Determination Of Soil Parameters Research Articles

Infiltration in Porous Media Using Centrifuge with Moving Arm

Numerical modelling of unsaturated-saturated flow under centrifugation with moving arms is studied. A numerically efficient approximation is presented for mathematical model based on Richard's nonlinear and degenerate equation expressed in terms of effective saturation using Van Genuchten-Mualem ansatz with soil parameters in unsaturated zone. The method is suitable for determination of soil parameters via the solution of inverse problem in an iterative way. Using centrifuge offers significant time savings and provides us with many data for the parameter estimation. The present implementation of our method requires only very cheap measurements of global characteristics.

Sask method for testing hydraulic conductivity of soils by flat dilatometer (dmt)

Abstract DMT is one of the most popular methods of determining soil parameters needed to design a safe construction. Apart from the basic outcome parameter obtained from DMT measurements hydraulic conductivity (k) can be determined, previously proposed DMTA and DMTC methods were modified. The basic idea of the method is that the return of the deformed membrane is due to soil and water pressure. In the proposed SASK method the hydraulic conductivity of the soil is determined by measuring time-varying pressures A and C. Research has been performed at the experimental site of the Department of Geotechnical Engineering, WULS. In the paper, the assumptions of the new method for determining the hydraulic conductivity k are presented. The proposed method allows us to determine a reliable value for the hydraulic conductivity of clay soils. Using this method, the value of hydraulic conductivity (k = 5,47*10-11) is similar to the results of BAT, DMTA and laboratory measurements.

Uncertainty Characterization in the Design of FlowDiversion Structure Profiles Using Genetic Algorithm and Fuzzy Logic

Flow diversion head works are constructed across rivers to divert flow into irrigation, navigation, or power generation channels. Hydraulic structures, such as weirs or barrages, are integral parts of these diversion head works. The optimal design of these hydraulic structures is generally obtained by considering the deterministic values of hydrogeological parameters. However, there is a high degree of local soil variability and imprecision in the determination of soil parameters, such as the safe exit gradient. The seepage head also exhibits a high degree of variability, depending on complex hydrological and metrological factors. This work considers the hydrogeological parameters safe exit gradient and seepage head as imprecise or uncertain. An optimization-based methodology is presented to incorporate uncertainty in the safe exit gradient and seepage head in the optimization formulation and obtain the optimum structural dimensions that minimize the total cost. The subsurface flow consideration is embedded in the optimization formulation. The nonlinear optimization formulation (NLOF) solution procedure using a genetic algorithm (GA) is implemented to demonstrate the characterization of uncertainty in design and hence, overall cost from the uncertain safe exit gradient and seepage head. The limited evaluation shows the potential applicability of the proposed methodology.

Determination of Pressure-Saturation-Permeability Relations by Centrifugation

In this work we discuss the problem of coupled saturated and unsaturated flow in porous media under centrifugation. Our mathematical model is described by Darcy's equation in saturated region and Richard's nonlinear and degenerate equation in unsaturated region. We use Van Genuchten model with soil parameters and express the Richard's equation in both head and saturation. Our numerical method is based on space discretization. We reduce the problem to an ODE system with an algebraic condition to keep the water mass balance (DAE system). In our mathematical model we consider two interfaces separating fully saturated, partially saturated and dry subregions. Our goal is the determination of soil parameters. We control the input/output of infiltrated water in the sample. The only measurements concerning the sample require the measuring of the time moments in which the moving water achieves prescribed values of momentum. These data are sufficient to determine the soil parameters.

Determination of Soil Parameters in Apple-Growing Regions by Near- and Mid-Infrared Spectroscopy

Soil quality monitoring is important in precision agriculture. This study aimed to examine the possibility of assessing the soil parameters in apple-growing regions using spectroscopic methods. A total of 111 soil samples were collected from 11 typical sites of apple orchards, and the croplands surrounding them. Near-infrared (NIR) and mid-infrared (MIR) spectra, combined with partial least square regression, were used to predict the soil parameters, including organic matter (OM) content, pH, and the contents of As, Cu, Zn, Pb, and Cr. Organic matter and pH were closely correlated with As and the heavy metals. The NIR model showed a high prediction accuracy for the determination of OM, pH, and As, with correlation coefficients ( r) of 0.89, 0.89, and 0.90, respectively. The predictions of these three parameters by MIR showed reduced accuracy, with r values of 0.77, 0.84, and 0.92, respectively. The heavy metals could also be measured by spectroscopy due to their correlation with organic matter. Both NIR and MIR had high correlation coefficients for the determination of Cu, Zn, and Cr, with standard errors of prediction of 2.95, 10.48, and 9.49 mg kg −1 for NIR and 3.69, 5.84, and 6.94 mg kg −1 for MIR, respectively. Pb content behaved differently from the other parameters. Both NIR and MIR underestimated Pb content, with r values of 0.67 and 0.56 and standard errors of prediction of 3.46 and 2.99, respectively. Cu and Zn had a higher correlation with OM and pH and were better predicted than Pb and Cr. Thus, NIR spectra could accurately predict several soil parameters, metallic and nonmetallic, simultaneously, and were more feasible than MIR in analyzing soil parameters in the study area.

A Numerical Model of Transient Unsaturated Flow Under Centrifugation Based on Mass Balance

Numerical modeling of unsaturated flow in porous media under centrifugation is studied. A precise and numerically efficient approximation is presented for the mathematical model, based on Richards’ nonlinear and degenerate equation expressed in terms of effective saturation using the Van Genuchten–Mualem ansatz. The main difference with other methods is the utilization of a nonlocal condition based on mass balance. The method is suitable for determination of soil parameters, including the saturated conductivity, via the solution of an inverse problem in an iterative way. First, the fully saturated sample is centrifugated with a free outflow boundary during some time interval. Next, the output boundary is sealed and the sample is centrifugated for a prescribed time interval, or up to the creation of an equilibrium. Finally, the centrifugation is continued with a free outflow boundary. This procedure can be repeated to increase the information to drive the inverse problem. The application of the present method requires only non-intrusive, cheap measurements: rotational momentum and/or gravitational center of the sample, and optionally, the amount of expelled water.

Using Global Characteristics of a Centrifuge Outflow Experiment to Determine Unsaturated Soil Parameters

Several centrifugation scenarios enabling the determination of soil parameters for saturated‐unsaturated flow in porous media are presented, investigated, and discussed. Only global characteristics of the infiltration process in a sample are used, so that only simple, noninvasive measurements are performed. The characteristics can be transient measurements of the rotational momentum, or of the gravitational center, or of the water amount injected and expelled from the sample. No information about the saturation or the head distribution in the sample is required. This setup is different from the common multioutflow experiments. We give numerical proof that this method allows for fast determination of soil parameters in comparison to traditional measurements based on equilibrium conditions. The mathematical model of infiltration is represented by Richards′ strongly nonlinear and degenerate equation expressed in terms of soil parameters in the van Genuchten‐Mualem ansatz. The parameter identification process is realized in an iterative way applying the Levenberg‐Marquardt method. Numerical experiments support the efficiency of the analyzed method and allow one to identify the optimal centrifugation scenario for imbibition and drainage to be applied when using global characteristics.

Capillary electrophoresis characterisation of humic acids: application to diverse forest soil samples

Environmental contextAnalysis of soil organic matter is important for understanding turnover and stabilisation processes of organic carbon in soils. Capillary electrophoresis is used here to investigate humic acids from soils of diverse forest sites, and show that the patterns of signals are indicative of soil characteristics. The method provides useful information of soil types and complements the existing set of methods for humic acid characterisation. AbstractAnalyses of humic substances provide very useful information about turnover characteristics and stabilisation processes of soil organic matter in environmental soil samples. The present study investigates 113 samples of forest soils from three different layers (undecomposed litter (L), if present, mixed samples of F (intermediate decomposed) and H (highly decomposed) organic matter (FH) and upper mineral soil layers (Ah horizon) from 0 to 5 cm) by extracting humic acids (HAs) and recording electropherograms. Five signals of these electropherograms were evaluated and correlated with basic parameters from soil (organic carbon, Corg, and total nitrogen, Nt, and extraction yields of HAs) and HAs (total carbon, Ct, and Nt), and with signals from photometry, mid-infrared and fluorescence spectroscopy. The developed method was able to separate HAs from different soil layers by calculating a discriminant function based on the five evaluated electrophoretic signals. The dataset of this work opened the opportunity to correlate the observed electrophoretic signals with the other determined soil parameters and spectroscopic signals. This can be seen as a very important step in the direction to assignments of the obtained electrophoretic signals. Soil characteristics were reflected quite well by this method and, combined with the other approaches, it is suitable for applications in further studies.

Distribution and Abundance of the Invasive Plant Species Chromolaena odorata L. in the Zamboanga Peninsula, Philippines

The ecology of the highly invasive plant species C. odorata is poorly studied in the Philippines in spite of the fact that it is hard to eradicate, a nuisance in plantations, and known to harm farm animals and decimate forage and native plant species. In order to determine the abundance and distribution of the species and its possible relationship with local ecological factors, we estimated in 75 transect lines the percentage cover of C. odorata and other plant species growing around it, and concurrently determined soil parameters (soil type, pH, total nitrogen, total phosphorus, total potassium, and % organic matter) in three Provinces of the Zamboanga Peninsula, Southern Philippines. Multivariate Canonical Correspondence Analysis (CCA) revealed no significant relationship between soil parameters and the abundance of C. odorata suggesting eurytopy to edaphic conditions. Peak abundance of C. odorata was associated with coconut, banana, mango, gemelina and mahogany plantation environments, and reduced abundance of native plant species. This study shows that C. odorata is highly adaptive and a potential threat to native plant biodiversity and agro-ecosystem sustainability, and that its distribution seems to be supported by plant monoculture system.

Effects of long-term fertilization on AM fungal community structure and Glomalin-related soil protein in the Loess Plateau of China

Arbuscular mycorrhizal fungi (AMF) are crucial for ecosystem functioning, and thus have potential use for sustainable agriculture. In this study, we investigated the impact of organic and mineral fertilizers on the AMF community composition and content of Glomalin-related soil protein (GRSP) in a field experimental station which was established in 1979, in the Loess Plateau of China. Roots and soils were sampled three times during the growing period of winter wheat in 2008. The treatments including: N (inorganic N), NP (inorganic N and P), SNP (straw, inorganic N and P), M (farmyard manure), MNP (farmyard manure, inorganic N and P), and CK (no fertilization). AMF communities of root and soil samples were analyzed using PCR-DGGE, cloning and sequencing techniques; and GRSP content was determined by Bradford assay. Our results indicated that spore density, GRSP, and AMF community varied significantly in soils of long-term fertilization plots at three different wheat growing stages. The effects of wheat growing period on AMF community in roots were much more evident than fertilization regimes. However, the diversity of AMF was low in our study field. Up to five AMF phylotypes appeared in each sample, with the overwhelming dominance of a Glomus-like phylotype affiliated to G. mosseae. GRSP content was correlated positively with organic carbon, total phosphorus, available phosphorus, soil pH, and spore densities, but correlated negatively with soil C/N (P < 0.05). The results of our study highlight that the richness of AMF in Loess Plateau agricultural region is low, and long-term fertilization, especially amendments with manure and straw, has beneficial effects on accumulation of soil organic carbon, spore density, GRSP content, and AMF diversity. Host phenology, edaphic factors (influenced by long-term fertilization), and habitats interacted to affect the AMF community and agoecosystem functioning. Additionally, soil moisture and pH make a greater contribution than other determined soil parameters to the AMF community dynamics in such a special semi-arid agroecosystem where crops rely greatly on rainfall.

Assessment of London underground tube tunnels - investigation, monitoring and analysis

Tube Lines has carried out a "knowledge and investigation programme" on the deep tube tunnels comprising the Jubilee, Northern and Piccadilly lines, as required by the PPP contract with London Underground. Many of the tunnels have been in use for over 100 years, so this assessment was considered essential to the future safe functioning of the system. This programme has involved a number of generic investigations which guide the assessment methodology and the analysis of some 5,000 individual structures. A significant amount of investigation has been carried out, including ultrasonic thickness measurement, detection of brickwork laminations using radar, stress measurement using magnetic techniques, determination of soil parameters using CPT, pressuremeter and laboratory testing, installation of piezometers, material and tunnel segment testing, and trialling of remote photographic techniques for inspection of large tunnels and shafts. Vibrating wire, potentiometer, electro level, optical and fibre-optic monitoring has been used, and laser measurement and laser scanning has been employed to measure tunnel circularity. It is considered that there is scope for considerable improvements in non-destructive testing technology for structural assessment in particular, and some ideas are offered as a "wish-list". Assessment reports have now been produced for all assets forming Tube Lines' deep tube tunnel network. For assets which are non-compliant with London Underground standards, the risk to the operating railway has to be maintained as low as reasonably practicable (ALARP) using enhanced inspection and monitoring, or repair where required. Monitoring techniques have developed greatly during recent years and further advances will continue to support the economic whole life asset management of infrastructure networks.

Performance functions for laterally loaded single concrete piles in homogeneous clays

A key parameter in the design of a laterally loaded pile is the determination of its performance level. Performance level of a pile is usually expressed as the maximum head deflection and bending moment. In general, uncertainties in the performance of a pile originates from many factors such as inherent variability of soil properties, inadequate soil exploration programs, errors taking place in the determination of soil parameters, limited calculation models as well as uncertainties in loads. This makes it difficult for practicing engineers to decide for the reliability of laterally loaded piles both in cohesive and cohesionless soils. In this paper, limit state functions and consequent performance functions are obtained for single concrete piles to predict the maximum bending moment, a widely accepted design criterion along with the permissible pile head displacement. Analyses were made utilizing three dimensional finite element method and soil-structure-interaction (SSI) effects were accounted for.

Characteristic and design soil parameters: use of statistics

This paper emphasises that the geotechnical parameter governing the occurrence of a limit state is not the point value as measured by a laboratory or field test, and this has important implications for the determination of soil parameters with statistical methods. Two confusing concepts in statistical soil mechanics are discussed: the modelling of innate variability by a random field model, and the distinction between population mean, mean value of a failure domain and sample mean. These two concepts are intrinsically related. This paper demonstrates that most of the confusions or dilemmas associated with the characteristic value and the use of partial material factors may be removed by considering appropriate probabilistic or statistical concepts. It needs to be emphasised that ‘considering’ does not equate to ‘routinely using’. For a sandy soil, it is argued that the methodology of taking a prudently assessed critical state friction angle as the design value is statistically consistent with the definition of the design value in Eurocode 7.

Finite-Element Parametric Study of the Consolidation Behavior of a Trial Embankment on Soft Clay

The paper presents a case study for numerical analysis of the consolidation behavior of an instrumented trial embankment constructed on a soft soil foundation. Details are given to the geological profile, field instrumentation, laboratory test results, and determination of soil parameters for numerical modeling. Embankment settlement is estimated based on one-dimensional consolidation analysis and nonlinear finite-element analysis following Biot's consolidation theory. Finite-element results are calibrated against the measured field data for a period of more than 3 years. Development and dissipation of excess pore pressure, long-term settlement, and horizontal displacement are predicted and discussed in light of sensitivity of embankment performance to some critical factors through a parametric study.

Calibration of dynamic analysis methods from field test data

In view of the heterogeneity of natural soil deposits and approximations made in analysis methods, in situ methods of determining soil parameters are highly desirable. The problem of interest here is the nonlinear dynamic behavior of pile foundations. It is shown in this paper that soil parameters needed for simplified dynamic analysis of a single pile may be back-calculated from the dynamic response of the pile measured in the field. A pile was excited by applying a large horizontal dynamic force at the pile-head level, and the response measured. In this paper, two different (simplified) methods of modeling the dynamic response of the pile are considered. One of the methods is based on the Winkler foundation approach, with the spring constant characterized by the so-called nonlinear p– y springs. The second method is based on the equivalent-linear finite element approach, with the nonlinearity of shear modulus and damping accounted for by employing the so-called degradation relationships. In the latter, the effect of interface nonlinearity is also considered. Starting with best estimates of soil parameters, the experimental data on the response of pile is used to fine-tune the values of the parameters, and thereby, to estimate parameters that are representative of in situ soil conditions.

Interprétation des essais pressiométriques

ABSTRACT The aim of this work is to develop soil parameter determination procedures from in situ testing and in particular from pressuremeter tests. In the first part of a joint paper, we present some experimental and numerical results of the combined influence of soil permeability and loading rate on the pressuremeter curve. The results highlight the influence of the drainage conditions on the undrained cohesion derived from the tests. The main conclusions are summarised by a diagram which characterises the drainage conditions during the pressuremeter test as a function of soil permeability, loading rate, as well as the dimension of the probe.

Uncertainty in Load and Resistance Factor Design Phi Factors for Driven Prestressed Concrete Piles

A database of 156 prestressed concrete piles was gathered to evaluate load and resistance factor design (LRFD) phi factors for eight AASHTO axial pile prediction methods. The majority of the piles had standard penetration test (SPT) data, with limited cone penetration test and laboratory information. In estimating the LRFD phi factors, variability associated with load test capacity estimation, as well as soil parameter assessment by means of in situ tests, was considered. Using an advanced first-order second-moment method, the LRFD phi factors were computed considering all variability (model, load testing, and soil parameters), as well as just the model (i.e., one of the eight AASHTO methods). Current AASHTO LRFD phi factors are shown to be high for some methods (i.e., α-Tomlinson and Meyerhof) and low for others (i.e., Schmertmann SPT). A number of prediction models are recommended for cohesive and cohesionless soils, as well as methods for determining soil parameters from in situ tests.

Determination of soil parameters by gamma-ray transmission

Gamma-ray transmission methods have been used accurately for the study of the properties of a porous medium such as soil. In this study, different soil parameters are determined by using gamma-ray transmission method. To this end, the soil samples were collected from various regions of Turkey and a NaI (Tl) detector measured the attenuation of strongly collimated monoenergetic gamma beam through soil samples. The mass attenuation coefficients of dry soil samples were calculated from the transmission measurements for different photon energies. Furthermore, the soil samples were irrigated by adding known quantities of water and the soil–water properties were examined. The local water saturation and porosity were estimated from the transmission measurements for each soil sample.

Determination of soil parameters via the solution of inverse problems in infiltration.

In this paper, we propose an efficient method for the identification of soil parameters in unsaturated porous media, using measurements from infiltration experiments. The infiltration is governed by Richard's nonlinear equation expressed in terms of effective saturation. The soil retention and hydraulic permeability functions are expressed using the Van Genuchten-Mualem ansatz in terms of the soil parameters. The mathematical algorithm is based on a transformation of Richard's equation to a system of ordinary differential equations completed by the governing equation for the movement of the wetness front. This system can be efficiently solved by specialized packages for the solution of stiff systems of ODE. The unknown parameters are determined using the optimization approach of minimizing a cost functional for the discrepancy between the model output and the measurements. The gradient and Hessian of the solution with respect to soil parameter vector are determined using automatic differentiation. Several numerical experiments are included.

Determining Soil Water Characteristics for Application of WEPP Model in South Florida

Knowledge of soil water characteristics, such as soil hydraulic conductivity, soil erodibility, and soil water retention, are required for the application of a surface hydrology model in south Florida. However, these data are limited for the soils of south Florida. Also, there are no standard methods for determining soil hydraulic properties such as saturated hydraulic conductivity, erodibility, and water retention values. The objectives of this study were: 1) to calculate soil erodibility using results from rainfall simulation; 2) to compare different methods for calculating soil hydraulic conductivity, soil erodibility, and soil water retention values; and 3) to evaluate how the results from these different methods would affect evapotranspiration, storm water runoff, crop growth, and soil erosion in the model. Three typical soils from the region were used for this study: Krome (sandy loam, moderately well drained), Chekika (silty clay loam, poorly drained), and Perrine Marl (sandy loam, very poorly drained). Field research (including model calibration and rainfall simulation) was used to determine soil water parameters. While using various methods to determine soil parameters (calibrated, measured, and estimated) in a hydrologic model, significant discrepancies of simulated hydrologic variables were observed. Therefore, caution should be exercised when predicting critical parameters for hydrologic models. If a model, such as the Everglades Agro-Hydrology Model (EAHM), is used for comparison of different management practices, slight errors in estimated parameters are acceptable. However, if the model is used to assess possible changes in the hydrologic regime of south Florida, the accuracy of simulated values is important and in need of further investigation.