Key Takeaways & Executive Findings
- •• Increased slurry concentrations and pressures generally improve filter cake formation, but excessive pressure can compromise its integrity. • Dijkstra's algorithm applied to pore network models identified primary seepage pathways, emphasizing the role of near-vertical throat clusters. • Growth line orientation in coral reef limestone is the primary factor controlling macroscopic slurry infiltration behavior. • CT scanning before and after infiltration provides critical insights into pore structure and connectivity changes.
Abstract
Reef limestone is buried in the continental shelf and marine environment. Understanding the mechanisms governing filter cake formation in coral reef limestone strata is essential for various engineering activities in coastal areas, including slurry pressure balanced (SPB) shield tunneling, which are currently not well understood. This study systematically investigates the slurry infiltration characteristics of different coral reef limestone types with inherent anisotropy, identified by growth line orientations, through a series of micro-infiltration column tests. Multiple slurry concentrations and pressures were used to analyze their effects on slurry infiltration dynamics and filter cake formation. Pre- and post-infiltration CT scanning was conducted to examine skeletal morphology and reconstruct the pore network structure of coral reef limestone samples. The results show that while increased slurry concentrations and pressures generally improve filter cake formation, excessive pressure can compromise filter cake integrity. By employing Dijkstra’s algorithm in a pore network model, the study identified primary seepage pathways, highlighting the significant role of near-vertical throat clusters in the infiltration process. A comprehensive analysis of pore structure and connectivity indices before and after infiltration revealed that the orientation of growth lines in coral reef limestone is the primary factor influencing macroscopic slurry infiltration behavior. These findings offer valuable insights for the design and execution of tunneling projects through coral reef limestone formations, especially in coastal regions.
1. Introduction
In recent years, slurry pressure balanced (SPB) shield tunneling technology has become an indispensable method for underwater tunnel construction due to its excellent adaptability, particularly in complex soil conditions [1]. During the shield tunneling process, fine particles in the slurry infiltrate the excavation face, forming a filter cake, which is a layer of solid material that forms on the surface of a porous medium when a slurry or fluid mixture passed through it. This process is crucial for maintaining slurry pressure within the chamber and providing initial support to the surrounding soil [2]. The quality of the filter cake directly influences its supporting effect. If the filter cake is poorly compacted or structurally unstable, slurry may infiltrate deeper into the soil layers, resulting in insufficient support pressure and posing a threat to the stability of the excavation face [3]. Therefore, understanding the infiltration behavior of slurry particles in different soil layers and their effects on the surrounding strata is essential for improving tunneling efficiency and ensuring construction safety. With the increasing depth of tunnel construction and the growing complexity of environmental conditions, studying slurry infiltration characteristics in various soil types, particularly in weak strata and low-water-tightness environments, has become a key focus for advancing shield tunneling technology.
The development of artificial islands and the exploration of energy resources in the coral reefs of the South China Sea may lead to a significant demand for underground tunnel construction in coastal areas [4]. Coral reef limestone is the predominant stratum in the region, characterized by a porous, brittle biological skeletal structure, complex textures, and heterogeneity inherited from its sedimentation process.
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Jiahe Bai, Xin Huang (2025). Slurry infiltration characteristics of coral reef limestone based on infiltration column tests and CT scanning. SinoTechIntel Verified Research. https://doi.org/10.1016/j.ijmst.2025.09.010
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Frequently Asked Questions
What is the main objective of this study?
The study aims to systematically investigate the slurry infiltration characteristics of different coral reef limestone types, focusing on filter cake formation and the influence of growth line orientations, using infiltration column tests and CT scanning.
How does slurry concentration and pressure affect filter cake formation?
Increased slurry concentrations and pressures generally improve filter cake formation, but excessive pressure can compromise its integrity, potentially leading to deeper infiltration and reduced support pressure.
What role do pore network models play in this research?
Pore network models, combined with Dijkstra's algorithm, help identify primary seepage pathways, highlighting the significant role of near-vertical throat clusters in the infiltration process.
Why is the orientation of growth lines important?
The orientation of growth lines in coral reef limestone is the primary factor influencing macroscopic slurry infiltration behavior, as it affects pore structure and connectivity.
What are the practical implications of this study?
The findings offer valuable insights for the design and execution of tunneling projects through coral reef limestone formations, especially in coastal regions, by improving understanding of filter cake formation and slurry infiltration.
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