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Sodic Soils: Properties
Published in Brian D. Fath, Sven E. Jørgensen, Megan Cole, Managing Soils and Terrestrial Systems, 2020
Swelling and dispersion of sodic aggregates destroy soil structure, reduce the porosity and permeability of soils, and increase the soil strength even at low suction (i.e., high water content). These adverse conditions restrict water storage and transport. Soils are, therefore, either too wet immediately after rain or too dry within a few days for optimal plant growth. Thus, the range of soil water content that does not limit plant growth and function (“nonlimiting water range”) is very small.[5] Dense, slowly permeable sodic subsoils reduce the supplies of water, oxygen, and nutrients needed for obtaining maximum potential yield. During the rainy season, even with prolonged ponding of water on the surface, only a small increase in water content occurs in subsoil. The low porosity leads to slow internal drainage and water redistribution within the profile.[6] This reduction in water storage causes crop water stress during prolonged dry periods. Subsoil as a source of water and nutrients becomes more important in dryland cropping regions than in irrigated soils.
Soil Basics
Published in Frank R. Spellman, Land Subsidence Mitigation, 2017
Now that we have defined soil, let’s take a closer look at a few of the basics pertain- ing to soil and some of the common terms used in any discussion related to soil basics. Soil is the layer of bonded particles of sand, silt, and clay that covers the land surface of the Earth. Most soils develop in multiple layers. The topmost layer, topsoil, is the layer of soil moved in cultivation and in which plants grow. This topmost layer is actu- ally an ecosystem composed of both biotic and abiotic components—inorganic chem- icals, air, water, and decaying organic material that provides vital nutrients for plant photosynthesis, as well as living organisms. Below the topmost layer is the subsoil, the part of the soil below the plow level, usually no more than a meter in thickness. Subsoil is much less productive, partly because it contains much less organic matter.
A permafrost foundation analysis
Published in Jean-François Thimus, Ground Freezing 2000 - Frost Action in Soils, 2020
Permafrost foundations are designed and constructed using either an active or a passive method (Johnston, 1981). The active method is best applicable for mean ground temperatures > −3 °C and it is used when cooling is not feasible. Typical techniques are thawing and consolidation of the subsoil or soil replacement with a thaw stable material. The passive method is best applicable at lower ground temperatures because its basic idea is to maintain the thermal regime below 0 °C throughout the year. Typical techniques for that are ventilation ducts through the fill pad below the foundations (Fig. la) and refrigeration for instance mechanically in a similar manner as in artificial skating rinks or by means of natural convection devices (Fig. lb).
Monitoring of an instrumented geosynthetic-reinforced piled embankment with a triangular pile configuration
Published in International Journal of Rail Transportation, 2023
Van Duc Nguyen, Qiang Luo, Tengfei Wang, Liang Zhang, You Zhan, Tri Phuong Nguyen
Over the last decade, high-speed rail lines have been extensively constructed throughout East Asia, Europe, and North America [1] with a view to expanding travel choices, improving mobility, reducing congestion, boosting productivity, and tackling the energy crisis. Trains generally run at an operating speed of 200 to 350 km/h, while the French Train à Grande Vitesse (TGV) achieved a maximum speed of 574.8 km/h on the new Ligne à Grande Vitesse Est européenne (LGV Est), setting a record for a commercial rolling stock on steel wheels. The ride quality and safe operation of high-speed trains demand that long-term settlement of the track foundation should be strictly restricted, posing new challenges with regard to construction techniques of high-speed rail [2,3]. As the rail network further expands, geotechnical auxiliary infrastructure will be increasingly constructed on problematic soils – such as expansive soil, liquefiable soil, and weak or soft soil [4]. Excessive settlement and possible bearing failure may occur, adversely affecting the performance of project earth structures on soft soil. Accordingly, ground improvement is employed to stabilize or improve poor subsoil conditions. Among various ground modification techniques, geosynthetic-reinforced piled (GRP) embankments are emerging as a feasible and relatively economical solution to support high-speed railways [5].
Effect of saline intrusion on the properties of cohesive soils in the Red River Delta, Vietnam
Published in Marine Georesources & Geotechnology, 2020
Nguyen Ngoc Truc, Lena Mihova, Toshifumi Mukunoki, Duc Minh Do
Saline intrusion becomes highly sensitive as salt in water contacts with clay particle in young sediments. The cohesive soils in very soft, soft, or medium state are normally more sensitive to salt than that in stiff state. Cohesive soils of young sediment in the RRD are nearly in soft to medium state. Previous studies have proven that the properties of soil change when soil is affected by saline water. The change depends on clay mineral type and saline solution concentration (Truc and Mihova 2015; Komine 2007a, 2007b). The changes in the properties of subsoil directly influence the stability of coastal infrastructure, for example, the foundation of river dikes and sea dike systems, road embankment, and civil constructions. The intrusion of saltwater into soil layers, that is, the existence of salt in cohesive soil, may lead to the reactions between cations in seawater and clay minerals in sedimentary soil.
Evaluating the influence of climate and subgrade type on the benchmarking of pavement management efficiency
Published in International Journal of Pavement Engineering, 2021
Harish Shivaramu, Seosamh B. Costello, Theunis F. P. Henning
Agriculturally, shrinkage and swelling aids in the movement of moisture and nutrients in the subsoil, which is essential for plant growth. However, from an engineering standpoint, expansive soils with high shrinkage potential could be problematic in the construction and maintenance of various civil engineering structures, pavements in particular. This shrink-swell behaviour of soils could cause significant structural damage and premature deterioration of road networks (Al-Taie et al. 2016).