Sharif Digital Repository

This paper describes results of an advanced suction controlled triaxial test device on a loessial soil in an attempt to define the constitutive relationship between suction stress and matric suction (suction stress characteristic curve) for highly collapsible soils. Due to the presence of void spaces with different degrees of collapse potential within the soil matrix, the collapse phenomenon in loess is believed to be a continuous-stepwise reduction in volume rather than a sudden drop during wetting. Due to this unique volume change behavior, the definition of the suction stress characteristic curve for loess may require a soil-specific experimental testing approach capable of making precise... 

Over past decades, extensive research has been performed on the measurement of land subsidence as a result of compaction of aquifer. This paper describes results from a new field-monitoring system to evaluate changes in matric suction and temperature profiles in soil layers over an extended time period. The monitoring system used in this study consists of inserting dielectric sensors into a 105 m borehole, drilled in a site in Ardabil Plain, The monitoring results from the site were used to calibrate predictions from HYDRUS-1D. The physical and hydraulic properties of the soil materials in different layers were obtained through performing some soil characteristics and filter paper tests... 

A suction-controlled ring device has been developed to continuously measure the coefficient of lateral soil pressure in deformable unsaturated soil samples from the at-rest to the active condition under application of increasing vertical pressure and controlled matric suction. The device incorporates a thin aluminum specimen ring equipped with horizontal strain gages for recording the lateral soil strains. In addition, a sensor recording water volume changes is utilized to continuously monitor the degree of saturation of the soil sample during tests. The matric suction within the soil texture is controlled using the axis translation technique. In order to verify the performance of the ring... 

The large heterogeneity in soil surface conditions makes it impracticable to obtain reliable estimates of soil hydraulic parameters for areas larger than few squared kilometers. However, identifying these parameters on a global scale is essential for many hydrological and climatic applications. In this study, a new approach named Drainage from Drydown (DfD) is proposed to estimate the coefficients of drainage using soil moisture observations. DfD firstly selects multiple drydown events when surface runoff and evapotranspiration rates are negligible compared to the drainage rate. Secondly, by inverting the soil water balance equation, the drainage coefficients are obtained. Synthetic... 

Evapotranspiration is one of the main components of water and energy balance. In this study, we compare two ET products, suitable for regional analysis at high spatial resolution: The recent WaPOR product developed by FAO and METRIC algorithm. WaPOR is based on ETLook, which is a two-source model and relies on microwave images. WaPOR is unique as it has no limitation under cloudy days, but METRIC is limited by clouds. METRIC and WaPOR are more sensitive to land surface temperature and soil moisture, respectively. Using two years (2010 and 2014) of data over Lake Urmia basin, we show that in most areas, ET from METRIC is higher than WaPOR and the difference has an ascending trend with the... 

This paper presents a study on the simulation of cone penetration tests (CPTs) using the discrete element model (DEM) method. This study’s main objective is to investigate the effect of different modeling parameters and simulation configurations on the ability of three-dimensional DEM simulations to replicate realistic CPT tip resistance (qc) and friction sleeve shear stress (fs) measurements. The CPT tests were simulated in virtual calibration chambers (VCCs) containing particles calibrated to model the behavior of sand. The parameters investigated included the granular assembly properties, interparticle contact parameters, particle–probe interface characteristics, and simulation... 

As a non-invasive method, photographic imaging techniques offer some interesting potentials for characterization of soil moisture content in unsaturated porous media, enabling mapping at very fine resolutions in both space and time. Although less explored, the wealth of soil moisture data provided by photographic imaging is also appealing for the estimation of unsaturated soil hydraulic parameters through inverse modeling. However, imaging data have some unique characteristics, including high susceptibility to noise, which can negatively affect the parameter estimation process. In this study a sequential data assimilation approach is developed to simultaneously update soil moisture content... 

Rare earth elements (REEs) are becoming significant due to their huge applications in many industries, large-scale mining and refining activities. Increasing usage of such metals pose negative environmental impacts. In this research ICP-MS has been used to analyze soil samples collected from former ex-mining areas in the depths of 0–20 cm, 21–40 cm, and 41–60 cm of residential, mining, natural, and industrial areas of Perak. Principal component analysis (PCA) revealed that soil samples taken from different mining, industrial, residential, and natural areas are separated into four clusters. It was observed that REEs were abundant in most of the samples from mining areas. Concentration of the...