Internal Instability in Soils: A Critical Review of the Fundamentals and Ramifications

Abstract

Seepage-induced fine-particle migration that leads to a change in the conductivity of a soil matrix is referred to as internal instability. This could jeopardize the structural integrity of the soil matrix by initiating suffusion (or suffosion), a form of internal erosion. Susceptibility to suffusion has been studied mostly under extreme laboratory conditions to develop empirical design criteria, which are typically based on the particle size distribution. The physics governing the process have not been comprehensively uncovered in the classical studies because of experimental limitations. Mainstream evaluation methods often over-idealize the suffusion process, holding a probabilistic perspective for estimating constriction sizes and fines migration. Prospective studies on constitutive modeling techniques and modern computational techniques have allowed a more representative evaluation and deeper insight into the problem. Recent advances in sensing technologies, visualization, and tracking techniques have equally enriched the quality of the data on suffusion. This paper sets out to present the long-standing knowledge on the internal instability phenomenon in soils. An attempt is made to pinpoint ambiguities and underscore research gaps. The classical empirical studies and modern visualizing techniques are integrated with particle-based numerical simulations to strengthen the theoretical understanding of the phenomenon.

Comprehension of Energy-Based Methods for Investigating Soil Suffusion Uncertainties

“…Numerous studies have explained how pore fluid conductivity and surface conductance affect the electrical resistance of soil. To ascertain the impact of geotechnical features, electrical resistivity experiments have also been performed on commercial soils [3,[22][23][24][25]. Electrical resistivity must be associated with geotechnical parameters that can be measured in a laboratory because pore water and surface charge characterisation studies cannot be performed during a standard geotechnical investigation.…”

“…Different processes result in erosion, each of which is capable of causing destruction [2]. Suffusion, also known as internal instability, is a long-term phenomenon whereby small soil particles are carried away by a soil seepage flow through spaces between larger ones [3]. It indicates that a soil matrix's particle size distribution and the selective erosion of tiny particles from it do not match the requirements for self-filtering [4].…”

Soil Suffusion under the Dual Threat of Rainfall and Seismic Vibration

“…This type of erosion is often associated with combined rainfall and seismic vibrations, which can cause the soil to become saturated and increase the water pressure within the soil [83]. The water pressure causes soil particles to be dislodged and carried away, leading to the formation of voids and cavities within the soil [90][91][92]. Over time, these voids and cavities can grow and cause the soil to become unstable, leading to the failure of soils and the structures on soil [18,67,73].…”

Response Surface Methodology: The Improvement of Tropical Residual Soil Mechanical Properties Utilizing Calcined Seashell Powder and Treated Coir Fibre

“…In the statistical design of experiments, a wide variety of experimental conditions are tested, and mathematical models are used to generate predictions for responses outside the scope of the original experiment. The results can then be subjected to statistical and numerical analyses that yield useful information for potential real-world applications [44][45][46][47].…”