固化淤泥破碎重塑后抗剪强度及孔隙结构变化规律

Changes of the shear strength and pore structure for solidified sludge after crushing and remodelling

关键词:  固化淤泥  破碎  重塑土  抗剪强度  孔隙结构

Key words:  solidified sludge  crushing  remodeled solidified soil  shear strength  pore structure

摘要:

为明确固化淤泥破碎重塑后的强度变化规律及其微观机制,促进固化淤泥破碎重塑土的工程应用。本文采用工业废渣基固化剂,对固化淤泥和破碎重塑土开展一系列直剪试验、扫描电镜（SEM）试验和压汞（MIP）试验,研究了固化剂掺量、破碎前养护龄期和后养护龄期对破碎重塑土抗剪强度的影响,并结合微观形貌和孔隙结构特征分析,探讨了破碎重塑土抗剪强度变化的微观机制。结果表明:初期重塑土的抗剪强度随固化剂掺量的增加和前养护龄期的延长而增长,其内摩擦角在25°~50°,与固化淤泥接近,黏聚力在20~125 kPa,较固化淤泥显著降低；破碎重塑土的抗剪强度主要来源于土团之间的摩擦咬合作用,土团强度越高,内摩擦角越大；随着后养护龄期的增长,破碎重塑土的土团颗粒及孔隙被水化产物胶结填充,黏聚力增长显著,但内摩擦角变化较小；固化淤泥中以孔径0.01~0.10 μm的小孔隙和0.1~1.0 μm的中孔隙为主,且中孔隙随着固化剂掺量的增加和养护龄期的增长逐渐转化为小孔隙；破碎重塑后,初期重塑土中的小孔隙体积明显减少,孔径超过1 μm的大孔隙及超过10 μm的裂隙孔隙显著增加,中孔隙体积变化不明显。

Abstract:

To investigate the macroscopic strength changes and the underlying microscopic mechanisms of solidified sludge (SS) after crushing and remodelling, which enhances the engineering applications of crushed and remodeled solidified sludge (CRSS), a series of direct shear tests, scanning electron microscopy (SEM) analyses, and mercury intrusion porosimetry (MIP) tests were conducted on both SS and CRSS to examine the effects of curing agent content, pre-curing age, and post-curing age on the shear strength characteristics of CRSS. Furthermore, the microstructure and pore structure characteristics analyses were performed to explore the intrinsic mechanisms underlying the shear strength changes in CRSS. The results indicate that the shear strength of the initial CRSS increases with both curing agent content and pre-crushing curing age. The internal friction angle of the initial CRSS is comparable to that of SS, ranging from 25° to 50°, while cohesion decreases significantly, varying from 20 kPa to 125 kPa. The shear strength of CRSS primarily originates from the friction and interlocking between soil aggregates, where higher aggregate strength corresponds to a greater internal friction angle. As the post-curing age increases, soil aggregates and the pores between them in CRSS are cemented and filled with hydration products, resulting in a significant increase in cohesion while causing minimal changes in the internal friction angle. In SS, the pore structure is predominantly characterized by small pores with diameters ranging from 0.01 μm to 0.10 μm and medium pores from 0.1 μm to 1.0 μm. With increasing curing agent content and curing age, medium pores in SS are progressively transformed into small pores. In CRSS, the volume of small pores decreases significantly, accompanied by a notable increase in large pores with diameters ranging from 1 μm to 10 μm and fissure pores larger than 10 μm, while the volume of medium pores remains largely unchanged.