CivilEng, Volume 3, Issue 1 (March 2022) – 10 articles

With flooding and other weather events intensifying, more cost-effective erosion and flood control systems are needed. Vetiver (Chrysopogon zizanioides (L.) Roberty), is part of an arsenal of sustainable, low cost, and green infrastructure tools to reduce the risks of erosion, landslides, and flooding. This study investigates vetiver and its broader application to transportation planning. Based on a literature review and interviews with experts, vetiver as a green infrastructure tool is summarized. An evaluation framework was devised in which the plant’s effectiveness to stabilize hillsides and manage stormwater is investigated. This framework is applied to a recent highway flooding case where vetiver could have been used. While site-specific conditions and roadway requirements are critical to its effectiveness as a mitigation tool, additional pathways to understanding, acceptance, and use of vetiver to support transportation resilience requires convergence in engineering, design, and planning disciplines. Understanding barriers to the adoption of vetiver will also support efforts to increase other green infrastructure tools in transportation planning. Improvements in policies, standards, guidance and training and education on vetiver and green infrastructure will support the mitigation of transportation disruptions and community resilience. Full article

Concrete is increasingly utilized in the construction field in Southern Nevada. This area has an arid and hot summer and freezing cold winter conditions. These extreme conditions affect the properties of fresh concrete, which can cause cracking. Hot weather conditions may adversely affect both fresh and hardened concrete properties. Even though practices can minimize the detrimental effects, good quality control of fresh concrete, from mixing to finishing, is crucial under hot weather conditions. The objective of the present study is to evaluate the seasonal consistency of concrete quality, considering strength and slump properties. Another objective of this research is to determine the relationship between the seasonal air temperature variations and those of freshly batched concrete. Results indicate that strength and slump remain constant with varying air and concrete temperatures during pour. Additionally, during the hot season (air temperature above 27 °C (80 °F)), fresh concrete’s temperature is lower than the air’s temperature, in contrast during the cold season (air temperature below 16 °C (60 °F)), fresh concrete’s temperature is higher than the air’s temperature. Fresh concrete temperature and air temperature are similar in the range of 60 to 80 °F. Therefore, to limit the use of additional water or admixtures it is recommended to pour concrete when the air temperature is in the range of 16° and 27 °C (60 to 80 °F). Full article

This paper presents a review of selected tunnel stability models that have been developed and used in calculating the minimum tunnel face pressure as described by original authors. Furthermore, this paper provides a comparison of required tunnel face pressure obtained from analytical models, based either on limit equilibrium method or the limit analysis method (upper bound theorem) and numerical models using the finite element method. The numerical results are presented in charts for the comparative study to discuss the influence of cover depth to tunnel diameter ratio (C/D), internal friction of the soil ($\phi$), and cohesion (c) on normalized support pressure ($p_u/\gamma D$) for each model. To verify the accuracy of the selected models, a comparison of the results of seven tunnel stability models with the results of the physical models is carried out. In a ground composed of two layers, a comparison of the required tunnel face pressure is presented. The results show that the wedge–silo models provide higher support pressure than the conical block models. Moreover, the support pressure using the conical block models is only dependent on the friction angle and not on the C/D ratio. Finally, the results of wedge-silo models indicate more significant dependence of the required support pressure on the C/D ratio especially for the lower friction angle. Full article

The combined length of the sewerage and clean water pipe infrastructure in the UK is estimated to be about 800,000 km. It is prone to failure due to its age and the inadequacies of the current pipe inspection methods. Fibre-optic cable sensing is an attractive way to continuously monitor this infrastructure to detect critical changes. This paper reviews the existing fibre-optic sensor (FOS) technologies to suggest that these technologies have better sensing potential than traditional inspection and performance monitoring methods. This review also discusses the requirements for retrofitting an existing pipeline with an FOS. It also demonstrates that there is a need for further research into methods applicable to non-pressurised pipelines, as there is very little existing literature that focuses on partially filled pipes and pipes with gravity fed flows. Full article

Conducting laboratory direct shear tests on granular materials is a common practice in geotechnical engineering. This is usually done by following the ASTM D3080/D3080M-11 (hereafter named ASTM), which stipulates a minimum required value of 10 for specimen width (W) to the maximum particle size (d_max) ratio. Recently, a literature review performed by the authors showed that the minimum required W/d_max ratio given in the ASTM is not large enough to eliminate the specimen size effect (SSE). The minimum required W/d_max ratio of ASTM needs to be revised. In this study, a critical analysis is first made on existing data in order to identify the minimum required W/d_max ratio. The analysis shows that more experimental data obtained on specimens having W/d_max ratios between 10 and 50 are particularly necessary. To complete this need, a series of direct shear tests were performed on specimens having different d_max by using three shear boxes of different dimensions. The results show once again that the minimum required W/d_max ratio of 10, defined in the ASTM, is not large enough to eliminate the SSE. Further analysis on these and existing experimental results indicates that the minimum required W/d_max ratio to remove the SSE of friction angles is about 60. These results along with the limitations of this study are discussed. Full article

This study investigates the high contents of cementitious materials in Portland cement concrete and assesses the required (f’_cr) and actual (σ) compressive strength of concrete specimens. A linear optimization technique identifies the required binder content to reach f’_cr. Standard specifications have required concrete overdesign (OD) for decades, but few studies have evaluated the actual magnitude of OD from field data. The compressive strength of 958 cylinders prepared in the field represented 8200 m³ of ready-mixed concrete with 300 and 450 kg/m³ of cementitious are analyzed. The actual OD appears to be 7 to 21% higher than required. The required 28-day compressive strength of concrete was achieved in less than seven days. Therefore, the content of the cementitious materials could be reduced by 6 and 17% so that concrete could reach f’_cr without cementitious overconsumption. Reducing cementitious content is recommended to improve construction quality and optimize resource utilization. Among the main reasons for this recommendation are the estimated substantial long-term savings, increased concrete durability and more rational use of natural resources required to build the structures. Full article

The determination of shear strength parameters for coarse granular materials such as rockfill and waste rocks is challenging due to their oversized particles and the minimum required ratio of 10 between the specimen width (W) and the maximum particle size (d_max) of tested samples for direct shear tests. To overcome this problem, a common practice is to prepare test samples by excluding the oversized particles. This method is called the scalping scaling down technique. Making further modifications on scalped samples to achieve a specific particle size distribution curve (PSDC) leads to other scaling down techniques. Until now, the parallel scaling down technique has been the most popular and most commonly applied, generally because it produces a PSDC parallel and similar to that of field material. Recently, a critical literature review performed by the authors revealed that the methodology used by previous researchers to validate or invalidate the scaling down techniques in estimating the shear strength of field materials is inappropriate. The validity of scaling down techniques remains unknown. In addition, the minimum required W/d_max ratio of 10, stipulated in ASTM D3080/D3080M-11 for direct shear tests, is not large enough to eliminate the specimen size effect (SSE). The authors’ recent experimental study showed that a minimum W/d_max ratio of 60 is necessary to avoid any SSE in direct shear tests. In this study, a series of direct shear tests were performed on samples with different d_max values, prepared by applying scalping and parallel scaling down techniques. All tested specimens had a W/d_max ratio equal to or larger than 60. The test results of the scaled down samples with d_max values smaller than those of field samples were used to establish a predictive equation between the effective internal friction angle (hereafter named “friction angle”) and d_max, which was then used to predict the friction angles of the field samples. Comparisons between the measured and predicted friction angles of field samples demonstrated that the equations based on scalping scaling down technique correctly predicted the friction angles of field samples, whereas the equations based on parallel scaling down technique failed to correctly predict the friction angles of field samples. The scalping down technique has been validated, whereas the parallel scaling down technique has been invalidated by the experimental results presented in this study. Full article

Fiber-reinforced asphalt concrete (FRAC) was tested using limestone, PG 64-22 binder, and 20% reclaimed asphalt pavement (RAP). After mixing fibers with different lengths and dosages, they were extracted and recovered to evaluate their dispersion in the FRAC. The uniaxial fatigue test, IDEAL CT test, and flow number test were performed on FRAC with different fiber lengths and asphalt contents. The balanced mix design (BMD) approach was then used to analyze the uniaxial and flow number test results in order to evaluate the effect of aramid fibers on fatigue and rutting resistance of the pavement. The dispersion test showed that the 19 mm and 10 mm aramid fibers at a dosage rate of 0.5 g/kg provided the best dispersion. The 19 mm fibers showed better performance test results than the 10 mm and 38 mm fibers. The BMD approach provided ranges of asphalt contents to produce mixes with certain resistances to fatigue and rutting. The BMD approach also demonstrated the effect of fibers with different lengths on increasing the resistance to fatigue and rutting. The study concluded that the 19 mm fibers with a dosage of 0.5 g/kg produce best results. The BMD approach is a good tool that can be used to refine the mix ingredients, including additives such as fibers, in order to optimize pavement resistance to various distresses such as fatigue cracking and rutting. Full article

This paper examines the scour problems related to piers-on-bank bridges resulting from frequently flooded and/or constricted waterways. While local scour problems for bridge piers in riverine channels have been addressed extensively in the literature, there have been few studies addressing piers-on-bank scour scenarios. A comprehensive three-dimensional finite element analysis using the element removal (ER) technique has been performed on a recently constructed bridge with an observable scour problem on multiple piers. The analysis is further extended to study the effect of “combined scour” or extensive erosion of soil between adjacent piles. Three different loading cases were considered in the study, and the results demonstrated that the effects of local and combined scours on bridge drilled shaft foundations can be significant under the combined actions of axial, lateral loads and bending moments. Specifically, the most critical case of combined scour is when maximum moment effect is applied to the piers. The results of this study show that the interaction of soil displacement fields between adjacent piles should be investigated for bridge crossings with piers-on-bank, with a high risk of flooding during the moderate-to-low probability of the occurrence of precipitation events, as they can increase the pile head displacements and the bending moments in the soil and result in the early failure of bridges. Full article