固废粉煤灰对水泥搅拌桩力学性能的影响研究

Study on the influence of solid waste fly ash on mechanical properties of cement mixing piles

摘要

为了解决饱和淤泥质软土地基承载力低、含水率及含碱量高的问题，合理实现资源循环利用及固废处理，以广州南沙区小虎岛粒珠水闸泵工程软土地基加固工程为例，将粉煤灰、水泥作为胶凝材料制成浆液，研究不同配比粉煤灰水泥搅拌桩抗压强度的影响规律。研究结果表明：水灰比从0.45增加至0.55,试件无侧限抗压强度上升，但水灰比增长至0.65,试件无侧限抗压强度出现下降，且下降速率小于上升速率，水灰比为0.55时试件抗压强度最大；粉煤灰掺入量为20%的试件在不同水灰比、龄期下其无侧限抗压强度均较大；现场试桩20%粉煤灰掺入量的芯段整体上较均匀；芯样抗压强度随着取样深度的增加呈现先增大后减小的趋势，试验试桩芯样抗压强度在5.0~8.4 m深度较1.05~2.75 m深度分别增大了10.74%、4.23%、10.34%,在10.0~12.4 m深度较5.0~8.4 m深度分别减小了2.99%、3.38%、4.69%,水泥粉煤灰搅拌桩提高了粉质黏土及淤泥质土的地基承载力；粉煤灰与水泥土产生化学反应生成水化产物C—S—H凝胶、钙矾石(AFt),结构致密，其形成的黏结力提高了水泥土力学强度。

Abstract

In order to solve the problems of low bearing capacity, high water content and high alkali content of saturated muddy soft soil foundation, and reasonably realize the recycling of resources and solid waste treatment, taking the soft soil foundation reinforcement project of Xiaohudao Lizhu Sluice Pump Project in Nansha District of Guangzhou as an example, fly ash and cement were used as cementitious materials to make slurry, and the influence law of compressive strength of fly ash cement mixing piles with different proportions was studied. The result show that when the water-cement ratio increases from 0.45 to 0.55,the unconfined compressive strength of the specimen increases, but when the water-cement ratio increases to 0.65,the unconfined compressive strength of the specimen decreases, and the decrease rate is less than the increase rate. When the water-cement ratio is 0.55,the compressive strength of the specimen is the largest. The unconfined compressive strength of the specimens with 20% fly ash incorporation is larger under different water-cement ratios and ages. The core section of the field test pile with 20% fly ash incorporation is relatively uniform as a whole;the compressive strength of the core sample increases first and then decreases with the increase of the sampling depth. The compressive strength of the core sample of the test pile increases by 10.74%,4.23% and 10.34% respectively in the depth of 5.0~8.4 m compared with the depth of 1.05~2.75 m, and decreases by 2.99%,3.38% and 4.69% respectively in the depth of 10.0~12.4 m compared with the depth of 5.0~8.4 m. The cement fly ash mixing pile improves the foundation bearing capacity of silty clay and muddy soil. The chemical reaction between fly ash and cement soil produces hydration products C—S—H gel and ettringite( AFt). The structure is dense, and the bonding force formed improves the mechanical strength of cement soil.

关键词

粉煤灰 / 水泥搅拌桩 / 试桩试验 / 软土地基

Key words

fly ash / cement mixing pile / pile test / soft soil foundation

Author summay

刘智华(1977—), 男, 助理工程师, 学士, 主要从事建筑施工。E-mail: [e-mail]

基金资助

国家自然科学基金项目(52174086)