Abstract
Lean cemented sand and gravel (LCSG) materials are subjected to unloading‐loading when an LCSG dam is opened for water drainage and then refilled or a roadbed base is subjected to repeated wheel loads. To investigate the behavior of the LCSG materials under loading‐unloading, previous studies utilized the complete loading triaxial test. In contrast, in this study, the consolidated drained triaxial tests in the unloading and reloading paths for materials with cementing agent contents of 60 and 100 kg/m3 under different confining pressures, for which each curve generates three loading‐unloading cycles, were applied to investigate the unloading and reloading mechanical behavior. Experimental results indicated that the unloading and reloading behavior of the LCSG materials produced stress‐strain curves exhibiting a crescent‐shaped hysteresis loop, which differs from that exhibited by coarse‐grained soil. Although the shape of the crescent‐like hysteresis loop was preserved as stress levels increasing, it gradually expanded. Compared with that of the typical triaxial test, the cohesive force and the increasing internal friction angle increased. Further, as the confining pressure increased, the crescent‐like hysteresis loops tapered, shear strength increased linearly, and the modulus of resilience increased nonlinearly; the latter’s rate of change, however, decreased. The change in volumetric strain was small during unloading as the stress level changed.
Highlights
With the increasing speed and scale of urbanization, the demand for stone materials in the construction of real estate, municipal, transportation, and water conservancy infrastructure has increased sharply, leading to the rapid rise and growth of the stone quarrying market; mountain excavations have become widespread. e ceaseless mining has had a negative impact on the ecology of mountainous areas, and a large quantity of waste stone materials is produced
lean cemented sand and gravel (LCSG) materials are used in engineering applications involving complex stress conditions, such as those experienced by dams or roadbed bases. erefore, some scholars have performed static triaxial tests, which are typically used in geotechnical engineering, to study the mechanical properties of this type of roller-compacted concrete with low cementing agent content. rough triaxial tests on LCSG materials, Wu et al [5] analyzed the peak strength, initial modulus, and other mechanical properties at different curing ages and confining pressures. rough triaxial shear tests, Younes et al analyzed the characteristics of their stress-strain curve, including the strength, initial elastic modulus, and dilatancy by changing the confining pressure and cementing agent content [6,7,8,9,10]
A crescent-shaped hysteresis loop is formed that is slightly different from that observed for coarse-grained soils, the hysteresis loop of which is an elliptic curve [15, 16]. e main reason is that, in the case of coarse-grained soils, only plastic deformation occurs in the unloading and reloading process; in the LCSG material, in addition to the plastic deformation, the cementing agent of the material imparts a certain viscosity to the aggregate particles
Summary
With the increasing speed and scale of urbanization, the demand for stone materials in the construction of real estate, municipal, transportation, and water conservancy infrastructure has increased sharply, leading to the rapid rise and growth of the stone quarrying market; mountain excavations have become widespread. e ceaseless mining has had a negative impact on the ecology of mountainous areas, and a large quantity of waste stone materials is produced. LCSG material is a type of concrete with low cementing agent content that can be used for dams, roads, and other construction projects [1, 2]. Erefore, some scholars have performed static triaxial tests, which are typically used in geotechnical engineering, to study the mechanical properties of this type of roller-compacted concrete with low cementing agent content. Rough triaxial tests on LCSG materials, Wu et al [5] analyzed the peak strength, initial modulus, and other mechanical properties at different curing ages and confining pressures. Rough triaxial shear tests, Younes et al analyzed the characteristics of their stress-strain curve, including the strength, initial elastic modulus, and dilatancy by changing the confining pressure and cementing agent content [6,7,8,9,10]. Those research results do not reflect the unloading and loading mechanical properties of LCSG materials in real-life projects such as an LCSG dam that is opened for water drainage and refilled or a roadbed base that is subjected to repeated wheel loads
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