Soil Strata Research Articles

Characterization of Mechanical Behavior of Ultra-Small Clearance Tunnel Construction in Upper Soil and Lower Rock Composite Strata

It is hard to grasp the deformation law of the surrounding rock and the force characteristics of the support structure during the construction of ultra-small clearance tunnels in upper soil and lower rock composite strata. Based on the ultra-small clearance tunnel in Li Shuping, Tongxin Expressway, Guizhou, this paper adopted a combination of numerical simulation and field monitoring to analyze the influence of different burial depths and soil-rock interface positions on the deformation of the surrounding rock and the internal forces of the support structure of the ultra-small clearance tunnel. The conclusions are: (1) the monitoring data show that the stress in the steel frame of the leading tunnel increases first by the influence of proximity construction, and then decreases and reaches a stable value after the secondary lining is applied, and the stress at the arch waist of the soft soil layer furtherest from the side of the middle rock column is greater than that in the rock layer on the side of the middle rock column; (2) the position of the soil-rock interface has a significant influence on the initial support force of the first tunnel, and the bending moment of the structure increases with the downward movement of the soil-rock interface and the increase in the burial depth; (3) the influence of the soil-rock interface position on the initial support moment of the first tunnel is greater than the influence of proximity construction, a point to which attention should be paid during construction; and (4) when the soil-rock interface is located below the foot of the arch, the deformation of the surrounding rock of the following tunnel will be larger than that of the first tunnel. The results can provide a reference for the design and construction of ultra-small clearance tunnels in upper soil and lower rock composite soft strata and soil strata.

Deep SOC stock dynamics under contrasting management systems: Is the EPIC model ready for carbon farming implementation?

Process-based models have been recognized as cost-effective tools to assess carbon farming mechanisms through quantifying the C fluxes in the agroecosystems. A result-based approach is suggested however the wide variability of agricultural environments makes further model implementation necessary to limit the uncertainty of the results, especially on deep soil organic carbon (SOC) stock estimation and stratification and in agroecosystems characterized by a shallow water table. In this study, a comprehensive soil and crop dataset collected over a seven-year period from different pedoclimatic conditions across the Veneto Region (NE Italy) was used for EPIC model calibration and validation of SOC stock dynamics. Experimental data included yields from several crops (corn, winter and spring wheat, rapeseed, and soybean), continuous monitoring of soil water content, and SOC stocks (1872 total samples within the 0–50 cm soil profile) under conventional, cover crop and conservation agriculture systems. Modelling was performed by testing two N-C sub-models (CENTURY and PHOENIX), which differentiated in terms of mineralization/immobilization rates.Results showed that the procedure was able to obtain parameters valuable for most of the management system and pedoclimatic condition, reproducing well the tested variables. The EPIC model acceptably captured soil water dynamics (Nash-Sutcliffe coefficient – NSE – was up to 0.26), especially in the topsoil. Furthermore, simulation of weed—crop competition in conservation agriculture strongly contributed to properly explain the variability in crop production among the contrasting agricultural systems (R2 ranged from 0.51 to 0.71). Likewise, EPIC skillfully simulated SOC stocks within the 0–50-cm profile regardless of the sub-model used (NSE was up to 0.64). Moreover, the model acceptably captured the profile SOC stratification among the different management practices. This study highlights the EPIC robustness for predicting SOC stocks and assessing with high accuracy carbon farming results.

Study on Transverse Seismic Response Characteristics of Large Diameter Vertical Double-Layer Overlapping Pipe Jacking in the Soil-Rock Composite Stratum

The sharp change of stiffness in the soil–rock combination stratum is the weak point in the seismic design of the pipe jacking structure. To study the seismic response characteristics of vertical double-layer overlapping pipe jacking, based on the typical soil–rock combination strata in Jinan, two electric power pipe jacking tunnels of 3.6 m diameter were studied as the research objects, where the upper pipe jacking is located in the soil and the lower pipe jacking is located in the composite stratum of half soil and half rock. The soil–rock-overlapping tunnel system was deemed as a plane strain problem. By using the dynamic time history method and considering the non-linearity of material, the seismic response characteristics of a vertical overlapping pipe jacking tunnel under seismic wave were discussed from five aspects, acceleration response, displacement response, stress response, soil interlayer response and the influence of soil–rock combination stratum. The results indicate that under the action of ground motion, the peak acceleration and relative horizontal displacement of the upper pipe jacking are greater than those of the lower pipe jacking; small pipe jacking spacing will lead to the aggravating earthquake failure effect; due to the stiffness difference, the relative horizontal displacement and stress of pipe jacking structure at the soil–rock interface change abruptly. The vertical double-layer arrangement of the pipe jacking increases the buried depth, and the stratum is prone to be uneven hardness. Therefore, the seismic design and relevant structural measures of large diameter vertical overlapping pipe jacking structure should be strengthened.

Detection of Soil Contamination Using Electrical Resistivity Tomography and Induced Polarization Methods By Tank Model

Resistivity and induced polarization surveying were originally developed for mineral exploration but are now the of outcome new applications in the field of environmental and engineering geophysics. This paper describes an experimental setup used to carry out resistivity tomography and induced polarization tests (in the time domain) that are used in geological and geophysical surveys to characterize soil and rock. The test setup is carried out in the laboratory via the Tank model developed for this purpose. The paper describes a laboratory system used to study the influence of different contaminants in a small-scale soil stratum using two geophysical methods and describes how the behaviors of resistivity and chargeability result in contaminated and uncontaminated soils. The results of a geophysical survey were performed to identify a contaminator in the Tank model. Both techniques provided evidence of contamination. In general, the electrical resistivity method was better than the induced polarization method in providing distinct values for most kinds of contamination, Except for the contamination with salt water, both methods gave significant results.

Assessment of Heavy Metals Concentrations in Some Irrigated Soils of Dadin-Kowa Dam, Gombe State, Nigeria

This study assessed heavy metals concentration in some irrigated soils of Dadin Kowa Dam, Gombe State Nigeria. The soils were collected along transect lines (different sampling points) within the farms and samples were taken to the laboratory for analysis. The analysis was conducted using (Thermo Fisher Scientific) Energy Dispersive X-ray Fluorescence Spectroscopy. The results give the following metals with their mean concentrations: Mo (8.200 and 8.926), Zr (432.990 and 440.236), Sr (204.358 and 87.142), Rb (47.642 and 42.533), Zn (44.165 and NA), Cu (42.161 and NA), Fe (43090.640 and 24846.236), Mn, (992.881 and 397.248), Cr (140.456 and 88.054), V (56.842 and 27.159), Ti (2403.982 and 1421.486), Ca (3344.789 and 982.722), K (4706.758 and 3172. 047), S (466.152 and 310.510), Ba (933795.090 and 959675.238) and Nb (26.285 and 24.964) were obtained from the onion and cabbage farmssoils samples respectively (Values in part per millions (ppm)). The degree of pollution of the soils studied were ascertained and compared with literature toxicity data. Other pollution indices like Enrichment factor, Clarke ratio, Coefficient of variation, Contamination factor, Metal Pollution Index and Geo- Accumulation Index were assessed also and found out that the contamination level for the soils is tolerable for irrigation. At α = 0.01 significant level, positive correlation exists between Fe and Cu, Zn and Ca while Zn and Rb; Ca and Rb have significantly negative correlation between them. By implications, these results showed that the complexes of some elements within the soil strata could influence the presence of other given elements. Therefore, Dam irrigation area soils studied showed relatively low state of pollution for the elements determined.

Modelling and analysis of penetration resistance of probes in cultivated soils.

At present, the measurement of tillage depth is mainly based on manual measurement, but the manual raking method results in low measurement accuracy and high labor intensity. Due to the complexity of soil, theoretical research on tillage depth is relatively scarce. In order to provide a new research direction and research idea for soil stratification, topsoil was taken as the research object of this paper. The correlation between penetration resistance and penetration depth of a probe in a cultivated soil was studied, and a mathematical model was established. There is a certain similarity between the process of spherical cavity expansion and the process of probe penetration, so we introduced the theory of spherical cavity expansion into the modeling of penetration resistance of the cultivated soil. In this paper, the spherical cavity expansion theory of unsaturated soil was used as the basis for solving the penetration resistance. And the unified strength criterion was employed as a yield condition of the soil to set a stress solution and a displacement solutionin into of the probe penetrating into the elasto-plastic zone of the cultivated soil to determine the model of expansion force. We have carried out indoor tests to revise the expansion force model. Firstly, according to the range of soil density and water content in the field, the soil densities were classified into 1.1×103kg/m3, 1.2×103kg/m3 and 1.3×103kg/m3, and the water contents were divided into 10%, 15% and 20%. In addition, the orthogonal tests were performed at different levels. The soil was put into the barrel, and the probe was inserted into the soil in the barrel at the speed of 8mm/s to determine the test values of the change of the probe penetration resistance with depth. Finally, the expansion force model was fitted with the results of the indoor test, and coefficient B was introduced to express the influence degree of density and water content on the resistance. Coefficient B was substituted into the expansion force model to obtain the penetration resistance model of the cultivated soil. Through the goodness of fit analysis of the penetration resistance model, the results show that the overall average goodness of fit of the penetration resistance modelat was up to 0.871 at different water contents and densities, which was a good fit and could present novel insights into the study relating to soil stratification theory.

Migration and redistribution of LNAPL in inclined stratified soil media

Leakage of light non-aqueous phase liquid (LNAPL) into soil can cause serious environmental issues. In this study, a two-dimensional device with adjustable dip angles was designed to investigate the migration and redistribution of LNAPL in natural inclined stratified soil media by the light transmission visualization (LTV) technology. The captured experimental images were processed to obtain the diesel distribution based on gray value which could represent the LNAPL saturation distribution. LNAPL may not be able to penetrate through the fine-coarse interface due to the capillary barrier effects. In this case, the vertical and horizontal migration distances (V and H), contaminated area (S), as well as deviation angle (γ) of centroid increased with the dip angle. Increasing the leakage amount to more than 30 mL would result in LNAPL breakthrough at the 10°-inclined interface, leading to much larger V, H, S, and γ than those at 10 mL, while 20-mL LNAPL failed to break through. In the latter case, a lower leakage rate than 10 mL/min would cause larger H and γ but similar V or S in the long term. This study could enrich the understanding of LNAPL contamination in vadose zone, providing reference for the prediction and treatment in realistic inclined contaminated sites.

Morphometric analysis of shel dedumal watershed using remote sensing remote sensing and GIS

Morphometric analysis is the measurements and mathematical analysis of the land surface configuration, shape and dimension of the landforms. The efficiency of the drainage network is very important for understanding the processes of landform formation, soil physical properties and erosion characteristics. The present study is focused on the evaluation of morphometric parameters for conversation of soil and water on delineated in the basin. Furthermore, morphometric analysis of watershed using geospatial data and GIS techniques and slope analysis were also utilized to propose the suitable soil and water conservation measures in the basin. The results obtained in the analysis revealed that the Shel Dedumal basin tributaries is an 5th order drainage basin which describe that the texture is homogeneous or homogeneity still exist and lack of structural control in soil strata. The relief ratio (R h ), the elevation difference (R h or H) and circularity ratio (R c ) was found to be 10.73, 222.0 and 0.42, respectively which represents the basin having moderate relief and gentle to moderately high slope. Some areas of the basin are characterized by variation in Lithology and topography. The mean values of bifurcation ratio (R b) observed as 4.52 and circularity ratio (R c ) observed as 0.42 of the entire basins shows a moderate but not strong structural control or structural disturbances. An extreme high value of ruggedness number (R n ) observed as 11.83 which indicate the structural complexity of the terrain. The Moderate drainage density (D d ) and circularity ratio (R c ) was observed as 2.63 and 0.42, respectively which indicates the basin is highly permeable subsoil and vegetative cover. The form factor (F f ), the elongation ratio (R e ) and circularity ratio (R c ) was observed as 0.39, 0.71 and 0.42 respectively which is indicating elongated basin with lower / flatter peak flows of longer duration than the average and also the elongation ratio (R e ) values indicating moderate to slightly steep ground slope in basin which is indicating possibility for soil erosion and other soil and water conservation works.

Wastewater Characterization of Chiniot Drain and Evaluation of Groundwater Contamination Using Water Quality Index (WQI) and GIS Techniques

Groundwater pollution is considered a major concern in today’s world. Most industries in Pakistan produce untreated wastewater, extracting from and contaminating a nearby water source and the soil. This study was conducted in the Nithar Ke area of Chiniot District to assess the impact of the flow of wastewater over the area on groundwater quality. It aimed to: (1) investigate the conditions of industrial wastewater; (2) study the spatial variability of different parameters in groundwater using a GIS map; and (3) check the appropriateness of groundwater for drinking purposes using the water quality index (WQI). Physical and chemical characteristics, including pH, electrical conductivity, total dissolved solids, TSS, CO3, HCO3, chlorides, alkalinity, total hardness, Ca, Mg, arsenic, copper, chromium, nickel, iron, manganese, and sulfate, were tested using groundwater samples, and variance in groundwater was analyzed using a GIS (geographic information system). The water quality index (WQI) was developed for the Nithar Ke area to determine the appropriateness of the groundwater for drinking purposes. WQI values were determined within the range of 41 to 89.5, which showed a poor to good water quality. It was discovered that parameters such as BOD, COD, iron, and TDS had average concentrations of 192 mg/L, 264 mg/L, 2.62 mg/L, and 6039 mg/L, respectively, in the polluted water, which exceeded the permissible limit. Iron and manganese were the most common contaminants found in that area. The biplot and correlation circle showed that iron and turbidity had a positive relationship. Further study on soil stratification and soil characteristics is recommended in this area for a detailed analysis of the causes of metal contamination.

Impact of long-term fertilization in no-till on the stratification of soil acidity and related parameters

The increasing cost of fuel and machinery used in conventional tillage systems makes no-till management (NT) an enticing alternative for small-grain producers. However, the application of fertilizers to the soil surface under NT has been shown to lead to the stratification of pH and other soil acidity parameters near the soil surface. Despite that, only a few works have reported the soil acidity stratification of the arable layer and were restricted to highly weathered acid soils of the tropics. Therefore, our objective was to quantify soil pH, exchangeable aluminum (AlKCl), aluminum saturation (Al%), soil organic carbon (OC), and cation exchange capacity (CEC) by depth in the topsoils across different levels of nutrient management in three long-term continuous NT wheat studies in the southern Plains of US. Plots were sampled after the winter wheat (Triticum aestivum L.) harvest in the summer of 2019 at sampling depths of 0–15 cm, and 0–2.5, 2.5–5, 5–7.5, 7.5–10, 10–12.5, and 12.5–15 cm. Treatments included an unfertilized check and a combination of increased rates of nitrogen (N) in addition to phosphorus (P) and potassium (K) application across all study locations. It was found that stratification occurred for all soil acidity parameters tested in the study, with higher OC and AlKCl, and lower pH near the soil surface. Patterns of soil pH and OC stratification were generally related to the rate of annual N fertilization. The long-term N fertilization significantly reduced soil pH in the topsoil (0–15 cm) and stratified soil layers, especially at the higher application rates. Regardless of the soil sampling depth, pH decrease was significantly related to the amount of N applied. Also, N fertilization significantly increased AlKCl and Al% but decreased the sum of Ca2++Mg2++K++Na+ both in the whole topsoil or layers. AlKCl and Al% were increased exponentially and linearly with increasing N rate and were for 0–15 cm and stratified layers, respectively. AlKCl was exponentially (inversely) related to soil pH for both sampling methods. Nitrate (NO3) was inversely related to soil pH until up to 21.9 ± 2.6 mg NO3N kg−1. Although not at the same magnitude, non-fertilized plots were likewise stratified for the tested parameters, which indicates other effects of NT on the stratification rather than the fertilizer addition. Overall, the buffer index (BI) was lower if the soil is sampled from 0 to 2.5 cm than 0–15 cm. Attention regarding sampling depth in NT areas is essential for accurate soil attributes monitoring.

Harmonic grounding impedance of rods in horizontally stratified soils using ABCD-matrix approach

Grounding electrodes play a fundamental role in the operation of power systems. In this context, precise computation of grounding impedance must consider the frequency-dependence of the soil parameters and the ground organized in stratified layers of soil. This paper proposes an ABCD matrix approach to compute the harmonic grounding impedance of rods buried in frequency-dependent stratified soils directly in the frequency domain. This technique is based on the traditional ABCD matrix used for overhead multi-phase transmission lines extended to grounding systems. In this approach, each rod segment is modeled as a short transmission line where the equivalent harmonic grounding impedance is calculated. Then, the Ground Potential Rise (GPR) waveforms are computed by lightning currents injected into the rods buried in different scenarios. Results indicated that the ABCD matrix approach has shown a good agreement with those obtained using a full-wave electromagnetic software FEKO. The frequency-dependence of the soil electrical parameters causes a significant modification in the harmonic impedance of grounding rods which reduces the GPR peaks considerably, being this reduction more pronounced in homogeneous and 2-layer soils. The proposed technique is an attractive tool since that considers the frequency dependence on each layer of soil, with a low computational cost and good accuracy from 100 Hz up to 1 MHz.

Numerical study on pile group efficiency for piles embedded in cohesive and cohesionless soils

This paper aims to study the efficiency of pile groups with various numbers of piles and pile spacing. Axial loading tests on pile groups and also single piles were simulated using a three-dimensional finite element program to obtain the load-settlement curve and the ultimate bearing capacity of the piles which was later used to estimate the pile group efficiency. In this study, the piles were embedded in cohesive and cohesionless soils. The stress-strain responses of the soils and the concrete pile and pile cap were simulated using the Mohr-Coulomb and the linear elastic models, respectively. The numerical-based pile group efficiencies were then compared to those computed using the published formulas. To verify the findings, a series of parametric studies on pile groups embedded in stratified soil was performed where the parameters of the soils were derived based on a back analysis on a case study of a single pile axial loading test in South Jakarta. The results show that the axial pile group efficiency in cohesive soil would be less than or equal to one, whereas in cohesionless soil would be more than or equal to one, especially at pile spacing more than three times the pile diameter. Meanwhile, similar results as found in cohesionless soil were obtained for the stratified soil case.

Experience of strengthening the soil base with parallel lifting of the foundation structure

The article shows the positive experience of fixing the soil base and strengthening the foundation with the parallel restoration of the normative state of the underground and above-ground structures of the facility. The accidents at the considered objects is caused by the formation of significant voids under the foundation. Foundations at the objects are represented by monolithic reinforced concrete slab and strip. Recommendations are given on the development of design solutions, organization of work, and the compositions of injection mortars are analyzed. Injection compositions were presented on the basis of cement and sand-cement mixture, the argumentation of the use of these compositions on specific engineering-geological conditions is given. Stabilization of the foundation was additionally made by strengthening with "Atlant" piles. The variants of the object geometric position correction by mortar injection into the contact layer and into the active soil strata are presented. The development of a reliable solution for reinforcement is possible only if there are an accurate data of the geotechnical conditions of the construction site, a detailed visual and instrumental survey of building structures. The processes of fixing soil foundations with parallel lifting of underground and above-ground structures are provided today with the necessary level of equipment development. However, it is necessary to ensure its technologically correct use, adapted to a specific situation. The options for solving emergency situations considered in the article can be used as proven design solutions at facilities with similar engineering and geological conditions and foundation structures.

Numerical Study on Load Bearing Capacity of Root‐Caisson Foundation

Innovation has been made in the caisson foundation to support a very large structure resting over a soft soil stratum known as the root‐caisson foundation. This technique was executed in China‐Yangtze River Bridge. The root caisson foundation was first implemented in the Yangtze River bridge and discovered that the root improves soil structure interaction and increases vertical bearing capacity by 100%. In the present research, a numerical study of root‐caisson foundation under combined vertical and horizontal loading was performed using ABAQUS software. Analysis was performed by varying the parameters of root caisson such as the inclination of roots (30°, 45°, 60°, and 90°) spacing(S) between the root floors with respect to diameter (D) of the caisson as (0.5°D, 0.6°D, and 0.75°D) with different loading conditions and results were compared with normal traditional caisson with the same length (L) to diameter (D) ratio. From the test results, the load‐settlement behavior of caisson is nonlinear for individual vertical, and lateral load tests and also the same for the combined loading conditions. It is found that the root‐caisson has a higher load bearing capacity as compared to that of the traditional caisson. Moreover, in combined loading, the load bearing capacity increases considerably, compared with the ultimate vertical and lateral load capacity.

Detection of the foreign object positions in agricultural soils using Mask-RCNN

Objects in agricultural soils will seriously affect the farming operations of agricultural machinery. At present, it still relies on human experience to judge abnormal Gounrd-penetrting Radar (GPR) signals. It is difficult for traditional image processing technology to form a general positioning method for the randomness and diversity characteristics of GPR signals in soil. Although many scholars had researched a variety of image-processing techniques, most methods lack robustness. In this study, the deep learning algorithm Mask Region-based Convolutional Neural Network (Mask-RCNN) and a geometric model were combined to improve the GPR positioning accuracy. First, a soil stratification experiment was set to classify the physical parameters of the soil and study the attenuation law of electromagnetic waves. Secondly, a SOIL-GPR geometric model was proposed, which can be combined with Mask-RCNN's MASK geometric size to predict object sizes. The results have proved the effectiveness and accuracy of the model for position detection and evaluation of objects in soils; then use the improved Mask RCNN method to compare the feature extraction accuracy of U-Net and Fully Convolutional Networks (FCN); Finally, the operating speed of agricultural machinery was simulated and designed the A-B survey line experiment. The detection accuracy was evaluated by several indicators, such as the survey line direction, soil depth false alarm rate, Mean Average Precision (mAP), and Intersection over Union (IoU). The results showed that pixel-level segmentation and positioning based on Mask RCNN can improve the accuracy of the position detection of objects in agricultural soil effectively, and the average error of depth prediction is 2.87 cm. The results showed that the detection technology proposed in this study integrates the advantage of soil environmental parameters, geometric models, and artificial intelligence algorithms to provide a high-precision and technical solution for the GPR non-destructive detection of soils. Keywords: foreign object, soil object, position, agricultural soil, Mask R-CNN, GPR image DOI: 10.25165/j.ijabe.20231601.7173 Citation: Li Y H, Wang C F, Wang C Y, Deng X L, Chen S D, Zhao Z X, et al. Detection of the foreign object positions in agricultural soils using Mask-RCNN. Int J Agric & Biol Eng, 2023; 16(1): 220–231.

Soil Stratum Tides

AbstractRiver deltas, where ocean tides can often freely propagate into the river, are focal points of human settlement. Beneath the delta surface, groundwater stored in the soil strata fluctuates with river tides, resulting in pressure variations within the soil strata. Here, we introduce a novel ultra‐weak fiber‐optic instrument to test the hypothesis that tide‐induced groundwater level variations induce periodic soil stratum deformation. Using borehole deployments ranging over 70 m in the subsurface of the Yangtze Delta, we observe semidiurnal and spring–neap cycles of soil stratum deformation and reveal its dependence on lithology and depth. This allows us to coin the new term “soil stratum tide,” defined as the periodic deformation of soil strata in response to pressure fluctuations induced by tides in open water. High‐accuracy monitoring of the breathing of tidal deltas enables calibrating Earth observation systems, analysis of delta subsidence, and safeguarding of infrastructure jeopardized by soil stratum deformation.

Dynamic analysis of a laterally loaded rectangular pile in multilayered viscoelastic soil

Rectangular piles are usually used as the foundation for many infrastructures, but there are fewer theoretical solutions for the lateral vibration. This study presents a semi-analytical methodology for the dynamic analysis of laterally loaded rectangular pile in multi-layered viscoelastic soils. The pile-soil system is modeled as a continuum, the horizontal continuous displacement model is proposed as products of the separating variables function. The coupled governing equations for rectangular pile-soil system in the frame of Euler-Bernoulli beam and modified Vlasov model are derived with the aid of Hamilton's Variation principle and calculus of variations. The physical mechanisms of soil reaction and dynamic equilibrium equation are interpreted by employing thin-layer element of soil. The dynamic responses are solved analytically and numerically by an iterative procedure. The verification and accuracy of the research are obtained thorough comparison with the relevant examples from the literatures and finite element analysis. The effects of cross-section shapes and soil stratification on the complex dynamic response are investigated and discussed in detail.

Seismic Behaviour of Shallow Tunnelling Method Tunnels Accounting for Primary Lining Effects

The shallow tunnelling method (STM) is usually used to construct shallow tunnels buried in soft ground. It consists of primary lining and secondary lining (tunnel). In the seismic design of STM tunnels, it is usually assumed that the secondary lining (tunnel) is resistant to all seismic effects. However, the soil–primary–secondary lining system may generate complex interaction phenomena during ground shaking. Compared with the case where the primary lining is not considered, the existence of the primary lining alters the seismic response of the secondary lining (tunnel). The paper attempts to investigate this complex interaction, focusing on the response of the secondary lining (tunnel). The full dynamic time history analysis is adopted to investigate the interaction in the transversal direction. A case history of the Hohhot (China) arched STM tunnel buried in a stratified soil deposit has been analyzed. Two tunnel configurations for a two-dimensional plane strain model of STM tunnels in Hohhot are studied and compared, including a model with primary lining and one without primary lining. A numerical parametric analysis was conducted to elucidate critical response characteristics of STM tunnels. Salient parameters that may affect the dynamic response of the tunnel were studied, including the characteristics of ground motion, the characteristics of contact interface, the characteristics of the soil, and the characteristics of the tunnel lining. The response characteristics of the tunnel are compared and discussed, including horizontal acceleration, deformation mode, lining internal force, and lining damage. The results show that the primary lining has a significant influence on the magnitude and distribution of the seismic response, especially considering the nonlinearity of the soil and the nonlinear characteristics of the tunnel lining. The effect of primary lining on the seismic response is about 5%–35 %.

Continued decline of global soil moisture content, with obvious soil stratification and regional difference

Soil is an important component connecting atmosphere and vegetation, and is an important ‘regulator’ of slope hydrological process. Global warming accelerates the global water cycle, and Soil Moisture Content (SMC) will change, but this change is not yet clear. Here, we study the global trend of SMC at different depths over the past 70 years and the next 70 years, based on the GLDAS-NOAH025 dataset and precipitation and temperature data from 15 CMIP6 models. We found that compared with the long-term average of 70 years, the global 0-200 cm SMC is decreasing at a rate of 1.284 kg/m2 per year from 2000 to 2020, and the area showing a significant decreasing trend accounts for 31.67 % of the global. Over the past decade, 0-200 cm SMC reduction rate (2.251 kg/m2) doubled. Global warming and precipitation reduction are the main reasons for the attenuation of SMC at different depths in the global from 2000 to 2020. Under the SSP126, SSP245, SSP370 and SSP585 scenarios, the global 0-200 cm SMC will continue to decay in the future, and the area showing a significant reduction trend accounts for 22.73–49.71 % of the global, but the stratified soil and regional differences are obvious. The attenuation of SMC will further aggravate the global water cycle and enhance the variability of extreme meteorological disasters. We will face more severe soil drought problems.

Coupled flow in saturated soil around a vertical grounding rod HVDC considering underground water's action

• Coupled fluxes in soils due to current injection into HVDC ground rods are analyzed. • Phenomenon involving the fields of electromagnetism, thermal and hydraulics. • It takes into account the effect of an underground flow. • Results include temperature, velocity and pore pressure in a stratified saturated soil. The phenomenon of coupled fluxes in soils given the injection of current in HVDC (High Voltage Direct Current) ground rods is a multiphysics problem, involving different fields, including electromagnetism, thermal and hydraulics. In some regions where precipitation is intense or due to the presence of an aquifer, the saturated condition of the soil is particularly important for the analysis of the behavior of the environment, based on the active flows. In this study, the water velocity around the ground rod is investigated, as well as the pore pressure and temperature in a transient regime, considering the Joule effect, the performance of the electro-osmotic flow and the action of the underground velocity. Such phenomena are involved by temperature-dependent parameters. The study methodology is based on simulations adopting the finite element method for the coupling of physics in a saturated and stratified soil. The validation of the results for the Joule effect shows a maximum temperature error in the order of 3.3%. As a result, it was possible to infer, through a parametric sweep, the parameters that most favor the increase in temperature, velocity and pore pressure in the medium porous. The results presented serve as a reference for HVDC grounding system designs.