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<p>Hydraulic fracturing is a promising approach for the efficient exploitation of flammable ice reservoirs, for which Mode-I fracture toughness (<i>K</i><sub>IC</sub>) is a key indicator of fracturability. Given the similar physical–mechanical properties of flammable ice and ordinary ice, this study employs synthetic ice-bearing loose sediments as flammable ice analogs to investigate Mode-I fracture behaviors. Artificial specimens with six controlled ice saturation levels (<i>S</i> = 0–90%) were prepared, and notched semi-circular bend (NSCB) tests combined with digital image correlation (DIC) were conducted to examine the effects of <i>S</i> on fracture behaviors and fracture process zone (FPZ) evolution. A DIC-based criterion was developed to identify the FPZ initiation. Low saturation specimens exhibited brittle failure with minimal pre-peak deformation, whereas higher saturations enhanced ductility, delayed crack initiation and mitigated abrupt propagation. Both peak load and <i>K</i><sub>IC</sub> followed a non-monotonic, upward-opening quadratic relation with <i>S</i>, showing slow initial growth, a slight drop at 30% saturation, and a rapid increase thereafter. At 90% saturation, the mean <i>K</i><sub>IC</sub> reached 0.347 MPa·m<sup>1/2</sup>, 3.88 times higher than the dry value. FPZ initiation shifted from 65–70% of peak load for <i>S</i> ≤ 30% to 85–90% for <i>S</i> ≥ 50%. FPZ width stabilized near 4.8&#xa0;mm beyond 30% saturation, while final length decreased at <i>S</i> = 30% and then increased sharply to about 9&#xa0;mm (over twice the dry value) at <i>S</i> = 70%. These FPZ characteristics explain the transition from brittle to ductile fracture morphologies, offering quantitative insight into ice-induced toughening in flammable ice analogs.</p>

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Mode-I Fracture Behavior and Fracture Process Zone Evolution of Synthetic Ice-Bearing Loose Sediments Simulating Flammable Ice

  • 期刊论文

  • 发表日期：

    2026年3月30日

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  • Zizhen Wang,
  • Deshui Ni,
  • Jiapei Du,
  • Kaixiang Shen,
  • Weidong Zhou,
  • Annan Zhou

摘要

Hydraulic fracturing is a promising approach for the efficient exploitation of flammable ice reservoirs, for which Mode-I fracture toughness (KIC) is a key indicator of fracturability. Given the similar physical–mechanical properties of flammable ice and ordinary ice, this study employs synthetic ice-bearing loose sediments as flammable ice analogs to investigate Mode-I fracture behaviors. Artificial specimens with six controlled ice saturation levels (S = 0–90%) were prepared, and notched semi-circular bend (NSCB) tests combined with digital image correlation (DIC) were conducted to examine the effects of S on fracture behaviors and fracture process zone (FPZ) evolution. A DIC-based criterion was developed to identify the FPZ initiation. Low saturation specimens exhibited brittle failure with minimal pre-peak deformation, whereas higher saturations enhanced ductility, delayed crack initiation and mitigated abrupt propagation. Both peak load and KIC followed a non-monotonic, upward-opening quadratic relation with S, showing slow initial growth, a slight drop at 30% saturation, and a rapid increase thereafter. At 90% saturation, the mean KIC reached 0.347 MPa·m1/2, 3.88 times higher than the dry value. FPZ initiation shifted from 65–70% of peak load for S ≤ 30% to 85–90% for S ≥ 50%. FPZ width stabilized near 4.8 mm beyond 30% saturation, while final length decreased at S = 30% and then increased sharply to about 9 mm (over twice the dry value) at S = 70%. These FPZ characteristics explain the transition from brittle to ductile fracture morphologies, offering quantitative insight into ice-induced toughening in flammable ice analogs.