Iranian Journal of Science and Technology, Transactions of Civil Engineering最新文献

The use of standard penetration test blow count (SPT- N) to obtain shear wave velocity (Vs) profiles in the absence of geophysical field test data is a common practice. This study uses a set of SPT-N profiles from Islamabad, Pakistan, to develop Vs profiles using empirical SPT-N and Vs empirical correlations. A set of SPT-N and Vs correlations based on the frequency of their use for seismic site response studies in the region were selected. A suite of one-dimensional site response analyses is then performed on the generated Vs profiles. The 13 input ground motions were chosen to be compatible with the site class B of the newly enacted building code of Pakistan (BCP 2021). A set of 546 1D nonlinear site response analyses were carried out and site response outputs were compared with the corresponding design spectra of the building code of Pakistan. The site-specific comparisons revealed that the calculations of region-specific empirical correlations are more compatible with the code design spectrum for site class C, whereas the outputs using empirical correlations of other regions are more compatible with the code design spectrum for site class D. Based on a comparative analysis, suitable empirical correlations for engineering practices in Islamabad, Pakistan are recommended.

Ensuring structural stability against shearing and sliding is crucial in civil engineering, necessitating a comprehensive analysis of shear strength characteristics. This study aims to explore the shear strength of highly plastic clay under varying conditions of strain rate and frequency, coupled with different combinations of normal and shear loads. Both static and dynamic loading experiments were conducted to evaluate the shear strengths. Static tests employed a strain-controlled loading setup with a maximum displacement of 25 mm, applying constant ramp rate alongside varied normal loads and varied ramp rates at constant normal load. Dynamic tests, under stress-controlled conditions, investigated: (i) varying normal stress levels while maintaining constant shear stress and frequency, (ii) different shear stress levels while keeping normal stress and frequency constant, (iii) different frequencies while holding normal and shear stresses constant. The findings indicate a significant correlation between higher shear modulus values and increased ramp rates and normal loads. Conversely, dynamic shear modulus decreases with escalating shear strain and loading cycles. Moreover, within a fixed number of loading cycles, dynamic shear modulus rises with augmented normal and shear loads but declines with higher frequencies, maintaining other parameters constant. These insights contribute to enhancing the understanding of soil behaviour under varying loading conditions, critical for designing resilient structures.

Selecting the appropriate material is crucial for the successful performance of printed elements. The present study aims to develop a strong and lightweight 3D-printed sand mortar using E-glass waste powder. It evaluated the material’s fracture energy, compressive strength, and ultrasonic pulse velocity properties through three-point bending experiments. Mixture specimens were prepared with varying E-glass volume contents of 5%, 10%, 15%, and 20%. The experiment concluded that the control mixture was brittle, while the addition of E-glass increased the fracture energy of the dune sand mortar by 21% to 143%. The compressive strengths of all specimens were higher than 25 MPa and up to 48 MPa. Ultrasonic pulse velocity confirmed the high quality of the E-glassy mortar specimens. It also performed manual flow ability tests to examine the printability and buildability of the mortar mixes. Using recycled E-glass waste in 3D printing enhances the buildability and resistance to the brittleness of lightweight mortar.

To address the issue of resource utilization regarding discarded geotextile, this study innovatively mixed discarded geotextile fibers (DGFs) uniformly into cement-stabilized diabase waste residue as a base filler for road construction. The effect of DGF content on the mechanical properties (MPs) of DGF-reinforced cement-stabilized diabase waste residue was examined via unconfined compressive strength (UCS) and splitting tensile strength (STS) tests. Dry shrinkage (DS), temperature shrinkage (TS), and freeze-thaw cycle (FTC) tests were conducted to investigate the durability change rule of the material under complex environmental conditions. The “anchoring” mechanism of DGFs in cement-stabilized diabase waste residue was analyzed via scanning electron microscopy (SEM). The results show that for a DGF content of 0.2%, the UCS and STS of the specimen reach their peak values. At this moment, with the coefficients of DS and TS minimized, optimal resistance to shrinkage is achieved. Incorporating DGFs significantly enhanced the FTC residual strength ratio of cement-stabilized diabase waste residue specimens compared to those without DGFs. Furthermore, the SEM results further reveal that the DGFs were gradually wrapped with cement hydrates, and their two ends were embedded in the matrix of the cement-stabilized diabase waste residue, acting as “bridges”. Embracing the environmental protection concept of “treating waste with waste”, this study highlights the potential of DGFs as reinforcement materials for cement-stabilized diabase waste residue, introducing a novel approach to the resource utilization of discarded geotextiles.

The objective of this paper is to estimate the equivalent permeability of the rock surrounding the tailrace tunnel of the Azad Dam pumped storage power plant, using geostatistical methods. The permeability of the rock mass is a critical factor that influences the estimation of water flow rates. Since the tunnel passes through various geological units with different permeabilities, it is crucial to estimate the equivalent permeability for each unit in order to predict the water seepage from that unit into the tunnel. In order to estimate the permeability along the tunnel and underground structures, twelve exploratory boreholes were drilled, and water pressure tests were conducted. Due to the distribution of the exploratory boreholes, a study and statistical analysis are necessary to determine the permeability of the rock mass for each geological unit. Using geostatistical log kriging, multiple indicator kriging with four thresholds, and multiple indicator kriging with five thresholds, the permeability of the rock mass at the tunnel route was estimated. The results indicate that at least 40% of the rock mass has low permeability, while the remaining mass of the tunnel passes through rocks with moderate to high permeability. The accuracy of the estimated permeability values was evaluated by predicting the water inflow into the tunnel using the estimated permeability values and comparing it to the observed flow. Numerical models were generated for each geological unit to estimate the water inflow into the tunnel, based on the results of the geostatistical methods. Log kriging, multiple indicator kriging with four thresholds, and multiple indicator kriging with five thresholds were used to calculate the water inflow, resulting in 94.15, 94.15, and 127.5 L per second, respectively. The results of the modeling were compared to the observed water flow into the tunnel. Comparing the modeling results to both the statistical methods and observed values showed errors of 31.2%, 31.2%, and 6.9%, respectively. Of the three methods, the multiple indicator kriging computational method with five thresholds was found to be the most accurate, with the least amount of error and the closest approximation to the actual value. As a result, it was selected as the best method.

This research aims to optimize the mechanical performance of a geopolymer paste derived from fly ash (FA) using the Central Composite Design (CCD) method. The study also explores mechanosynthesis as a modern technique to create a pre-geopolymer powder, which is then used to develop the paste. Key factors considered include grinding speed and duration, curing time and temperature, and NaOH concentration. Twenty-nine geopolymer pastes were prepared based on the CCD experimental matrix, and their compressive strength (MPa) and bulk density (g/cm³) were measured after 28 days of ambient solidification. The structural properties of the raw materials and resulting geopolymer samples were analyzed using X-ray diffraction (XRD) and Fourier-transform infrared (FTIR) spectroscopy. Morphological characteristics were examined with Scanning Electron Microscopy (SEM) and Energy-Dispersive X-ray (EDX) spectroscopy. The compressive strength of the samples ranged from 11.22 to 32.41 MPa, while bulk density varied from 1.31 to 1.62 g/cm³. The optimized conditions for the highest-performing geopolymer paste (46.47 MPa and 1.64 g/cm³) were identified as a grinding speed of 300 rpm, grinding time of 15 min, curing time of 24 h, curing temperature of 80 °C, and a NaOH concentration of 10 M. The performant geopolymer paste demonstrated a low-porosity structure primarily composed of dense amorphous sodium aluminosilicate gel. Future research could explore the application of different raw materials and additives to enhance the properties of geopolymer pastes further. Additionally, investigating the long-term durability and environmental impact of these materials can provide deeper insights into their potential for sustainable construction applications.

This study focuses on developing new expressions correlating hydraulic conductivity (K) in binary mixed soils with intergranular porosity (n_eq) and overall regularity (OR). Through a series of constant head hydraulic conductivity tests on three types of coarse-grained soils, varying proportions of low plastic river silt (S_p = 0% to 40%) were mixed with sand. Initially, sand-river silt binary assemblies were prepared with an initial relative index (I_d = 0.92). Analysis reveals significant influences of particle shape factors on hydraulic conductivity. The study elucidates the relevance of overall regularity (OR), shape factor (SF), and intergranular porosity (n_eq), introducing two novel parameters: [(OR)^0.5 × SF × n_eq] and [(1 + EG)/(SD)⁵ × (n_eq)^0.02]. The experimental findings highlight the robust predictive capability of these multi-variable expressions in systematically determining hydraulic conductivity. Such insights hold particular significance in geotechnical engineering, especially in understanding hydraulic responses within binary granular systems. Ultimately, this research contributes to a more profound comprehension of soil behavior and carries substantial practical implications for a wide array of engineering applications, facilitating more accurate predictions and design considerations in geotechnical projects.

Bus services are the predominant means of public transport due to their ability to accommodate a large population, particularly in the context of rapid population expansion in Dhaka. An e-ticketing service has been implemented on Dhaka’s public buses to give passengers a better travel experience. The main objective of this research is to assess the service quality attributes of e-ticketing facilities and their impact on the acceptance of the system. A questionnaire survey was carried out to get the users’ perception of twenty-two (22) service quality variables of the e-ticketing system. The survey collected a total of 261 responses from public bus service users. A Structural Equation model was developed to determine the relationship between four dimensions of the E-ticketing system: “E-ticketing Machine,” “Inconveniences,” “Bus Fare,” “Service features,” and “Service Acceptance.” Among all four constructs, “Inconveniences” has the highest total impact on the acceptance of the new system. E-ticketing machines also have a significant effect on the fare system. Outcomes from this study will help policymakers better understand the newly implemented e-ticketing service and resolve the inconveniences and issues related to the service. Properly addressing service quality attributes will ensure better overall service performance in the future.

The occurrence of the alkali–silica reaction (ASR) in granite manufactured sand concrete reduces its durability and service life. However, the combination and effect of different mineral admixtures on inhibiting ASR in granite-manufactured sand concrete and the in-depth understanding of the inhibition mechanism still need to be further explored. Therefore, this study accordingly analyzed the alkali activity of granite manufactured sand and the more active aggregates were selected to investigated the inhibitory effects of fly ash (FA), silica fume (SF), and slag (BS) mineral admixtures on the occurrence of ASR in mortar when used individually or together, as well as their optimal dosages; and XRD and SEM observations were analyzed to explore the mechanisms through which the mineral admixtures inhibited the ASR in the granite manufactured sand mortar specimen. The results indicate that: The existence of excessive ASR expansion in granite manufactured sand concrete, when the content of active sand was the most unfavorable, the ASR in the mortar specimen was the strongest and the corresponding expansion rate was the largest; otherwise, the intensity of the ASR in the mortar as weakened and the expansion rate was reduced; controlling the contents of alkali and active aggregates in the cementitious system to avoid the most detrimental proportions can alleviate the effects of ASR; the optimal contents of FA, SF, and BS individually were 30%, 20%, and 5%, respectively; and ASR was most effectively inhibited in the granite manufactured sand mortar when 5% SF was mixed with 5% FA or 5% BS; the inhibition of ASR in granite manufactured sand mortar is affected by the content of the active components as well as the particle fineness of the included admixture; the greater the content of active components, the smaller the average particle size and the better the inhibition effect. Finally, the considered admixtures were shown to inhibit ASR by reducing the total alkali content in the mortar and slowing the formation of ASR gel; generating C–S–H gel through the pozzolanic reaction with the calcium hydroxide cement hydration product, reducing the chances of contact between potassium and sodium ions and the active aggregate; and improving the microstructure of the interfacial transition zone and densifying the structure of the slurry, thereby impeding the diffusion of alkali to the interior.

Accurate simulation of hydrological processes in watersheds is of great importance. The accuracy of rainfall and temperature data plays a crucial role as effective inputs in hydrological models, such as the Soil and Water Assessment Tool (SWAT) model, significantly impacting the accuracy of the model outputs. This is despite the insufficiency of climatological stations in watersheds. Therefore, the present study aimed to evaluate the SWAT model in runoff simulation using rainfall and temperature from ground stations in comparison with the data derived from satellite images. To do this, rainfall and surface temperature data were extracted the number of 14,608 images from three-hour Tropical Rainfall Measuring Mission (TRMM) product and the number of 1826 images from Moderate Resolution Imaging Spectroradiometer (MODIS) products in Taleghan dam watershed, from 2009 to 2015. Minimum and maximum daily air temperatures were estimated from Land Surface Temperature (LST) data through multiple regression analysis. The Soil and Water Assessment Tool (SWAT) model was executed under four different scenarios: the first involved using rainfall and temperature data exclusively from ground stations, in the second, rainfall was sourced from TRMM images and temperature from ground stations, the third strategy combined ground station rainfall data with MODIS temperature data, and the fourth strategy utilized satellite-derived data for both rainfall and temperature inputs. Findings from the study revealed that the SWAT model demonstrated the most accurate runoff simulations when incorporating satellite-derived data. Specifically, the Nash–Sutcliffe Efficiency (NSE) values were 0.67 and 0.83 for daily and monthly time scales, respectively, indicating superior performance compared to using solely ground station data. When ground station data alone were employed, the NSE values were slightly lower at 0.62 and 0.7 for daily and monthly time scales, respectively. These results underscore the effectiveness of utilizing satellite-derived data as inputs for hydrological models, particularly in regions where there is a scarcity of observational data. This suggests that satellite data can play a crucial role in enhancing the accuracy and reliability of hydrological modeling, offering valuable insights for improved water resource management in data-constrained environments.