PAM高聚物顶管用浆液扩散深度分析

Depth Analysis of Slurry Diffusion in Top Pipe of PAM Polymer

注浆减阻作为顶管施工中的一个重要环节,减阻效果直接影响顶管工程的质量。为研究顶管用减阻泥浆的扩散机理,选用PAM作为泥浆外加剂,利用正交试验、流变特性试验确定泥浆的最优配比和流体性质。基于广义达西定律和相关流体力学理论,推导了PAM高聚物顶管用浆液在砂土地层中的渗透扩散深度计算公式。结合海口美兰机场二期外排水4#~5#井顶管工程,对比分析了是否考虑浆液自重两种条件下注浆压力、地层渗透系数和地下水压力对浆液渗透扩散深度的影响。结果表明:PAM顶管用浆液的最优配比为:纳基膨润土:纯碱:PAM:水=9%:1.3%:0.13%:89.57%。浆液流型符合有屈服值的幂律流体;浆液在砂土中的扩散深度随初始注浆压力、地层渗透系数的增大而增大,随地下水压力的增大而减小。

As an important part of pipe jacking construction,the effect of drag reduction directly affects the quality of pipe jacking project.In order to study the diffusion mechanism of drag-reducing slurry for pipe jacking,PAM was chosen as slurry admixture,and orthogonal test and rheological property test were utilized to determine the optimal ratio and fluid properties of the slurry.Based on the generalized Darcy's law and related fluid mechanics theory,the calculation formula for the penetration and diffusion depth of PAM polymer slurry for pipe jacking in sandy soil stratum is deduced.The effects of grouting pressure,formation permeability coefficient and groundwater pressure on the penetration and diffusion depth of slurry under the conditions of whether or not to consider the self-weight of slurry were comparatively analyzed in conjunction with the jacking project of 4#~5#wells of external drainage of the second phase of Haikou Meilan Airport.The results show that:the optimal ratio of PAM slurry for pipe jacking is:Na-bentonite:soda ash:PAM:water=9%:1.3%:0.13%:89.57%.The flow pattern of the slurry conforms to the power law fluid with yield value,the diffusion depth of slurry in sandy soil increases with the increase of initial grouting pressure,formation permeability coefficient,and decreases with the increase of groundwater pressure.