فهرست مطالب mehran karimpour-fard

The difference in climatic conditions across the country and low investment capacity in waste management systems makes it unrealistic to establish the same prescribed design for the bottom liner of municipal solid waste landfills. In this paper, a semi-performance-based approach for the proper design of liners in these landfills has been proposed. This approach has been used in the development of the technical evaluation guidelines and environmental criteria for municipal and hazardous waste landfills. Therefore, different climatic and hydrogeological conditions were considered. The rate of leachate infiltration into leachate collection system in different climates corresponding to high, medium and low precipitation was calculated using the HELP model and considered as a representative parameter of climatic conditions. The rate of waste deposition, which indicates the size of landfill, was introduced as the length of landfill along groundwater direction. Groundwater velocity, hydraulic conductivity and thickness of the aquitard were used as hydrogeological parameters. The resulting scenarios (324 scenarios) were defined in POLLUTE v7 and the chloride migration in five liner options were modeled. The results show that as the landfill is larger and the hydraulic conductivity of the aquitard is higher, the maximum contaminant concentration in the aquifer and the required time period to reach the maximum concentration will increase and decrease, respectively, by reducing the different layers of the liner system and decreasing groundwater velocity. Finally, the optimum liner for all climatic and hydrogeological conditions is proposed based on modeling results.

Geotechnical studies constitute a key part of civil engineering projects that have economic and qualitative implications for the structure and its safety during both construction and operational phases. In addition to requiring time and expenses, borehole drilling, soil sampling, and geotechnical testing can at times lead to irreparable losses and damage, such as the explosion of gas pipes or the collapse of adjacent buildings. For typical buildings, such tests can be skipped with the help of geographical information system (GIS) analysis functions. In this study, the geographical coordinates about the location of previous geotechnical studies conducted during the construction of residential structures have been determined, to create an appropriate database and with the use of GIS interpolation functions, zoning maps are prepared and presented to offer a general visualization of the geotechnical status of the area. Therefore, in this study, the geotechnical data of 170 boreholes drilled in Rasht, including soil strength parameters for individual soil layers to a depth of 12 m from ground level were collected and implemented in GIS interpolation functions. Thus, raster layers were created and after selecting the best interpolation method, zoning maps for geotechnical parameters were plotted. Results showed that overall, more than 99% of the study area has an SPT number higher than 10 and an internal friction angle lower than 28 degrees. Qualitatively, aggregate soils in the study area were generally composed of medium sandy soils while most cohesive soils in the area fall in the category of stiff.

A series of laboratory large-scale model tests were conducted on piled raft founded on sand with different compaction levels. The numbers of piles are 1, 4, 5 and 9. All the piles are 40 cm in length and the slenderness ratio is 20. In these tests, the variation of load improvement ratio (LIR), load-sharing ratio (αp) and settlement ratio (SR) are reported for different relative densities and number of piles. Moreover, the variation of ultimate bearing capacity of piled raft system was investigated for different conditions. Results showed that LIR ratio will be more noticeable in loose state in comparison to dense sand, and also increasing the number of settlement reducing piles proved to decrease the SR values or increasing the SIF values in other words. In the end, a sensitivity analysis was performed to investigate the influence of each parameter in affecting the performance of the piled raft system. Based on the sensitivity analyses, relative density of soil was proven to be the most effective parameter in comparison to the number of piles. Finite element analyses have also been performed using the ABAQUS software. The numerical results from the FEM were first validated with the experimental results and then parametric study was carried out to investigate the effect of load eccentricities. It was shown that the ultimate bearing capacity of the piled raft foundation decreases significantly with an increase in the load eccentricity.

The effect of aging on dynamic properties of Municipal Solid Waste (MSW) including damping ratio and shear modulus was investigated in the current research. For this purpose, a series of cyclic Consolidated Undrained (CU) triaxial tests were performed on fresh and old reconstituted cylindrical specimens, taken from Mansoory Prototype Land ll (MPL) placed in Kahrizak Land ll, Tehran, Iran. The results showed that the shear modulus of old samples (7.5 years old) was more than that of the fresh ones. This trend can be attributed to decomposition of waste over time, which leads to reduction in organic content and, consequently, increment of brous waste particles (plastics) of the old samples. On the other hand, the results also indicated that the damping ratio was partially dependent on the composition of the specimen and it slightly decreased with increasing the age of MSW. The high percentage of organic content in fresh specimens can be consideredas the main reason for this behavior. Finally, the normalized shear modulus reduction and strain-dependent material damping curves were prepared for both ages of retrieved MSW from Kahrizak Center Land ll (KCL). The results of the current study are in the range reported in the technical literature and can be used as reliable data for seismic purposes.

Stone column technique has been successfully applied for the foundation improvement. A rigid box with dimensions of 1.5 × 1.5 × 1.2 m equipped with a jacking-pump system was used to loading the stone column reinforced bed. Laboratory tests are carried out on stone columns with 6.3 cm diameter and different patterns surrounded by loose sand. The parameters varied in this experimental and numerical investigation are length, diameter and number of stone columns. The number of stone columns in these tests are 4, 5 and 9 and lengths of stone columns are 30, 40 and 50. A 40 × 40 × 2 cm steel plate is used as the model foundation. In these tests, the variation of bearing capacity ratio (BCR) and settlement reduction factor (SRF) are reported for different length and number of stone columns. The results show that by increasing the number and length of stone columns, BCR value will increase and SRF value will decrease. Finite-element analyses have also been performed using the ABAQUS software. The numerical results from the FEM were first validated with the experimental results and then some parametric analyses were conducted to investigate the effect of stone column diameter.

In this study, the critical depth of un-braced open cuts is investigated using physical and numerical modeling carried out by the centrifuge machine at the Iran University of Science and Technology and a FISH code developed in the finite difference software, FLAC, respectively. The undrained shear strength of the soil was measured using Unconfined Compression Test (UCT), Miniature Vane Shear Test (MVST), and Pocket Penetrometer Test (PPT) and the results were used to develop a statistical correlation between the soil water content and its strength. In addition, upper and lower bound limit analysis solutions were used as benchmarks to verify the results. Finally, the values of critical excavation depth obtained through numerical analysis and centrifuge modeling in this study were compared with those estimated by the limit analysis and limit equilibrium methods.

Clayey soils are the most common material used for water sealing and undertake an important role in controlling landfill-related pollution. Organic liquids can adversely affect the effectiveness of clay liners by drastically increasing their hydraulic conductivity. The aim of this study is to investigate and compare the permeability in two types of clay with different plasticity, exposed to the flow of kerosene and diesel as non-polar immiscible liquids and ethanol as a miscible liquid with an intermediate dielectric constant. The effects of plasticity and water content for a given compactive effort are also investigated. Two different clayey soils with different plasticity were provided and their physical properties determined. Next, modified constant-head permeability tests were conducted on the samples. Results show that the lower dielectric constant of the organic fluids, leads to an increase in hydraulic conductivity. Research has shown that organic fluids shrink the diffuse double layer due to their lower dielectric constant and reduce its thickness. Shrinkage of the double layer leads to higher permeability and lower plasticity in the soil. As a result, the void space for the passage of the fluid increases. With the decrease the dielectric constant from 80.1 to 1.8, permeability is increased up to 1800 times. On the other hand, results show that for a clay with a higher liquid limit and plastic limit, permeability for all the liquids investigated in the research is lower.

Three common approaches to determine the axial pile capacity based on static analysis and in-situ tests are presented, compared and evaluated. The Unified Pile Design (UPD), American Petroleum Institute (API) and a SPT based methods were chosen to be validated. The API is a common method to estimate the axial bearing capacity of piles in marine environments, where as the others are currently used by geotechnical engineers. Seventy pile load test records performed in the northern bank of Persian Gulf with SPT profile have been compiled for methods evaluation. In all cases, pile capacities were measured using full scale static compression and/or pull out loading tests. As the loading tests in some cases were in the format of proof test without reaching the plunging or ultimate bearing capacity, for interpretation the results, offset limit load criteria was employed. Three statistical and probability based approaches in the form of a systematic ranking, called Rank Index, RI, were utilized to evaluate the performance of predictive methods. Wasted Capacity Index (WCI) concept was also applied to validate the efficiency of current methods. The evaluations revealed that among these three predictive methods, the UPD is more accurate and cost effective than the others.

The main task in the design and construction of impermeable liners in landfills is to block the migration of pollutants to the groundwater systems or to reduce its rate to a reasonable amount. That is why environmental regulations force governments to construct engineered waste dumps for waste management purposes. These liners are exposed to various types of chemical, biological, and physical processes and are affected by the leachate which is produced from decomposition of waste materials accompanying methane gas. The leachate includes a lot of components such as water and different types of salts. For this reason, the geotechnical characteristics of clay liners which are evaluated in laboratories using distilled water or tap water might be far different from the representative sample of the in-situ conditions. There are some evidences regarding the effect of these salts on the physical and mechanical properties of clay barriers which could affect the long-term performance of these liners. Since the main criterion for impermeable bottom liners in landfills is their hydraulics conductivity, the increase of this parameter could have a considerable environmental impact. This paper embraces the results of a recent study on the effect of three inorganic salts, NaCl, CaCl2 and MgCl2 on some geotechnical properties of a common used clay soil in impermeable bottom barrier in Kahrizak landfill, the main waste disposal center of the Tehran Metropolitan. Also the effect of bentonite content by adding different percentage of this special clay mineral, 10 and 20 percent, on these properties was investigated. Laboratory tests like liquid limit, compaction, 1D consolidation and free swell tests were performed for this purpose. Results indicated that all of these salts could have a considerable effect on the geotechnical properties of the mixtures. The main reason of such effects is the changes which occur in diffuse double layer of clay particles.