Root depth and leaf area ratio are two important features of a plant and exhibit a coupled relation. Assessing their coupled effects on induced soil suction is essential for analyzing the performance ...of a green infrastructure, such as water storage/drainage in green roofs and stability of a vegetated slope. Previously soil moisture induced by vegetation was often presented deterministically without considering the overall effects of leaf and root characteristics in a probabilistic manner. The main objective of this study is to investigate the influence of coupled variations in root and leaf characteristics on vegetation-induced soil suction. In addition, the coupled effects were analyzed using statistical approach. Different combinations of the leaf area index and root depth of the same plant were assessed. Probabilistic analysis was then conducted by computing suction profiles in form of quantiles. It was found that the biggest variability in suction profiles occurs at around 0.6 times the root depth and the minimum occurred at near surface and at maximum root depth. This depth at 0.6 times root depth corresponds to the maximum root density. It implies that the probabilistic analysis becomes more and more important while assessing suction profiles near the maximum root density.
•Spatial and temporal dynamics of grass density and shoot growth rate in urban green space were rarely explored.•Field monitoring was conducted in the urban green space for one year (i.e., life ...period of selected species).•The hypothesis of uniformity in grass density and shoot growth rate during life period of deciduous species was not found to be true.•Significant spatial and temporal variations in growth dynamics were found during monitoring period.
It is evident that grass density (GD) and shoot growth rate (SGR) governs the differential settlement of substructure, groundwater recharge, and stability of green infrastructure. GD and SGR are usually assumed to be constant during the entire life period of vegetation. However, spatial and temporal dynamics of GD and SGR in urban green space were rarely explored previously. The main objective of this study is to explore the spatial and temporal dynamics of GD and SGR in urban space vegetated with deciduous species (mix grass i.e., Poaceae and Bauhinia purpurea). Field monitoring was conducted in the urban green space for one year (i.e., life period of selected species). The monitoring period includes the growth period and gradual wilting period. Substantial spatial variation of GD was found during the first six months. GD away from the tree trunk was found to be 1.02–56.3 times higher than that near the tree trunk during the first six months. Thereafter, any spatial variation of GD was not found in the next six months. Unlike the GD, SGR was found to vary during the entire life period of mix grass. In addition, SGR away from the tree trunk was found to be 1.1–4.6 times higher than that near the tree trunk. Any relationship between GD and rainfall depth was not found. Whereas, SGR mainly depends on rainfall depth. The hypothesis of uniformity in GD and SGR during the life period of deciduous species was not found to be true.
AbstractThe utility of waste fly ash, especially class F, in agriculture, geotechnical, and geoenvironmental applications have increased manifold. In most of these cases, precise determination of ...water retention characteristics (WRCs) of fly ash is mandatory. The WRC is generally expressed in terms of graphical relationship between water content and suction. There are not many studies that deal with the critical evaluation of fly ash WRC and its uniqueness. With this in mind, experiments were conducted on a Class F Indian fly ash using different measurement procedures. A tensiometer has been used for measuring matric suction in fly ash. This is primarily because of the fact that a cohesionless material like fly ash with its silt dominated particle size will not exhibit a very high range of suction. The results obtained in this study clearly indicate that the near saturation and desaturation portion of WRC could be determined using tensiometer measurements. On the basis of the results, the parameters of commonly used WRC equations have been reported for the fly ash. Analysis has been done to understand the influence of compaction conditions on fly ash WRC. It has been demonstrated that the WRC of fly ash established by using different procedures may not be unique, and initial compaction state influences the fly ash WRC.
Celotno besedilo
Dostopno za:
DOBA, FGGLJ, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Purpose
The purpose of this paper is to numerically investigate the combined effects of canopy (leaf area index LAI) and root properties (root distribution function Rdf and root area index RAI) on a ...suction induced in soil-root composite under three different scenarios.
Design/methodology/approach
Richards equation coupled with sink term was solved using a commercial finite element package “HYDRUS” to investigate suction induced in soil-root composite.
Findings
Scenario 1 unveiled that soil-root composite induces 1 to 20 per cent higher suction than bare soil under the absence of transpiration. From Scenario 2, value of suction at depth of maximum RAI in case of linearly decreasing Rdf was found to be higher than that of other Rdfs. However, depth of suction influence zone (SIZ) for uniform Rdf and non-linear Rdf was found to be 10 and 11 per cent higher than that of linearly decreasing Rdf. Depth of evaporation dominant zone (EDZ) for uniformly decreasing Rdf and non-linear Rdf was found to be 1.08 to 3 times higher than that of linearly decreasing Rdf. From Scenario 3, influence of LAI on depth of SIZ is minimal. Depth of EDZ was found to decrease with the increase in LAI. Based on simple calculation on infinite slope stability, influence of variation in root and shoot properties was found to be significant on its factor of safety.
Research limitations/implications
Numerical constitutive model has limitations that it does not consider aging of plant. This model is only applicable for a particular set of soil conditions. A long-term study is required in this field to further quantify parameters for improving calibration and modeling performance.
Practical implications
Following are the practical implication: consideration of vegetation properties into engineered design of green infrastructure (slopes in this case) and selection of vegetation with appropriate characteristics in design for enhancement of stability of green infrastructure.
Originality/value
Contents of this paper are original, and they have not been submitted to any other journal.
AbstractCompacted landfill liner is an integral part of a waste management system, which minimizes the migration of harmful contaminants to geoenvironment and groundwater. Low hydraulic conductivity ...is the most important requirement for geomaterial used as compacted landfill liners. Because of this, high plastic geomaterials are preferred for such applications. Therefore, plasticity characteristics can be used as an initial guideline for assessing the suitability of materials used as a landfill liner. Such guidelines are important because of the fact that hydraulic conductivity determination is extremely time consuming for plastic geomaterials, and a quick assessment of material properies is always expected in the planning stage of the project. The existing methodology on the basis of plasticity criterion is not suitable for high-plastic soil, which otherwise is a very useful material for landfill liners. Considering this, the present study deals with the re-evaluation of plasticity-based criterion for assessing the suitability of medium and high-plastic geomaterials used as a compacted landfill liner. The development of the criterion is on the basis of the test results of bentonite–fly ash mix, which is used to represent a wide range of plasticity. The proposed criterion is further verified on the basis of the data reported in the literature. The present study also demonstrates the potential application of fly ash in combination with bentonite for landfill liner construction.
Celotno besedilo
Dostopno za:
DOBA, FGGLJ, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Soil–water characteristic curve (SWCC) is one of the input components required for conducting the transient seepage analysis in unsaturated soil for estimating pore water pressure (PWP). SWCC is ...usually defined by saturated volumetric water content (θ
s
), residual water content (RWC) and air entry value (AEV). Mathematical model of PWP could be useful to unearth the important SWCC components and the physics behind it. Based on authors’ knowledge, rarely any mathematical models describing the relationship between PWP and SWCC components are found. In the present work, an evolutionary approach, namely, multi-gene genetic programming (MGGP) has been applied to formulate the relationship between the PWP profile along soil depth and input variables for SWCC (θ
s
, RWC and AEV) for a given duration of ponding. The PWP predicted using the MGGP model has been compared with those generated using finite element simulations. The results indicate that the MGGP model is able to extrapolate the PWP satisfactory along the soil depth for a given set of boundary conditions. Based on the given AEV and saturated water content, the PWP along the depth can be determined from the newly developed MGGP model, which will be useful for design and analysis of slopes and landfill covers.
Tensiometer is one of the most popular and simple instrument for in situ and laboratory measurement of negative pressure or suction in soils. Such measurements in the top soil or root zone are useful ...for automated optimized irrigation scheduling for different vegetation. The top soil accommodates various salts/contaminants whose main source is storm water runoff, irrigation water and application of crop fertilizers. These salts accumulate in the soil due to evaporation. It is an established fact that tensiometer measures only soil matric suction with the help of a ceramic interface. It is believed that osmotic effect of salts present in the soil does not influence tensiometer measurements. However, there is no systematic experimental verification in the literature to understand the influence of salt laden soil on tensiometer measurements. It needs to be ascertained that the pore size of the tensiometer ceramic will not exhibit semi-permeable membrane characteristics leading to osmotic effect. Such verification is important as it would influence the irrigation scheduling of crops. It is also of interest to know whether the osmotic suction (due to the salts) would increase the water retention characteristics and hence the irrigation requirement. If so, then the tensiometer based irrigation scheduling would be an underestimate of the actual irrigation requirement of crops. To investigate these issues, the present study has performed controlled laboratory suction measurements using tensiometer in a locally available soil, contaminated with known concentration of inorganic salt solution. The total suction of the same salt laden soil has been measured using the WP4 dew point potentiameter technique. The results indicate negligible influence of salts present in the soil on tensiometer measurements. The study demonstrates the incapability of tensiometer to assess the osmotic component of salt present in the soil. This would result in the under prediction of water retention and hence irrigation requirement of the soil.
Experiments were conducted to measure the suction of a locally available silty soil and commercially available white clay, using a Dewpoint PotentiaMeter (WP4). The results were used to develop the ...soil–water characteristic curves (SWCCs), for these soils and evaluating various fitting functions, in high suction ranges. Efforts have also been made to demonstrate the influence of the soil type and dry unit weight on the soil suction. The study brings out the observation that dry unit weight has negligible influence on the soil suction and parameters effecting SWCC.
Celotno besedilo
Dostopno za:
DOBA, FGGLJ, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
PDF
