Thin Soil Layer Research Articles

Soil nitrogen transformation in different land use and implications for karst soil nitrogen loss controlling

A large amount of cropland in the Southwestern (SW) China karst area has been abandoned since the implementation of the Grain for Green project at the end of the last century, which significantly impacted the biogeochemistry cycle in soil. However, the effect of cropland abandonment on the soil nitrogen (N) cycle and the N loss process is still little understood. N content and isotope analysis were used to assess karst soil’s N fate and explore the N loss process in SW China. Soil samples were collected from four land uses, cropland (CR), abandoned CR (AC), shrubland and grassland (SG), and secondary forest (SF), by seasonal in a typically mixed land-use karst catchment at six soil depths. The results showed that the average soil particulate organic N (PON) content increased from 1.58 ± 0.49 g kg−1 to 2.70 ± 1.82 g kg−1, whereas average dissolved nitrate (NO3–-N) content decreased from 10.77 ± 8.87 mg kg−1 to 1.72 ± 1.84 mg kg−1 during revegetation. There was a decreasing amount of PON and dissolved N (NH4+-N、NO3–-N、TDN) content from surface to the bottom of the soil profile and large variation mainly occurred in 0 – 30 cm in the soil profiles of four different land uses, which suggests N transformation mainly occurred in topsoil (<30 cm). Mineralization was the major nitrogen transformation process that affected PON content and δ15N-PON values. The highest δ15N-PON fractionation (-5.0‰) in the soil profiles of the four types of land use caused by mineralization was detected in SF. Variation of N content and isotope values in soil profiles after cropland abandonment suggested that the loss of NO3–-N in karst catchment mainly came from the topsoil of cropland. Overall, N loss from the topsoil of cropland should pay more attention, while cropland abandonment can effectively reduce the loss of dissolved N from the thin karst soil layer.

A simplified non-axisymmetric pile-soil interaction model for pile integrity testing analysis

A simplified model of non-axisymmetric pile-soil interaction (NPSI) that considers both vertical and radial motions of the pile body is developed and applied to the investigation of pile integrity test (PIT) with eccentric hammer impact. The pile is treated as a simplified three-dimensional (3D) continuum and the soil along the pile shaft is simulated as a series of independent thin soil layers, while the soil under the pile base is defined by the fictitious soil-pile model. Theoretical solution of the velocity-time history of each point on the pile top section is deduced by integral transformation technique. Based on the NPSI model, characteristics of test signals of PIT for large-diameter piles under non-axisymmetric condition are analyzed. The optimal testing position for acquiring signals, which minimizes the influence of high frequency (HF) interference resulting from the pile body 3D effect, is identified. Findings from this study provide the basis for accurate interpretation of the PIT of large-diameter piles with eccentric hammer impact.

Jardim de Sequeiro: uma técnica paisagista inovadora na estética e na qualidade ambiental, inspirada no Cerrado

Abstract The “Jardim de Sequeiro” (rainfed garden) is an innovative technique of naturalistic and seasonal rainfed gardening developed by Prof. Julio Pastore and a team of professionals and students at the University of Brasilia (UnB). The first experimental garden was planted at the Instituto Central de Ciências (ICC), an iconic brutalist building at the University of Brasília and a landmark of modern Brazilian architecture. The garden extends through the 732 meters of the mega-structure, encompassing more than 5,000 square meters of rooftop gardens planted on a thin layer of soil. The experimental garden is primarily grown from seeds, making it a dynamic space. Beginning with fast-growing species, plants bloom in succession throughout the summer and early autumn. The garden is “rainfed,” relying entirely on rainfall for water, and it withers and dries with the onset of the winter drought. As such, it can be considered a garden-installation: a temporary occupation that is redesigned and improved every year. Conceived and planned during the initial months of the COVID-19 pandemic, the garden’s first cycle occurred between December 2020 and May 2021, when the university was closed. Despite the difficulties inherent to the pandemic period, the innovative nature of the project has yielded promising results.

Research and Design of Ecological Restoration Machinery for Rock Desertification--Multifunctional Mountain Seeder

A grassland carbon sink is a grassland planting activity with special requirements to implement carbon sink measurement and monitoring of the growth process of forage grasses on the land where the baseline has been determined, with the main purpose of increasing carbon sink. The development of grassland carbon sink is extremely beneficial to achieve the two important deployments of carbon peaking and carbon neutrality. Grasslands with one-fourth area in the south are limited by the rugged topography of the karst landscape and thin soil layer, and the efficiency of pasture planting is low. For the above problems, our team proposes a design around mountain pasture cultivation to reduce carbon emissions and apply it to increase carbon sinks in grasslands of stone desertification areas. The design can provide a concrete solution for restoring the ecological environment and enhancing the carbon sink capacity of grassland in stone desertification areas, and also provide a technical guarantee for local herders to increase their income and productivity. This work has the advantages of high market potential, low cost, composite multi-functional automatic operation, and high planting efficiency with a small size, which has good promotion value. It effectively reduces carbon emissions while improving vegetation cover and establishes a new model of combining green restoration and agricultural production in mountainous areas.

A state dependent constitutive model for unsaturated soil-steel interfaces considering bonding effect

The frictional behaviours between unsaturated soils and structure are controlled mainly by the complex phenomena that develop within a thin soil layer close to the contact area. The constitutive model for soil-structure interfaces (SSI) must be established to predict the performance of related soil-structuresystems accurately. Multi-stage suction-controlled ring shear (RS) tests with three different upper annular platens were carried out on an equal number of statically compacted samples of Shanghai clay under controlled suction states for a given net normal stress. A state dependent constitutive model for unsaturated soil-structure interfaces based on critical state concept considering bonding effect was proposed. In all stress conditions, the tested and predicted results for smooth interface and rough interface are well matched.

Coumarin biosynthesis genes are required after foliar pathogen infection for the creation of a microbial soil-borne legacy that primes plants for SA-dependent defenses

Plants deposit photosynthetically-fixed carbon in the rhizosphere, the thin soil layer directly around the root, thereby creating a hospitable environment for microbes. To manage the inhabitants of this nutrient-rich environment, plant roots exude and dynamically adjust microbe-attracting and -repelling compounds to stimulate specific members of the microbiome. Previously, we demonstrated that foliar infection of Arabidopsis thaliana by the biotrophic downy mildew pathogen Hyaloperonospora arabidopsidis (Hpa) leads to a disease-induced modification of the rhizosphere microbiome. Soil conditioned with Hpa-infected plants provided enhanced protection against foliar downy mildew infection in a subsequent population of plants, a phenomenon dubbed the soil-borne legacy (SBL). Here, we show that for the creation of the SBL, plant-produced coumarins play a prominent role as coumarin-deficient myb72 and f6’h1 mutants were defective in creating a Hpa-induced SBL. Root exudation profiles changed significantly in Col-0 upon foliar Hpa infection, and this was accompanied by a compositional shift in the root microbiome that was significantly different from microbial shifts occurring on roots of Hpa-infected coumarin-deficient mutants. Our data further show that the Hpa-induced SBL primes Col-0 plants growing in SBL-conditioned soil for salicylic acid (SA)-dependent defenses. The SA-signaling mutants sid2 and npr1 were unresponsive to the Hpa-induced SBL, suggesting that the protective effect of the Hpa-induced shift in the root microbiome results from an induced systemic resistance that requires SA-signaling in the plant.

The Influence of Stand Structure on Understory Herbaceous Plants Species Diversity of Platycladus orientalis Plantations in Beijing, China

Species diversity is a crucial index used to evaluate the stability and complexity of forest ecosystems. Studying the relationship between stand structure and understory herbaceous plants species diversity is useful for managers to formulate the best forest structure optimization method with the goal of improving herbaceous species diversity. In this research, Platycladus orientalis plantations in Beijing were taken as the research object. Pearson’s correlation analysis was used to explore the single-factor correlation between stand structure and understory herbaceous plants species diversity; furthermore, a typical correlation analysis and multiple linear regression were used to explore the multi-factor correlation and analyze the dominant stand structure parameters affecting understory herbaceous plants species diversity. In the range of stand structures studied, the results showed that canopy density was negatively correlated with the Shannon–Wiener index and Simpson index (p &lt; 0.01), and tree density was negatively correlated with the Shannon–Wiener index (p &lt; 0.05). In terms of stand spatial structure, the mingling degree was positively correlated with the Shannon–Wiener index, Simpson index, Margalef richness index and Pielou evenness index (p &lt; 0.05), while the uniform angle was negatively correlated with the Pielou evenness index (p &lt; 0.05). The correlation coefficient of the first group of typical variables in the typical correlation analysis was 0.90 (p &lt; 0.05); from this group of typical variables, it can be concluded that canopy density is the most influential indicator affecting the comprehensive index of understory herbaceous plants species diversity, with a load of −0.690, and the Shannon–Wiener index and Simpson index are the most responsive indicators of changes in the comprehensive index of stand structure, with loads of 0.871 and 0.801, respectively. In the process of the management of Platycladus orientalis plantations under a low altitude, south slope, thin soil layer and hard soil parent material, in order to improve the herbaceous species diversity, the canopy density of the overstory and tree density should be appropriately reduced. Additionally, it is necessary to regulate the horizontal spatial structure of stands. When the trees are randomly distributed and the mingling degree is high, the species diversity of herbs can be increased.

Defining Composition and Function of the Rhizosphere Microbiota of Barley Genotypes Exposed to Growth-Limiting Nitrogen Supplies.

The microbiota populating the rhizosphere, the interface between roots and soil, can modulate plant growth, development, and health. These microbial communities are not stochastically assembled from the surrounding soil, but their composition and putative function are controlled, at least partially, by the host plant. Here, we use the staple cereal barley as a model to gain novel insights into the impact of differential applications of nitrogen, a rate-limiting step for global crop production, on the host genetic control of the rhizosphere microbiota. Using a high-throughput amplicon sequencing survey, we determined that nitrogen availability for plant uptake is a factor promoting the selective enrichment of individual taxa in the rhizosphere of wild and domesticated barley genotypes. Shotgun sequencing and metagenome-assembled genomes revealed that this taxonomic diversification is mirrored by a functional specialization, manifested by the differential enrichment of multiple Gene Ontology terms, of the microbiota of plants exposed to nitrogen conditions limiting barley growth. Finally, a plant soil feedback experiment revealed that host control of the barley microbiota underpins the assembly of a phylogenetically diverse group of bacteria putatively required to sustain plant performance under nitrogen-limiting supplies. Taken together, our observations indicate that under nitrogen conditions limiting plant growth, host-microbe and microbe-microbe interactions fine-tune the host genetic selection of the barley microbiota at both taxonomic and functional levels. The disruption of these recruitment cues negatively impacts plant growth. IMPORTANCE The microbiota inhabiting the rhizosphere, the thin layer of soil surrounding plant roots, can promote the growth, development, and health of their host plants. Previous research indicated that differences in the genetic composition of the host plant coincide with variations in the composition of the rhizosphere microbiota. This is particularly evident when looking at the microbiota associated with input-demanding modern cultivated varieties and their wild relatives, which have evolved under marginal conditions. However, the functional significance of these differences remains to be fully elucidated. We investigated the rhizosphere microbiota of wild and cultivated genotypes of the global crop barley and determined that nutrient conditions limiting plant growth amplify the host control on microbes at the root-soil interface. This is reflected in a plant- and genotype-dependent functional specialization of the rhizosphere microbiota, which appears to be required for optimal plant growth. These findings provide novel insights into the significance of the rhizosphere microbiota for plant growth and sustainable agriculture.

CFD-based three-dimensional modeling of an adhesively detaching soil layer in a channel flow with sudden expansion

Cleaning is an important process step in the food industry, especially to avoid contamination during increasingly frequent product changes. The equipment is cleaned almost daily causing high ecological and economic expenses. Predicting the cleaning time required to remove a thin soil layer for given operating conditions can prevent the use of unneeded resources. The purpose of the present contribution is to apply a recently published model for an adhesively detaching soil at the next level of geometrical complexity. To this end, a square duct with a stepwise expansion of each wall is considered. The Reynolds numbers of the flows investigated are between 13,000 and 39,000, based on the hydraulic diameter of the upstream duct. In a square duct, the flow is three-dimensional due to secondary flows of the second kind, and the existing model for two-dimensional flow needs to be extended in the first step. In course of that, a simple method is presented for the consideration of turbulent fluctuations in the calculation of the hydrodynamic loads. The model is validated using cleaning experiments in a fully developed channel flow without step. After that, it is applied to the channel flow with sudden expansion. Various cleaning parameters, such as the soil mass coverage and the flow velocity, are varied and the quality of the model predictions is investigated. The results are compared with experiments in a channel flow with sudden expansion. Good agreement between experiments and simulation is achieved, proofing that the model can be used to investigate the cleaning in complex, three-dimensional flow scenarios.

Perennial Groundwater Zone Formation Processes in Thin Organic Soil Layers Overlying Thick Clayed Mineral Soil Layers in a Small Serpentine Headwater Catchment

Groundwater zone formation in the soil layers of a headwater catchment is an important factor that controls volumetric and chemical changes in streamflow; it also induces shallow landslides. Previous studies have suggested that the groundwater zone in soil layers generally forms transiently atop low-permeability layers in response to rainfall. This study focused on an unchanneled hollow in a serpentine headwater catchment, where a semi-perennial to perennial groundwater zone was observed in thin organic soil layers (OSLs) overlying thick clay mineral soil layers (CMLs), even during dry periods. We conducted detailed observations in this catchment to clarify the formation processes of the semi-perennial to perennial groundwater zone. The results showed that water is supplied from the CMLs to the OSLs as unsaturated upward flow in areas where the OSLs are dry. This water then accumulates in the downslope hollow, which sustains the groundwater zone in the OSLs during dry periods. The frequent and long-term occurrence of upward flow can be attributed to differences in the hydraulic properties of OSLs and CMLs. This process prevents the OSLs in the hollow from drying, presumably causes volumetric and chemical changes in streamflow, and reduces the stability of OSLs.

Application of Eurocode 7 for the analysis and design of veneer cover soils in static and seismic load conditions

Veneer is intended as a relatively thin cover soil layer placed on a slope. Veneer cover soil systems in containment facilities such as landfills, liquid disposal and reservoirs involve geosynthetic-soil interfaces. The main design criterion for protective veneer covers is to ensure that no sliding occurs above the geosynthetic or the existing soil slope. The design of the protective veneer covers should include the stability of the lining system under the effect of the gravity forces, equipment loadings, seismic actions and pore water pressures. The limit equilibrium method used in the present paper for the evaluation of veneer stability has been derived from the method of Koerner and Soong (1988) and adapted to the limit state design offered by Eurocode 7 with reference to the Resistance Factor Approach (RFA). Serviceability limit state considerations are included in the design method for completeness.

Cleaning of simple cohesive soil layers in a radial flow cell

A radial flow cell (RFC, inlet tube radius 0.95 mm and gaps of 1–4.2 mm) was used to investigate the removal of two thin (80–230 µm thick) model soil layers from glass and 304 stainless steel substrates by the flow of water at 20 °C. Under the flow conditions employed (Reynolds numbers 200–1400), inertial effects give rise to recirculation zones and regions of high shear stress on the bottom, soiled plate. The soils were dried layers of (i) instant coffee and (ii) a domestic abrasive cleaning suspension comprising fine particulates in a soluble matrix. Cleaning data exhibited a constant local erosion rate which varied strongly with radial position. For both soils, cleaning involved the growth of a circular cleaned region and redeposition of particulate matter in a ring at locations close to the foot of the secondary recirculation zone predicted by 2D axisymmetric CFD simulations. Removal beyond this location was observed with the coffee layers, indicating that cleaning for this soil was controlled primarily by simple diffusion mechanisms. The effect of channel aspect ratio and flow rate on the location of recirculation zones and shear stress distributions was investigated. The local cleaning rate in these steady flows was not linked simply to local wall shear stress.

Shear Characteristics of Soil—Concrete Structure Interaction Interfaces

The shear characteristics of the interfaces between soil and concrete structures are essential for the safety of the structures. In this study, a large-scale direct shear test apparatus was developed to measure the mechanical parameters of soil–concrete interfaces under conditions with different soil types, soil moisture contents, and interfacial filling materials. The results showed that the shear stress of the soil–concrete interface increased initially and then became stable with the increase in the shear displacement. The shear displacement of the sandy soil when the shear stress became stable was smaller than that of the clayey soil. The silty sand–concrete interface had a smaller friction angle than the interface with the medium-coarse sand. Moreover, with the increase in the soil moisture content, the friction angle of the clayey soil–concrete interface decreased rapidly, whereas the cohesion first increased and then decreased, and the peak cohesion was near the plastic limit of the soil. Under the same moisture content, the friction angle and cohesion of the clay–concrete interface was reduced by filling the interface with a thin layer of sandy soil, while filling the silty sand–concrete interface with a thin layer of silt reduced the friction angle and increased the interfacial cohesion. Nonetheless, the filling had little impact on the overall shear strength of the interface.

Carbon saturation deficit and litter quality drive the stabilization of litter-derived C in mineral-associated organic matter in long-term no-till soil

Long-term no-till cropping systems can induce significant differences in the mineral associated organic matter (MAOM) saturation levels but little is known on the effect of MAOM saturation on “new” C stabilization from added litter in different fractions of soil organic matter (SOM). We assessed the effect of C saturation deficit (Csd) in the MAOM on C stabilization in different SOM fractions in the surface layers of a sandy clay loam Acrisol under five no-till cropping systems adopted over 36 years in a field experiment. The cropping systems with varying C inputs led to a range of C content and Csd in the MAOM (<20 µm) in a thin soil layer (0–5 cm). In each field plot with different Csd levels, 13C-labeled litter from shoot biomass of black oat (grass) and vetch (legume) was added at a rate equivalent to 4.5 Mg ha-1C in PVC collars. After 15-month field incubation, soil was sampled and physically fractionated. Higher C stabilization in MAOM was observed for legume than grass-derived C in the top 0–2.5 cm layer, but only for soils with higher C stabilization capacity. When litter-derived C stabilization in MAOM was limited by its previous C level close to saturation, C incorporation was greater in the intra- and inter-aggregate SOM fractions. Our findings revealed that Csd and litter quality affect C stabilization in surface soil layers of no-till soils, and when C stabilization in MAOM is low due to saturation of the MAOM fraction, the C accrual occurs preferentially in labile and intra-aggregate fractions in long-term no-till soils. Therefore, sustainable management practices that promote continuous and diversified C inputs involving legume cover crops are crucial to sustain C incorporation in relatively stable forms in long-term no-till soils.

Reexamination of Eruptive Activity of Akanfuji in the Me-Akan Volcano, Eastern Hokkaido, Japan

Eruption history of Akanfuji in the Me-akan volcano, eastern Hokkaido, has been examined by comparing multiple natural outcrops. In a previous study, at least 17 layers of scoria fall deposits were recognized. To obtain more detailed geological information and reexamine the eruptive activity of Akanfuji, we conducted trench surveys. At each survey site, the scoria fall deposits from Akanfuji are layered with a total thickness of several tens of centimeters to 1 m. A light brown volcanic ash layer is deposited just under the lowest layer of Akanfuji, and the fresh glass in the light brown volcanic ash shows the glass composition of the volcanic ash that erupted at Tarumai volcano 2500 BP. In addition, volcanic ash ejected from Ponmachineshiri of the Me-akan volcano is deposited on top of the newest deposits in the Akanfuji series with a thin soil layer in between. The volcanic ash ejected from Ponmachineshiri contains patches of volcanic ash from the Mashu volcano that erupted 1000 years ago. Therefore, Akanfuji was active from about 2500 to 1000 years ago. Akanfuji ejected scoria fall deposits at least 17 times (Akf-1 to Akf-17), and assuming that it erupted an average number of times during the activity period, it would be once every 90 years. The eruption rate was estimated to be 0.12 km3 DRE/ka.

Load-Settlement Behaviour Analysis Based on the Characteristics of the Vertical Loads under a Pile Group

The nonlinear load-settlement behaviours of vertically loaded pile groups containing various numbers of piles (up to a few hundred piles in a group) are analysed using the method proposed by Lee and Xiao. This back-analysis method assumes the “local shear displacement” of a thin layer of disturbed soil along the pile–soil interface and the soil outside the interface is assumed to be linear elastic. Parametric studies are conducted to examine the load-displacement behaviours of the rigidly capped pile groups. Factors such as the number of piles in a group, pile slenderness (L/D), and pile spacing (S/D) are examined to study the effects on the performance of pile groups up to the failure state. Some phenomenological features of large pile groups under nonlinear conditions, which are difficult to obtain through an elastic analysis, are revealed in the present analysis.

Analytical modelling of soil porosity and bulk density across the soil organic matter and land-use continuum

The thin layer of soil at the earth’s surface supports life, storing water and nutrients for plant uptake. These processes occur in the soil pore space, often half the soil volume, but our understanding of how this volume responds to environmental change is poor. Convention, has been to predict soil porosity, or its reciprocal bulk density (BD), from soil texture using pedotransfer functions (PTFs). A texture based approach, invariant to environmental change, prevents feedback from land use or climate change to soil porosity. Moreover, PTFs are often limited to mineral soils with < 20% soil organic matter (SOM) content. Here, we develop an analytical model to predict soil porosity, or BD, as a function of SOM. We test it on two comprehensive, methodologically consistent, temperate national-scale topsoil data sets (0–15 cm) (Wales, n = 1385; Great Britain, n = 2570). The purpose of the approach is to generate an analytical function suitable for predicting soil porosity change with SOM content, while providing insight into the main grain-scale factors determining the porosity emergence. The newly developed function covering the entire SOM gradient allows for impacts of land use, management or climate change to feedback on soil porosity or bulk density through decadal dynamic changes in SOM.

Impacts of forestland vegetation restoration on soil moisture content in humid karst region: A case study on a limestone slope

Forestland vegetation restoration changes the state of soil water storage and consumption, leading to changes in soil water content. Many scholars have conducted research on the soil water content of restored forestland vegetation in different climatic regions. However, due to the uniqueness of the karst environment, the research findings from other humid regions may not be indicative of the impacts of forestland vegetation restoration on the soil water content in humid karst regions. In this work, the soil water content of four sample plots with different restoration durations in a karst region was examined. The results showed that the soil water contents of the sample plots with different restoration durations differed significantly. As the restoration process of the forestland vegetation progressed, the soil water content decreased, but the range of reduction was small. There was a significant negative correlation between forestland vegetation restoration duration and soil water content (P < 0.01), and the Spearman correlation coefficient between the two was −0.621. At different soil depths and in different seasons, the soil moisture content also decreased with increased restoration duration. Compared with humid non-karst regions, the karst environment bedrock possessed thin soil layers and strong water permeability, which further amplified the effect of vegetation restoration on the reduction of soil moisture content.

Rainwater transformation to runoff and soil loss at the surface and belowground on soil-mantled karst slopes under rainfall simulation experiments

Karst slopes have thin soil layers covering bedrock and feature multiple near-surface soil-rock interfaces (SRIs), which can produce hydrological processes that differ from those of nonkarst slopes. This study investigated the differences in the proportions of rainwater transformed into surface and belowground runoff and measured soil loss on soil-mantled karst slopes with different hydrological situations: bedrock with fissures (HS-1) and without fissures (HS-2). The rainfall intensity was 50 mm/h. Three slope gradients (5°, 15° and 25°) were applied, and surface runoff (SR), subsurface flow (SF), underground fissure flow (UFF) and soil-rock interface flow (SRIF) were collected during rainfall. No SR was produced on 5° slopes in either treatment. The proportion of rainwater absorbed by soil (RH) was approximately 34%-46% of the rainwater, with no significant differences (p > 0.05) between HS-1 and HS-2. On the 5° and 15° slopes, 28%-61% of the rainwater was transformed into UFF under HS-1, and 29%-50% of the rainwater was transformed into SRIF under HS-2. On the 25° slope, the SRIF and UFF proportions were<18%. Bedrock fissures greatly affected the type of runoff but had little effect on the near-surface soil water. The SR and SF amounts were 29%-67% and 3%-38% higher in HS-2 than in HS-1, respectively. Due to bedrock fissures, on average, 6% of rainwater was lost as underground flow during rainfall, and the extra rainwater, 30% on average, flowed along the SRI underground, potentially forming UFF. This difference occurs because the infiltrating rainwater that reaches the SRI can freely drain through bedrock fissures in HS-1 but not in HS-2. The soil loss via SF, SRIF and UFF was very low (<0.05 g/L). Therefore, slope gradients and bedrock fissures both have major effects on rainwater transformation, and soil loss via rainfall impact is very slow on soil-mantled karst slopes.

A New Apparatus for Shear-Seepage Testing at the Clayey Soil-Structure Interface

Abstract In high earth-rockfill dams, large shear displacement exists in the contact area between the earth core and the concrete cushion at the bottom and on both sides of the banks of a river valley. Exposed to a high hydraulic gradient, seepage erosion is likely to occur in this area. A practical measure is to compact a thin layer of clayey soil with high plasticity such that it lies between the earth core and the concrete cushion. It is crucial to evaluate the capabilities of a clayey soil for this thin layer. A new apparatus modified from a conventional triaxial apparatus is developed to test the seepage characteristics of the clayey soil-structure interface under large relative shear conditions. Compared to the previous device, the new device can achieve a larger relative shear displacement that is closer to the actual condition while providing stress and a seepage state with a simple testing procedure. This apparatus consists of a soil-structure model, a vertical loading system, two back-pressure systems, and a monitoring system. The vertical loading system allows the soil-structure displacement to develop at a constant speed. Two back-pressure systems can simulate the high hydraulic gradient and the consolidation state of the specimen. The monitoring system automatically records the force load, the volume of water outflow, and the volume change in the pressure chamber. Basic tests and shear-seepage tests were conducted using this device to validate its efficiency and reliability. The results indicate that the permeability of the soil-structure interface decreases with the shear displacement over a large range. A finite element (FE) analysis was carried out to reveal the strain-stress and seepage state inside the specimen to explain the seepage mechanism.