Tetra Tech (Canada)

Effective bond strength at the interface between conventional concrete (CC) and high-performance fiber-reinforced cementitious composites (HPFRCC) is vital for applications like shear key for bridge joints. This study investigated the suitability of HPFRCC incorporating various constituents (cement, slag, as well as nano-silica), with only basalt fiber pellets (macro-BFP) or hybrid fiber systems including macro-BFP and micro-polyvinyl alcohol (PVA) fibers. BFP is a new emerging class of basalt fiber strands protected by a polymer coat. Experimental results (slant shear, pure shear, rebar pull-out, etc.) were used to develop modeling [homogenization/finite element modeling (FEM)] components to evaluate the effect of HPFRCC mixture design parameters on the mode of failure and bonding capacity with CC and steel rebar. After verification, these model components were integrated in a full-scale shear key joint model to project the field performance of the developed HPFRCC. The results revealed that nano-silica had a significant effect at improving the HPFRCC bonding strength capacity with CC and steel reinforcement. Whilst increasing BFP dosage (4.5%) in the nano-modified composites resulted in reduction of the interfacial bonding with CC, it significantly improved the rebar interfacial bonding and ultimate shear key capacity of the joint. Comparatively, the inclusion of 1% micro-PVA fibers in the nano-modified composites comprising macro-BFP resulted in the highest increase in shear resistance force, interfacial bonding with precast CC and shear reinforcement dowels, and ductility which suggests their promising potential to be employed in shear key jointing applications.

Endocannabinoids (eCBs) are lipid neuromodulators that suppress neurotransmitter release, reduce postsynaptic excitability, activate astrocyte signaling, and control cellular respiration. Here, we describe canonical and emerging eCB signaling modes and aim to link adaptations in these signaling systems to pathological states. Adaptations in eCB signaling systems have been identified in a variety of biobehavioral and physiological process relevant to neuropsychiatric disease states including stress-related disorders, epilepsy, developmental disorders, obesity, and substance use disorders. These insights have enhanced our understanding of the pathophysiology of neurological and psychiatric disorders and are contributing to the ongoing development of eCB-targeting therapeutics. We suggest future studies aimed at illuminating how adaptations in canonical as well as emerging cellular and synaptic modes of eCB signaling contribute to disease pathophysiology or resilience could further advance these novel treatment approaches.

Abstract An innovative optimization‐simulation framework is applied to a case study of the Province of Quebec, Canada, to optimize the spatial distribution of green infrastructure (GI), the capacity and location of gray infrastructure, and the parameters specific to real‐time control (RTC) operating rules of a sewer system for reducing combined sewer overflows (CSOs) frequency and volume. GI, gray infrastructure, and RTC are applied either individually or in integration through eight optimization scenarios which are simulated over a nine‐year period of historical rainfall data. Among all scenarios, spatial optimization of GI with RTC leads to maximal CSO volume reduction (98%) and is the most cost‐effective option analyzed (70$/m3 of seasonal average CSO reduction compared to 140$/m3 for the scenario involving gray infrastructure alone). However, it requires a high GI implementation level and the CSO frequency under this scenario is sensitive to varying GI design parameters. The findings suggest that the best alternative for CSO control is the integration of the optimization of green and gray infrastructures with RTC as it still provides high CSO volume reduction (95%) and remains a cost‐effective solution (90$/m3 of CSO reduction), while providing robustness under cost and design uncertainties.

Abstract In this study, a new transverse post-tensioning (TPT) technique for box girder bridges is investigated, where TPT is applied at the top flange of the girder resulting in eliminating the in...

Abstract Coarse-grained deltas are often characterized by steep foreslopes (often more than 10°) that are traversed by delta-front channels. The channels thus erode into relatively steeply inclined bedding. In this context, the slopes flanking the channels can be steeper than the friction angle since they include a component of dip related to the delta-front slope as well as the channel-related erosion slope. In this study, part of the Busu River delta (Papua New Guinea) was imaged using a high-resolution multibeam bathymetry survey over an area where the angle of the slopes flanking the channels locally reaches 50°. A detailed analysis of the delta slope morphology has revealed an additional source of instability due to erosion within the main channels. In some places, erosion cuts into the channel flank forming a local knickpoint inclined in a direction approaching that of the bed dip. The cut can then initiate breaching or static liquefaction failure from that point up to the crest of the interfluve resulting in a V-shaped gully.

A highwall failure at an open pit coal mine in western Alberta, Canada occurred on 9 July 2017. A larger failure occurred on 5 August 2017. Radar monitoring successfully identified this second failure prior to the event. The initial assessment of the failure mechanism suggested toppling of steep bedding. The stratigraphy of the highwall consists of thinly to thickly bedded sedimentary strata dipping south at angles of about 65 to 70° into the wall. Neither failure resulted in injury or damage to vehicles or infrastructure, however, mining of the pit was suspended pending an assessment of the wall stability and the development of an appropriate reentry mining plan. Following the failure, two principal hazards remained. The eastern portion of the highwall slope was characterised by potential rockfall hazards beneath the failed slope area. The western portion of the slope was characterised by a larger rock mass which had not failed and presented a toppling hazard and potential debris runout hazard. Prior to re-entry into the pit, a re-entry strategy was developed to allow mining of the remaining coal to be completed safely. The overall stability of the slope geometry was evaluated using RS2™ finite element modelling methods, and re-entry strategies involving crest unloading to reduce the remaining failure hazard were assessed. A rockfall analysis for the eastern portion of the slope was completed using RocFall™, calibrated against observed conditions. A runout analysis of the western portion of the slope was completed using Dan-W™, calibrated against observed conditions. The results of the rockfall and runout analyses were used to design appropriately sized berms located at the toe of the slope. The re-entry plan incorporated the rockfall berm design, a rockfall runout setback distance for the berm, and crest unloading on two sequential single benches. The mitigation strategy was supplemented by radar monitoring. This paper summarises the analyses that were completed to develop a safe, fit-for-purpose re-entry strategy that has since been successfully implemented.

The Barrage des Quinze Dam is a concrete sluice dam consisting of 19 spillway sections, each of which is approximately 7.6 metres wide and 14.5 metres deep. Rehabilitation efforts being performed on the dam include demolition and improvement of the roadway and spillway sections and grouting to mitigate under-seepage. Multiple approaches to grouting were undertaken to mitigate seepage under the existing dam during the rehabilitation work. The initial grouting was completed with basic cement-water grouts followed by grouting with the addition of Celbex, a thixotropic agent. This approach was successful for all but 5 sluice bays of the dam. Final grouting for the final five sluice bays was planned as a multiple phase approach with low mobility and balanced stable grouts using sodium silicate for set control. The substantial high water flows (leakage) beneath the dam between the concrete/rock contact and within fractures in the upper rock formation created a challenging situation to create a cutoff. A grouting solution was developed that involved implementing several different grouting methods and materials including balanced high mobility grouts (HMG); low mobility grouts (LMG); polyurethane grout; and sodium silicate. This final program was completed in winter conditions requiring special equipment and techniques. The project was successfully completed through the winter months in northern Quebec Province using special measures to protect the work space and provide heating for grout materials for proper injection and cure. The work was completed within the required schedule to enable use of the dam gates to manage spring flows.

An investigation was undertaken in soil from the Canadian polar circle [Yellowknife (YELL), Iqaluit (IQA), and Cambridge Bay (CAM)]. Twenty four soil samples (YELL = 3, IQA = 15, CAM = 6) were collected with the depths of 0–20 cm below surface. Eighty major PCBs congeners were analyzed and twenty two PCBs were detected. Concentrations of PCBs in IQA were found to be the highest (0.11–1111 ng/g on dry weight basis), following in decreasing order: CAM (0.07–145 ng/g) and YELL (0.4–7.1 ng/g). Contamination profiles of PCB congeners were different between Iqaluit samples, while PCBs congener profiles were similar in Yellowknife and Cambridge Bay areas. The background sample sites were chosen to be representative of clean and undisturbed soils. The large difference in concentrations observed between dumpsites and background soil samples suggest PCB deposition into these dumpsites from materials discarded within. This is yet another evidence to show that previously pristine Polar Regions are increasingly getting contaminated through human activities. PCBs are excellent industrial markers in this forensic investigation.