高渗透砂层含核桃壳泥浆特性及渗透成膜试验研究

Rheological properties and filter-cake formation performances of slurry containing walnut shell in high-permeability sand stratum

泥水盾构在高渗透地层带压开舱时常遇到泥浆漏失及泥膜闭气性不足导致的开挖面失稳问题。由于颗粒密度大、界面结合性弱,传统的含砂泥浆分散稳定性较差,成膜质量欠佳。提出了一种以轻质有机材料核桃壳为添加颗粒的新型盾构泥浆,为了研究该泥浆在高渗透地层的成膜及闭气效果,自主研发了泥浆渗透-成膜-闭气的全过程试验系统,开展了含核桃壳泥浆的流变、渗透成膜及泥膜闭气特性测试试验,分析了核桃壳改善成膜质量的作用机理。结果表明:核桃壳与膨润土泥浆的匹配性较好,可明显提高泥浆的胶体率和分散稳定性,同时保证了较高的凝胶强度和良好的流动性。与含砂泥浆相比,核桃壳颗粒的增稠效果和颗粒间的软接触模式使高渗透地层的泥浆成膜更容易,泥膜致密性和耐高气压能力也有明显提升。

In the high-permeability stratum,the slurry shield often encounters the problems of slurry leakage and poor air-tightness of filter cakes,leading to the instability of excavation face.Due to the high particle density and weak interfacial bonding,the traditional slurry containing sand has poor dispersion stability and poor filter-cake quality.In this study,a new type of shield slurry with walnut shell as the additive particle is proposed.In order to study the filter-cake formation and airtightness effects of the slurry in the high-permeability stratum,the whole process test system for the slurry permeation,filter-cake formation and air tightness is developed,and the tests on the rheology,slurry permeation and airtightness characteristics of the slurry containing walnut shell are performed.The mechanism of improving the filter-cake formation quality by the walnut shell is analyzed.The results show that the matching between the walnut shell and the bentonite slurry is better,which can obviously improve the colloidal ratio and dispersion stability of slurry,and ensure high gel strength and good fluidity.Compared with those of the slurry containing sand,the thickening effects of the walnut shell particles and the soft contact mode between particles make the slurry filter-cake formation in high-permeability stratum easier,and the density and high pressure resistance of the slurry filter cakes are also significantly improved.