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The use of geotextiles to postpone reflective cracks in asphalt overlay is a popular practice, so researchers are eager to calculate its structural value. This research study has focused on this issue for geotextiles used in the roads of Iran. Twelve sections from the Tehran-Qom road were tested each examined before and after construction of the overlay. The tests were of the Falling Weight Deflectometer type, and at least twelve tests were conducted each time. The data from five sections (four for developing the model and one for evaluating the output) allowed a new mathematical model to be developed. For the seven remaining sections, some foreign and Iranian geotextiles were used as interlayers. The mean structural value for all of the geotextiles was equivalent to that of a 2.92 cm-thick Hot Mix Asphalt overlay, while that for only the Iranian sections was equivalent to 2.28 cm. Economic evaluations, based on construction costs, showed that in 2011 the use of geotextiles was economical in Iran, because fuel and bitumen subsidies had been eliminated and different geotextile brands had been brought to market in the country.

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Pile foundations are frequently used in industrial projects in southwest lowlands of Iran. Although high setup of shaft resistance

is usually reported in the area, no reliable formulation or guidelines are available for considering the increased capacity in design

applications. Therefore, the pile design practices are usually not optimized. The main objective of this paper is presenting a site

specific formulation for setup effects of a utility plant in southwest Iran in which a good database of prestressed concrete driven

piles is available. Fajr-II Petrochemical site in PetZone of Mahshahr accommodating a utility plant is selected as the database of

the current study. The setup factor (A) and the reference time (t0) are evaluated through processing of a relatively large database

of this well-supervised piling project. As the main portion of variations of driven piles capacity with time is related to shaft, only

shaft resistance variations are considered in this research. The shaft capacity variations are derived from signal matching analysis

on PDA tests. Reliability of PDA tests has been confirmed through comparing with the static load test results. Influence of driving

the surrounding piles on setup factor is also investigated. The results show that the average setup factor (A) and the reference time

(t0) of 0.30 and 0.01 day, respectively, are proper values for estimating the long term capacity in this region. Evaluation of the

results indicates that driving 8 piles around the test pile has increased the “A” factor average of 40% resultingin increase of the

shaft capacity about 19% in one month and 22% in one year, in comparison with the tested piles with no surrounding piles driven.

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Corrosion of reinforcing steel and other embedded metals is the main cause of severe deterioration in reinforced concrete structures which subsequently imposes adverse effects on ultimate and serviceability limit state performance of the whole structure. In this paper, a new corrosion detection method for reinforced concrete beams, based on wavelet analysis is presented. To evaluate the capability and efficiency of the method, a simply supported RC beam was modeled in 3-D taking into account the behaviors of concrete, steel and bond degradation. Deflection profile and mode shapes were extracted numerically and analyzed by wavelet transform. From the findings of the modeling, it can be concluded that this wavelet-based method is capable of detecting corrosion at its earliest stage. It is also concluded that both discrete and continuous wavelet transforms can be used and mother wavelet type has no significant effect on the results.

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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.

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In this paper, different aspects of the behavior of 2×2 pile groups under liquefaction-induced lateral spreading in a 3-layer soil profile is investigated using large scale 1-g shake table test. Different parameters of the response of soil and piles including time-histories of accelerations, pore water pressures, displacements and bending moments are presented and discussed in the paper. In addition, distribution of lateral forces due to lateral spreading on individual piles of the groups is investigated in detail. The results show that total lateral forces on the piles are influenced by the shadow effect as well as the superstructure mass attached to the pile cap. It was also found that lateral forces exerted on the piles in the lower half of the liquefied layer are significantly larger than those recommended by the design code. Based on the numerical analyses performed, it is shown that the displacement based method is more capable of predicting the pile group behavior in this experiment comparing to the force based method provided that the model parameters are tuned.

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This research shows the results of studies carried out to define and analyze the effect of aging on MSW behavior of Kahrizak Landfill, the biggest landfill in Iran. Studied samples consisted of fresh samples and also aged ones with 5.5, 14 and 21 years of age which were obtained by mechanical excavators in aged burial locations. Analyzing variation in MSW components illustrates that paste fraction of MSW decreases due to aging process while fibers show a rising trend. Also the moisture content and the organic content of MSW reduce below half of the initial values while the degree of decomposition (DOD) increase up to almost 60% after 14 years. These variations over the time are significantly related to the burying methods and environmental condition of burying location. Shear strength behavior of MSW material was analyzed by some CU tests using large scale triaxial apparatus (D=150mm, H=300mm) on remolded MSW specimens. General observations depict that with an increase in strain level, loading rises without any peak point on stress-strain curves. Fresh samples represent the lowest shear strength followed by 21, 14 and 5.5 year-old samples respectively. There is a direct relationship between fiber content and shear strength. Internal friction angle of aged samples decreases in comparison with fresh ones while cohesion has an inverse trend and rises over the time. According to the effect of burying condition on MSW characteristics, it seems that DOD factor is a more appropriate factor than age in order to analyze long-term behavior of MSW.

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Due to the existence of fibrous materials such as plastic fragments, the strength anisotropy of Municipal Solid Waste

(MSW) materials is the main source of differences between their mechanical response in direct shear and triaxial apparatus.

As an extension of earlier research on the mechanical behavior of MSW using a large traixail apparatus, results presented in

Shariatmadari et al. [1] and Karimpour-Fard et al. [2], the current study was programmed and executed. MSW samples were

tested using a computer controlled large shear box apparatus with normal stress levels ranging between 20 to 200 kPa. The

effect of fiber content, fiber orientation, aging and shearing rate on the response of MSW were addressed. The results showed

that shear strength of MSW increases with normal stress, although, in spite of the presence of reinforcement elements in MSW

and unlike the results from triaxial tests, no strain hardening could be observed in their mechanical response. An increase in

the shear strength of MSW was observed with increasing the shearing rate. Increasing the shearing rate from 0.8 to 19

mm/min, enhanced the shear strength of samples from 16 to 27% depending on the shear displacement level. Although, the

same trend was investigated in traixial tests, but lower rate-sensitivity in the mechanical response of MSW in direct shear tests

were observed.

Unlike the results of triaxial tests with aging process, mobilized shear strength level of MSW samples tested under direct

shearing decreased comparing fresh samples. It was also observed that altering the fiber content and their orientation could

affect the mechanical response and shear strength of the MSW. Additionally, there is an optimum fiber angle in MSW which

yields the highest level of shearing strength.

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Compared to quartz sand, the shear behavior of carbonate sand differs in  appearance, origin, and kind. Carbonate sand is found mainly in the northern coast of the Persian Gulf and the Oman Sea. In this research, a comparison is made between the shear behavior of carbonate sand retrieved from the eastern region of the Chabahar Port, located north of the Oman Sea, and quartz sand obtained from Firoozkooh, north of Iran. Both carbonate and quartz sands have identical and uniform particle size distributions. A total of 4 one-dimensional consolidation tests, and 16 triaxial consolidated-undrained (CU) tests under confining pressures of 100, 200, 400, and 600 kPa were performed with initial relative densities of 20%-80%. The results indicated that despite  their uniform properties,  including size and grading, the two types of sand  can differ in other  properties as  inherent interlocking, compressibility, stress-strain behavior, internal friction angle, changes in pore water pressure and stress path. For instance, Chabahar carbonate sand has more compressive potential than Firoozkooh sand because of the fragility of its grains. Moreover, the internal friction angle of carbonate sand is more than that of quartz sand. Quartz sand is more affected by initial relative density, whereas, carbonate sand is influenced by  inherent packing.

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To investigate the saturation induced collapse deformation behavior of rockfill material, a set of large-scale triaxial tests were conducted in saturated and dry-saturated conditions. Specimens were tested under various confining pressures. For dry-saturated tests, specimens were sheared in various stress levels. Results of all dry saturated tests indicate a sudden reduction in the specimen volume during the submerging process. The ratio of the minimum axial strength of a submerged specimen (at the end of the saturation process) to the shear strength of the specimen before saturation is defined as the coefficient of stress recovery, Csr. Results show that this ratio increases as the confining pressure increases, and decreases as the shear stress level increases. According to the results of dry-saturated tests, reduction values of the internal friction angle caused by saturation (c), the ratio of the elasticity modulus of the material after saturation to its elasticity modulus in dry condition, i.e., Ewet/Edry, and the saturation induced sudden volumetric strain (vc) decrease as the confining pressures increase. However the shear stress level does not have any meaningful effect on the variation of c, Ewet/Edry and (vc).

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In this study a series of cyclic triaxial tests were performed to examine the undrained dynamic resistance of silty sand reinforced with various arrangements of geotextile layers. The silt content of samples varies in percentage from 0, 10, 20, 30, 40 and 50%. A total of 32 laboratory cyclic triaxial tests have been performed on silty sand samples reinforced with geotextile layers in different depths. All tests were performed with 100 kPa confining pressure, subjected to an isotropic consolidated undrained (CIU) condition. The tests were conducted at a frequency of 2 Hz. Results indicate that both the geotextile arrangement and the silt content were most essential in the liquefaction potential of reinforced sands. An increase in the number of geotextile layers enhanced the cyclic resistance of reinforced samples against the liquefaction potential. It was also found that when the geotextile layer was posited near the top of the specimen (load application part) the liquefaction resistance would increase (e.g. for clean sands, the improvement of liquefaction resistance caused by the geotextile layer had a 0.2 depth, and the sample height was 5.5 times greater than the geotextile layer inserted in mid height of sample H). Based on the obtained results, effects of geotextile on liquefaction resistance decreased as fines content increased to about 33%. Further increase in the fines content however, would lead to higher in reinforcement advantages. The liquefaction improvement is more effective with a higher number of geotextile layers. The results also revealed that the reinforcement effect in FC≈33 % is at its lowest amount. 

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Seismic retrofit of masonry slabs in existing steel or masonry buildings has found special significance in current codes as failure of unstable jack arch slabs has been reported as a major reason for collapsing structures in Middle East deadly earthquakes. In this paper, three retrofit schemes are investigated and compared. The proposed rehabilitation techniques consist of a single X strapping, SXS, a double X strapping, DXS, and a two-way jack arch slab supported by a steel grid. Using experimental studies, advantages and disadvantages of each scheme are evaluated. In-plane stiffness and capacity of the diaphragm are adopted as the seismic performance index of each rehabilitation scheme. According to the obtained results, the jack arch slab systems designed and constructed based on proposed retrofit methods provide an appropriate alternative to other forms of flooring in seismic zones. DXS can greatly improve diaphragm performance in terms of in-plane stiffness, capacity and even energy dissipation of the diaphragm compared with the other two techniques. The second place belongs to SXS while the steel grid scheme has a minor effect on the in-plane stiffness of the diaphragm.

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This paper addresses the ambient vibration based finite element model updating of long span reinforced concrete highway bridges. The procedure includes ambient vibration tests under operational conditions, finite element modeling using special software and finite element model updating using some uncertain parameters. Birecik Highway Bridge located on the 81stkm of Şanlıurfa-Gaziantep state highway over Fırat River in Turkey is selected as a case study. Because of the fact that the bridge is the sole in this part of Fırat, it has a major logistical importance. The structural carrier system of the bridge consists of two main parts: Arch and Beam Compartments. In this part of the paper, the beam compartment is investigated. Three dimensional finite element model of the beam compartment of the bridge is constituted using SAP2000 software to determine the dynamic characteristics analytically. Operational Modal Analysis method is used to extract dynamic characteristics of the beam compartment by using Enhanced Frequency Domain Decomposition method. Analytically and experimentally identified dynamic characteristic are compared with each other and finite element model of the beam compartment of the bridge is updated by changing of some uncertain parameters such as section properties, damages, boundary conditions and material properties to reduce the differences between the results. It is demonstrated that the ambient vibration measurements are enough to identify the most significant modes of long span highway bridges. Maximum differences between the natural frequencies are reduced averagely from %46.7 to %2.39 by model updating. Also, a good harmony is found between mode shapes after finite element model updating.

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ABSTRACT The influence of the sand placement method above geotextile layer on interface shear strength behavior was investigated. Seven different types of woven and non woven geotextile were used with only poorly graded sand. The investigation involved placement of sand layer through inclined horizontal plane with different angles. This step constitutes a fundamental step for assessing soil to be deposited in different plane and therefore with different internal soil fabric. The interface shear strength was evaluated by using direct shear test. Although the investigated soil is uniform poorly graded sand, the influence of the deposit plane was significant especially for nonwoven geotextile. Differences in soil interface shear strength associated with the tested geotextiles samples shows that samples with higher mass per unit area and same opening sizes had the higher interface friction angle regardless the bedding plane. Influence of bedding plane on interface modulus of elasticity which used in most of interface modeling was investigated using Janbu’s formula. It is noted that the use of secant interface modulus of elasticity at 1% strain and at 50% of peak stresses gave a consistent prediction of n and Ku constant appear in Janbu’s formula for all types of geotextile. The above results were reflected in the prediction for interface molded such as Chen and Juran as shown. Therefore, the existing interface modeled is needed to be modified to account for the method that the sand is being placed above the geotextile layer.

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The behavior of Chamkhaleh sand and three other recognized sands namely, Babolsar, Firouzkuh and Standard (Ottawa) sands are compared using triaxial apparatus under undrained monotonic loading conditions. Chamkhaleh and Babolsar sands are supplied naturally from southern Caspian Sea shorelines, whereas artificial Firouzkuh and Standard sands were supplied commercially. Samples were prepared using wet tamping with regard to the reduced compaction effect at relative density of 15% under isotropic consolidation pressures of 100, 300 and 500 kPa. The results of triaxial tests have indicated that Chamkhaleh sand has much more dilation tendency than the other sands. In order to evaluate the reasons behind this behavior, the spherecity and roundness of all the four sand particles were measured using an image processing method. It was revealed that the spherecity of the four sands is not much different, but Chamkhaleh sand is more angular than the other sands. For comparison of the dilative response of the sands in undrained triaxial tests, a “dilation tendency index” is introduced. This index may be used as a criterion for measuring the dilation of sands in undrained tests. Results have shown that the internal friction angle under the steady state condition is more dependent on the shape of particles than the maximum strength condition. For spherecities greater than 0.5, the dependency rate of sand behavior on the roundness is decreased.

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The main objective of present study is to possible use of plastic waste materials for reinforcing clayey soils. An experimental study was planned to investigate compressibility and undrained shear behavior of clayey soil mixed with plastic waste. The mixtures were prepared with various amount of plastic waste (i.e. 0%, 0. 5%, 1.0%, 1.5% and 3.0% in dry weight) and interactive effect of plastic waste, plastic flexibility, confining pressure and initial density on the behavior of clayey soil was studied by performing compaction, consolidated undrained triaxial and oedometer consolidation test. The results show that plastic wastes do not affect compaction characteristics of clayey soil considerably and adding them to the clay more than a specific value (i.e. 1.0% in this research) causes to change undrained behavior of samples from contractive to dilative. In addition, beyond this specific value, it improves shear strength and reduces compressibility of clay. The rate of increase in shear strength and decrease in compressibility depends on the confining pressure, flexibility of plastic and initial density of samples. It is more noticeable when plastic waste in mixtures is relatively rigid and density and confining pressure are high. Moreover, plastic waste has a negative effect on the free swelling, swelling pressure and swelling index of samples, so that these parameters for plastic waste mixed clay are higher than the associated values of plain clay.

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The correlations and relationships between electrical resistivity and geotechnical parameters of soils have become very important for site investigation. However, there is a lack of understanding about the relationships between electrical resistivity and geotechnical parameter values. The resistivity piezocone penetration tests and laboratory tests have been conducted for geotechnical investigations of marine clay in Jiangsu province of China to establish quantitative relationships between electrical and geotechnical data. The geotechnical investigation reveals that electrical resistivity values are very low for marine clay in Jiangsu, ranging from 5 to 10 Ω m. The correlations between electrical resistivity and geotechnical parameters are examined using Spearman’s rank correlation test that is a rank-based test for correlation between two variables without any assumption about the data distribution. It was shown that the electrical resistivity has strong bonds with the moisture content, void ratio, salt content and plasticity index. In terms of quantitative relationships, good fitting relationships between electrical resistivity and selected geotechnical parameters are observed. The statistical analysis indicates that the electrical resistivity is a good indirect predictor of selected geotechnical parameters. The data studied demonstrates the usefulness of the in situ resistivity method in geotechnical investigations, which have an advantage over other geotechnical methods in cost performance.

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Fiber Reinforcement Concrete is mainly distinguished in their behavior in cracked tension zone which is called tension softening behavior. Wide researchers have been investigated this behavior and present many tensioned softening models. This paper presents a compression between four tension softening models including constant, linear, bilinear and exponential models in flexural behavior. In this study the behavior of rectangular beam section under four/three point bending test have been predicted by iteration procedure. These models has been compared in some parametrical properties. The result of this study shows variety in result for four used models and indicate concern in applied assumptions.

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In this study, the shear strength parameters of the Kaolinite clay, as the control material, and the Kaolinite clay reinforced by different percentages of two different types of crumb rubber content have been evaluated. The consolidated drained and unconsolidated undrained triaxial and California bearing ratio tests have been conducted on the control and crumb rubber reinforced soils. Addition of crumb rubber would improve shear strength parameters such as cohesion, friction and dilation angles, stiffness and the ductility of the reinforced soil. 5, 10 and 15 % (by the weight of dry soil) of crumb rubber content were used in this study which were undergone confining stress levels of 100, 200 and 300 kPa and an optimum crumb rubber content is found, which results in the maximum bearing capacity of the soil. Also, due to the non-linearity of the failure mode of reinforced soil and inadequacy of Mohr–Columb envelope for describing the behaviour, a failure mode is proposed for the clay soils reinforced by crumb rubber. This failure criterion is useful for failure envelope of clay-rubber matrix.

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Pile load tests and numerical analysis of a small-scale model pile in unsaturated clayey soil are presented in this paper. A small-scale model pile was simulated to bear a static axial loading in unsaturated soil using finite element method. All parameters used in the finite element method were obtained in laboratory tests, including the direct shear test, interface direct shear test, and filter paper method. The numerical analysis results were compared with the pile load test results. The results show that the general trend of pile load and pile head settlement relationship obtained by the numerical analysis shows a good consistence with the pile load test results. With increasing water content of the soil, the matric suction, dilatancy angle and shear strength decrease, and consequently the ultimate bearing capacity of pile decreases.

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During the entire life cycle of a pavement, highway agencies are expected to maintain adequate surface frictional properties to facilitate traction between car tires and pavement surface. Traditionally the repair method for a friction-deficient pavement surface is the application of a new surfacing layer. The monitoring and remedying practice is important however, it is a passive approach toward the problem. A more proactive approach would be to test the hot mix asphalt in the laboratory during its initial mix design stage to ensure that aggregate combinations used in the asphalt pavement will provide adequate friction over the life of the pavement. Toward this objective the polishing behavior of laboratory-prepared HMA specimens made of eight different job mix formulas has been studied in terms of friction values. In addition, a robust statistical analysis of the obtained surface friction values has also been carried out in an attempt to verify the success in developing this new asphalt polisher that is used to simulate the tire-pavement interaction. Furthermore, polishing behavior (i.e., polishing trend, rate of friction loss and absolute and percent values of decrease) were all fully investigated to capture surface frictional deterioration of HMA specimens. In conclusion, the new asphalt polisher showed a good degree of repeatability. Additionally, it has been concluded that the decrease in polish number is maximum during the first hour of polishing. With the passage of time the drop in friction decreases and stabilizes.