the aggregate particles satisfied the Talbot grading theory. The effects of the Talbot indices of aggregate particles and types and contents of cementing materials on the mechanical properties of CPB were analyzed. The AE characteristics and stress-strain behaviors of CPB were discussed. The results show that the specific Talbot index reflected the optimal strength and deformation properties of CPB is 0.45, and the maximum UCS is 7.6 MPa. The mechanical properties of CPB also can be optimized by changing the type of cementing material and increasing the content of cementing material. The effects of the Talbot indices of aggregate particles and types and contents of cementing materials on the crack damages reflected by the AE signals of CPB are mainly observed in the oa stage and ab stage during the loading process.
Highlights
Filling mining is a new technology which uses waste rocks, tailings, construction wastes, and other waste solid materials to crush, screen, bond, and fill in goaf [1, 2]. e advantages of this technology are as follows: controlling the rock movement, protecting the aquifer, and reducing the risks such as seepage disaster and rock burst [3,4,5,6].erefore, it is important to study the mechanical properties of cemented paste backfill (CPB) to reduce the surface subsidence and overlying strata failure [7]
To analyze the in uences of the Talbot indices of aggregate particles and types and contents of cementing materials on the mechanical properties of CPB, the reproducibility of CPB specimens should rst be discussed. e uniaxial compression tests were performed on four specimens with the same proportion (n 0.4, φ 0.15, cemented by m 100 g gypsum), the uniaxial compressive strengths (UCS) are 7.31, 7.49, 7.56 and 7.63 MPa, the average is approximately 7.50 MPa, and the coe cient of variation is only 1.83%. e peak strain ε1c is 18.19, 17.39, 19.67, and 21.40 × 10−3, respectively; the average is about 19.16 × 10−3; and the coe cient of variation is approximately 9.21%
To discuss the mechanical and acoustic emission (AE) characteristics of CPB, the stress-strain behavior should rst be analyzed. e typical axial stress-axial strain curve can be divided into ve stages, as shown in Figure 2 [37,38,39]. (1) e oa stage of pore compaction shows a concave stress-strain curve, (2) the ab stage of elastic deformation shows a linear relationship between stress and strain, (3) the bc stage of localized deformation shows a convex stress-strain curve, (4) the cd stage of strain softening shows the major load framework of CPB specimen being destroyed, and (5) the de stage of residual strength shows that the specimen can load a small axial stress depending on the unbroken bonding elements among the rock particles
Summary
Obtaining the optimal gradation of aggregate particles is beneficial for improving the strength of cemented paste backfill (CPB). The uniaxial compression tests with acoustic emission (AE) monitoring were performed on CPB, for which the aggregate particles satisfied the Talbot grading theory. E effects of the Talbot indices of aggregate particles and types and contents of cementing materials on the mechanical properties of CPB were analyzed. E results show that the specific Talbot index reflected the optimal strength and deformation properties of CPB is 0.45, and the maximum UCS is 7.6 MPa. e mechanical properties of CPB can be optimized by changing the type of cementing material and increasing the content of cementing material. E effects of the Talbot indices of aggregate particles and types and contents of cementing materials on the crack damages reflected by the AE signals of CPB are mainly observed in the oa stage and ab stage during the loading process The uniaxial compression tests with acoustic emission (AE) monitoring were performed on CPB, for which the aggregate particles satisfied the Talbot grading theory. e effects of the Talbot indices of aggregate particles and types and contents of cementing materials on the mechanical properties of CPB were analyzed. e AE characteristics and stress-strain behaviors of CPB were discussed. e results show that the specific Talbot index reflected the optimal strength and deformation properties of CPB is 0.45, and the maximum UCS is 7.6 MPa. e mechanical properties of CPB can be optimized by changing the type of cementing material and increasing the content of cementing material. e effects of the Talbot indices of aggregate particles and types and contents of cementing materials on the crack damages reflected by the AE signals of CPB are mainly observed in the oa stage and ab stage during the loading process
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