Effect Of Water Infiltration Research Articles

Laboratory Acousto‐Mechanical Study Into Moisture‐Induced Reduction of Fracture Stiffness in Granite

AbstractWater infiltration into fractures is ubiquitous in crustal rocks. However, little is known about how such a progressive wetting process affects fracture stiffness and seismic wave propagation, which are highly relevant for characterizing fracture systems in situ. We study the acousto‐mechanical behavior of a free‐standing fractured granite subjected to gradual water infiltration with a downward‐moving wetting front over 12 days. We observe significant differences (i.e., by an order of magnitude) in wave amplitudes across the fractured granite compared to an intact granite, with both cases showing a strong correlation between wave amplitudes and wetting front movement. Effects of water infiltration into the fracture and surrounding matrix on seismic attenuation are captured by a numerical model with parameters constrained by experimental data. Back‐calculated fracture stiffness decreases exponentially with the wetting front migration along the fracture. We propose that moisture‐induced matrix expansion around the fracture increases asperity mismatch, leading to reduced fracture stiffness.

An Experimental Study on the Unsaturated Soil Parameters Changes due to Various Degree of Saturation

Landslide is a natural disaster often occurring in Indonesia, associated with the rainy season. The slope failure mechanism is the main challenge in the slope stability analysis due to rainfall. The changing of the soil engineering properties under the effect of water infiltration during the rain should be fixed. In this study, the experimental studies were conducted to evaluate the unsaturated soil parameters changes, i.e., suction, cohesion, and internal friction angle, in various degrees of saturation. The filter paper tests were conducted to evaluate the matric suction of soil and develop the soil-water characteristic curve (SWCC) using the Soil Vision software. Fredlund and Xing, Van Genucthen, and Brooks and Corey fit the SWCC: The fitting equation developed by Fredlund and Xing resulted in the highest coefficient of determinant with R² of 0.91 and 0.97 for well-graded silty sand and silty sand curves, respectively. Thus, it was used to determine the correlation between saturation, cohesion, and matric suction. Shear strength parameters of soil samples were examined using a direct shear test method. The results show that the increase of the saturation degree reduces the soil suction and shear strength parameters. The result of this study is crucial to develop an understanding of the mechanism of slope failure.

Effects of water infiltration into an unsaturated streambed on debris flow development

Debris flows gain much of their mass by entraining material as they descend a steep channel, growing many times before the deposition begins on gentler terrain downstream. Understanding such development processes and mechanisms is essential for predicting the scale of a debris flow arriving downstream. Notably, some field observations revealed that bed sediment was unsaturated before and during debris flow descent over them, implying the infiltration of the debris flow interstitial water into the streambed. In this study, small-scale flume experiments were conducted to simulate debris flow development processes over an unsaturated bed to investigate the relationship between water infiltration into the streambed and debris flow development. Subsequently, we established a model that can represent an unsaturated debris flow, which has pores containing air in the upper flow layer. This model successfully quantified the scale effect of our experiments. Our experimental and theoretical results show that water infiltration into a streambed can change the type of debris flow from saturated to unsaturated and influence the velocity and depth of unsaturated debris flow. An unsaturated debris flow repeatedly accelerates and decelerates owing to the water infiltration into a streambed and local gradient change of a channel. Therefore, considering water infiltration into a streambed is essential for predicting the velocity and depth of unsaturated debris flow.

Physical and engineering properties of peat soil stabilized with the admixture of CACO3+rice husk ash due to water infiltration from surrounding areas

Peat is a type of soil with high organic content, very low bearing capacity, and high uneven settlement. Some methods to improve soil have been applied to peat in order to make it strong enough for civilization-building foundation situated on it. Peat stabilization is a method that is continuously developed considering that the cost it needs is lower and this approach is more environmentally friendly compared to other methods. The admixture of lime (CaCO3) and Rice husk ash, a new ecofriendly stabilizer material, has been applied to peat soil and showed a good result. However, in studies conducted previously, the effect of water infiltration from surrounding areas of soil was stabilized was not involved as variable influencing the change of parameter. Based on that, this laboratory study was carried out to model the real condition in the field when the stabilization is performed and to identify the physical and engineering changes of peat soil in the 10th, 20th, and 30th days of stabilization in its border and middle parts, with the percentage of material stabilizer 5%, 10%, 15% and 20% of the unit weight of the initial condition of peat. The result of laboratory test shows that the addition of admixture of lime (CaCO3) and rice husk ash can improve the physical and engineering properties of peat soil are stabilized. Water infiltration occurred on peat soil is stabilized has not affected the physical and engineering properties of the soil. It can be seen from the physical and engineering properties of the border and central parts of peat soil is stabilized that still have a similar value. It is assumed to be caused by CaSiO3 gel formed still needs a longer duration to become stable gel. However, in this initial study it was known that the more stabilizers added, made the better the parameters of the stabilized peat soil.

Wetting Induced Deformation of Soils Triggering Landslides in Pakistan

Shallow and deep seated landslides in natural slopes are often induced by rainfall. The cause of the failure is usually considered to be due to the decrease in effective confining stress due to a suction loss by water infiltration. However, rainwater infiltrates into the slope surface resulting in a reduction of shear strength of soil and deformation and failure may occur even without significant change in effective stress. It is thus essential to examine the deformation and failure characteristics of the soil induced by wetting. This study investigates on the wetting-induced deformations under isotropic compression condition and triaxial shearing condition using a triaxial test apparatus for unsaturated soils. Two soil samples collected from the active landslide sites from Pakistan were used to examine both the shear strength and deformation behavior during water infiltration at different levels of deviatoric stress by keeping the deviatoric stress constant during the water infiltration stage. The test results showed that, even though the deviatoric stress is kept constant during water permeation at different stress levels, the distortional deformation was exhibited due to wetting by a significant amount for both samples. The effect of water infiltration on the deformation behavior of unsaturated soil regarding the change in the degree of saturation and void ratio was also observed. There was a decrease in the void ratio for both specimens during increasing the degree of saturation at different level of deviatoric stress ratio. Under higher deviator stress, more decrease in void ratio and an increase of the degree of saturation were observed. Therefore, it can be said that deformation of soil due to water infiltration is a critical phenomenon and it should be considered while analyzing the soil behavior due to water infiltration by rainfall or rise in groundwater level, even if the slope is not failed, significant deformations may hinder the performance of natural slopes.

Effects of Water Infiltration into an Unsaturated Streambed on Debris Flow Development

Effects of Water Infiltration into an Unsaturated Streambed on Debris Flow Development

Effect of Water Infiltration, Injection Rate and Anisotropy on Hydraulic Fracturing Behavior of Granite

Hydraulic fracturing tests on Pocheon granite cylinders at seven different injection rates varying from 1 to 100 mm3/s were conducted. They were compared with sleeve fracturing tests in which borehole was sleeved, and therefore, water infiltration influence was excluded. Hydraulic fracturing behavior of granite is significantly influenced by water infiltration, which is closely related to the preexisting microcracks in granite as well as the cleavage anisotropy. There was a threshold injection rate to fracture the granite specimen under given stress conditions. When the injection rate is below the threshold, water infiltrated granite matrix with slow increment of injection pressure, and the specimen finally reached a full saturation without fracturing. Injection pressure developed nonlinearly with time during water infiltration, while approximately linearly when infiltration was excluded. For both hydraulic and sleeve fracturing tests, breakdown pressure increases with increasing injection rate. The breakdown pressures by sleeve fracturing were more than two times higher than those in hydraulic fracturing. X-ray computed tomography (CT) observations show that induced fractures are along the weaker cleavage parallel to the direction of the vertical stress. The higher breakdown pressure results in a larger aperture of fractures in hydraulic fracturing tests.

Effect of water infiltration through concrete block spillways on the slope stability of earth overflow dams

Using wedge-shaped concrete blocks (WSCB) to protect earth dams against overtopping has received much attention in recent years. The aim of this study is to assess the pattern of the infiltrated flow through the WSCBs system into the downstream shell of the earth dam. Moreover, its effects on the downstream slope stability are investigated using the finite-element analysis. A typical zoned earth overflow dam with the WSCB spillway is modelled. For this case study, the effects of depth and duration of overtopping as well as the permeability coefficient of the shell materials on the water infiltration pattern and the downstream safety factor are studied. The results show that if the permeability coefficient of shell materials is more than 10−3 cm/s, even for overflow with shallow depths, the infiltration rate and the extent of the saturated region will rapidly increase. Consequently, the safety factors will significantly decrease for such cases. However, if the materials with permeability coefficient less than 10−4 cm/s are chosen for the shell, using this type of spillway would not endanger the stability of the downstream slope.

Geotechnical and Rheological Characteristics of Saguenay Fjord Sediments Near the Transition from Solid to Liquid

This paper examines the geotechnical and rheological characteristics in terms of the transition from slide to flow in submarine landslides. This paper contains the results of a series of laboratory tests on the Saguenay Fjord fine-grained sediments. There are two types of tests: (1) vane shear tests in which intact and remolded samples are sheared and exposed to ambient water and (2) rheological tests performed on remolded sediment (with variable liquidity index) using a viscometer. The results explain the effect of water infiltration into soil. The sudden reduction in shear strength varied between about 300 and 800 Pa (Δw = 2–20%). The viscosity obtained from normalized flow curves (i.e., the logarithmic plot of shear stress versus the shear rate) were employed to characterize the rheology of soil. The mean value of viscosity (strength parameter in this case) as a function of shear rate from the results of fine-grained sediments varied between about 0.1 and 0.4. The values of yield stress and viscosity that were associated with the passage from the remolded to the fluidized state were in the range of 200 to 300 for Saguenay Fjord sediments.

Bioweathering related to groundwater circulation in cavities of magmatic rock massifs

Runoff flows not only on magmatic rocks massifs surface but also through their internal discontinuities, which define the secondary permeability of the rock. The effects, especially erosive, of the water movement on surface are well known although it is not the same with the effects of water infiltration through the rock. Especially, when it does so at low speed (trickles or seepage) granular disaggregation of the rock is produced at small scale, associated with a specific type of sediment (speleothems) of clast-supported open fabric which is able to store very small volumes of interstitial water, becoming a specific subterraneous microenvironment where some organisms develop their biological cycle totally or partially. Some products derived from the metabolic activity of these organisms incorporated to the infiltration water increase their ability to attack (weathering and dissolution) the rock. This process ends during the dry season when the troglobiont organisms die and the water-transported load, either dragged or in solution (mainly silicon), is sedimented forming the speleothems. The study of these deposits using several techniques, mineralogical, sedimentological, and biological (including metagenomics), indicates an influence of microorganisms on the formation of these deposits; therefore, it is correct to consider them as biospeleothems.

Comparison of snowpack on a slope and on flat land focusing on the effects of water infiltration

Water infiltration of snowpack plays an important role in the formation of wet avalanches. Several studies have examined water infiltration of snowpack on flat land. However, because water flow has a directional component parallel to the slope in snowpack on a slope, the effects of water infiltration into snowpack may differ between flat land and slopes, where avalanches are more likely to occur. From January 2012 to April 2012, we simultaneously observed snow pits on flat land and on a slope (40° incline; NE aspect). The observations showed that MFr (the ratio of the total thickness of the layers composed of melt forms to the thickness of all layers of the snowpack) was, on average, 23% higher for the snowpack on the slope than for the snowpack on flat land, despite the slope's being a shaded side slope. The largest difference between the MFr of the slope and that of the flat land was observed in early March, when MFr was 99% at the slope and 46% at the flat-land site. We analyzed these observations using a one-dimensional multi-layer snowpack model proposed by Katsushima et al. (2009). The model included parameterization of the vertical water-channel process in snowpack. Based on the results, to represent the MFr at each site, the amount of water infiltrating through vertical water channels was estimated at 27.4mm (2% of the total amount of water provided from the snow surface) for the slope and 797.2mm (54%) for the flat land. Our results indicate that in wet-snow regions, differences in the water infiltration process can generate notable differences between snowpack on a slope and that on flat land.

Stability analysis of rainfall-induced slope failure: a review

Rainfall is one of the most significant triggering factors for slope failures in many regions around the world. Numerous research studies have been conducted to investigate infiltration of rainwater into a slope, and the effect of water infiltration on slope stability. In this paper, a review of existing research on infiltration analysis and slope stability analysis under rainfall infiltration is presented. Studies on infiltration analysis with conceptual models, analytical analysis and numerical modelling are first reviewed. The typical pore water pressure profiles in the slope are then discussed. Subsequently, recent developments in analyses of slope instabilities under rainfall conditions using the limit equilibrium method and coupled hydro-mechanical modelling are summarised, and major findings on critical hydrological factors related to rainfall-induced landslides are summarised and discussed. Finally, several research topics are suggested for further study.

Effects of water infiltration and storage in cultivated soil on surface irrigation

Abstract Surface irrigation analysis and design require the knowledge of the variation of the cumulative infiltration water Z (L) (per unit area) into the soil as a function of the infiltration time t (T). The purpose of this study is to evaluate water infiltration and storage under surface irrigation in an alluvial clay soil cultivated with grape yield, and to determine if partially wetted furrow irrigation has more efficient water storage and infiltration than traditional border irrigation. The two irrigation components considered were wet (WT) and dry (DT) treatments, at which water applied when available soil water reached 65% and 50%, and the traditional border irrigation control. Empirical power form equations were obtained for measured advance and recession times along the furrow length during the irrigation stages of advance, storage, depletion and recession. The infiltration (cumulative depth, Z and rate, I) was functioned to opportunity time (to) in minute for WT and DT treatments as: ZWT = 0.528 to0.6, ZDT = 1.2 to0.501, IWT = 19 to−0.4, and IDT = 36 to−0.498. The irrigation efficiency and soil water distribution have been evaluated using linear distribution and relative schedule depth. Coefficient of variation (CV) was 5.2 and 9.5% for WT and DT under furrow irrigation system comparing with 7.8% in border, respectively. Water was deeply percolated as 11.88 and 19.2% for wet and dry furrow treatments, respectively, compared with 12.8% for control, with no deficit in the irrigated area. Partially wetted furrow irrigation had greater water-efficiency and grape yield than both dry furrow and traditional border irrigations, where application efficiency achieved as 88.1% for wet furrow irrigation that achieved high grape fruit yield (30.71 Mg/ha) and water use efficiency 11.9 kg/m3.

Impact of coal combustion waste on the microbiology of a model aquifer

The effects of water infiltration into an alkaline coal combustion waste burial site on the chemical and microbiological aspects of a meso-scale (2.44 m diameter × 4.6 m, height, 65 tonne) model aquifer were analyzed. The spatial and temporal effects of the alkaline leachate on microbial activity, numbers and diversity were examined in the model and compared with uncontaminated control materials. Within the saturated zone below the waste there was a pH gradient from 12.4 at the water table, immediately below the waste, to 6.0 at 3.5 meters from the waste, and elevated levels of arsenic and strontium in the pore waters. Microtox testing of the contaminated pore waters indicated high toxicity (a gamma value of 1 at dilutions of 45 to 110 fold). The leachate contamination was associated with a reduction in bacterial [3H] leucine incorporation from a high of 267 fmol g−1 h−1 in sediments below the contaminant plume to undetectable in the contaminated zone. In comparison, leucine incorporation rates in control column sediments were 899 fmol g−1 h−1. Similar toxic effects were evident in reduced total direct and culturable counts of bacteria. Observations also indicated a reduction in microbial diversity and development of alkaline-tolerant microbial communities. These results indicated that any failure of confinement technologies at disposal sites would adversely affect both the chemistry and microbiology of the underlying saturated zone.