Thickness Of Soil Layer Research Articles

A new kinematic wave model that describes lateral subsurface flow and percolation in hillslopes

Kinematic wave (KW) models are commonly used for flood forecasting in large river basins, but have limitations in their ability to simulate percolation effects. Here, we suggest an extended KW model wherein the vertical pressure head is under non-hydrostatic conditions. The proposed model uses the Brooks Corey and Mualem models to estimate the water retention curve and unsaturated hydraulic conductivity and adopts the pressure head gradient as a new variable to calculate runoff based on changing water content distributions over time due to percolation. The increase in the pressure head gradient with rainfall infiltration is determined from the relationship between water storage and pressure head distribution, while the decrease in pressure head gradient due to percolation is modeled as exponential decay with time. A comparison of the proposed KW model and a numerical solution of the Richards equation shows that the proposed KW model can reproduce the storage effect caused by percolation, delaying runoff and reducing peak discharge. The agreement between the proposed KW model and the Richards equation is high for soils with high water retention. Conversely, the agreement becomes lower for soil with low water retention or deep soil layer thickness, where the complexity of water content distribution requires further refinement. The proposed model can easily be incorporated into distributed models while low computational cost with keeping the important percolation effects.

Investigating soil layers with ground penetrating radar in the modern Yellow River Delta of China

AbstractSoil layers affect the vertical movement of moisture and salt, eventually resulting in land cover and land use pattern changes. This study explored the ability of ground penetrating radar (GPR) to detect soil layers in the modern Yellow River Delta of China and assessed its accuracy. It was found that soil moisture and salt had a strong dampening effect on the electromagnetic wave signal which resulted in blurred GPR images of the soil profile below 1 m. The cultivated soil layers of different crop types, such as rice, wheat, corn and cotton, were accurately identified in GPR images. To estimate an individual soil layer thickness, the propagation velocity of the electromagnetic wave was calculated using soil mass moisture content, and the propagation time was confirmed by comparing the GPR image with the amplitude–time plot of the soil profile. The estimated thickness was 1.02 times the thickness determined in the field and the average estimation error was 0.04 m, which was 24.09% of the soil layer thickness determined in the field. The second derivative value of envelope amplitude energy with time (SDEA) was used to describe the amplitude change in the soil layers. The SDEA has negative logarithmic and power function relationships with soil mass moisture content and electrical conductivity, respectively. The present results provide a reference database for future quantitative soil investigation in the sedimentary plain area using GPR.

ESTIMATION DES TASSEMENTS DIFFÉRENTIELS DES SOLS DE FONDATION DE BÂTIMENT : CONTRIBUTION DES SONDAGES DE RÉSISTIVITÉ ÉLECTRIQUE

To estimate differential settlements of building foundation soils, the site on which the structure is based must be geotechnically surveyed in order to determine the deformation parameters and the thickness of the compressible soil layers in various places. This involves conducting destructive surveys. In this study, the use of geophysical methods (electrical soundings) as a substitute for the conventional methods used was considered. The Schlumberger electrodes array was deployed at the level of a control borehole and at three projected footings. The combination of the results of the electrical soundings with the lithological section of the borehole reveals a significant correlation between the variations of cumulative resistivities and the lithological section of the subsoil. The thickness of the compressible layers at the level of the projected footings is estimated to vary between 5 and 6 m. Œdometric differential settlements have an estimated maximum value of 4.56 cm

Instability mechanism of overlying strata in a shallow interval goaf and structural model of the “W-shaped voussoir beam”

Abstract To study the failure mechanism of overlying strata (OS) in shallow insufficient mining areas, with a combination of such research approaches as field investigation, theoretical analysis, similarity simulation, and numerical simulation, this paper studies the temporal and spatial evolution of the failure mechanism of overlying stratum structure in a shallow-buried interval goaf. The results show that the creep failure of temporary coal pillar (TCP) in the interval goaf is a primary reason for the failure of the basic roof. With the failure of the basic roof, stress arches in the OS of the mining section become unstable, which expands the damage range of the overlying strata. Consequently, adjacent stress arches overlap with each other, forming a “trapezoidal–semi-elliptical arch” collapse shape. Thick soil layers gradually collapse to the ground surface, and the OS collapse as a whole into a trapezoid-like shape. Rotary failure appears in the basic roof of mining section, forming a W-shaped voussoir beam hinge structure. In this study, a structural model of a W-shaped voussoir beam in the OS is established, and the mechanical characteristics of rock blocks in the basic roof of overlying strata during different mining stages of the interval goaf are analyzed. Also, with a discrete element UDEC program, this study performs a simulation to verify the rationality of the W-shaped voussoir beam structural model of overlying stratum movement in the shallowly buried interval mining section.

Characteristics of dust plasma environment at lunar south pole

Unlike the Earth, the Moon lacks is not protected from the atmosphere and global magnetic field, and will be directly exposed to complex radiation environments such as high-energy cosmic rays, solar wind, and the Earth’s magnetotail plasma. The surface of the Moon is covered with a thick layer of lunar soil, and the particles in the soil with a diameter between 30 nm–20 μm are called lunar dust. In the complex environments such as solar wind or magnetotail plasma, lunar dust carries an electric charge and becomes charged lunar dust. Charged lunar dust is prone to migration under the action of the electric field on the lunar surface. Charged migrated lunar dust is easy to adhere to the surface of instruments and equipment, resulting in visual impairment, astronauts’ movement disorders, equipment mechanical blockage, sealing failure, and material wear, which affects the lunar exploration mission. As an important lunar exploration landing site, the lunar south pole receives special solar radiation and produces a special dust plasma environment due to its special location. In order to provide an environmental reference for lunar south pole exploration, it is necessary to explore the characteristics of the dust plasma environment in the lunar south pole and its impact. In view of the lunar south pole environment, The Spacecraft Plasma Interactions Software (SPIS) software developed by the European Space Agency is used to carry out modelling and simulation in this work. Through the simulation, the logarithmic distribution of the lunar dust space density in a range of 0–200 m at the lunar south pole, the potential distribution near the lunar surface, and the spatial distribution characteristics of plasma electrons and ions are obtained. The obtained lunar dust space density and lunar surface potential are similar to the previous theoretical derivation and field detection data, so the simulation results have high reliability. The spatial potential distribution and the spatial density distribution of electrons and ions in the lunar environment with and without lunar dust are compared. Finally, the conclusions can be drawn as follows. The space potential increases with altitude increasing. The potential at 0–10 m near the lunar south pole is about –40 V, and the space potential at 100 m is about –20 V. The density of lunar dust in an altitude range below 10 m is 10<sup>7.22</sup> m<sup>–3</sup>–10<sup>4.66</sup> m<sup>–3</sup>. The electron density in the dust plasma near the lunar surface is 10<sup>5.47</sup> m<sup>–3</sup>, and the ion density is 10<sup>6.07</sup> m<sup>–3</sup>, and both increase with altitude increasing. Charged lunar dust affects the spatial distribution of lunar dust, mainly through affecting the distribution of the space electric field, which leads to difference in electron distribution, but has little effect on ions.

An Analytical Stabilization of Landslide on Road Foundation Soft Ground Improvement by SDCM Columns

The deep cement mixing (DCM) method is a solution for reinforcing soft ground and has been applied in many countries. In Vietnam, the DCM method has also been experimented on and obtained positive results, especially in medium-scale and below-construction sites in the Mekong Delta where there is a thick layer of soft sediment soil. However, stiffened deep cement mixing (SDCM) column has barely been researched and experimented on. For this reason, the research on theory and design method for the SDCM column, especially using the SDCM column for reinforcing road foundation on soft ground is the main topic of this paper. The result from analysis using the finite element method has shown that the factor of safety of soft ground reinforced by the SDCM column has increased from 0.532 to 1.746.

Study on the behavior of short pile groups on soft soil with sand leveling using a smallscale physical model with schneebeli analog material

This paper examines the effectiveness of short piles on soft ground with leveling sand, using a 2D small model. The study focuses on the geology of the Mekong Delta, which consists of a thick layer of soft soil and a layer of leveling sand with a thickness of 2-5m. The use of small and short piles (less than 30x30 cm and 5m or less) is a viable option for low-rise buildings in such conditions. The model replaces the sandy soil with a Schneebeli analog material and the weak clay with EPS foam, while short reinforced concrete piles are replaced by steel bars of the square cross-section. The vertical load tests were conducted on groups of piles, with variable parameters such as pile spacing, s, and the distance from the pile tip to the boundary of two soil layers, H. The results show that when the pile spacing, s, is constant and the distance from the pile tip to the boundary of two soil layers, H, decreases, as well as the deformed soil area under the pile tip. Conversely, when the pile spacing, s, increases, the failure of the soil under the pile tip becomes more localized. The use of a footing increases the bearing capacity of the pile group but also increases the vertical strain of the foam layer in both vertical and horizontal directions. Overall, the study shows that reinforcing soil with short piles significantly improves bearing capacity, increasing it by 2.3 to 3.5 times compared to unreinforced soil.

A numerical test of soil layering effects on theoretical and practical Beerkan infiltration runs

AbstractWith reference to a more compacted and less conductive upper soil layer overlying a less compacted and more conductive subsoil, a simple three‐dimensional (3D) infiltration run is expected to yield more representative results of the upper layer than the subsoil. However, there is the need to quantitatively establish what is meant by more representativeness. At this aim, numerically simulated infiltration was investigated for a theoretically unconfined process under a null ponded head of water (d0H0 setup, with d = depth of ring insertion and H = ponded depth of water) and a practical Beerkan run (d1H1 setup, d = H = 1 cm). The considered layered soils differed by both the layering degree (from weak to strong; subsoil more conductive than the upper soil layer by 2.3–32.4 times, depending on the layering degree) and the thickness of the upper soil layer (0.5–3 cm). It was confirmed that water infiltration should be expected to be more representative of the upper soil layer when this layer is the less permeable since, for a 2‐h experiment, the instantaneous infiltration rates for the layered soil were 1.0–2.1 times greater than those of the homogeneous low‐permeable soil and 1.3–20.7 smaller than those of the homogeneous coarser soil that constituted the subsoil. Similarity with the homogeneous fine soil increased as expected as the upper layer became thicker. For a weak layering condition, the layered soil yielded an intermediate infiltration as compared with that of the two homogeneous soils forming the layered system. For a strong layering degree, the layered soil was more similar to the homogeneous fine soil than to the homogeneous coarse soil. Using the practical setup instead of the theoretical one should have a small to moderate effect on the instantaneous infiltration rates since all the calculated percentage differences between the d1H1 and d0H0 setups fell into the relatively narrow range of −18.8% to +17.4%. A sequential analysis procedure appeared usable to detect layering conditions but with some modifications as compared with the originally proposed procedure. The practical setup enhanced the possibility to recognize the time at which the characteristics of the subsoil start to influence the infiltration process. In conclusion, this investigation contributed to better interpret both the theoretical and the practically established 3D infiltration process in a soil composed of a less conductive upper soil layer overlying a more conductive subsoil and it also demonstrated that modifying the recently proposed sequential analysis procedure only using infiltration data could be advisable to determine the time when layering starts to influence the process.

Study on Stability of Elastic Compression Bending Bar in Viscoelastic Medium

In the southeastern coastal regions of China, thick layers of marine soft soil are widely distributed, exhibiting characteristics such as high compressibility, high porosity, low strength, high sensitivity, and easy thixotropy, and these viscoelastic behaviors of foundation soil have significant implications for elastic compression bending bar, as evidenced by issues such as post-construction settlement of roadbeds and long-term operation deviation of bridge pile foundations. In this study, a mechanical model of an elastic bar embedded in an elastic and viscoelastic medium, fixed at the base and free at the top, is established based on the Winkler foundation assumption. The deflection function of a bar subjected to both axial force and locally distributed horizontal load is derived using the Rayleigh-Ritz method. Utilizing the elastic-viscoelastic correspondence principle, the viscoelastic medium surrounding the bar is modeled as an elastic medium in which the ground reaction coefficient varies within phase space formulation. This study provides a robust theoretical foundation for soft soil foundation engineering projects and fills a significant gap in the literature by offering a comprehensive framework for understanding displacement in elastic bars within viscoelastic media. Drawing upon the derivation of the deformation function for elastic rods within a viscoelastic medium, the findings of this research hold significant applicability across a range of domains. These include, but are not limited to, the expansion of roadways in regions characterized by coastal soft soil, as well as the monitoring of deformation and lifespan in bridge pile foundations.

Analytical solution for axial load transfer of floating piles

This paper presents an analytical solution for the analysis of axially-loaded compressible floating piles embedded in a homogeneous elastic soil layer of finite thickness. The mathematical model is based on a Tajimi-type elastic continuum formulation, that allows deriving an accurate closed-form expression for the frictional stresses developing at the soil-pile interface. The pile and its underlying soil column are considered as one-dimensional axially deforming rods, and solution of their governing equations leads to closed-form expressions for pile and soil displacements and stresses. The proposed model provides results of similar accuracy to boundary integral solutions for the special case of floating piles in elastic half-space, and to numerical analyses for the general problem of floating piles embedded in a layer of finite thickness. As such, the model is used to prepare charts for the settlement analysis of floating piles in practice, based on a parametric analysis that unveils the sensitivity of the axial response of floating piles to the different problem parameters.

Fuzzy inference system model for the spectrum characteristic periods of the Türkiye Building Earthquake Code (2007)

Seismic design codes define response spectra with crisp numerical classifications of seismic parameters, which mainly affect the spectrum's shape and determination of seismic design loads. The efficiency of structural safety and construction costs depends on the optimum design and accurately determined seismic forces. As presented in the seismic design codes, several parameters are utilized to calculate the seismic design forces with response spectra. This study proposes a rule-based fuzzy inference system (FIS) model with fuzzy set numbers to determine the relevant parameters. By defining the soil profile thickness and shear wave velocity as inputs, the model generates the spectrum characteristic periods specified in the Türkiye Building Earthquake Code (TBEC 2007). The response spectra of twenty different samples with the FIS and crisp models were generated and compared to assess the model's superiority. Unlike crisp seismic code classifications, the proposed FIS model accounts for imperfections in soil group selection and topmost soil layer thickness, offering a more realistic representation of uncertainties and proving to be an effective tool for addressing linguistic vagueness in seismic response spectra analysis. The comparison between fuzzy and crisp output seismic parameters revealed significant differences in response spectra shape and spectrum intensity values. The FIS model-generated spectra were more conservative in certain building locations, while in others, they provided similar or lower values, suggesting potential cost savings in design. The FIS model demonstrates its efficacy in producing more accurate and robust designs by considering the uncertainties inherent in the problem. Furthermore, this approach has the potential to be extended to study seismic parameters of other design codes, although further research is required to comprehensively explore its capabilities and limitations.

Зимiвля східної субтропiчної прiсноводної креветки (Macrobrachium nipponense dе Haan, 1849) в умовах басейну р. Днiстер

Purpose. To study the characteristics of wintering of Macrobrachium nipponense in natural conditions of the Lower Dniester basin and experimental assessment of the effect of physical condition, soil composition and type of shelter on the survival of wintering shrimps. Methodology. The results of field and experimental studies conducted in 2018–2020 were used in the study. The locations and conditions of mass wintering of shrimps in natural conditions in the lower reaches of the Dniester River were studied. The abundance of wintering individuals was determined by the method of direct counting and their physical condition was analyzed. Shrimps were kept in a RAS at the Laboratory of Aquatic Bioresources and Aquaculture of Odesa State Ecological University, where environmental parameters were maintained as close as possible to the conditions of wintering under natural conditions. In chronic experiments, the selectivity and effect of the composition of natural substrates and the thickness of the soil bed on shrimp survival were investigated. The selection and effectiveness of the shrimp’s use of above-ground shelters of various natural and anthropogenic origin for shrimp wintering was assessed depending on their physical condition (presence or absence of injuries). Shrimp for experiments were caught in October - November in the lower reaches of the Dniester River and the Dniester estuary. The location of mass wintering of shrimps was recorded using a GPS navigator. Findings. It was established that shrimp M. nipponense in natural conditions of the Lower Dniester river winters in aboveground shelters (of natural and anthropogenic origin) or by burrowing into the soil. The shrimp’s choice of aboveground shelters for wintering in natural conditions depended on their physical condition. Injured individuals (lost claws and limbs) preferred easily accessible aboveground shelters (sheaves of grass, flooded snags). Healthy individuals wintered in cracks between plant roots and stones. A significant part of shrimps overwintered in aboveground shelters of anthropogenic origin. The most complex and reliable aboveground shelters of natural origin were occupied by the least damaged shrimp individuals. More than 59% of shrimps are buried in the soil (soil shelters) for wintering. Healthy individuals prefer sandy soils or soils that contain sand. The highest yield of healthy shrimp overwintering was observed on sandy or sandy-gravel soils with a thicker soil layer. The depth of burial of shrimp depended on soil composition. It was the maximum in soils consisting of sand, sand-gravel mixture and chernozem or chernozem with inclusions of gravel. The survival of wintering individuals was inversely dependent on the depth of burial. The maximum yield of uninjured individuals from wintering was observed when they were buried in the soil, the minimum — when using aboveground shelters. The share of surviving injured shrimp in soil shelters decreased in proportion to the severity of the injury. Maximum survival of injured individuals was ensured by wintering in aboveground shelters. Originality. For the first time, the data of field observations on wintering of alien shrimp M. nipponense in the conditions of the Lower Dniester basin are presented. Locations and conditions of mass wintering in natural conditions have been established. As a result of experimental studies, an analysis of the selectivity and effectiveness of the use of soil and aboveground shelters of various natural and anthropogenic origins by shrimp during wintering, their selectivity depending on the physical condition of wintering individuals (presence or absence of injuries) is given. Practical value. In the conditions of progressive climatic changes, one of the urgent tasks is the acclimatization of promising objects of aquaculture in new natural ecosystems. The obtained results can be used for the development of methods of anthropogenic reproduction and controlled cultivation of shrimp M. nipponense in aquaculture in the south of Ukraine. Key words: Dniester River, Macrobrachium nipponense, wintering, aboveground shelters, ground shelters, physical condition of individuals, survival.

Feasibility Assessment of a Magnetic Layer Detection Method for Field Applications

The lack of current data on the spatial distribution of soil erosion hinders the ability to predict soil erosion on slopes. To address this problem, we present a simple and sensitive soil erosion measurement method called the magnetic layer detection (MLD) method. This method can measure the changes in soil layer thickness (SLT) at a site featuring a pre-buried magnetic layer (ML) using the relationship between magnetic susceptibility and soil thickness, and then use this information to determine the erosion or accumulation at that point. To verify the adaptability and accuracy of this method, we designed three field tests. First, we conducted a simulated sediment siltation experiment using the erosion pin (EP) method as the control. This experiment demonstrated the accuracy of the MLD method for measuring SLT (Rad2 = 0.97, NSE = 88.14%, and RMSE = 1.17 mm). Next, a simulated rainfall experiment with the runoff plot (RP) method as a control was used to demonstrate the effectiveness of the MLD method under water erosion. The results demonstrated that this method can reliably estimate soil erosion on both bare plots (Rad2 = 0.83, NSE = 71.78%, and RMSE = 0.56 mm) and sparse grass plots (Rad2 = 0.90, NSE = 81.77%, and RMSE = 0.25 mm), with performance that is better than that of the traditional EP method. Finally, a soil scouring experiment, again with the RP method as a control, was designed to verify whether the MLD method could accurately measure the erosion of a slope after the soil was scoured by surface runoff. The MLD method could accurately measure the slope erosion (Rad2 = 0.91, NSE = 89.55%, and RMSE = 0.42 mm), with results superior to those of the traditional EP method. The MLD method’s results were similar to those from the laser scanner (LS) method, but more accurate and with less associated cost and data processing time. Therefore, the MLD method has potential as a reliable measurement method that can provide useful guidance for elucidating the spatial distribution of soil erosion and predicting slope soil erosion. This approach could be used to obtain raw data to quantify soil erosion on the Loess Plateau of China and beyond.

Localization of underground pipe jacking machinery: A reliable, real-time and robust INS/OD solution

Accurate positioning is important for guidance control in pipeline construction, but traditional approaches fail in GPS-denied environments. This paper addresses the underground localization problem for the pipe jacking machine by presenting an Inertial Navigation System (INS)/ODometry (OD) scheme. It is a loosely coupled navigation system that combines an INS and an OD to provide reliable, real-time, and robust location estimation in an enclosed and restricted space. The combination is achieved by a multi-sensor fusion algorithm to avoid the divergence of standalone INS. Compared with the traditional localization technologies, the advantage of the INS/OD scheme is that there is no performance degradation or service failure despite severe blockage of the thick soil layer due to the selection of dead reckoning-based sensors. Moreover, an Unbiased Finite Impulse Response (UFIR) filter serves as the fusion mechanism to improve the robustness against a prior knowledge of noise, considering unknown and time-varying noise statistics in practice. The INS/OD scheme is verified through a numerical simulation and employed on-site in a real underground sewage pipeline construction project. Despite the construction site being more than 10 meters deep underground, the INS/OD scheme continues to perform reliably and robustly in real-time, significantly benefiting the engineering guidance enterprise.

Habitat characteristics, population structure, distribution, and regeneration status of Taxus wallichiana in South Vietnam

Abstract. Hop NV, Xiong CC, Quy NV, Luong NT. 2023. Habitat characteristics, population structure, distribution, and regeneration status of Taxus wallichiana in South Vietnam. Nusantara Bioscience 15: 179-188. Taxus wallichiana Zucc. is an endangered plant species with high economic value, making it threatened to extinction. Biological information about this species is therefore essential for its conservation. This study is aimed to assess the habitat characteristics, population structure, distribution, and regeneration status of T. wallichiana in South Vietnam. Vegetation surveys were conducted from 2016 to 2021 in three regions in Lam Dong Province. The study revealed that it was distributed in regions with monsoon climate with a total extent of ??379.57 ha, with habitats located on the hillside, narrow shelves, dissected terrain, high slope, on feralite soil with light brown to yellow, red, the soil layer thickness over 0.3 m and in clusters or streaks. The study recorded 634 trees with a diameter at breast height (DBH)?25 cm and 137 trees with 6 cm ?DBH<25 cm. The trees were found primarily at 1401-1500 m above sea level in a mixed broadleaved-coniferous forest. The growth indicators of DBH and overall height (Hvn) developed strongly, but the stand volume was low owing to low tree density. The exponential function was the most suitable for simulating the relationship between Hvn and DBH. Seven thousand six hundred and seventy-three regenerating young individuals were recorded with low density. The density of the regenerating trees decreased as the tree height increased. The finding of this study suggests that T. wallichiana faces the danger of extinction, so solutions are required to conserve and develop this threatened species.

Numerical investigation of the penetration of torpedo anchors in sand-overlying-nonhomogeneous clay deposit

This study presents a comprehensive investigation of torpedo anchors penetrating into sand-overlying-nonhomogeneous clay deposit, with the main objective of predicting the anchor embeddment depth after it penetrates through the top sand layer. The behavior of the torpedo anchor and soil failure mechanisms during the installation process are analyzed using large deformation finite element (LDFE) methods. To validate the numerical models, comparisons are made with data from existing centrifuge and field tests. An extensive parametric study is then conducted, exploring a wide range of soil properties, soil layer thickness, anchor velocities, and parameters related to torpedo anchor geometry. Two intriguing findings emerge from the analysis. Firstly, there is an evolving soil failure, with the strain-softening region expanding in the clay near the boundary between the two soil layers. Secondly, the velocity profile during both the acceleration and deceleration stages varies with different sand layer thicknesses, displaying a nonlinear relationship with the anchor's final embedment depth. Based on the findings, a simple design procedure is developed to account for the influencing factors on the anchor installation depth. This procedure is expected to be valuable for engineers seeking to estimate the behavior of torpedo anchor installations in sand-overlying-nonhomogeneous clay soil deposits.

Displacement-based finite element approach on analysing flexible combined pile–raft foundation in layered soil

The present study proposes a new finite element methodology to analyse the behaviour of flexible combined pile–raft foundation (CPRF) situated in layered soil, in a displacement-based framework. The soil medium is idealised as an advanced elastic Pasternak medium and the piles and raft are modelled as bar and plate element, respectively. The two components of CPRF are analysed simultaneously and displacement compatibility is satisfied at the pile–raft junctions. A number of soil–structure interaction factors, which govern the behaviour of CPRF, are suitably subsumed in the analysis scheme. The proposed method is validated with available analytical and experimental studies. Further parametric studies, investigating the effects of soil layering and raft flexibility on the behaviour of CPRF, are explored. It is observed that the load sharing proportion between the components and the raft deformation pattern depend upon the thickness and position of the soft soil layer in a multilayered soil system. The thickness of the flexible raft plays a pivotal role in determining the behaviour of CPRF, founded in a multilayered soil profile. Thus, this research manifests notable advancement in understanding the behaviour of flexible CPRF in layered soil.

Performance of recycled waste aggregate mixed with crushed glass over a weak subgrade

Aggregate layers, 200–400 mm thick and formed of Construction and Demolition Waste (CDW) alone or mixed with 5%, 10% or 15% of Crushed Waste Glass (CWG), were used to improve the bearing pressure-settlement response of a weak sand bed. The results show bearing pressure of foundation beds with CDW layers is ∼ 1.6–2 times that of beds with the same thickness of sandy soil layers. Employing a 200 mm thick CDW layer (0.67 times of the footing diameter) can deliver a higher bearing pressure than sandy soil twice as thick. Bearing pressure increased with an increase in the CWG content of the CDW-CWG, although the trend flattened when the CWG content exceeded 10%. At a settlement level of 2% and a CDW-CWG layer 400 mm thick (1.33 times of the footing diameter), the improvement in bearing pressure was ∼ 21%, 44% and 52%, respectively with the use of 5%, 10% and 15% CWG as compared with no CWG. Adding CWG to CDW enables the thickness of the waste aggregate layer to be reduced by at least 25% while still increasing the system’s bearing pressure. It is concluded that CDW and CWG could beneficially aid foundation construction at the same time as reducing the environmental consequences of waste disposal and natural resource acquisition.

Elucidating the impacts of trees on landslide initiation throughout a typhoon: Preferential infiltration, wind load and root reinforcement

AbstractTyphoon‐induced landslides are widespread, damaging and deadly. In this study, we elucidated their spatiotemporal features through investigations in Southeast coastal China and proposed a numerical model that involves typhoon wind load, preferential infiltration and root reinforcement. The wind load is calculated through a combination of the autoregressive method and a multi‐degree‐of‐freedom tree swaying mode, transmitting to the slope through the wind–tree interaction. Taproots of trees are modelled as piles, and root–soil interfaces are modelled as preferential infiltration boundaries. Using the numerical model, we quantitatively assessed the impacts of wind load, rainfall infiltration and root reinforcement on the slope stability and compared results with cases in Waipaoa and Wairoa (New Zealand). Results suggest that the impacts of trees depend heavily on meteorological and geological conditions. Trees play a destabilizing role in Southeast China during a typhoon but a stabilizing role in the cases in New Zealand. For slopes in Southeast China with a thick soil layer (>root depth), strong wind load and preferential flow resulting from root–soil interfaces, rather than slope surface infiltration, significantly decrease the slope stability in a short time. Slope failure occurred in all scenarios that account for the preferential infiltration, and its combination with a Force 14 typhoon wind load can fail the slope at 10 h after the typhoon initiation. Differently, tree roots in cases in New Zealand can penetrate through the thin soil layer (<1 m) and provide considerable additional resistance to stabilize the slope.

Mapping the integrity of rock mass with GPR: case study in decommissioning mining

Slopes are built for the purpose of extracting ore, in the case of mining, or access roads in civil works. The excavation of slopes in tropical countries is facilitated by the thick layer of soil formed from the more intense weathering when compared to other countries. However, the residence time of water in the soil is relatively longer and consequently allows the accumulation and percolation of water through rock fractures even in the dry period. These factors induce a greater probability of occurrence of ruptures. Mines in the decommissioning phase must guarantee slope stability conditions even after closure in order to comply with legislation and environmental safety. In this work, the slopes of a decommissioning mine were investigated using geophysical methods (GPR) and structural analysis of the rock mass. The results were presented in the form of radargrams that correlate distance and depth of investigation. Structural data served as the basis for the execution of kinematic analyzes for planar and wedge ruptures. The analysis of the results allowed the correlation between electromagnetic signal attenuation zones, with the presence of water and the occurrence of ruptures. Thus, the GPR results allowed the recognition of structural discontinuities, accumulation zones and water flow.