磷石膏改良长江漫滩水泥搅拌桩试验研究  

Experimental study on cement mixing pile improved by phosphogypsum in yangtze river floodplain

作　　者：王涛 张赛 郝钢 郭晨 丁建文[2] WANG Tao;ZHANG Sai;HAO Gang;GUO Chen;DING Jianwen(Beijing Municipal Road&Bridge Co.,Ltd.,Beijing 100073,China;School of Transportation,Southeast University,Nanjing 211189,China)

机构地区：[1]北京市政路桥股份有限公司,北京100073 [2]东南大学交通学院,江苏南京211189

出　　处：《混凝土》2022年第5期167-172,共6页Concrete

基　　金：国家自然科学基金资助项目(51978159);“十二五”国家科技支撑计划资助项目(2015BAB07B06)。

摘　　要：针对粉土地层水泥搅拌桩止水帷幕施工过程中水泥土早期强度低、成桩质量差、易出现渗漏等问题,以工业副产品磷石膏和水泥为固化剂稳固粉土,通过无侧限抗压强度试验、柔性壁渗透试验、X射线衍射测试(XRD)和电镜扫描试验(SEM),研究了粉土固化土的力学性能、渗透性状以及固化机理。结果表明适量的磷石膏可加快固化土初期钙矾石(AFt)的生成,对止水帷幕的早期强度具有促进作用;AFt的膨胀性对水泥土的强度和渗透性状具有双重影响,AFt生成量较少时,可有效填充土体孔隙,提高水泥土强度和抗渗性能,AFt生成量较大时,因其体积膨胀会导致已生成的胶结体被破坏,从而引起改良土强度和抗渗性能降低。通过试验研究,建议在南京长江漫滩基坑止水帷幕施工中:水泥掺量为20%左右,磷石膏掺量为水泥掺量的10%左右,以实现基坑止水帷幕效果改良和废弃磷石膏的资源化利用。Tosolvethe problems of low cement-soil early strength,poor pile quality and appearance of leakage during the construction of cement mixing pile in silt layer,the industrial by-products phosphogypsum and cement are used as curing agent to stabilize silt,and the unconfined compressive strength test,flexible-wall permeameter tests,X-ray diffraction(XRD)and scanning electron microscopetest(SEM)are taken to investigate the mechanical properties,permeability properties and curing mechanism of solidified silt.The results show that proper amount of phosphogypsum can accelerate the formation of ettringite(Aft)at the early reaction stage and promote the early strength of the waterproof structure.The expansibility of ettringite has a dual influence on the strength and permeability of cement-soil.When the amount of AFt is small,it can fill the soil pores and improve the strength and permeability of cement-soil.When the amount of ettringite is large,AFt′sexpanding destroys the existing cementation and reduces the strength and permeability of solidified soil.Therefore,it is suggested that the cement content should be about 20% and the phosphogypsum content should be about 10% of the cement content in the construction of the waterproof structure of the Yangtze River floodplain in Nanjing,so as to realize the improvement of the waterproof structure and the resource utilization of wasted phosphogypsum.

关 键 词：粉土地层 水泥搅拌桩 磷石膏 强度与渗透性 微观特征 

分 类 号：TU528.01[建筑科学—建筑技术科学]