粗粒土地层加砂泥浆研制与渗透成膜特性研究

Developement of sand-mixed slurry and study of the permeation film-forming characteristics for coarse-grained soil layers

摘要:

防渗墙作为一种常用的垂直防护手段，在水电建设行业中备受青睐。但在粗粒土地层中进行防渗墙成槽施工时，因地层渗透性强，固壁泥浆漏失严重，导致成膜困难，槽壁垮塌事故频发。因此，为改善由泥浆渗透造成的槽壁稳定性问题，分别对造浆土、pH改性剂、流变改性剂进行优选得到基础液，再通过自主设计的泥浆渗透实验仪器优选粗砂为粗粒材料，构建粗粒土地层的防渗墙固壁泥浆体系，同时分析了粗砂粒径和加量对泥浆渗透成膜特性的影响。得出结论：粗粒土地层成槽泥浆体系配方为清水+4%黏土+4%钠基膨润土+0.2% 3.4模硅酸钠+0.18% 羧甲基纤维素钠+2.5% 0.154 mm砂粒；加砂泥浆在粗粒土地层中的成膜速度与成膜质量主要取决于粗砂的粒径与加量，随粗砂的粒径和加量的增大泥浆的成膜速度不断加快，随粗砂加量的增大，成膜质量不断降低；加砂泥浆的渗透成膜机制为：砂粒对粗粒土地层的初步改良、渗透带在地层中的稳定淤堵、泥皮在地层表面的滤失成膜，三者协同作用降低浆液的渗漏，维持粗粒土地层开挖面的稳定。研究成果对粗粒土地层的工程固壁泥浆优化配制具有理论指导作用，同时对类似工程也具有借鉴与参考价值。

Abstract:

As a commonly used vertical protection method， the cut-off wall is highly favored in the hydropower construction industry. However， during the trenching construction of cut-off walls in coarse-grained soil strata， because of strong permeahility， serious leakage of wall-fixing slurry often occurs， leading to difficulties in film-forming and frequent trench wall collapse accidents. Therefore， to improve the stability of trench walls caused by slurry permeation， the base fluid was optimized by selecting suitable clay， pH modifiers， and rheological modifiers. Subsequently， a self-designed slurry permeation experiment apparatus was used to select coarse sand as the coarse-grained material， forming a wall-fixing slurry system for cut-off walls in coarse-grained strata. The effects of coarse sand particle size and dosage on the slurry''s permeation and film-forming characteristics were also analyzed. The study concluded that the slurry system for trenching in coarse-grained strata consists of clean water+4% clay+4% sodium bentonite+0.2% 3.4-modulus sodium silicate+0.18% sodium carboxymethyl cellulose+2.5% 0.154 mm sand particles. The film-forming speed and quality of sand-added slurry in coarse-grained strata primarily depend on the particle size and dosage of coarse sand. As the particle size and dosage of coarse sand increase， the film-forming speed of the slurry accelerates， whereas the film-forming quality decreases with the increasing sand dosage. The permeation and film-forming mechanism of sand-added slurry involves three synergistic effects： the preliminary improvement of the coarse-grained stratum by sand particles， the stable clogging of the permeation zone within the stratum， and the filtration and film-forming of mud cake on the stratum surface. These combined actions reduce slurry leakage and maintain the stability of the excavation face in coarse-grained strata. The research findings provide guidance for optimizing the formulation of engineering wall-fixing slurry in coarse-grained strata and offer valuable references for similar engineering projects.