Effects Of Internal Erosion Research Articles

Experimental investigation of collapsible soils under oedometric loading: effect of internal erosion

Collapsible soils, geological formations characterized by pronounced structural instability upon saturation, present a significant challenge in geotechnical engineering. This experimental study aims to deepen our understanding of the mechanisms governing the behavior of these soils, which are particularly prevalent in arid and semi-arid regions subject to extreme hydrological cycles. Collapsible soils, sensitive to climatic variability, undergo profound alterations in their hydromechanical properties due to alternating periods of prolonged drought and intense rainfall events. These fluctuations induce significant modifications in the soil's pore structure, promoting the development of internal erosion phenomena such as suffusion. The results obtained from this experimental investigation on reconstituted samples highlight the combined influence of various factors, such as water content, dry density, particle size, and flow rate, on the collapse potential. It appears that fine particles play a predominant role in the formation of fragile structures, susceptible to collapse upon saturation. Moreover, the intensity and duration of infiltration significantly influence the propagation velocity of ultrasonic waves, thus offering a promising tool for monitoring the evolution of damage within the soil mass. Furthermore, this study provides essential insights for assessing the risks associated with collapsible soils and contributes to the development of more reliable characterization and modeling methods. It emphasizes the need to consider the complex interactions between the physical, chemical, and mechanical properties of the soil, as well as the influence of environmental conditions, for better control of the risks associated with these materials.

Stress stress-strain behavior of hydraulic filled coral sand subjected to internal erosion

Coral sand foundations lose fine particles under the action of groundwater infiltration. As the soil skeleton structure deteriorates, the foundation becomes uneven and may even collapse. In this study, a triaxial drainage shear test of coral sand is used as a quantitative control method for the loss of fine particulate soil, and the effect of internal erosion on the mechanical behavior of coral sand is evaluated. An experiment is used to demonstrate that erosion leads to a decrease in the peak shear strength and residual strength of coral sand. Erosion has different effects on coral sand with different fine particle contents, and the effects on the friction angles of coral and terrestrial sand are also different. The secant modulus E50 and peak secant modulus Ep gradually decrease as the loss of fine particles increases. The effect of fine particle loss on the peak secant modulus Ep is significant at fine-particle losses exceeding 10% for a fine-particle content of 20%. The loss of fine particles creates new pore spaces in the coral sand, which, in turn, affects the stability of the original soil skeleton. Erosion has been shown to have an effect on the gradational features of coral sand, leading to the phenomenon that the dilatancy effect increases as a function of the amount of erosion that takes place. To prevent uneven foundation settlement caused by subsurface erosion in engineering designs, it is important to consider the gradation characteristics and fine particulate content of coral sand, which affect the stability of coral reef foundations.

The effects of internal erosion on granular soils used in transport embankments

The flooding of embankments used for rail and other infrastructure has the potential to cause lasting weakening of slopes via the movement of fine particles induced by seepage. In laboratory experiments, internal erosion was induced in granular soil samples, with properties consistent with those used to construct transportation embankments, to assess how particle migration through, and out of, samples caused shear wave velocity, strength, stiffness and permeability changes. Shear wave velocity changes, measured using horizontal bender elements, of up to 19 % were observed following fine particle removal of up to 1 % of initial sample mass. Shear wave velocity change was found to be an indicator for identifying the development of permeability change during seepage-induced particle migration. Median measured permeability changes were +5 % and −34 % for samples containing 15 % and 30 % fines, respectively. The largest directly observed permeability and shear wave velocity changes occurred during the initial stages of seepage. Negative correlation was observed between mass of material removed from samples and peak friction angle. Following seepage, soils displayed a dual stiffness behaviour. Stiffness and strength changes were attributed to redistribution of fine particles and opening of pore spaces. Our results have implications for the monitoring of earthworks affected by flooding and seepage as the associated redistribution of fine particles may lead to large changes in slope properties.

A Numerical Analysis of the Leakage Characteristics of an Embankment Dam Slope With Internal Erosion

Leakage is a common defect of embankment dam slopes, and is usually accompanied by internal erosion. This study establishes a mathematical two-phase seepage coupling model that explicitly considers the effects of internal erosion. With the help of finite element software COMSOL Multiphysics®, we use this model to study the characteristics of fluid seepage, the fraction of leakage volume that is made up of migrated fine particles (migrated fine particles volume fraction), porosity, permeability, and displacement in the leakage process of a three-dimensional embankment dam slope, as well as to study the influence of the water level and leakage outlet size on the aforementioned features. Our results show that water seepage velocity gradually increases with time, especially at the downstream leakage outlet. Therefore, the erosion and migration of fine particles occur primarily at the downstream leakage outlet, resulting in a significant increase in the migrated fine particles volume fraction, porosity, and permeability. In addition, the maximum migrated fine particles volume fraction, the maximum porosity, and the maximum permeability in the slope increase nonlinearly with time. Curves for maximum displacement with a strength reduction factor can be divided into three stages: the early stable stage, the midterm nonlinear growth stage (creeping state), and the later rapid growth stage (instability state). We also find that the rise of the water level promotes the erosion and migration of fine particles on the slope and that the maximum migrated fine particles volume fraction and the maximum porosity increase with the water level. The values of the strength reduction factor for the creeping state decrease as the water level rises. Furthermore, the larger the size of the downstream leakage outlet, the larger the maximum migrated fine particles volume fraction and maximum porosity. However, the relationship between maximum displacement and strength reduction factor is nearly unaffected by the size of the leakage outlet.

Effects of internal erosion on the cyclic and post-cyclic mechanical behaviours of reconstituted volcanic ash

Internal erosion is the transportation of soil particles from within or beneath the main structure inside the ground due to seepage flow. Internal erosion impacts the mechanical and hydraulic behaviour of soil. The present study investigates the impact of internal erosion on the cyclic and post-cyclic mechanical behaviours of volcanic ash sampled from Satozuka, Japan. A series of experiments using volcanic ash with loose, medium, and dense conditions have been performed using an erosion triaxial apparatus. Further, reconsolidation after application of cyclic loading was considered to study the impact of reconsolidation on the post-cyclic mechanical behaviour. The results show that the cyclic resistance of eroded specimens is improved regardless of the percentage of eroded fines and the initial relative density. The higher cyclic resistance for the eroded specimens is found to be due to a decrease in the intergranular void ratio after the erosion, change in fabric, and pre-strain history during erosion. Reduction in the critical state friction angle (φcri) and peak stress ratio (Rpeak) for the monotonic loading due to cyclic loading is greater for the eroded specimens. However, reconsolidated eroded specimens show increases in φcri and Rpeak, which are lower than those of the non-eroded and eroded specimens without cyclic loading. This could be due to the change in the soil fabric during cyclic loading where the positive impact of erosion is lost after cyclic loading. Such limited recovery of deviatoric stress with deformation is density-dependent.

Experimental study on the evolution of the drained mechanical properties of soil subjected to internal erosion

Internal erosion can cause geotechnical structures to fail due to the loss of fine particles, which is induced by internal erosion that can weaken the mechanical properties of soil. Few studies have focused on the effect of internal erosion on the mechanical properties of soil. Accordingly, the present paper studies the evolution laws of the drained mechanical properties of soil due to internal erosion by conducting a series of triaxial consolidated drained shear tests and using the fine particle elimination method. The main conclusions of the study are as follows. Under the same confining pressure, the strain-softening phenomenon of the stress–strain curve will decrease with an increasing loss of fine particles, and a soil sample with a lower loss rate of fine particles will have a more dilative response. The loss of fine particles decreases the drained failure strength and drained internal friction angle. Mathematical relationships between the drained failure strength and the loss rate of fine particles and between the drained internal friction angle and the loss rate of fine particles have been established. A modified Duncan–Chang model that considers the loss of fine particles induced by internal erosion has been established.

Effects of Internal Erosion on Parameters of Subloading Cam-Clay Model

Internal erosion is widely detected in both natural deposits and earthen structures and potentially causes severe disasters. Suffusion is one of the modes of internal erosion in which fine particles in the soil are washed out along with water flow through pores formed by coarse particles. Mechanical consequences of internal erosion, specifically, suffusion, are not well investigated in term of constitutive modelling. Also, most of the present constitutive models concerning suffusion are validated by DEM simulations, not by actual soil response observed in soil tests. In this paper, triaxial seepage tests followed by drained compression on soil with 35% initial fines content under 50 kPa, 100 kPa and 200 kPa mean stresses are studied to investigate the applicability of the existing soil model to internally eroded soils. The subloading Cam-clay model is used to simulate the mechanical behaviour of eroded soils. After confirming that the model can capture key features of uneroded specimens, the evolution of model parameters with erosion is examined by back analysis of the eroded specimens. From the simulation on the eroded specimens, evolutions of the slope of normal compression line and initial stress ratio with erosion are quantified. The changes of model parameters with erosion provide a useful reference for investigating the mechanical behaviour of granular materials subjected to suffusion.

Influences of internal erosion on infiltration and slope stability

Rainfall-induced slope failures in natural terrains are destructive natural disasters. Transport of fine particles may be induced by the rainwater seepage in a natural terrain slope comprising mixed coarse and fine particles. In this study, the interaction of internal erosion and infiltration in a soil slope is investigated. A coupled model of unsaturated flow and internal erosion is established. The effects of internal erosion on pore water pressure profiles and slope stability are studied. Parametric studies on erosion parameters and hydraulic parameters are conducted. The results of the numerical example show that internal erosion occurs mainly in the zone within the wetting front, which accelerates the advance of the wetting front and decreases the slope stability. The coefficient of erosion flux rate, βer of the erosion law, is the main factor that affects the internal erosion. The effect of erosion on the wetting front movement is more significant with large values of βer. The effects of parameters i* and αer are less significant when compared with βer. When the rainfall flux is equal or greater than the saturated coefficient of permeability, the influence of internal erosion on water infiltration and slope stability is significant. The effect of internal erosion can be neglected as long as the rainfall flux is less than the saturated coefficient of permeability. When the air-entry value of the soil is greater, the influence of internal erosion on infiltration and slope stability becomes less significant.

Effects of internal erosion on mechanical properties evaluated by triaxial compression tests

Effects of internal erosion on mechanical properties evaluated by triaxial compression tests

Effects of internal erosion on mechanical properties of soil

Effects of internal erosion on mechanical properties of soil