Canadian Geotechnical Journal, Ahead of Print.
Enhancing the complexity of the hydraulic fractures to provide a wide channel for the injection of the agent is crucial for remediating low-permeability contaminated sites. This study involved a physical simulation experiment of large-scale true triaxial hydraulic fracturing in undisturbed soil, as well as field fracturing tests, to investigate fracture initiation mechanisms and the influence of different factors on fracture propagation. The study revealed a unique failure mode for low-permeability soils characterized by impact splitting, involving simultaneous tensile and shear failure. Three typical fracture propagation patterns emerged: (1) horizontal fracture, (2) parallel fracture, and (3) complex fracture. Silty clay predominantly exhibited horizontal fractures, while mucky clay facilitated the formation of complex fractures dominated by multiple transverse fractures. As the vertical stress difference coefficient increased from 1.0 to 1.5, the pressure on the fracture surface enhanced the connection between hydraulic fractures and natural fractures. Hydraulic fracturing in low-permeability soils necessitated large displacements and high-viscosity fracturing fluids to sustain fracture propagation. The field fracturing test results underscored that soil type and in-situ stress were the primary factors governing hydraulic fracture initiation and propagation. Identifying the optimal fracturing location was critical for achieving the maximum stimulated formation volume.

中文翻译：

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加强水力压裂以原位修复低渗透土壤：裂缝扩展的综合研究

加拿大岩土工程杂志，印刷前。
提高水力压裂的复杂性以提供宽阔的药剂注入通道对于修复低渗透污染场地至关重要。本研究通过原状土中大规模真三轴水力压裂物理模拟实验和现场压裂试验，研究裂缝起裂机制以及不同因素对裂缝扩展的影响。该研究揭示了低渗透土的一种独特的破坏模式，其特征是冲击分裂，涉及同时的拉伸和剪切破坏。出现了三种典型的裂缝扩展模式：（1）水平裂缝，（2）平行裂缝和（3）复杂裂缝。粉质粘土以水平裂缝为主，泥质粘土则易形成以多条横向裂缝为主的复杂裂缝。随着垂直应力差系数从1.0增加到1.5，裂缝表面的压力增强了水力裂缝与天然裂缝的连接。低渗透土壤中的水力压裂需要大位移和高粘度压裂液来维持裂缝扩展。现场压裂试验结果强调，土壤类型和地应力是控制水力裂缝起裂和扩展的主要因素。确定最佳压裂位置对于实现最大增产地层体积至关重要。