Thin Soil Layer Research Articles

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.

Estimating the Soil Erosion Response to Land-Use Land-Cover Change Using GIS-Based RUSLE and Remote Sensing: A Case Study of Miyun Reservoir, North China

Soil erosion by water is a major cause of land degradation. Agricultural practices and many other ecological environmental problems contribute to land degradation worldwide, especially in arid and semi-arid areas. Miyun County, which is located in a mountainous region of North China, is an important natural ecological zone and surface source of drinking water for Beijing and is very vulnerable to soil erosion due to its thin soil layer and human activities. Landsat images from 2003 and 2013 were used to analyze the land-use and land-cover change (LULCC) over this period. The revised universal soil loss equation (RUSLE) model integrated with Geographic Information System (GIS) was used to quantify soil loss and to map erosion risk. In addition, the response of soil erosion to LULCC was evaluated. The results showed that the areas under cropland, forest, and water bodies increased over the study period by 66.03, 243.44, and 9.01 km2, respectively. The increase in forested land indicated that the improved ground vegetation cover was due to the implementation of active ecological measures. Between 2003 and 2013, light soil erosion increased by 587.46 km2, and extremely severe soil erosion increased by 9.57 km2. The extents of slight, moderate, severe, and very severe soil erosion, however, decreased by 8.02, 445.21, 142.69, and 1.11 km2, respectively. A total of 57.5% of land with moderate soil erosion has been converted to light soil erosion, which could be highly beneficial for the improvement of vegetation control of soil and water losses. In terms of area, forestland exhibited the greatest increase, while moderate soil erosion exhibited the greatest decrease over the study period. Land-use change led to an alteration in the intensity of soil erosion due to changes or loss of vegetation. The conversion from high intensity soil erosion to low intensity was attributed to the implementation of ecological environmental protection. The results generated from this study may be useful for planners and land-use managers to make appropriate decisions for soil conservation.

MPM Modeling of Cone Penetrometer Testing for Multiple Thin-Layer Effects in Complex Soil Stratigraphy

Cone penetrometer testing (CPT) is a frequently used soil characterization technique for liquefaction assessment; however, this technique has shortcomings in accurately characterizing very thin soil layers having thicknesses less than two to three times the diameter of the cone. In this study, the material point method (MPM) is used to generate numerical “measured” (or “blurred”) CPT tip resistance (qm) in complex soil profiles. Results show that MPM is capable of accurately simulating qm in soil profiles with layers as thin as 20 mm, even when using basic constitutive models and simplified drainage conditions. It is further shown that MPM simulations are able to replicate the tendency of the CPT to smear the boundaries between very thin, interbedded soil layers in a way that obscures their true thickness and stiffness (typically referred to as thin-layer, transition-zone, or multiple thin-layer effects). While previous numerical studies of CPT have been performed in profiles composed of two or three layers, this study considers highly interlayered profiles with upwards of 27 soil layers. Difficulties of developing and implementing multiple thin-layer corrections are presented. It is shown that a numerical framework like MPM can generate a larger set of data for the development and validation of multiple thin-layer correction procedures with the aim of improving liquefaction severity predictions in complex soil profiles.

Geant4 Simulation of Precipitated Activity-to-γ-Dose Rate Conversion Factors for Radon and Thoron Decay Products

The results of modeling the conversion factor from rainfall-deposited unit activity of gamma-emitting radon and thoron daughter decay products to their created gamma-radiation dose rate as a function of height above the Earth’s surface using the Geant4 toolkit are presented in this paper. Thin layers of water, soil, and air, with the height of 0.1–10 mm, are considered as the source in order to examine whether the composition of the radiation source environment affects the simulation result. Cases with different absorber-atmosphere densities are simulated. The contribution of each radionuclide 212Bi, 214Bi, 212Pb, 214Pb and 208Tl to the total gamma background was determined. The dependence of dose rate growth during the precipitation period on the detector position in relation to the area covered by precipitation was investigated numerically. The obtained conversion factors are universal values, because do not depend on soil type (material) on which radionuclides are deposited by precipitation. These coefficients can be used for solving both direct tasks of radiation background recovery during precipitation and inverse tasks of determining the intensity and amount of precipitation by the known gamma background, as well as tasks to decipher the gamma background by the shape of the response to various phenomena. Also in this work, it is shown how thoron decay products can affect the response shape of gamma background on atmospheric precipitation.

Modeling of Drying‐Induced Soil Curling Phenomenon

AbstractDrying‐induced soil curling is commonly observed in nature. In order to investigate the change of water distribution in soil caused by drying and curling, a series of drying tests is performed on thin soil layers in the laboratory. A discrete element model (DEM) is then proposed to simulate soil desiccation curling. The outermost particles are selected as the surface of the model to address the importance of surface evaporation. Moisture distribution change during drying is governed by both surface evaporation and moisture exchange between DEM particles. The results show that the model can capture the main features of the soil curling process from concave curling () to convex curling (). The model enables variation in moisture gradient during the drying process. The trend of the curling development obtained from the model agreed well with the laboratory observation. A newly exposed surfaces in the model can provide a more realistic moisture distribution and influence the curling behavior. Generally, the drying‐induced soil curling process and extent are associated with the change in moisture gradient along the depth. The movement of tensile stress concentration change from the upper layer in the early drying stage to the lower part of the sample in the late drying stage is the intrinsic mechanical factor responsible for the initial concave curling deformation and the subsequent fallback and convex curling phenomenon. Curling deformation in the present model is compared with other existing explanations on desiccation curling. The influences of evaporation rate and hydraulic conductivity on the model performance were also discussed. It is found that a higher evaporation rate and a lower hydraulic conductivity would result in a higher extent of curling during drying.

石漠化生境对三叶木通生长及生理特性的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 石漠化生境对三叶木通生长及生理特性的影响 DOI: 10.5846/stxb202102250522 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家重点研发计划项目（2016YFC0502604）；贵州省科技计划重大专项课题（黔科合平台人才[2017]5411-06，黔科合平台人才[2017]5788）；贵州省高层次创新型人才培养计划项目（黔科合人才[2015]4031） Effects of rocky desertification habitat on growth and physiological characteristics of Akebia trifoliata Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:石漠化生境土层浅薄、干旱贫瘠，许多植物难以生存。三叶木通作为石漠化生境适生物种之一，探究其对石漠化生境的应答机制对综合治理石漠化生境具有一定的理论和实际意义。在贵州省贵阳市花溪区和安顺市关岭县两地分别选取石漠化生境和普通生境（对照）种植三叶木通，并进行为期一年的观察，探究石漠化生境对三叶木通根、茎、叶等不同器官的生长和生理特性的影响，并利用主成分分析出三叶木通在石漠化生境的主要响应指标。结果显示，与对照相比，石漠化生境下的三叶木通表现出如下特征：（1）植株较矮、茎较细、叶片数较少等生物量的减少，使其适应石漠化生境；（2）叶片叶绿素a/b （Chla/b）和相对含水量（RWC）呈现降低趋势，从而使叶片净光合速率（Pn）、蒸腾速率（Tr）、气孔导度（Gs）和水分利用率（WUE）均呈下降趋势，胞间CO2浓度（Ci）呈升高趋势，利于适应石漠化生境；（3）丙二醛（MDA）含量和叶片相对电导率（RC）呈现升高趋势，说明石漠化生境对三叶木通细胞膜系统造成损伤（氧化损伤和渗透损伤），而通过其根中过氧化氢酶（CAT）、茎中过氧化物酶（POD）和叶片中超氧化物歧化酶（SOD）活性升高来防御氧化造成的伤害；通过增加可溶性蛋白（SP）、脯氨酸（Pro）等渗透性调节物质含量，防御渗透压造成的伤害；（4）主成分分析表明，MDA、POD和SP在三叶木通对石漠化应答中起着主要作用。研究揭示了三叶木通响应石漠化生境的生长及生理调节机制，为三叶木通用于石漠化综合治理提供理论基础的同时，也为进一步阐明三叶木通抵抗石漠化逆境的分子机理、提高三叶木通抗逆性提供参考依据。 Abstract:The rocky desertification habitat has a thin soil layer and is arid and barren. Many plants are sometimes difficult to survive. Akebia trifoliata is one of the species that can grow in rocky desertification habitats. Exploring its response mechanism to rocky desertification habitats has certain theoretical and practical significance for comprehensive management of rocky desertification habitats. In Huaxi District of Guiyang City and Guanling County of Anshun City, Guizhou Province, rocky desertification habitat and the common habitat (control) were selected to plant Akebia trifoliata and observed for one year. We explore the impact of rocky desertification habitat on the growth and physiological characteristics of different organs such as the roots, stems and leaves of Akebia trifoliata, and use principal component analysis to the main response indicators of Akebia trifoliata in the rocky desertification habitat. The results show that the Akebia trifoliata in the rocky desertification habitat exhibits the following characteristics than the common habitat (control):(1) the reduced biomass, such as shorter plants, thinner stems and fewer leaves, so as to adapt to the rocky desertification habitat; (2) leaf chlorophyll a/b (Chla/b) and relative water content (RWC) indicated a decreasing trend, so that the leaf net photosynthetic rate (Pn), transpiration rate (Tr), stomatal conductance (Gs) and water use efficiency (WUE) presented a downward trend, and the intercellular CO2 concentration (Ci) had a rising trend, and then conducive to adapted to the rocky desertification habitat; (3) the content of malondialdehyde (MDA) and relative electrical conductivity (RC) of leaves showed an increasing trend, indicating that the rocky desertification habitat caused damage (oxidative damage and osmotic damage) to the cell membrane system of Akebia trifoliata. It protects against damage caused by oxidation by increasing the activities of catalase (CAT) in roots, peroxidase (POD) in stems and superoxide dismutase (SOD) in leaves. It protects against damage caused by osmotic pressure by increasing the content of osmotic adjustment substances such as soluble protein (SP) and proline (Pro); (4) principal component analysis showed that MDA, POD and SP play a major role in the response of Akebia trifoliata to rocky desertification. This study reveals the growth and physiological regulation mechanism of Akebia trifoliata in response to rocky desertification habitats, provides the theoretical basis for Akebia trifoliata's comprehensive management of rocky desertification habitats. Meantime, this study could further clarify the molecular mechanism of Akebia trifoliata resisting rocky desertification habitats, and provide a reference basis for improving its resistance to adversity. 参考文献 相似文献 引证文献

筇竹构件生物量积累分配特征及其与土壤物理性质的关系

PDF HTML阅读 XML下载 导出引用 引用提醒 筇竹构件生物量积累分配特征及其与土壤物理性质的关系 DOI: 10.5846/stxb202103290815 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家林业公益性行业科研专项(201204103);中央财政林业科技推广示范资金项目([2018]TG14号);中央财政林业科技推广示范资金项目([2019]TG14号);江苏省研究生科研创新计划(NO.KYCX21-0925) Biomass of accumulation and allocation characteristics of Qiongzhuea tumidinoda components and its relationship with soil physical properties Author: Affiliation: Fund Project: National forestry public welfare industry scientific research project (201204103); Forestry science and technology promotion demonstration fund project of the central government ([2018] No. tg14); Jiangsu graduate scientific research innovation program (no.kycx21-0925) 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:以大关县3种土层深度0-40 cm、0-80 cm和0-120 cm的天然筇竹林为研究对象,在个体水平上研究了竹子构件生物量分配特征及其与土壤物理性质的相关关系,以期为筇竹林适宜立地条件选择、适地适竹及定向培育提供的理论指导。结果表明:(1)同一土层深度,土壤含水量、最大持水量、毛管持水量、毛管孔隙度和总孔隙度均呈现出随土层增加而增加的趋势,而土壤容重和非毛管孔隙度则呈现出随土层增加而减少的趋势,且薄土层和厚土层各土壤物理因子差异显著(P＜0.05)。(2)随着土层厚度的增加,筇竹总生物量以及构件秆、枝、叶、蔸、鞭和根生物量表现出增加的趋势,且不同土层厚度差异显著(P＜0.05)。(3)随着土层厚度的增加,筇竹构件枝、叶、蔸、鞭、根生物量分配相应增加,秆生物量分配则相应减少,但各处理间差异并不显著(P＞0.05)。(4)土壤物理因子对筇竹构件生物量分配有着显著影响(P＜0.05),单一土壤物理因子对筇竹构件生物量分配特征的重要性大小排序为土壤含水量＞总孔隙度＞最大持水量＞容重＞毛管孔隙度＞毛管持水量＞非毛管孔隙度。结论:土壤物理因子沿土层厚度的变化对筇竹构件生物量分配产生了重要影响,在土壤物理性质较差的生境中,筇竹会优先将生物量分配给秆,并通过减少叶生物量来响应水分缺失的不利环境,这对筇竹林立地条件选择有指导意义,即筇竹宜选择较深厚土层经营,以促进生物量积累和种群生长。 Abstract:The depth of three types of soil layers (0-40 cm, 0-80 cm, and 0-120 cm) in Daguan County, Yunna Province were chosen as the research object to analyze the biomass allocation characteristics of Q. tumidinoda components at the individual level and their relationship with soil physical properties. This study provided a theoretical guidance for the selection of suitable site conditions, the suitable sites of bamboo and directional cultivation. The results showed that: (1) at the same soil depth, soil water content, maximum water holding capacity, capillary water holding capacity, capillary porosity and total porosity increased with the increasing of soil layer, while soil bulk density and non-capillary porosity decreased with the increasing of soil layer. There were significant differences in soil physical factors between thin and thick soil layers (P<0.05). (2) With the increasing of soil layer thickness, the total biomass and biomass of culm, branch, leaf, stump, rhizome and root of Q. tumidinoda presented increasing trends, and there was significant difference among the thickness of different soil layers (P＜0.05). (3) With the increasing of soil thickness, the biomass allocation of branch, leave, stump, rhizome and root increased, while the biomass allocation of culms decreased, but there was no significant difference among the treatments (P＞0.05). (4) Soil physical factors had significant effects on biomass allocation of Q. tumidinoda components (P＜0.05). The order of importance of single soil physical factor to biomass allocation characteristics of Q. tumidinoda components was soil water content＞total porosity＞maximum water holding capacity＞bulk density＞capillary porosity＞capillary water holding capacity＞non capillary porosity. In conclusion, the changes of soil physical factors along the soil thickness had an important influence on the biomass distribution of Q. tumidinoda components. In the environment with poor soil physical properties, Q. tumidinoda would preferentially allocate the biomass to the culm and reduce the leaf biomass to respond to the adverse environment of water loss. This was of guiding significance to the selection of site conditions of Q. tumidinoda forest, that was, Phyllostachys pubescens should choose deeper soil layer for management, so as to promote biomass accumulation and population growth. 参考文献 相似文献 引证文献

亚热带岩溶区典型常绿和落叶树种的蒸腾特征及其对环境因子的响应

植物蒸腾是水循环的重要组成部分，为了解亚热带岩溶区树木的蒸腾耗水情况，探究气候和水文地质条件对植物蒸腾的影响，运用Granier热耗散探针技术，对亚热带岩溶区次生林内的常绿树种女贞（L.lucidum）和落叶树种刺槐（R.pseudoacacia）的树干液流进行了连续监测，并同步监测了气象因子及土壤含水率（SMC），探讨在不同时间尺度下两种生活型树种的蒸腾特征及其对环境因子的响应。结果表明：（1）在季节尺度下，影响两树种整树蒸腾量（ET）的主要因子为太阳辐射强度（Rs）、气温（T）和水汽压亏缺（VPD）；女贞蒸腾量（ET_L）表现为夏季（1.29 kg/h） > 春季（0.57 kg/h） > 冬季（0.15 kg/h） > 秋季（0.13 kg/h），刺槐蒸腾量（ET_R）表现为夏季（0.90 kg/h） > 春季（0.31 kg/h） > 秋季（0.16 kg/h） > 冬季（0.04 kg/h）。（2）在日尺度下，晴天两树种ET呈现出明显的单峰日变化，且主要影响因子均为T、VPD和Rs；但由于常绿和落叶树种的生理特征差异，降雨时ET_L受到抑制，而ET_R则显著提升。（3）从昼夜层面来看，两树种夜间蒸腾量不足日蒸腾总量的35%。在夜雨现象和树木生理特征的影响下，秋冬季夜间蒸腾量占比明显高于春夏季，刺槐的平均夜间蒸腾量及其占比（1.56 kg，24.1%）高于女贞（1.08 kg，13.9%）。;Plant transpiration is an important part of water cycle in ecosystem, that is, the process of water transfer from soil to atmosphere through plants. It is driven by solar radiation, air temperature, air humidity and wind speed, and also affected by soil water storage capacity. Understanding and quantifying the influence mechanism of transpiration is an important basis to explore the water consumption of vegetation and the water balance of ecosystem. However, although the climate conditions in the subtropical karst area are good, there is a drought period of 4-5 months. At the same time, plants are often affected by water stress because of the thin soil layer and low water holding capacity of soil in karst area. The study of plant transpiration characteristics helps us understand the water consumption of trees in subtropical karst areas, and is also of great significance for exploring the impact of climate and hydro-geological conditions on plant transpiration. Granier's thermal dissipation probe method was used to continuously monitor the trunk sap flow of the evergreen tree species (L.lucidum) and the deciduous tree species (R.pseudoacacia) in the secondary forest in the subtropical karst area. The meteorological factors and soil moisture content (SMC) are also monitored simultaneously. Our purpose is to analyze the transpiration characteristics of two life-form tree species and their responses to environmental factors on different time scales. The results show that:(1) at the seasonal scale, the main factors affecting the whole-tree transpiration (ET) are solar radiation intensity (Rs), air temperature (T) and vapor pressure deficiency (VPD). The transpiration of L.lucidum (ET_L) is shown as summer (1.29 kg/h) > spring (0.57 kg/h) > winter (0.15 kg/h) > autumn (0.13 kg/h), transpiration of R.pseudoacacia (ET_R) is shown as summer (0.90 kg/h) > spring (0.31 kg/h) > autumn (0.16 kg/h) > winter (0.04 kg/h). (2) On the daily scale, the ET of the two tree species shown obvious single peak curve on sunny day, and the main factors affecting transpiration are T, VPD and Rs. However, due to the differences in the physiological characteristics of evergreen and deciduous tree species, ET_L is weakened during rainfall, while ET_R is significantly increased. (3) in terms of day and night, the nocturnal transpiration of the two tree species accounts for less than 35% of the total daily transpiration on average. Affected by the phenomenon of night precipitation and the physiological characteristics of trees, the proportion of nocturnal transpiration in the autumn and winter is significantly higher than that in the spring and summer. At the same time, the average daily nocturnal transpiration and its proportion of R.pseudoacacia (1.56 kg, 24.1%) is higher than that of L.lucidum (1.08 kg, 13.9%).

Effect of soil-rock interface position on seismic response of subway station structure

For subway stations in a site with thin soil layers on the engineering rock, the lower part of the subway station is embedded in the hard rock mass and the upper part is buried in the soil layers. The presence of the soil-rock interface may lead to significant increase to the seismic responses of the adjacent soil masses and underground structures. In this paper, the effect of the soil-rock interface position on the seismic response of a two-story and three-span subway station structure is investigated by numerical analyses. It is found from the numerical analyses that a most detrimental soil-rock interface position exists and makes the underground structure have maximum responses under a given artificial earthquake motion. For the upper floor, the most detrimental soil-rock interface position is near the middle slab. For the lower floor, the most unfavorable soil-rock interface position is near the bottom slab. Softer site generally leads to greater structural responses under the same intensity of ground motion excitation. On the basis of the above findings, three earthquake motions included above an artificial earthquake motion and other two real earthquake motions and three burial depths of structure are further studied. Same conclusions can be obtained for the structure with different burial depths or subjected to different input earthquake motions. The conclusions drawn from the numerical examples of this paper may be useful for seismic design of subway station structure buried in shallow soil layers on rock.

Determining the Height of Water-Flowing Fractured Zone in Bedrock-Soil Layer in a Jurassic Coalfield in Northern Shaanxi, China

The height of the water-flowing fractured zone is the most important technical parameter for water prevention and control in a coal mine. Due to the numerous factors affecting the water-flowing fractured zone, it is difficult to accurately identify the zone. Currently, no effective way exists for determination of the water-flowing fractured zone in a soil layer. To accurately determine the development law of the water-flowing fractured zone in the bedrock-soil layer of a Jurassic coalfield in northern Shaanxi, China, we conducted a comprehensive study using microresistivity scanning imaging technology, apparent density logging, long-range gamma logging, observation on drilling flushing fluid consumption, physical simulation, and numerical simulation. The following results were obtained: (1) The ratio of the height of the water-flowing fractured zone to the mining height was 28.3–28.5, which was obtained by microresistivity scanning imaging technology, whereas the ratio of the height of the water-flowing fractured zone to the mining height was 28.1–29.1, determined by apparent density logging, long-range gamma logging, physical simulation, and numerical simulation. The microresistivity scanning imaging results were consistent with those obtained by other methods. (2) Based on the thickness of the soil layer and the bedrock, the height model of the water-flowing fracture zone was divided into four regions, that is, the thick bedrock-thick soil layer region, thick bedrock-thin soil layer region, thin bedrock-thin soil layer region, and thin bedrock-thick soil layer region. A mathematical model describing the difference between the thickness of the water-flowing fractured zone and the bedrock and the thickness of the soil under the condition of bedrock-soil was established. (3) We conclude that microresistivity scanning imaging technology can accurately detect the height of the water-flowing fractured zone in a soil layer, and the apparent density logging and long-range gamma logging can precisely detect the height of the water-flowing fractured zone in bedrock. This is a new comprehensive method for research on the height of the water-flowing fractured zone that can provide a reliable basis for water prevention and control in mines.

Robust identification and characterization of thin soil layers in cone penetration data by piecewise layer optimization

Cone penetration testing (CPT) is a preferred method for characterizing soil profiles for evaluating seismic liquefaction triggering potential. However, CPT has limitations in characterizing highly stratified profiles because the measured tip resistance (qc) of the cone penetrometer is influenced by the properties of the soils above and below the tip. This results in measured qc values that appear “blurred” at sediment layer boundaries, inhibiting our ability to characterize thinly layered strata that are potentially liquefiable. Removing this “blur” has been previously posed as a continuous optimization problem, but in some cases this methodology has been less efficacious than desired. Thus, we propose a new approach to determine the corrected qc values (i.e. values that would be measured in a stratum absent of thin-layer effects) from measured values. This new numerical optimization algorithm searches for soil profiles with a finite number of layers which can automatically be added or removed as needed. This algorithm is provided as open-source MATLAB software. It yields corrected qc values when applied to computer-simulated and calibration chamber CPT data. We compare two versions of the new algorithm that numerically optimize different functions, one of which uses a logarithm to refine fine-scale details, but which requires longer calculation times to yield improved corrected qc profiles.

Comparison of models for predicting cleaning of viscoplastic soil layers by impinging coherent turbulent water jets

Different approaches to model the cleaning of (i) very thin and (ii) thin soil layers by impinging water jets are compared to evaluate their predictive capabilities. Cleaning experiments were performed with coherent 2 mm and 3 mm diameter water jets (Re > 10,000) impinging on flat layers of an insoluble, viscoplastic petroleum jelly. The jelly exhibited creep below the yield stress and Herschel-Bulkley behaviour above it. A two-film shear-driven model for case (i) gave very poor predictive capability, partly due to the complex soil rheology. Case (ii) data were compared to modified versions of the phenomenological model of Fernandes and Wilson (2020), and a fully-coupled CFD model of the liquid and soil motion using the volume of fluid method. The modifications to the former did not improve its accuracy. The latter gave a good prediction of the initial cleaning behaviour for the case considered: the high computational cost precluded extensive testing.

EARTH RETAINING STRUCTURES THAT ALLOW ROAD INFRASTRUCTURE PROJECTS COASTING A FLYSCHIOID ROCK VALLEY

This note concerns the main geotechnical features of two road infrastructures, located in northwestern Italy. They are adjoining and situated from km 31+500 to km 35+600 of the national road “Strada Statale n. 45 di Val Trebbia”, along Trebbia river valley, across the Ligurian Apennines. The road, mostly in the half-way section, coasts a valley featured by orographic slopes with an average slope of 25°-30°, which rise up to 1100m above sea level. The stratigraphy, starting from the top level to the deepest, shows: a thin layer of eluvial-colluvial soil; a layer, 3-5m thick, of fractured rock, and underneath the hard marl substrate that belong to the flyschioid formation of Ronco. In this context, to widen the carriageway, improve the design speed of the road section and carry out the works under traffic, a systematic use of earth retaining structures has been conceived. Thanks to the experience taken from the works of the previous project, a more conservative geotechnical characterization has been adopted in the second one. This has meaning for the lithotype called intact rock, in the equivalent Mohr-Coulomb model, a significant reduction in cohesion against a slight increase of friction angle; furthermore, a correspondent variation resulted for the fractured rock.

Latent Heat Flux (Evapotranspiration) in Summer Season on Rooftop Greening Soil with Bamboo Charcoal Sublayer at a Building in West Japan

The effect of a thin and light greening system with bamboo charcoal layer for water retention on heat fluxes, in particular latent heat flux (evapotranspiration rate), under no irrigation condition, on the rooftop of a building in Higashi-Hiroshima, West Japan, was investigated. In April 2019, lawn seeds (Zoysia tenuifolia) were sown which were germinated, reached a height of 70 mm by May when 100% of the vegetation area was covered. The air temperature and humidity at two different heights (0.3 m and 1.8 m) above greening soil surface, latent, and sensible heat fluxes were estimated. Bowen ratio was employed to collect the data on surface heat balance and soil water content during the summer season (June to September) in 2019 on the rooftop of a building in Higashi-Hiroshima, West Japan. The latent heat during daytime for a week without rainfall in each month was compared with the evapotranspiration rate. Owning to the vegetation development, the ground heat flux on greening soil surface decreased from -400 W/m2 to -200 W/m2 (flux from air to soil) during sunny daytime in July, and it was less than -100 W/m2 in August, although net radiation was maintained around 800 W/m2 over the season except in September. The monthly net radiation flux for an entire day (daytime and nighttime) ranged between 55 and 125 W/m2 (average: 95 W/m2) for the summer season of which 32-66% (average: 48%) was occupied by latent heat. Evapotranspiration from greening soil ranged between 1.24 and 1.82 mm/day, averaged at 1.51 mm/day throughout the season, which corresponded to about 26% of total rainfall over the season ( r 2 = 0.88 , p &lt; 0.01 ; S . E = 0.06 ) between the estimated and measured values. These observations suggested that the thin and bamboo coal light soil layer greening system, even without constant irrigation, could maintain the development of lawn grass and transformed more than half of net radiation to latent heat, i.e., evapotranspiration, insulating most ground heat in midsummer, which may be mostly due to bamboo charcoal sublayer.

Urban Pit-Building Insects Are Attracted to Walls for Multiple Reasons.

Simple SummaryWormlions are small fly larvae that dig pit-traps in loose soil to hunt ants and other prey. Their natural habitat is caves, but they are also abundant in Mediterranean cities below man-made shelters, even in thin layers of soil. They are especially common next to building walls. First, we show that wormlions are indeed closer to walls than expected by chance. Next, we tested several explanations for this observation: the possible effect of soil depth, soil particle size, shade, and prey abundance. We could not find a single explanation for the wormlion’s proximity to walls, and in each site, a different set of explanations held true. The final step was to conduct an experiment. We placed wormlions on clear sand either in the center or next to the wall and observed whether they moved after a day. Those placed in the center moved over longer distances, and we interpret this result to indicate that those adjacent to the wall are more satisfied with their location. Our study provides an example for how animals take advantage of human-made changes in the habitat and prosper in urban habitats.Whereas most animals find urban habitats to be inferior to natural habitats, some “urban specialist” species thrive there. Wormlions present such an example. Common in Mediterranean cities, they cluster in thin layers of loose soil below man-made shelters. Wormlions are fly larvae that dig pit-traps in loose soil and hunt small arthropods. Our first aim was to determine whether wormlion pits accumulate next to walls. Wormlion pits were indeed closer to walls than expected by chance at most of the study sites. We examined possible factors behind this apparent preference, combining field observations and experiments, laboratory work, and theoretical analysis. We examined the effect of soil depth, particle size, shade, and prey abundance. Each factor provided a partial explanation for the wormlions’ proximity to walls, but none provided an overall explanation. We developed a spatially explicit simulation model, demonstrating under which conditions wall-adjacent positions are favored. Finally, we created artificial microhabitats, and placed wormlions either in the center or next to the wall. The wormlions in the center moved over longer distances than those next to the wall and did so more in the wall’s direction. The abundance of walls may help to explain the success of wormlions in urban habitats.

Some Peculiarities of Arable Soil Organic Matter Detection Using Optical Remote Sensing Data

Optical remote sensing only provides information about the very thin surface layer of soil. Rainfall splash alters soil surface properties and its spectral reflectance. We analyzed the impact of rainfall on the success of soil organic matter (SOM) content (% by mass) detection and mapping based on optical remote sensing data. The subject of the study was the arable soils of a test field located in the Tula region (Russia), their spectral reflectance, and Sentinel-2 data. Our research demonstrated that rainfall negatively affects the accuracy of SOM predictions based on Sentinel-2 data. Depending on the average precipitation per day, the R2cv of models varied from 0.67 to 0.72, RMSEcv from 0.64 to 1.1% and RPIQ from 1.4 to 2.3. The incorporation of information on the soil surface state in the model resulted in an increase in accuracy of SOM content detection based on Sentinel-2 data: the R2cv of the models increased up to 0.78 to 0.84, the RMSEcv decreased to 0.61 to 0.71%, and the RPIQ increased to 2.1 to 2.4. Further studies are necessary to identify how the SOM content and composition of the soil surface change under the influence of rainfall for other soils, and to determine the relationships between rainfall-induced SOM changes and soil surface spectral reflectance.

Evaluation of a cone penetration test thin-layer correction procedure in the context of global liquefaction model performance

Engineering geologists routinely perform liquefaction hazard assessments using data from the cone penetration test (CPT). However, the volume of soil mobilized by the CPT acts as a low-pass filter on the true stratigraphy, potentially removing information such as the data defining a thin layer of soil or the interface between two dissimilar soils. The Boulanger and DeJong (2018) CPT inversion procedure, which aims to correct these effects, is herein evaluated in the context of CPT-based liquefaction model performance. Using over 15,000 case-histories from 24 earthquakes parsed into 2 datasets, 18 different liquefaction models are studied, resulting in 36 performance trials. In 1 of these trials, the CPT inversion procedure increases model efficiency to a statistically significant degree, but in 23 others it significantly decreases efficiency. This decline in performance tends to grow as profiles become more stratified. To explore remedies, a liquefaction triggering curve is rederived from inverted CPT data, such that its training and forward implementation are made consistent. Nonetheless, this exacerbates the decline in prediction efficiency. Ultimately, the results of this study are not a direct assessment of the pioneering Boulanger and DeJong (2018) procedure. However, the results do provide evidence that this procedure – when applied to existing CPT-based liquefaction models – may provide no demonstrable performance benefit.

Numerical study of reinforced natural slope by retaining wall with prestressed anchor

The slope design under geological and hydraulic conditions has always been a different geotechnics problem. There have been potential main landslide and an undisturbed thin layer of saturated clays soil under the slopes in urban construction development area of Miliana city province of Algeria; its terrain is mountains. The landslide was framed by gravity creeping of thin layer of alluvium and mares cracks along steep clays. The favorable sliding surface larger than 2500 m2 had destroyed the foundation of the building. In order to learn from the comparison between stabilized and non-stabilized slopes with different improvement, the authors also investigated the slopes reinforced by retaining wall with prestressed anchor and discussed their behavior parameters. Based on finite element method, the analysis of slope stability under natural conditions is discussed first, then the support structure of retaining wall and anchor reinforced and their effect of slope stability are analyzed, and also the slope stability of each case is able to be compared. The results show that the stability of slope was significantly improved after reinforcement, and anchor reinforced with retaining wall has obvious reverse anchoring effect on soil. By comparing the factor of safety, stress level and displacement field before and after slope reinforcement, it is found that better reinforcement results can be achieved if strong reinforcement is applied upon the regions with high sliding surface. Furthermore, the increase in stress level at the zone dangerous is more favorable of improving the safety of the critical region.

A laboratory-scale phytocover system for municipal solid waste landfills

ABSTRACT A tremendous increase in municipal solid waste (MSW) generation and its poor management is observed in almost all the developing countries. Landfilling, though undesirable, is an unavoidable disposal option with leachate generation and landfill gas (LFG) emissions as its major inescapable consequences. To evade these dismal outcomes of waste contentment, plant-soil based cover options are being studied widely. In the present study, an attempt was made to employ locally available plants for the phytoremediation of landfills. The experimental set-up was designed using 100 kg of MSW which was laid over with a thin soil layer of 30 cm. The efficiency of the laboratory-scale experimental set-up of 1 m3 volume was assessed in terms of trace element remediation and LFG oxidation. The initial and final parameters were finally assessed and compared. Plant species were found to develop a strong root zone, thereby reducing the infiltration of water into the waste mass. The present study showed a reduction in LFG emissions of 11.12%, 54.38%, and 32.12% in the deep zone, root zone, and topsoil zone, respectively. Furthermore, the study of the microbes, influencing soil chemical characteristics, could be helpful for designing an appropriate phytocover under diverse climatic conditions of India.

Climatic and biotic influences on isotopic differences among topsoil waters in typical alpine vegetation types

Hydrogen and oxygen isotopes have been widely used to investigate global hydrologic cycles. However, the most studies of soil water isotopes have overlooked the importance of O-horizon that may potentially influence the accurate evaluation of hydrologic processes, especially in the alpine ecosystem with thin soil layers. To address this knowledge gap, soils were sampled from the O-horizon and the 0–10 cm soil layer from 107 sites in the grasslands and woodlands of the Western Sichuan alpine ecosystem in order to evaluate the influence of climatic and biotic factors on the isotopic differences (expressed as the logarithmic of effect sizes, lnRR), which represented the difference of δ2H and δ18O between the O-horizon and the 0–10 cm soil layer. The isotopic differences between the O-horizon and the 0–10 cm soil layer were significantly different in the grasslands, but not in the woodlands. The influence of climatic factors on the lnRR was limited relative to the biotic factors, and the influence of climate contrasted with expectations based on an evaporation principle. Rather, aboveground biomass (AGB) was significantly correlated with the lnRR between and within the soil water from different vegetation types. Consequently, the observed differences were mainly related to the vegetation conditions that influence the microclimates within canopies. Therefore, the investigations of hydrological processes may inaccurately estimate their influences when not separately considering the especially high stable isotope values of the O-horizon in grasslands of alpine regions with thin soil layers. In particular, the influence of O-horizon should be considered in the areas where AGB is less than 100 t/hm2.