In this study, mortars containing locally available natural pozzolan (NP) in Almadinah Almunawara, Kingdom of Saudi Arabia, were investigated as a partial substitute for sand or cement in mortars and silica fume (SF). The benefit of using local NP powder as a replacement for cement is that it reduces the carbon dioxide emission during the cement manufacturing process, whereas the benefit of using local NP as fine aggregates is that it reduces the density of the produced mortars and improves its properties because of its pozzolanic effect. Because of these reasons, there is a need to develop an effective predictive model to estimate the compressive strength of mortars with partial replacement of cement or sand with NP and with SF as a replacement for cement at 28 days. Data of 68 cubic specimens of 50 mm were established through experimental work with other researchers, and they were chosen to create a database for the proposed model. There were three input parameters: a) level of partial substitution of cement with NP powder, b) level of partial substitution of sand with NP, and c) level of partial substitution of cement with SF. The output parameter was compressive strength. Best correlations were obtained between the compressive strength and sand replacement with NP. To predict the compressive strengths of cement mortars containing NP and SF, multivariate regression models were proposed and compared to find the best one. It was concluded that the full quadratic model was the best model with highest correlation when compared with other proposed models.

This research demonstrates the results of an investigation into the California bearing ratio (CBR) of granular soils from Qassim region, Saudi Arabia, using multilinear regression (MLR), pure quadratic (PQ) models, and gene expression programming (GEP) methods utilized to develop mathematical models for estimating the CBR based on basic soil index properties. In this study, samples were collected from different borrowing pits in the Qassim area. Forty-three samples of soil were taken and transferred to a laboratory for examination. Seven multilinear regressions and seven PQ models were investigated, while four GEP models were made. The selection of each model variable depends on soil indices, grouping into grain size distribution, Atterberg limits, and compaction parameters. The results of this analysis showed that the PQ model had a higher accuracy [coefficient of determination (R2) = 0.89, root mean square error (RMSE) = 16.006, uncertainty (U95) = 16.17, and reliability = 57%] than the multilinear regression model, which has a lower accuracy model [R2 = 0.811, RMSE = 20.791, U95 = 15.569, and reliability = 51%]. The best GEP model yields [R2 = 0.776, RMSE = 22.552, U95 = 15.787, and reliability = 53%]. Furthermore, sensitivity analysis was conducted to distinguish the influences of different input variables on CBR; it was found that fines percentage (F200), maximum dry density (MDD), and optimum moisture content (OMC) are the most influential variables.

The increase in the left-turn demand is the main cause of congestion at conventional intersections, and the traditional countermeasures are inadequate to solve this congestion due to the high changes in demand. This paper looks at the justifying threshold to redesign a signalized intersection from a conventional intersection (CI) to a continuous flow intersection (CFI) and create performance guidelines for decision-makers and professionals deciding to consider the alternative. A performance comparison between the CI and CFI was conducted to define the main parameters affecting the operational performance. To accomplish the paper’s objective, candidate locations that have already implemented the CFI were identified, and the location with sufficient data for analysis was selected. After the consideration of different evaluation tools, microsimulation (VISSIM 8) was utilized to model the before and after conditions of the location. Using the field data, signal optimization and driving behavior parameter sensitivity analysis were performed to calibrate the models to replicate real-life conditions. Afterwards, an experiment was designed to examine the different factors that affect the efficiency of each design. The experiment involved 72 different configurations of CFI and CI with 5 different volume levels and used two measures of effectiveness, average vehicle delay, and capacity to assess the results. The results were used to develop guidelines that will help the decision-makers to decide which design should be considered, which will result in developing a decision support system that will accelerate finding which design is superior to others.

Traffic congestion at intersection is one of the significant socioeconomic concerns worldwide. To tackle this challenge, researchers and practitioners are researching and executing different plans to control and manage long queues and delays. The general department of traffic in Saudi Arabia has implemented a new signal timing pattern in a number of signalized intersections that were designed with an additional flashing green phase complemented with law enforcement cameras (SAHER) to improve the capacity and safety of signalized intersections. This research aims to evaluate the impact of flashing green intervals on driver behavior and traffic efficiency of five signalized urban intersections equipped with SAHER in the Al-Qassim region, Saudi Arabia. Analyses for the current situation (base scenario) and proposed scenarios (without SAHER) are performed and validated using the microsimulation model (VISSIM) with field collected data at the selected intersections. The results showed that, despite fewer improvements in vehicle delays, the intersections without SAHER and flashing green intervals yield shorter queue lengths than the intersections with SAHER and flashing green intervals. Further, it was also revealed that drivers tend to stop early and start late in the case of SAHER due to fear of red light fines, thus not utilizing the full green split and yellow time. Analysis for the average vehicle delay and queue lengths is also conducted to assess the efficacy of implemented green light flashing with SAHER on driver behavior and operational efficiency of the selected intersections.

Groundwater is the main source of fresh water in arid regions. The Saq aquifer is a transboundary sandstone groundwater layer that extended into Saudi Arabia and Jordan. The groundwater level of the aquifer is depleted due to extensive pumping with negligible natural recharge. The objective of this study is to predict the artificial recharge supplied from runoff into the Saq aquifer for a selected area in the Qassim region, KSA using mathematical models. The maximum weekly and daily rainfall was quantified at different return periods for urban areas using graphical and probability distribution methods. The predicted surface water from rainfall is suggested to be stored in ponds, consequently the required volume of ponds was estimated according to the results of weekly maximum rainfall and various return periods. The stored surface water is proposed to be recharged into the groundwater aquifer via designed wells. The estimated quantity of the surface runoff was 4·106 m3, 6.2·106 m3, and 10.3·106 m3 for return periods 25, 50 and 75 years respectively. The study is applicable for similar aquifers that suffer from non-renewable resources.