Strength behaviour of stacked phosphogypsum incorporating dissolution–recrystallisation equilibrium

Zhang Zheng Cai, Han Ke, Peng Ze Zhang, J. Lan, Peng Cheng Ma, Jie Hu, Bo Xiao, Yunmin Chen
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Abstract

Large phosphogypsum (PG) stacks risk dam failure, with an insufficient consensus on the shear strength parameters for stability analysis. To this end, a combination of scanning electron microscopy (SEM) and triaxial tests was undertaken to investigate the underlying mechanism between crystal structure and shear strength of in situ and remoulded PG samples. The shear strength and deformation of PG were significantly affected by dissolution and recrystallisation. Dissolution weakened the cementation between particles, leading to a stabilisation of approximate 11 kPa under different confining pressures in the initial shear stage. The hardening phenomenon was related to the formation of cluster crystals under saturated conditions. An increase from 1.57 to 1.73 in the critical state stress ratio on remoulded samples occurred as the K0 consolidation time increased from 4 to 28 days. The compressive deformation of PG is accompanied by chemical consolidation, which is mainly impacted by the consolidation conditions (saturation) rather than the consolidation time. In the engineering design of the PG stacks, φ’ could be taken to a higher value at saturation and c’ could be higher when the dry density is higher than 1.2.
包含溶解-重结晶平衡的堆叠磷石膏的强度行为
大型磷石膏(PG)堆存在溃坝的风险,而稳定性分析所需的剪切强度参数尚未达成充分共识。为此,我们结合扫描电子显微镜(SEM)和三轴测试,研究了原位和重塑 PG 样品的晶体结构与剪切强度之间的内在机制。PG 的剪切强度和变形受到溶解和再结晶的显著影响。溶解削弱了颗粒之间的胶结,导致在初始剪切阶段不同约束压力下的稳定度约为 11 kPa。硬化现象与饱和条件下团簇晶体的形成有关。随着 K0 固结时间从 4 天增加到 28 天,重塑样品的临界状态应力比从 1.57 增加到 1.73。PG 的压缩变形伴随着化学固结,而化学固结主要受固结条件(饱和)而非固结时间的影响。在 PG 堆料的工程设计中,饱和状态下的φ'可取较高值,当干密度高于 1.2 时,c'可取较高值。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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