فهرست مطالب

Civil Engineering - Volume:16 Issue: 10, 2018
  • Volume:16 Issue: 10, 2018
  • تاریخ انتشار: 1397/08/01
  • تعداد عناوین: 20
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  • Stiffness Degradation and Damping Ratio of Sand-Gravel Mixtures Under Saturated State
    Meysam Bayat, Abbas Ghalandarzadeh * Pages 1261-1277
    The aim of this research was to explain the effects of gravel content using the intergrain state concept, relative density and confining pressure on G max, G/G max–γ and D–γ curves and the reference strain (γ r). A total of 45 G–γ and D–γ curves derived from resonant column testing and cyclic triaxial testing along with S-wave velocity measurements obtained using the bender element technique were assessed. The test specimens were prepared with different gravel contents (0, 30, 50, 75 and 100%) under different relative densities (10, 30 and 60%) and mean effective confining pressures (100, 300 and 600 kPa). Comparison of the G max results of the resonant column and bender element tests was also carried out. The desired excitation frequencies and ratios λ/D 50 and d/λ (where λ is wavelength, d is transmission path length and D 50 is average particle size) were determined based on the bender element tests results. The test results were used to evaluate the empirical equation for prediction of G max and to develop a new prediction equation with which to estimate γ r. The results of the tests were used to validate previous models and empirical curves.
    Keywords: Dynamic properties , Gravel content , Cyclic triaxial , Bender element , Resonant column
  • Analysis of Displacement Response of the Ermenek Dam Monitored by an Integrated Geodetic and Pendulum System
    Salih Alcay, Cemal Ozer Yigit*, Cevat Inal, Ayhan Ceylan Pages 1279-1291
    This paper studies the structural behavior of the Ermenek arch dam, the second highest dam in Turkey. The investigated period covers the stage of the last-quarter part of first filling (1 and 1/2 year) and the begging of its operational lifetime (1 year). Displacement responses of the dam to temperature load and water load are assessed in detail based on both geodetic and pendulum monitoring records. In addition, the present study explores the possibility and advantage of integrating pendulum-measured signals with geodetic-measured signals for the dam deformation monitoring. The analysis results reveal that pendulum-derived displacements at four gallery levels, along the vertical cross section of the dam, which exhibit periodicity and linear trend with different slope due to seasonal temperature oscillation and linearly increased reservoir level, respectively. Comparative evaluation of the results shows that there is very good agreement between geodetic-derived displacement in radial direction at the middle of the crest and corresponding pendulum-derived displacement.
    Keywords: Concrete arch dam , Micro-geodetic traditional network, Direct, inverted pendulums, Integrated structural health monitoring
  • Numerical and Experimental Study of the Optimal Location of Concrete Piles in a Saturated Sandy Slope
    Mohammad Hajiazizi *, Moslem Bavali, Ali Fakhimi Pages 1293-1301
    The stability of a soil slope, reinforced by a concrete pile, is studied both experimentally and numerically in this work. Our study suggests that when the concrete pile is located in the middle of the slope (at x/r = 0.5), the soil structure collapses under a pressure of 10.9 kPa that is the highest overburden pressure to cause instability of the tested reinforced sandy slope. However, when the pile is located in the upslope (at x/r = 0.75) or downslope (at x/r = 0.25), the slope failure occurs under a pressure of 7.8 or 3.12 kPa, respectively. Therefore, our experimental work suggests that a pile located at the middle of the slope can provide the optimum reinforcement of the soil structure studied in this work. The nonlinear numerical modeling of the slope was conducted as well. The numerical study shows consistent results with those from the physical observation confirming that the slope mid-point is the optimum place for the slope reinforcement.
    Keywords: Slope reinforcement , Optimal pile, location , Concrete pile, Sandy slope
  • Thermal Regime Analysis and Protective Measure Evaluation for Wide Embankment in Permafrost Regions of Qinghai-Tibet Plateau
    Tao Ma*, Tao Tang, Xunhao Ding, Xiaoming Huang, Yongli Zhao Pages 1303-1316
    This study analyzed the effects of a wide embankment on the thermal regime of permafrost and evaluated the feasibility of different measures to protect the permafrost underlying the wide embankment. Based on a specific embankment section of the Qinghai-Tibet highway and field observed data, a finite-element model was built and verified to conduct thermal analysis. Based on numerical analysis, the temperature fields and thawing depths of embankments with different widths were analyzed. The influences of different protective measures on the thermal stability of embankments were evaluated. The findings indicate that, after embankment construction, the annual ground temperature and maximum thawing depth increase with time. Thus, the embankment construction causes serious disturbance of the thermal stability of permafrost. An embankment with a larger width has a lower thermal stability. The results also show that raising the embankment height, setting a crushed stone layer, or setting an expanded polystyrene (EPS) layer can improve the thermal stability of an embankment. However, the improving effect of a single protective measure is not obvious for wide embankments with widths larger than 26 m. A combination of a crushed stone layer and an EPS layer provides the best protective effect on the thermal stability of a wide embankment. Thus, it is recommended as a protective measure for wide embankments of expressways in permafrost regions of the Qinghai-Tibet Plateau.
    Keywords: Permafrost region, Thermal regime , Wide embankment, Protective measure
  • Development of a Risk-based Methodology for Rock Slope Analysis
    Mahsa Moghadami , Ali Mortazavi * Pages 1317-1328
    The objective of this research is to develop a geotechnical risk assessment methodology to concurrently identify and quantify important risk elements in rock slopes. Thus, important geotechnical issues affecting a high rock slope were categorized into three major critical risk groups after a comprehensive literature review and field observation program. A set of knowledge-based fuzzy inference rules were established to set up membership functions and calculate risk index (RI) for each critical risk element (CRE). The CREs were ranked on the basis of the calculated RI. The developed risk algorithm was employed to assess the geotechnical risks associated with the right abutment slope of Vanyar dam, Iran. The analysis results showed that the presence of high water level (RI 4.47), shear strength of discontinuities (RI 4.27), and presence of shear or fault zones in the slope (RI 4.01) were the most critical elements which affected the slope stability, respectively. According to calculated risk indices the engineers should pay more attention to the underground water level in the dam abutments. The proposed method could provide scientific decision-making basis for varying risk levels associated with rock slope engineering and can be used as an aid in corresponding risk control measures. The obtained results indicated that the developed algorithm is beneficial in providing guidelines for design and remedial measures to improve slope construction and performance. The present study proposes a methodology based on a combination of project management, risk modelling, and geotechnical engineering.
    Keywords: Risk modelling , Decision making , Rock slopes , Fuzzy synthetic system
  • Critical Tendon Bond Length for Prestressed Ground Anchors in Pullout Performance Tests Conducted in Sand
    Hakki O. Ozhan*, Erol Guler Pages 1329-1340
    In this study, pullout performance tests were conducted on five prestressed ground anchors having different tendon bond and unbonded lengths. The tendon bond lengths of the tested anchors varied from 4 to 10 m, whereas the unbonded lengths were in the range of 8–16 m. The tests were performed separately on a dense, gravelly sandy soil slope with an inclination of 90° in Cottbus, Germany. The anchors were inclined downwards at an angle of 15° below the horizontal. The results indicated that three of the five anchors did not satisfy the acceptance criteria as outlined in DIN 4125 Standards. According to the acceptance criteria, the line that was composed of the elastic displacements of the unbonded length had to remain between two specific limit lines. Although the elastic displacements of the unbonded tendons were taken into account for the acceptance of the anchors, the length of the unbonded tendon did not have a significant effect on stability. The anchors having unbonded lengths of 8, 13, and 15 m failed, whereas the anchors with unbonded length of 9 and 16 m were accepted after the termination of the performance tests. However, the tendon bond length was proved to be an important parameter that contributed to the acceptance of the tested anchors. Test results indicated that anchors having tendon bond lengths longer or shorter than 6 m were rejected.
    Keywords: Anchor tendon coefficient , Performance test , Prestressed ground anchor , Tendon bond length Unbonded length
  • Centrifuge Model Test on Unsaturated Expansive Soil Slopes with Cyclic Wetting–Drying and Inundation at the Slope Toe
    Tie, lin Chen, Cheng Zhou*, Guo, li Wang, En, long Liu, Feng Dai Pages 1341-1360
    The influence of dry unit weight and matric suction on the shear strength and deformation characteristics of unsaturated expansive soil was studied by triaxial tests. Artificial rainfall system and lighting–winding system were, respectively, set up for the unsaturated expansive soil slope centrifuge models to simulate wetting–drying cycles. Three kinds of centrifuge model tests concerning different sequences between centrifuge running and wetting–drying cycles on slope surface and inundation at the slope toe were conducted on the unsaturated expansive soil slope models with two different dry unit weight, water contents and slope ratios. The slope settlement and horizontal displacement, failure mechanism, and cumulated cracks on unsaturated expansive soil slope centrifuge models were investigated and analyzed. It was found that the crack accumulation induced by wetting–drying cycles or softening behavior induced by inundation at the slope toe was crucial to understanding the rainfall-induced progressive failure, which occurred from the slope toe and developed upwards in unsaturated expansive soil slopes. Therefore, cover layer should be built for unsaturated expansive soil slopes from rainfall infiltration into the cracks induced by wetting–drying cycles, and at least enough drainage measures should be taken to reduce water infiltration into the unsaturated soil slope and inundation at the slope toe.
    Keywords: Unsaturated expansive soil , Soil slope , Rainfall infiltration, Wetting–drying cycle, Inundation, Centrifuge
  • Stability Evaluation of Un-braced Cuts
    Habib Shahnazari*, Reza Jamshidi Chenari, Mehran Karimpour Fard, Sogol Heshmati Pages 1361-1369
    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.
    Keywords: Critical depth, Centrifuge test, Limit analysis , Upper-, lower-bound solutions
  • Experimental and Numerical Analysis of XCC Pile-Geogrid Foundation for Existing Expressway Under Traffic Load
    Feng Yin, Hang Zhou *, Hanlong Liu, Jian Chu Pages 1371-1388
    A series of dynamic large-scale model tests and three-dimensional finite element analyses for XCC pile composite foundation are conducted to investigate the dynamic behavior and the settlement of XCC pile composite foundation of existing expressway under traffic load. The test and FE results are presented in the variation of dynamic stress, distributions of skin friction, deviator stress, and the settlement of XCC pile composite foundation. The test results reveal the transfer mechanism of dynamic stress, and a linear relationship between the transferred stress and traffic load is found. Also, XCC piles can improve the stability of composite foundation because of lower neutral point and less sensibility to the traffic load. The distribution characteristics of deviator stress in the horizontal and vertical direction have been found by the numerical simulation. A modified model for predicting the traffic-load-induced settlement of XCC pile composite foundation is proposed. The asymmetric settlement of XCC pile composite foundation is revealed.
    Keywords: XCC pile composite foundation, Dynamic, large-scale model, FE analysis , Dynamic response , Settlement
  • Properties of Drained Shear Strength of Expansive Soil Considering Low Stresses and Its Influencing Factors
    Jie Xiao, Heping Yang, Junhui Zhang* , Xianyuan Tang Pages 1389-1398
    The shallow failure of most expansive soil slopes undergoing wet–dry cycles occurs during or after long-term rainfall. According to the actual failure state of an expansive soil slope, the conventional direct shear equipment with low normal stresses was used to evaluate the effects of initial dry density, initial moisture content, and number of wet-dry cycle with or without loading on drained shear strength for the compacted expansive soil from Nanning, China. The saturated drained direct shear tests were also performed on the natural expansive soil specimens from Nanning by considering the influence of wet–dry cycles with loading and low normal stresses. Furthermore, consolidated drained triaxial compression tests on compacted specimens were conducted. The test results show that the drained shear strength of expansive soil was primarily affected by the magnitude of normal stresses, and also influenced by the initial moisture content, initial dry density, and number and type of wet–dry cycles. It is more realistic to consider the effect of loading during wet–dry cycles than that without loading. The effective drained shear strength envelopes with low normal stresses were plotted and well fitted by the generalized power function. At low normal stress levels, the drained shear strength still decreased with the increasing number of wet–dry cycles, and the effective cohesion intersects tended to be zero after being subjected to eight wet–dry cycles. This provided a theoretical basis for properly interpreting the shallow failure of expansive soil slopes.
    Keywords: Expansive soil, Drained shear strength , Nonlinearity , Wet–dry cycle , Generalized power function
  • Analytical Model for Natural Frequency of SDOF System Considering Soil–Pile–Structure Interaction
    Amir Mohammad Amiri, Ali Ghanbari *, Mahdi Derakhshandi Pages 1399-1411
    Exact estimation of vibration fundamental period of structures plays a vital role in their designing procedure. The proposition of a relatively exact expression which considers the effects of a pile group on the fundamental period of the structures was of less interest to the previous researchers. This study aims to propose an analytical model and expression so as to estimate the free vibration period of the structures located on a pile group. To reach the objectives of this study, several numerical analyses have been carried out using the method of equivalent spring which takes into account the effects of soil–pile–structure interaction on the fundamental period of the structures and an approximate expression based on the obtained data from the numerical studies has been proposed. In the next step of the study, the effects of a pile group on the fundamental period of the structures have been analyzed analytically. To this end, a five degrees-of-freedom analytical model and its corresponding expression have been proposed considering the soil–pile–structure system. The numerical modeling has been performed using the direct method due to the neglect of the soil in analytical expression and the necessity of considering the participation of the soil around piles, and the results have been compared with those of the proposed analytical expression. The soil mass participation coefficient (λ) has been obtained to modify the analytical expression using the discrepancy between the results of the two different methods. The comparison between the results of the proposed expression and those of case and numerical studies confirms that the proposed expressions benefit from a relative accuracy and can be used as an initial criterion in designing procedure.
    Keywords: Soil–pile–structure interaction , Free vibration , Analytical formula , Steel frame , Numerical study
  • Field Tests on Influencing Factors of Negative Skin Friction for Pile Foundations in Collapsible Loess Regions
    Haofeng Xing *, Liangliang Liu Pages 1413-1422
    As a reliable building foundation form, piles are driven into collapsible soil layers to ensure stability of foundations. Because of water immersion, significant subsidence occurs on collapsible loess; then negative skin friction emerges on the pile surface, which eventually causes serious bearing capacity failures of pile foundations. Relying on water immersion tests of multiple piles in Lanzhou, China, this study analyzed the influencing factors of negative skin friction for pile foundations in collapsible loess regions. The main factors studied in this research are cumulative relative collapse amount, pile type, and change in loess collapsibility. The results demonstrate that the maximum negative skin friction has a negative correlation to the cumulative relative collapse amount, which is determined by the degree of difficulty of the emergence of the shear fracture surface. Owing to the compaction effect of the driven pile and surcharge load of the exploded pile, their negative skin frictions increase in varying degrees compared to that of the bored concrete pile. At the same test site, the changes in loess collapsibility are mainly affected by natural moisture content and dry density. Increases in both the natural moisture content and dry density reduce the loess collapsibility, immersion settlement rate, and negative skin friction of pile. The loess collapsibility can be improved by surcharge loading and pre-watering to reduce the adverse effect of negative skin friction on pile foundations in engineering applications.
    Keywords: Collapsible, loess , Negative skin friction , Pile foundations , Influencing factors , Collapse amount
  • SPT–CPTU Correlations and Liquefaction Evaluation for the Island and Tunnel Project of the Hong Kong–Zhuhai–Macao Bridge
    Wei Duan, Guojun Cai*, Songyu Liu, Yu Du, Liuwen Zhu, Anand J. Puppala Pages 1423-1434
    Considering the importance and complexity of the island and tunnel project for the Hong Kong–Zhuhai–Macao Bridge (HZMB), simple piezocone penetration (CPTU) testing has difficulties evaluating soil mechanics and characteristics accurately. Since geotechnical engineers are more familiar with standard penetration tests (SPT) and related design procedures, there is a necessity for reliable SPT–CPTU correlation so that CPTU data can translate to SPT design. This paper reviews existing correlations in the literature between SPT and CPTU, which depend on grain size, fines content or the soil behavior-type index. Since geologic contexts have not been investigated in the existing correlations, a linear function with zero-intercept SPT–CPTU correlations has been developed for every engineering geological unit layer, and the correlations were applied in liquefaction potential evaluation in cases where there was a lack of SPT data. For verification, this liquefaction evaluation was also carried out using both CPTU and SPT testing, and site-specific qt/N ratios of 0.11, 0.16, 0.30 and 0.41 for different soil categories are presented. The developed SPT–CPTU correlations are in accordance with existing correlations in the literature, and the results also reveal that the developed correlations and the liquefaction evaluations are essential for site investigation and geotechnical design in the HZMB area, especially providing a reference for similar engineering surveys.
    Keywords: CPTU, SPT, Hong Kong–Zhuhai–Macau Bridge (HZMB), Liquefaction evaluation
  • Consolidation Behavior of Structured Clayey Soils: A Case Study on Shiraz Fine Alluvial Strata
    Iman Memarzadeh, Ali Lashkari*, Piltan Tabatabaie Shourijeh Pages 1435-1444
    Owing to bond structure forming through depositional history and aging, natural sedimentary soils behave differently, in comparison to their reconstituted/destructured counterparts. Herein, consolidation behaviors of high-quality undisturbed and completely reconstituted samples of a fine alluvial clayey soil from Shiraz are studied. Experimental findings elucidate the impact of bond structure on virgin oedometric consolidation of undisturbed clayey samples, in so far as void ratio for such soils experiences insignificant change at vertical effective stresses lower than yield stress (about 105 kPa). Nevertheless, beyond the yield stress, structured specimens exhibit a rapid change in void ratio with vertical effective stress, in comparison to that of the completely reconstituted ones. Finally, with extensive bonding destructuration under elevated normal effective stress, disparity between normal consolidation curves of initially structured and fully reconstituted specimens becomes negligible. It is shown that evolution of void ratio with vertical effective stress for Shiraz structured fine soil can be reasonably simulated using constitutive equations reported in the literature.
    Keywords: Structured soil , Reconstituted soil , Clay , Yield stress, Normal consolidation line , Unloading - reloading line
  • Analysis of Negative Skin-Friction on Single Piles by One-Dimensional Consolidation Model Test
    Hyeong, Joo Kim, Jose Leo Mission*, Tae, Woong, ParkPeter Rey Dinoy Pages 1445-1461
    The computer program pile negative skin friction (PileNSF) was developed by the authors to predict the bearing capacity of a pile embedded in a consolidating ground due to surcharge loading. The program uses a one-dimensional analytical soil-pile model, which was formulated based on the nonlinear load-transfer method and Mikasa’s generalized one-dimensional consolidation theory. To investigate the development of negative skin friction on single piles, as well as to validate the computer program (PileNSF), a laboratory model test was performed in this study. The clay layer was subjected to increasing surcharge loads to simulate actual field conditions. Results showed that as excess pore pressure decreases and as surcharge load increases, the dragload and downdrag on pile increases. The measured values of soil settlement, excess pore water pressure, and axial force on pile were compared with the predicted values obtained from the computer program. The results of the computer program (PileNSF) showed to be in good agreement with the measured data. Therefore, negative skin friction on single piles can be effectively predicted using the computer program, PileNSF, provided that reasonable parameters are used in the analysis. After validating the program, a parametric study was carried out to study the influence of various pile design parameters on negative skin friction.
    Keywords: Piles , Negative skin friction , Nonlinear load-transfer method , Consolidation theory, Downdrag , Dragload
  • Discrete Element Modeling of Drained Triaxial Test: Flexible and Rigid Lateral Boundaries
    Seyed Mohammad Binesh*, Ehsan Eslami, Feizabad, Reza Rahmani Pages 1463-1474
    In the present paper, drained triaxial test on granular materials is simulated by discrete element method. Two types of boundary conditions including rigid and flexible boundaries are modeled in the tests. To simulate flexible boundary condition, a new algorithm based on linking the MATLAB and PFC3D codes is proposed. In this algorithm, triaxial test samples are simulated in PFCD3D and the spatial coordinates of particles are transferred to MATLAB code. Then, boundary particles are identified by irradiation from centerline of specimen and their identities are transferred back to PFC3D to impose boundary forces. The presented algorithm is relatively simple and there is no need of tessellation at the boundary surface. Besides, employment of MATLAB code improves the efficiency of computations. Imposition of confining pressure via normal forces to the outer surface of boundary and precise identification of boundary particles in large deformation are other advantages of the proposed algorithm. After validation of the proposed algorithm by some experimental tests, a comprehensive survey has been performed on micro- and macro-behavior of samples simulated by rigid and flexible boundaries.
    Keywords: Rigid boundary , Flexible boundary , Discrete element, Triaxial test
  • The Efficiency of the Ability of Isolation Piles to Control the Deformation of Tunnels Adjacent to Excavations
    G. Zheng, F. J. Wan, Y. M. Du, Y. Diao, Y. W. Lei, X. S. Cheng * Pages 1475-1490
    There is a lack of research on the mechanisms by which isolation piles affect displacements in deep soil layers and the use of isolation piles to control the displacement and deformation of the existing tunnels adjacent to deep excavations. This paper examines a large, deep excavation project in which isolation piles were used to protect a nearby existing tunnel. A finite-element model that considers the small-strain characteristics of the soil was used to simulate this project. After the numerical model is verified, it is used in a parametric analysis of the mechanisms by which isolation piles control the displacement of deep soil layers and the deformation of tunnels near excavations. The results show that isolation piles have both a barrier effect and a traction effect on the surrounding soil and adjacent tunnels. When the traction effect is larger, isolation piles can exacerbate the horizontal displacement of the soil and tunnel within a certain depth range and actually increase tunnel deformation. Burying the isolation piles reduces this traction effect and improves their ability to isolate tunnels from displacement. All else being equal, isolation piles more efficiently control deformation if they are near the tunnel.
    Keywords: Deep excavation , Isolation pile , Tunnel, Traction effect, Barrier effect
  • A Simplified Approach for Axial Response of Single Precast Concrete Piles in Cement-Treated Soil
    Anhui Wang, Dingwen Zhang *, Yaguang Deng Pages 1491-1501
    Precast concrete (PC) piles reinforced with cement-treated soil have been successfully applied to soft ground improvement in China’s coastal regions. However, very few analytical approaches have been proposed to predict their responses to axial loading. This paper presents a simple analytical approach for the prediction of the axial response of a single PC pile in cement-treated soil based on the shear displacement approach. The analysis considers the pile–treated soil-surrounding soil interaction and the non-homogeneity of subsoil shear modulus. The closed-form solutions for the axial force and displacement along the pile shaft as well as the load–displacement response are quickly deduced. A comparison with the measured response of a single PC pile with cement-treated soil reinforcement is performed to verify the effectiveness and accuracy of the proposed approach. Finally, using this approach, a parametric study was further conducted to clarify the influence of the related parameters on the axial response of the reinforced PC pile. The results show that increasing the subsoil shear modulus can significantly improve the bearing performance of the reinforced PC piles that are subjected to axial loading. The ultimate bearing capacity of the reinforced PC pile increases by approximately 20% for every 100 mm increase in the diameter of outer cement-treated soil. Moreover, the pile-head displacement reduction is generally proportional to the increase in the elastic modulus and the diameter of the inner PC pile.
    Keywords: PC pile in cement-treated soil , Axial response , Analytical approach, Axial force , Displacement
  • Effects of Landfill Leachate on Mechanical Behaviour of Adjacent Soil: a Case Study of Saravan Landfill, Rasht, Iran
    Nader Shariatmadari *, Behnam Askari Lasaki, Hasan Eshghinezhad, Pourya Alidoust Pages 1503-1513
    Urban waste in most cities of Iran is dumped without proper standards of landfill construction. Improper implementation of waste barriers leaks off leachate into the surrounding areas, causing soil contamination and other serious environmental problems. The main goal of this study is to determine the possible effects of leachate on the geotechnical properties of contaminated soils around the dump site and estimating a safe zone for a landfill site. In this regard, uniaxial compression, direct shear, consolidation and permeability tests were carried out on several samples to assess the possible effects. SEM tests were also conducted to precisely assess the geotechnical parameters and clarify the possible changes in soil characteristics. Results showed that by increasing leachate concentration, maximum uniaxial and shear stresses decrease, and the volumetric strain increases. This behavior continues by getting closer to the contamination source. A decreasing trend in the cohesion and coefficient of permeability and a relatively low decreasing trend in the internal friction angle (φ) were also observed as the contamination concentration increased. According to the results, a 600 m distance from the contamination source is proposed as a safe zone, in which the soil holds its initial properties. This study provides additional insight into the effects of leachate on the spoil texture of soil.
    Keywords: Municipal solid waste , Leachate, Contaminated soil, Geotechnical properties , Safe zone
  • The Influence of Dynamic Replacement Method on the Adjacent Soil
    Jerzy S?kowski*, S?awomir Kwiecie?, Piotr Kanty Pages 1515-1522
    The purpose of this paper is to report on the field tests for the formation of a single DR (dynamic replacement) column and its influence on the surrounding weak soil deposit. The influence of the column formation has been assessed with piezocone and dilatometer measurements, as well as by changes in the strength and deformation parameters obtained from the field tests. These measurements were carried out during and after the column formation and at varying distances from the column. The tests carried out have shown that soil close to the column became weaker during the column formation. As a result the soil stiffness and strength were found to increase over time. The weaker the soil was in natural state, the more significant the strengthening effect became. That indicates that changes occurring around a DR column are complex. The measurements suggest that the changes in soil structure have a tendency to be dependent on the distance from the column, elapsed time and the type and the initial condition of the soil.
    Keywords: Dynamic replacement , Field tests , Soil strengthening, Parameter changes , Adjacent soil