Soil Mechanics Principles Research Articles

Stability analysis of an unsaturated expansive soil slope subjected to rainfall infiltration

Shallow failures occur frequently in both engineered and natural slopes in expansive soils. Rainfall infiltration is the most predominant triggering factor that contributes to slope failures in both expansive soils and clayey soils. However, slope failures in expansive soils have some distinct characteristics in comparison to slopes in conventional clayey soils. They typically undergo shallow failures with gentle sliding retrogression characteristics. The shallow sliding mass near the slope surface is typically in a state of unsaturated condition and will exhibit significant volume changes with increasing water content during rainfall periods. Many other properties or characteristics change such as the shear strength, matric suction including stress distribution change with respect to depth and time. All these parameters have a significant contribution to the expansive soil slopes instability and are difficult to take into consideration in slope stability analysis using traditional slope stability analysis methods based on principles of saturated soil mechanics. In this paper, commercial software VADOSE/W that can account for climatic factors is used to predict variation of matric suction with respect to time for an expansive soil cut slope in China, which is reported in the literature. The variation of factor of safety with respect to time for this slope is computed using SLOPE/W by taking account of shear strength reduction associated with loss of matric suction extending state-of-the art understanding of the mechanics of unsaturated soils.

The influence of soil suctions on the deformation characteristics of railway formation materials

Abstract Changing climatic conditions worldwide are causing changes in moisture conditions of railway formations and slopes, thereby either strengthening or weakening them. Current railway formation design methods do not take into account the changing moisture conditions over the predicted life of a railway formation. These changes in soil strength are due to the influence of soil suctions. The basic principles of unsaturated soil mechanics are well established in the field of geotechnics, and this study joins an international body of work that seeks to apply unsaturated soil theory to the field of railway and pavement formation materials. This study comprised box testing of subgrade and subballast formation materials at different moisture contents to demonstrate the behaviour of these two materials relative to each other. The formation models were instrumented with tensiometers to monitor the effect of cyclic loading and loading frequency on material behaviour and soil suction under typical heavy haul loading (26 tonne/axle). The study also investigated the evolution of suctions present in railway formation materials as well as practical aspects relating to suction measurement under cyclic loading conditions. Suctions were successfully measured in both the subgrade and subballast materials subjected to cyclic loading, demonstrating the different suction magnitudes generated by the materials under typical railway formation conditions. The well-drained subballast material was found to generate low magnitudes of suction over a large range of degrees of saturation (1 kPa – 15 kPa), while the less well-drained subgrade material was found to generate a greater range of suctions (1 kPa – 95 kPa) with a smaller variation in the degree of saturation. The deformability of the subgrade material depended to a greater on the moisture state and soil suctions compared to the subballast material and showed a large variation in deformability as a function of its moisture state. At its wettest, the subgrade material experienced deformation exceeding the allowable failure limit, while the subgrade material deformed less than the subballast material at its driest. The subballast deformation was significantly affected by the loading frequency and less by its moisture state due to the low suctions present. The findings of this study have practical implications for both in-situ and laboratory testing of railway formation materials and emphasized the importance of the moisture state of the formation during the railway service life.

Implications on Characterizing the Extremely Weak Sherwood Sandstone: Case of Slope Stability Analysis Using SRF at Two Oak Quarry in the UK

In the past, engineering geology mainly focused on soil and hard rocks, with little attention paid specifically to weak/soft rocks, defined by a UCS below 25 MPa (ISRM in Int J Rock Mech Min 18:85–110, 1981). Weak rock is an intermediate, which is difficult to analyze, and requires application of both soil and rock mechanics principles. The Sherwood Sandstone Group (SSG) in Nottinghamshire (UK) is often characterized as weak rock, containing extremely weak members, which display a UCS between 0.6 and 1 MPa according to the definition from BS 5930:2015 (British Standards Institution 2015). Little research has been conducted on the locally extremely weak members of the Sherwood Sandstone Group, in particular the Nottingham Castle Sandstone Formation, and engineering projects within this unit can face major design challenges. This study aims at investigating the intact material, characterizing the SSG and analysing the stability of a slope in a quarry between two water-filled silt lagoons at the Two Oak Quarry, close to Mansfield. Laboratory testing, including UCS tests, triaxial tests, tensile tests and Slake Durability tests, is conducted on the two geological units present on site, the Nottingham Castle Sandstone Formation and the Lenton Formation. From the analysis presented herein it is observed that the strength decreases as the degree of saturation increases, which can lead to a complete disintegration of the rock. In addition, the durability of the rock is determined, ranging from very low to moderately high, which has major implications on the longterm stability of the slope. The impact of the weathering on the long-term stability is difficult to establish and an estimation of the disintegration is conducted by comparing block sizes. A structural assessment confirms that failure along discontinuities is possible and requires further investigation. The Finite Element Analysis and the Limit Equilibrium Method are used for the assessment of the stability. Since similar factor of safety (FoS) are determined, both methods are considered applicable to the project, with limitations being detected when modelling discontinuities, impacting the design and the FoS. A suitable slope geometry is proposed, based on the intact material properties, the weathering characteristics, the heterogeneity of the material and structural features.

Volume change behavior of bentonite-sand mixture under constant suction condition

The unsaturated state of soil can raise many geotechnical problems upon wetting-drying cycles such as volume change resulting in collapse or swell, change in the shear strength, and change in the hydraulic conductivity. The classical principles of soil mechanics for saturated soil are often not suitable for explaining these phenomena. An experimental work was carried out to study the volume change behavior of Bentonite-Sand mixture under constant suction condition. A mixture of 30% Calcigel bentonite and 70 % Haider sand (30B) were tested in this study. The applied suction was kept constant through the tests. Thirteen 30B specimens were tested under constant suction condition. Two different initial states (slurry and loose) were chosen to examine the effect of initial state on the volume change at unsaturated state. The results of first group (initially slurry state) show that once the suction was applied the compressibility of the specimens in this group followed the isotropic NCL up to 255 kPa suction. Subsequently, the slope of compression curve decreased. The results of increasing suction for initially slurry state show that the slope of compression lines became near to zero for suction higher than 600 kPa. Moreover, when applied suction is lower than the air-entry value, saev, the soil behaviors as the saturated soil. Therefore, the effective stress equation can be applied. The results of second group (initially loose state) show that the unsaturated preconsolidation pressure increases as the constant suction increases. The slopes of the unsaturated over consolidated paths in all tests were closed to the slope of saturated over consolidated path (Cr), while the slopes of the unsaturated normal consolidated (yield) state are higher than the slope of saturated NCL. Finally the results show that the slope of the unsaturated NCL is higher (steeper) than the slope of saturated NCL.

Modelling of paste ram extrusion subject to liquid phase migration and wall friction

Extrusion of solid-liquid particulate pastes is a well-established process in industry for continuously forming products of defined cross-sectional shape. At low extrusion velocities, the solids and liquid phases can separate due to drainage of liquid through the interparticle pores, termed liquid phase migration (LPM). The effect of wall friction, die shape and extrusion speed on LPM in a cylindrically axisymmetric ram extruder is investigated using a two-dimensional finite element model of paste extrusion based on soil mechanics principles (modified Cam-Clay). This extends the smooth walled model reported by Patel et al. (2007) to incorporate a simplified Tresca wall friction condition. Three die entry angles (90°, 60° and 45°) and two extrusion speeds are considered. The extrusion pressure is predicted to increase with the Tresca friction factor and the extent of LPM is predicted to increase with decreasing ram speed (both as expected). The effects of wall friction on LPM are shown to be dictated by the die shape and ram displacement: there are few general rules relating extruder design and operating conditions to extent of LPM, so that finite element-based simulation is likely to be needed to predict the onset of LPM accurately.

Effects of residual suction and residual water content on the estimation of permeability function

Soil-water characteristic curve (SWCC), which defines the relationship between water amount in the soil and matric suction, contains key information for the application of unsaturated soil mechanics principles to engineering practice. Best fit equations are commonly used for representation of the SWCC for unsaturated soils. Normally, these best fit equations are mathematically continuous and governed by a few fitting parameters. Either volumetric water content, θw or normalized volumetric water content, Θ, is adopted in the different best fit equations. If θw is used to establish SWCC, the parameter related to residual suction, Cr needs to be defined prior to fitting process of SWCC data. On the other hand, if Θ is used to develop SWCC, the residual volumetric water content, θr, needs to be defined prior to fitting process of SWCC data. Results of analyses in this study indicate that the performance of the best fit equation is not affected by the value of Cr, but it is significantly affected by the value of θr. As a result, the performance on the estimation of the permeability function is also affected by the value of θr. Different types of soils are used to investigate the effect of Cr and θr on the performance of the best fit equation and the estimation of the permeability function.

Fabrication and Mechanical Characterization of Hydrogel Infused Network Silk Scaffolds.

Development and characterization of porous scaffolds for tissue engineering and regenerative medicine is of great importance. In recent times, silk scaffolds were developed and successfully tested in tissue engineering and drug release applications. We developed a novel composite scaffold by mechanical infusion of silk hydrogel matrix into a highly porous network silk scaffold. The mechanical behaviour of these scaffolds was thoroughly examined for their possible use in load bearing applications. Firstly, unconfined compression experiments show that the denser composite scaffolds displayed significant enhancement in the elastic modulus as compared to either of the components. This effect was examined and further explained with the help of foam mechanics principles. Secondly, results from confined compression experiments that resemble loading of cartilage in confinement, showed nonlinear material responses for all scaffolds. Finally, the confined creep experiments were performed to calculate the hydraulic permeability of the scaffolds using soil mechanics principles. Our results show that composite scaffolds with some modifications can be a potential candidate for use of cartilage like applications. We hope such approaches help in developing novel scaffolds for tissue engineering by providing an understanding of the mechanics and can further be used to develop graded scaffolds by targeted infusion in specific regions.

A general analytical solution for the evolution of cliffs accounting for strength degradation, seismic action, formation of tension cracks and seepage

The evolution of natural slopes over time is ruled by several concurrent physical phenomena, namely the strength of its component geomaterials and their weakening over time due to weathering processes, the occurrence of seismic events, seepage and the formation of tension cracks. The paper presents analytical solutions obtained considering a succession of discrete failure events (landslides) progressively altering the slope morphology over time. The model, derived in the framework of limit analysis assuming plane strain conditions, provides a tool for the assessment of whether manufacts and/or infrastructures located on a slope subject to various natural degradation phenomena will be affected by the occurrence of failures.Unlike current empirical and semi-empirical models of slope evolution, the analytical solution that is here presented is derived by applying principles of soil and rock mechanics, therefore it is of general validity, so that no ad–hoc calibration against past observations of the evolving slope is needed. This analytical technique only requires knowledge of the (geotechnical) parameters characterising the geomaterials comprising the slope of interest, namely angle of shearing resistance, ϕ, cohesion, c, tensile strength, unit weight, together with knowledge of the relevant seepage scenarios, strength degradation processes, and seismic events likely to occur.Results show that that earthquake loading and seepage can substantially decrease slope stability, increase the volume of material sliding away during each landslide event and alter the evolution of the slope over time, while tensile strength exhibits a less strong influence especially as strength degradation progresses. Dimensionless ready-to-use charts are provided for the benefit of practitioners.

Performance of Residual Soil as Cover System for a Sanitary Landfill in Singapore

AbstractA large amount of construction waste creates problems related to cost and space for disposal, especially for countries with limited land like Singapore. Therefore, it is important to choose a suitable landfill management system (e.g., cover system) for optimization of landfill area in Singapore. In this paper, the performance of a cover system for minimizing rainwater infiltration into a sanitary landfill in Singapore is presented. The cover system was designed using principles of unsaturated soil mechanics. In this study, a residual soil from Old Alluvium with a low coefficient of unsaturated permeability was used in the cover system. Comprehensive geotechnical instrumentation was installed in the landfill area to monitor the pore-water pressure changes within the cover system and landfill during and after rainfall. Laboratory tests were conducted to characterize the index and engineering properties of the residual soil for the cover system under saturated and unsaturated conditions. The finite-e...

Use of Dual Capillary Barrier as Cover System for a Sanitary Landfill in Singapore

Construction and demolition of buildings together with the reconstruction of roads produce a lot of solid wastes every year. These wastes create problems related to cost and space for disposal, especially for countries with limited land area like Singapore. Therefore, it is important to choose suitable landfill management system (i.e. cover system) for optimization of landfill area in Singapore. Landfill cover offers many geo-environmental benefits, including reducing water infiltration, isolating waste and controlling landfill gases. In Singapore the cover system is located within the unsaturated zone above the groundwater table. Therefore, it is necessary to incorporate unsaturated soil mechanics principles in designing the cover system for the landfill. Soil properties in the unsaturated soil zone affect the rate of wetting front movement from the ground surface. As a result, the rates of changes in pore-water pressures during and after rainfall will vary in accordance with the characteristics of unsaturated soil properties. In this study, the performance of dual capillary barrier (DCB) in minimizing rainwater infiltration into a sanitary landfill in Singapore was investigated. The DCB consists of fine recycled asphalt pavement (RAP) and coarse RAP as the materials for the fine- and coarse-grained layers, respectively. The recycled materials were used in the DCB to reduce the cost associated with the construction of a cover system in the field and to maintain environmental sustainability. Laboratory tests were conducted to characterize the index properties and hydraulic properties (i.e. soil–water characteristic curve (SWCC) and permeability function) of the RAP for the cover system under saturated and unsaturated conditions. The SWCC and permeability function were used in the finite element seepage analyses to study the effect of climate change on the soil cover system. The results from the seepage analyses show that the DCB was effective in minimizing rainwater infiltration into the sanitary landfill.

Application of fitting parameters in best fit equation

Soil-water characteristic curve (SWCC) contains key information for the application of unsaturated soil mechanics principles to engineering practice. SWCC variables such as air-entry value, residual suction and residual saturation are commonly referred to for estimation of other unsaturated soil properties. Though there are clear definitions for these SWCC variables, it is difficult to measure them directly in laboratory and these SWCC variables are commonly estimated from SWCC. Hydraulic conductivity of unsaturated soil is the major property that controls water flow in soil. The laboratory measurement of hydraulic conductivity is time consuming and costly. Therefore, hydraulic conductivity is also commonly estimated from SWCC. Normally, SWCC is represented by a best fit equation which is typically governed by few fitting parameters. These fitting parameters can be obtained from a best fit procedure and are proven to be dependent on each other. Fredlund and Xing’s (1994) equation is one of the popular equations commonly used by researchers and there are only three fitting parameters such as “a”, “n”, “m” in this equation. Correlation equations between SWCC variables, hydraulic conductivity and the fitting parameters such as “a”, “n” and “m” are presented in this paper. In addition, the variability in the determined SWCC variables and hydraulic conductivity due to the variation in these fitting parameters is also discussed in this paper.

Unsaturated Soil Mechanics Principles to Remove and Replace Mitigation for Expansive Clays

The efficacy of removal and replacement as a mitigation alternative for expansive soil is discussed in view of numerical unsaturated flow/deformation results. Observations with respect to selection of depth and replacement soil type (similar, more, or less permeable than underlying expansive clay) are presented in the context of unsaturated flow and stress/deformation principles. Comparisons are made between various remove and replace options on the basis of extent and degree of wetting (changes in soil suction) and on ground surface total and differential movements. Selection of optimal removal and replacement depth and replacement material type requires consideration of unsaturated flow principles and understanding of the role of both net normal stress and matric suction in unsaturated soil response. Complexities in the unsaturated flow process which impact the efficacy of the remove and replace method are primarily because of the highly nonlinear nature of the unsaturated soil storage function (SWCC) and hydraulic conductivity function. Further, because the unsaturated hydraulic conductivity of soils depends on the value of soil suction, placement water content of the replacement layer has significant effect on performance. The net result is that the impact of various remove and replace options is not always intuitive. The findings presented, although not encompassing of all possible removal and replacement configurations or surface flux conditions, set the stage for application of remove and replace mitigation methods based on fundamental unsaturated soil mechanics principles.

An advanced process-based distributed model for the investigation of rainfall-induced landslides: The effect of process representation and boundary conditions

Extreme rainfall events are the major driver of shallow landslide occurrences in mountainous and steep terrain regions around the world. Subsurface hydrology has a dominant role on the initiation of rainfall-induced shallow landslides, since changes in the soil water content affect significantly the soil shear strength. Rainfall infiltration produces an increase of soil water potential, which is followed by a rapid drop in apparent cohesion. Especially on steep slopes of shallow soils, this loss of shear strength can lead to failure even in unsaturated conditions before positive water pressures are developed. We present HYDROlisthisis, a process-based model, fully distributed in space with fine time resolution, in order to investigate the interactions between surface and subsurface hydrology and shallow landslides initiation. Fundamental elements of the approach are the dependence of shear strength on the three-dimensional (3-D) field of soil water potential, as well as the temporal evolution of soil water potential during the wetting and drying phases. Specifically, 3-D variably saturated flow conditions, including soil hydraulic hysteresis and preferential flow phenomena, are simulated for the subsurface flow, coupled with a surface runoff routine based on the kinematic wave approximation. The geotechnical component of the model is based on a multidimensional limit equilibrium analysis, which takes into account the basic principles of unsaturated soil mechanics. A series of numerical simulations were carried out with various boundary conditions and using different hydrological and geotechnical components. Boundary conditions in terms of distributed soil depth were generated using both empirical and process-based models. The effect of including preferential flow and soil hydraulic hysteresis was tested together with the replacement of the infinite slope assumption with the multidimensional limit equilibrium analysis. The results show that boundary conditions play a crucial role in the model performance and that the introduced hydrological (preferential flow and soil hydraulic hysteresis) and geotechnical components (multidimensional limit equilibrium analysis) significantly improve predictive capabilities in the presented case study.

Some Misconceptions in Pile Insertion Analysis of Offshore Platforms in Shengli Chengdao Oilfield

According to some actual cases of pile insertion analysis, combined with specialty norms and principles of soil mechanics in this paper, a few common misconceptions in pile insertion analysis of offshore platforms in Chengdao Oilfield are summarized. Type of common misconceptions, causes and adverse effects are analyzed, and countermeasures are put forward to correct misunderstandings and improve the accuracy of pile insertion calculation and analysis. Cases of analysis errors can be easily found because of unclear soil layer classification, difficultly recognized geotechnical properties, inaccurately divided layer uniformity, inadequately considered structure and soil interaction responses, etc. in offshore platforms pile insertion analysis, thus many unnecessary losses appear in oilfield production. By improving survey quality, using a variety of means of investigation, paying more attention to soil layer uniformity in well field, properly evaluating strength of laminated soil, doing anti-slip platform evaluation when pile is inserted too shallow, etc. can reduce errors effectively.

Tailings Subaerial and Subaqueous Deposition and Beach Slope Modeling

The tailings beach slope is a fundamental parameter for the design and operation of tailings storage facilities because it affects the tailings storage capacity, pond levels, and phreatic surfaces within the containment structures. Understanding tailings beach development is particularly important for thickened and paste tailings facilities, where the tailings can form a self-stacking structure. This paper presents a theoretical tailings deposition model that can describe the formation of tailings beach slopes in both subaerial and subaqueous deposition environments. The depositional behavior and deposition mechanisms are investigated from both geotechnical and hydraulic engineering perspectives. The model is developed to capture deposition mechanisms based on the principles of soil mechanics and fluid mechanics. The governing differential equations can be solved using a numerical technique, and the solution scheme can readily be implemented in computer languages. Case studies for subaerial deposition demonstrate that the modeling results are in agreement with laboratory flume testing and field measurements. The proposed model considers geotechnical and rheological properties of tailings, water pressures, operation parameters, and site topographic conditions. A sensitivity study was carried out to provide insight into the effects of influencing factors on the beach slope.

Development of Soil-Water Characteristic Curve for Flexible Base Materials Using the Methylene Blue Test

AbstractThis study describes an experimental investigation of the methylene blue test to determine the methylene blue value (MBV) and quantitatively generate the soil-water characteristic curve (SWCC) for unbound aggregate material based on the predicted percent fines content (PFC). The traditional methylene blue test has been improved significantly in terms of time, sample size, and method for analyzing the results. These improvements enable the methylene blue test to be not only a laboratory test but also a field test. This improved methylene blue test methodology is used to generate the SWCC for unbound aggregate material. The relationship between the MBV and the PFC value is established. The principles of unsaturated soil mechanics are taken into account to develop regression models for determining the four fitting parameters in a previously developed SWCC equation by using the predicted PFC value, which are then used to generate the SWCC for the unbound aggregates. The proposed method is validated by...

Southwestern Skyscraper: The Gulf Building

Once the tallest tower in the American Southwest, the Gulf Building (today the JPMorgan Chase Building) marked a turning point in the application of the principles of soil mechanics to foundation design.

Quantitative Interpretation of Tracks for Determination of Body Mass

To better understand the biology of extinct animals, experimentation with extant animals and innovative numerical approaches have grown in recent years. This research project uses principles of soil mechanics and a neoichnological field experiment with an African elephant to derive a novel concept for calculating the mass (i.e., the weight) of an animal from its footprints. We used the elephant's footprint geometry (i.e., vertical displacements, diameter) in combination with soil mechanical analyses (i.e., soil classification, soil parameter determination in the laboratory, Finite Element Analysis (FEA) and gait analysis) for the back analysis of the elephant's weight from a single footprint. In doing so we validated the first component of a methodology for calculating the weight of extinct dinosaurs. The field experiment was conducted under known boundary conditions at the Zoological Gardens Wuppertal with a female African elephant. The weight of the elephant was measured and the walking area was prepared with sediment in advance. Then the elephant was walked across the test area, leaving a trackway behind. Footprint geometry was obtained by laser scanning. To estimate the dynamic component involved in footprint formation, the velocity the foot reaches when touching the subsoil was determined by the Digital Image Correlation (DIC) technique. Soil parameters were identified by performing experiments on the soil in the laboratory. FEA was then used for the backcalculation of the elephant's weight. With this study, we demonstrate the adaptability of using footprint geometry in combination with theoretical considerations of loading of the subsoil during a walk and soil mechanical methods for prediction of trackmakers weight.

Finite-element analysis of the failure and reconstruction of the main dam embankment at Abberton Reservoir, Essex, UK

An existing 15·5 m high main dam embankment at Abberton Reservoir in Essex was completed in August 1938, since when its performance has been satisfactory. However, the upstream embankment shoulder of the original dam suffered a deep-seated failure through its foundation towards the end of construction in July 1937, 9 days before a similar and well-known failure occurred at Chingford Reservoir in close proximity to Abberton. Whereas the failure at Chingford became an important case in the history of soil mechanics through the involvement of Karl Terzaghi and marked one of the first applications of modern soil mechanics principles, the failure at Abberton has remained largely unknown, until recently when raising of the existing dam started to be considered. This paper describes advanced finite-element analyses which were carried out to investigate the failure of the original dam at Abberton and the stability of the existing main dam. The parameters used in the constitutive models were derived on the basis of the available site investigations and laboratory testing and on experience in the back-analysis of other failures in London Clay. The analyses demonstrated that the upstream shoulder of the original embankment failed through the mechanism of progressive failure, which involved the top of the stiff plastic London Clay rather than the overlying alluvium in the foundation. The relatively rapid rate of embankment filling, achieved by using modern earth-moving equipment, contributed significantly to the original dam failure. The analyses also demonstrated satisfactory behaviour of the existing dam during reconstruction, the first impounding and in the long term, with its response being similar to that observed. Thus the constitutive models used and parameters derived were successfully calibrated against the observed behaviour of both the original and existing main dams at Abberton, and could be used in predicting the behaviour of the dam during and after its proposed raising.

Use of recycled crushed concrete and Secudrain in capillary barriers for slope stabilization

A capillary barrier is a two-layer cover system having distinct hydraulic properties to minimize water infiltration into the underlying soil by utilizing unsaturated soil mechanics principles. In this study, a capillary barrier system was designed as a cover system for a residual soil slope to maintain stability of the slope by minimizing infiltration during heavy rainfalls in the tropics. The capillary barrier system (CBS) was constructed using fine sand as the fine-grained layer and recycled crushed concrete aggregates as the coarse-grained layer. The coarse-grained layer is commonly constructed using gravels or granite chips. However, due to scarcity of aggregates and in consideration of environmental sustainability, recycled crushed concrete aggregates were used as the coarse-grained layer in this project. The suitability of recycled crushed concrete aggregates as a material within the coarse-grained layer of a CBS is subject to the hydraulic property requirement. For comparison, another CBS was constructed using fine sand as the fine-grained layer and a geosynthetic (Secudrain) as the coarse-grained layer. The performance of each constructed CBS on the residual soil slope was monitored using tensiometers installed at different depths — from 0.6 to 1.8 m below the slope surface — and a rainfall gauge mounted on the slope. An adjacent original slope without the CBS was also instrumented using tensiometers and piezometers to investigate the performance and effectiveness of the CBS in reducing rainwater infiltration and maintaining negative pore-water pressures in the slope. Real-time monitoring systems were developed to examine pore-water pressure, rainfall, and groundwater level in the slopes over a 1 year period. Characteristics of pore-water pressure distributions in the residual soil slope under a CBS with recycled crushed concrete aggregates and in the original slope during typical rainfalls are highlighted and compared. The measurement results show that the CBS was effective in minimizing rainwater infiltration and therefore, maintaining stability of the slope.