Hossein Moayedi

Zeta Potentials of Suspended Humus in Multivalent Cationic Saline Solution and Its Effect on Electro-Osomosis Behavior

The surface electrical charge was measured for laboratory grade organic soil colloidal particles by varying pH between 2 and 11 and at 0.001, 0.01, 0.1, and 1.0 mol/L of cationic saline solution (CaCl2, Na2Sio3, Al2(SO4)3, MgCl2, and Na2CO3) concentrations. The zeta (ζ) potential values showed low sensitivity to pH in salt solutions. The ζ potential of pure organic soils varied from +7.5 mV at pH 2.8 to −28.5 mV at pH 11.3. The ζ potential calculation of humus particles in distilled water showed an increase in ζ potential value beyond pH > 3.3, which could be due to charge development at the humic substances by direct transfer of H+ from organic soil to water. The surface electrical charge was almost zero at pH 3.25. Colloidal charge reversal was observed at several stages according to the electrolyte concentrations and chemical reagents. It was also found that using high molarities of multivalent saline solution (e.g., CaCl2, Na2Sio3, Na2CO3, and MgCl2) as electrolytes led to very high ζ potential values and consequently high electro-osmotic conductivity (Ke). On the basis of the results of this research, it is recommended that the ζ potential of the soils be determined before any application of electrokinetic (EK) treatment.

Physico-Chemical and Shrinkage Properties of Highly Organic Soil Treated with Non-traditional Additives

The changes in the shrinkage and physicochemical properties of untreated and treated organic soil using several chemical additives were investigated. In order to evaluate the effect of each chemical solution on the peaty soil environment different experiments namely; shrinkage limit, unconfined compressive strength (UCS), pH test, and water content were undertaken. The results of the laboratory experiments are further proved and interpreted using the X-ray diffraction, scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy tests. The result unveils the structure of the treated soil significantly changed depending upon the used additive type and concentrations. The rate of shrinkage largely decreased when sodium silicate additives are used. In addition, it was observed that UCS value increased up to 500% and water content reduced up to 50% in comparison with untreated samples, depend on the amount of used non-traditional additives. The SEM micrographs of the sample before and after treatment validate the results obtained and analyzed from experiments.

A Critical Review on Filter Design Criteria for Dispersive Base Soils

Dispersive soils have become common materials for the construction industry. Highly susceptible to internal erosion and piping, dispersive soils must only be used with specific engineering measure in order to avoid failures that were often catastrophic. In an earth dam, clayey soils are used for the core and sandy materials are used for the filter to retain the eroded core soils and prevent their migration. In the absence of first-rate core material, dispersive soils have been used instead. This paper provides a review of the current knowledge and experiences regarding filtration of core soils, particularly the dispersive ones. The engineering problems associated with the use of dispersive soils are discussed and significant findings from previous studies on protective filters are summarized. It is worthy to note that the current review considers both, the conventional, rather empirical filter design criteria based on particle sizes and the current, quite theoretical state-of-the-art filter design criteria based on constriction sizes, with discussion given on the advantages and disadvantages of both. The information provided by this review should be handy for the study, design, construction, and operation of related geotechnical and geo-environmental projects.

The Rheology Properties of Peat Treated with Sodium Silicate System Grouts

In the present study, the effect of sodium silicate stabilizers on the flowability and soil volume reduction are investigated. Two secondary additives are also admixed in order to assess their effects. Accordingly, a series of viscosity, shrinkage limit, and pH tests were performed to assess the effects of the mentioned cationic reagents as a suitable grout. It is observed that the sodium silicate grout has a viscosity higher than water and causes a very high soil volume reduction during the air curing. The reduction in the soil’s volume was reduced significantly when secondary additives were used. The microstructure analysis performed to help understanding the reason of highly soil’s volume reduction due to presence of sodium silicate reagent.

Sensitivity analysis of slopes affected by possible earthquake loading and heavy rainfall: Case study

The effect of seismic loading on slope failure is studied both experimentally and analytically to establish the spatial and temporal process of failure initiation and propagation during possible earthquake loading or heavy rainfall. For such purpose different limit equilibrium modeling were carried out and factor of safeties against sliding caused by both excess earthquake loading and heavy rainfall were found. As for this study, two parameters normally taken into account which were soil properties changing as well as exerted seismic loading. Moreover to show the reality and importance of the main objective of this research, two of the constructed slopes in Malaysia were selected and modeled. The factor of safety against landslides in normal condition (without any extra seismic loading consideration) at Johor was 1.293, 1.425 and 1.301 using ordinary, bishop and Janbu methods, respectively. Also, factor of safety against slope failure at Besut was 1.508, 1.637 and 1.519 according to ordinary, bishop and Janbu methods, respectively. As a result, mentioned slopes will collapse applying even low seismic loading of 0.2 g. Internal friction angle reduction more than 25% also caused significant decrease in the slope’s factor of safety.

Malaysian Experiences of Peat Stabilization, State of the Art

Peat has been considered as an organics remnant that suffers decomposition process throughout times under overburden pressure. Composition of peats normally consists of organics materials which sometimes exceed 75% specifically from woods that grows in marshes and places in conditions where deficiencies of oxygen exist. Usually peat area related with swampy and normally a low shear strength region. High compressibility is significant and often related to problematic soil for construction purposes. In this article, extensive number of studies are reviewed to understand the behavior of the peat after being stabilized. New findings indicated that the peat contents differs from one location to another, thus inevitably gives different behavior. Many improvisation methods have been put forward such as chemical stabilization, cement stabilization, deep mixing and fiber reinforcement to name a few to enhance the strength properties of the peat. This is mainly for construction reliability purposes. However, the suitability of the ground improvement for peat thus depend on its fundamental properties and cost involve for any dedicated ground construction work. This paper review the properties of peat in Malaysia and reviewed recent development in the peaty soil stabilization in Malaysia. It is also compared the materials used for the peat stabilization and the expansive clay soils as the main two problematic soils.

Modification of landslide susceptibility mapping using optimized PSO-ANN technique

In the present study, we applied artificial neural network (ANN) optimized with particle swarm optimization (PSO) for the problem of landslide susceptibility mapping (LSM) prediction. Many studies have revealed that the ANN-based techniques are reliable methods for estimating the LSM. However, most ANN training models facing with major problems such as slow degree of learning system as well as being trapped in their local minima. Optimization algorithms (OA) such as PSO can improve performance results of ANN. Existing applications of PSO model to ANN training have not been used in area of landslide mapping, neither assess the optimal architecture of networks nor the influential factors affecting this problem. Hence, the present study focused on the application of a hybrid PSO-based ANN model (PSO-ANN) to the prediction of landslide susceptibility hazardous mapping. To prepare training and testing datasets for the ANN and PSO-ANN network models, large data collection (i.e., a database consists 168970 training datasets and 42243 testing datasets) were provided from an area of Layleh valley, located in Kermanshah, west of Iran. All the variables of PSO algorithm (e.g., in addition to the network parameter and network weights) were optimized to achieve the most reliable maps of landslide susceptibility. The input dataset includes elevation, slope aspect, slope degree, curvature, soil type, lithology, distance to road, distance to river, distance to fault, land use, stream power index (SPI) and topographic wetness index (TWI), where the output was taken landslide susceptibility value. The predicted results (e.g., from ANN, PSO-ANN) for both of datasets (e.g., training and testing) of the models were assessed based on two statistical indices namely, coefficient of determination (R2) and root-mean-squared error (RMSE). In this study, to evaluate the ability of all methods, color intensity rating (CER) based on the result of above indices was developed. Apart from CER, the total ranking system was also used to rank the obtained statistical indexes. As a result, both models presented good performance, however, according to the introduced ranking system, the PSO-ANN model could perform a better performance compared to ANN. According to R2 and RMSE values of (0.9717 and 0.1040) and (0.99131 and 0.0366) were found for training dataset and values of (0.9733 and 0.111) and (0.9899 and 0.0389) obtained for testing dataset, respectively, for the ANN and PSO-ANN approximation models, it can be resulted that PSO-ANN model showed higher reliability in estimating the LSM compared to the ANN.

Improvement of Settlement Problems of Fibrous Peat

The distribution of peat deposits can be found in many countries and peat-land constituents from 5 to 8% of earth land surface, where approximately 60% of the wetlands are peat. An increasing growth of the population leads to the necessity of peat-land utilization for development purposes. This article describes a laboratory study on the effect of different binders on the settlement of fibrous peat. The effect of the sodium silicate, ordinary Portland cement and kaolinite on the settlement of peat is investigated through Rowe Cell consolidation test. At the end of this study, it is shown by increasing sodium silicate (within 2.5%), cement and kaolinite on treated peat, they are able to improve settlement of fibrous peat much more than conventional binders like pure cement

Preventing landslides in times of rainfall: case study and FEM analyses

Purpose – The purpose of the paper is to present a new method of controlling through susceptible slopes in order to reduce the risk of landslides.Design/methodology/approach – Geotechnical and geological characteristics were collected and different FEM analyses were carried out in a case study of the Alasht valley in Northern Iran in order to determine susceptibility to landslides and consider appropriate countermeasures. Gravel drain piles have a real feel of reducing the pore water pressure in times of seismic loading, so they are used as a remediation method. The results clearly show their effects and an increase in safety as a result.Findings – Since the water table situation has a significant effect on stability, the present study focused on an example of using a seepage controlling system and its effect on the safety factor for different slopes in the area of Alasht, Northern Iran. Several FEM analyses were carried out on a landslide susceptible case. The results from FEM analysis of different slope...

The effect of discontinuities on stability of rock blocks in tunnel

This paper presents the results of an investigation that was carried out using important parameters such as discontinuities in forming rock block and instability in tunnel. The discontinuities like bedding and joints are one of the most important factors compared with parameters such as engineering features of rock mass. In this review, numerous features like Rock Quality Designation (RQD), rock classification (RMR), stress and strain, and distributions of discontinuities in a sample tunnel were evaluated. However, most of them were suitable in the tunnel, but because of creating more intersection points in critical zone, the movement of blocks in tunnel roof and wall of the tunnel are possible. It also demonstrates the simple factors such as step-over joints in rock mass, having important effect in instability.