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By Kamil Nuzha, Jianchao Li, Bashar S. Qubain

A 52-story high rise building in Philadelphia is constructed adjacent to a 3-story historic structure, supported on a rubble foundation at a depth of 2.4 m (8 ft) below grade. The high rise is supported on a mat foundation at a depth 36 ft below grade with an average service contact pressure of 670 kPa (14 ksf). Evidently, the existing foundation requires underpinning but extra care is necessary to safeguard the historic building. A detailed finite element analysis showed that the mat foundation would settle about 38 mm (1.5 in). Although such settlement would be acceptable for the high rise it would cause intolerable distress to the historic building by dragging down its underpinning. To minimize the settlement impact, an innovative micropile solution was implemented to safely transfer the underpinning load into the underlying mica schist bedrock and prevent the existing building from being overstressed by the mat foundation. The specifics of the micropile pile design and associated details are presented herein. The new building was completed almost two years ago and the adjacent historic building has been functioning well without any signs of distress.

Oct 31, 2023

By Mirza Shafiq Ibrahim, Martin Hudson, Rishabh Singhvi, Saiful Islam

The Landmark Apartment building is a 34-story high-rise constructed in West Los Angeles. The high-rise was constructed within a portion of the footprint of an existing parking structure with four subterranean levels. The foundations of the new high-rise were cast-in-place drilled hole (CIDH) piles in order to limit settlement of the new construction relative to the existing parking structure spread footing foundations. In order to construct within the parking structure, a gloryhole had to be cut in the parking structure at the location of the new high-rise footprint, necessitating temporary bracing of the parking structure basement walls. The temporary bracing had to be accomplished using both tie-back anchors and internal bracing (rakers) in order to provide lateral restraint for the basement wall. The internal bracing required its own set of foundations, including micropiles and tie-back anchors to laterally restrain the micropile caps. The foundation system for the new high-rise had to be split into two major pile caps on either side of the temporary micropile cap foundation for the bracing system, with the temporary micropile cap tie-back anchors threading between the permanent structure drilled shafts. In addition, groundwater was located just beneath the bottom-most slab of the parking structure, requiring dewatering of pile cap excavations. With high groundwater conditions, drilling mud was required to install the CIDH piles. These design challenges were accomplished successfully and meeting the requirements for foundation performance and seismic performance of the structure. The multiple challenges of temporary works also required careful coordination of dewatering, shoring installation, and foundation installation among the various disciplines.

Oct 31, 2023

By John Roxas, Rodrigo Fragachan, Alex Gossen, Jakub Szary

The Gilmore Place development is mixed-use transit-oriented development in Burnaby, British Columbia, Canada. The development replaces the underutilized space surrounding the existing Gilmore SkyTrain Station and overhead SkyTrain guideway that bisects the site with three support piers fully contained within the building footprint. The site includes six combined office and residential towers, including the tallest tower in British Columbia when constructed at 64 stories. Below grade development includes a phased temporary support of excavation. The first phase involves the excavation of a 14,200m2 pit up to depths of 30.5m below street grades removing about 42,475m3 of soil. Support of excavation included 1,229 secant piles and 2,689 strand anchors of high-capacity, achieving working loads of up to 1800kN. Each of the three SkyTrain piers are supported by a single 3.0m diameter caisson. To facilitate excavation below each caisson supported pier and encapsulate them by the base building structure, temporary support measures were developed. Bracing included sets of 22.0m long inclined 610mm diameter x19mm thick steel pipe raker braces connected at the base of each pier and three rows of jackable frames connected to the piers and temporary shoring walls. This shoring system is one of the most challenging shoring systems in Metro Vancouver as the original SkyTrain pier foundations had to be exposed. Secant piles were installed down to bedrock around the existing caissons utilizing a custom low headroom drill rig. A robust automated instrumentation program was established to monitor movements of the shoring wall and SkyTrain infrastructure in real time, and to provide immediate alerts to the design and construction team should movements exceed predetermined thresholds established by the design team. The monitoring program indicated movements of the guideway, station, and supporting piers were below the maximum tolerances during the excavation phase of construction and enabled the continued use of the transportation system without disruption or jeopardizing public safety.

Oct 31, 2023

By Seth Knihtila, Bryce Niekamp, Adam Running

The current home of the Seattle Kraken NHL team is the Climate Pledge Arena in Seattle, Washington. The renovation of the existing 1962 World’s Fair Pavilion transformed the aging and outdated facility into a modern 900,000 square ft., 17,000 seat arena with all modern amenities. Although the existing arena already extended below grade, it included minimal event and amenities space, and did not meet the current needs for a sports and entertainment venue. In order to transform the arena, the site was further excavated to about 60 ft. (18.3 m.) below grade in order to provide additional space and access. The challenge: the existing roof was to remain in place with the majority of the expansion occurring below grade. The existing roof was underpinned on a series of 67 drilled shafts installed with low headroom equipment. In addition, support of the new arena structure required deep foundation support consisting of 117 drilled shafts of varying diameter and depth within the excavation. The primary support of excavation system or shoring system selected was permanent soldier piles and lagging with permanent tiebacks. This installation of the shoring system and excavation had to be completed with the iconic concrete roof, weighing in at 22,000 tons, suspended in place on temporary steel support framing and drilled shafts. The support of excavation system consisted of four elements: the primary perimeter excavation, snorkels, pylon shoring, and the south buttress shoring and support, each of which had their own unique design and construction challenges. In the end, the construction team installed approximately 178,000 square feet of permanent shoring, including 500 soldier piles and 130,000 linear ft. of tiebacks. The performance of the drilled shaft installation was monitored by CSL testing. The performance of the shoring system was monitored by geotechnical instrumentation and performed as predicted in our analysis.

Oct 31, 2023

By Tae H. Lee, Tae-gyun Jung, Sangchul Bang, Guen-woo Park, Sungmin Kim

ADVACT Co., Ltd. of Korea designed, fabricated, and installed a meteorological tower on behalf of Korea South-East Power Co. Ltd. near Yeosu, Korea, in April, 2021. This tower was of its first kind in Korea, where the tower would gather meteorological data for a period of 19 months and then be retrieved, moved and installed at a new location for same data gathering purposes. The meteorological tower’s foundation utilized three-leg suction piles that are 28 m long and 4.12 MN in weight. The super-structure is 69 m high and 6.19 MN in weight with concrete fill. Both suction piles and the super-structure were fabricated and assembled on land and then transported as a single unit to the first site. All-in-one suction installation of the entire unit was completed in approximately 14 h. In November, 2022, the entire tower was retrieved, inspected, transported to the second site, and then installed successfully. This paper describes brief details of the design, construction, and installation of the tower supported on three-leg suction pile foundation. The design of the suction piles considered the conditions of both sites to ensure the stability of the tower when operational at both sites.

Oct 31, 2023

By Peter Sudkamp, Ariel Sarno, Andrew J. King

The design and installation of elliptical shafts for the City of Baltimore, Maryland DPW Contract SC-940, “Hydraulic Improvements to the High-Level Sewer Shed Collection System” (SC-940) will be discussed as a case study for elliptical shafts as an alternative to standard circular, rectangular, or square shafts. The project involved construction of 21 shafts varying from 6 meters (m) to 12 m (20 feet (ft) to 40 ft) in depth. Eighteen (18) of 21 shafts were constructed utilizing liner plate and ring beams including 15 elliptical shafts. Construction challenges included site condition difficulties, namely grouting of boulder cavities, keeping the correct orientation of the slender shaft elements, and minimizing impacts to the construction schedule from the added time necessary to stagger the liner plates, ring beams, and blocking. However, utilizing an elliptical shaft design allowed for property features to remain accessible, management of conflicting utilities within the excavation footprint, and reduced shoring and disposal cost. Ultimately, the decision to utilize elliptical shafts provided a cost saving over traditional shoring options.

Oct 31, 2023

By Paul Creswell, Hannah Davies

London City Airport’s only runway perches on a narrow finger of land close to the old city of London. Formally the central quay of the Royal Docks, the runway is encircled by redundant deep-water berths that were heavily bombed during World War II before its conversion to an airport in the late 1980’s. The owners’ need to increase capacity drove the addition of a parallel taxiway to the runway formed of a 20acre reinforced concrete deck supported by piles over the dock. This paper presents a number of the challenges experienced during the installation of over 1000 piles into the existing dock using cased rotary bored techniques under polymer support fluid for the expansion of the airport. The complex nature of London geology, including features which have not been seen in this detail before, across a site that extended over 1000m in length, required significant time and resources to determine the contributing factors to a number of piles collapses. The most significant causes were locally instability in the Thanet Sand Formation due to faulting and loss of dilatancy associated with post deposition shearing as well as a disturbed ground and groundwater regime due to puncturing of the puddle clay dock liner during UXO clearances. This paper will discuss these challenges encountered and how they were overcome.

Oct 31, 2023

By Joe Smith, Roberto Rodriguez, Francisco Ciruela-Ochoa

Drilled-In Displacement Piles (DDPs) present some advantages over other deep foundation solutions making them suitable for challenging conditions encountered at John F. Kennedy (JFK) International Airport Headhouse Expansion Project. For one, elevated railway tracks required the installation to occur with as little as 12 ft of clearance. Secondly, their ease of installation and overall material requirements deemed them more efficient than traditional micropiles from a schedule and cost point of view. Lastly, the low vibrations induced by DDPs to the surrounding sensitive structures were crucial for an operational airport. All combined contributed to the final decision of recommending this foundation system for the Project. This paper documents the use of DDPs for the Project and documents the design and specification process along with load testing program results and observations made during the construction of production elements from a case history perspective.

Oct 31, 2023

By Takefumi Takuma, Masashi Nagano, Yuichi Matsuoka

Pressed-in sheet pile bulkheads were built as part of an environmental cleanup known as the Gowanus Canal Environmental Remediation Project in Brooklyn, New York. These pressed-in piles minimized the potential settlement and displacement along the existing canal frontage and nearby buildings. The sheet piles were fully interlocked to be impervious, which was verified with non-declutching sensors. The soil conditions consisted of a top layer of contaminated soft sediment with debris and underlying sand and gravel layers with equivalent N-values ranging from 20 to 100. Coated Z-shaped sheet piles in lengths of up to 70 feet were installed.

Oct 31, 2023

By Weiran Zuo, Wanzhong Yin, Jin Yao, Keqiang Chen, Qiuyue Sheng, Liu Liu

It is important to investigate the liberation properties of gangue minerals and establish liberation models for low-grade iron ores to reject gangue early. In this study, three types of iron ores from different iron deposits were ground to different particle size distributions by locked-cycle grinding and batch grinding. The liberation distribution of quartz, the most dominant gangue mineral among the three types of iron ores, was tested by Mineral Liberation Analyzer (MLA). Afterward, the liberation distribution of the three types of quartz was fitted using the beta distribution function, and their shape parameters were related to particle sizes to develop the liberation model. MLA test results showed that the liberation distribution of quartz with different grinding methods was basically the same. The developed liberation model predicted the liberation distribution of quartz in low-grade iron ores from different iron deposits well, and its coefficient of determination (R2) was between 0.90 and 0.98. This study deepens the understanding of the liberation rules of quartz in low-grade iron ores from different iron deposits, and on this basis, a more efficient liberation model based on the beta distribution function is developed.

Oct 18, 2023

By A. Yadav, B. Behera, G. S. P. Singh

The size of chain pillars in the Indian geo-mining conditions is primarily decided in accordance with the regulatory provisions. These provisions are of little help for deep longwall workings, exceeding the cover depth of 360 m. Furthermore, these provisions are primarily meant to support pillars in bord and pillar workings. They may not be suitable for the chain pillars owing to a significant difference in layouts and functional requirements. Hence, it is imperative to develop a method to evaluate the stability of the chain pillar considering the complex loading and geo-mining conditions. To this end, a machine learning-based model was developed in this study to assess the stability of the chain pillars under high depth of cover considering the field-representative conditions. The data for this work was generated by conducting a parametric study using a field-validated numerical model. The strength and deformability parameters of the caved, fractured, and continuous deformation zones were established by calibrating the numerical model outcomes against the site-specific field observations. The developed ML model was used to evaluate the influence of pillar width, pillar height, cover depth, abutment angle, face length, coal strength, moduli ratio of the roof and floor strata to the coal seam, and the elastic modulus and unit weight of the overburden on the chain pillar stability. An interesting finding of this study showed that the factor of safety of the chain pillar increased with the increasing abutment angle, which may be indicative of the confining effect of the abutment angle on the pillar. Eventually, the ML model was verified by comparing its outcomes with the calibrated numerical model for a typical longwall working from Indian geo-mining conditions.

Oct 18, 2023

By Deniz Akbay

The strength of rocks and soil is a crucial design parameter in engineering projects, and it can be determined through various test methods such as uniaxial compressive strength, tensile strength, and shear strength. The point load index test is a popular indirect test method for predicting the uniaxial compressive strength of rocks. However, the reliability of the point load index’s estimation of uniaxial compressive strength of rocks is questioned due to the wide range of coefficients that are used to predict uniaxial compressive strength of rocks using point load index values. Factors such as the shape and type of rock specimen, practitioner, and test apparatus used can affect the accuracy of the point load index test. This study investigated the effect of four different specimen shapes used in point load index test (diametral, axial, block, and irregular lump tests) in predicting the uniaxial compressive strength. The rock samples were tested using four test procedures which are called diametral, axial, block, and irregular lump tests. The results showed that the irregular lump test was the most accurate in predicting uniaxial compressive strength, with the highest correlation coefficients and lowest mean absolute percentage errors. The point load index test can be used as a reliable predictor of uniaxial compressive strength of rocks when the irregular lump test is preferred.

Oct 18, 2023

By Hao Zhang, Mi Zhou, Lichun Jiang, Xihong Zhang

This study investigates the roof stability of underground limestone mining in the presence of stratified joints during the excavation process. An analytical solution is derived to predict the stresses and deformation of underground tunnel structures, with the structure simplified as a double-hinge arch. The accuracy of the analytical model is validated through comparison with finite element modeling results. A parametric study is then conducted to assess the influence of different design parameters on the optimization of tunnel stability during excavation. The results indicate that the best stability of the tunnel can be achieved in engineering practices when the applied load (q) is 5 MPa and the joint inclination angle (θ) is 45°, with the roof span and thickness set at either 12 m and 8 m or 15 m and 10 m. These findings provide valuable design guidance for underground limestone mines with stratified joints.

Oct 18, 2023

By Brendan Donnelly, Lasitha Piyathilaka, Jung‑Hoon Sul, Sanghyun Jeong, Benjamin Probyn

Premature failure of armoured face conveyor (AFC) chains due to corrosion is a significant proportion of the unplanned downtime experienced on longwall equipment. The AFC chains are constantly in contact with water and wet coal. The premature failure issue of AFC chains has become more prominent since the introduction of longwall top-coal caving with its additional AFC. Reverse osmosis (RO) is a popular water treatment method for reducing salinity and dissolved solids, but its impact on the corrosion of the AFC chains is unclear. This study has been commissioned to investigate the direct effects of RO water on the corrosion of AFC chains. An immersion test was carried out using AFC chain steel submerged in two water samples: untreated dam water and treated water from an RO treatment plant. Elemental analysis was conducted for both water samples, and four corrosion indices were measured for both water samples. The RO water more vigorously dissolves calcium carbonate scales leading to increased corrosion of the AFC chains although the dam water has much higher levels of calcium, chloride, sulphate, sodium, and magnesium. Bicarbonate ions are the main alkaline factor of water that provides the buffering capacity to acids. Decreased alkalinity without balancing other ions in water causes high corrosivity and decreased scaling tendencies.

Oct 16, 2023

By M. Frenzel, D. Ebert, K. Bachmann, A. D. Renno, R. Möckel, J. Gutzmer, J. Krause

With the increasing demand for metalliferous and mineral raw materials and the consequent depletion of the global natural resource base, the possible utilization of secondary raw material sources is receiving more and more attention. In the present study, we present results from a detailed vanadium deportment study of three basic oxygen furnace slag (BOS) samples known to containing elevated bulk concentrations of vanadium. Complementary analytical methods that were used to quantify the abundance and composition of V-containing phases include SEM-based automated mineralogy, X-ray fluorescence analysis, and X-ray powder diffraction as well as electron probe microanalysis. The vanadium deportment was quantified using Monte-Carlo simulations of the data obtained from automated mineralogy and electron microprobe analysis. The total V concentrations identified by XRF are between 1.7 and 2.2 wt.% V. The most important hosts of vanadium are larnite-, brownmillerite- and portlandite-solid solutions. In two samples Ca carbonates also significantly contribute to the V deportment, while wuestite, lime, and native iron do not contribute significantly to the vanadium deportment. A thorough consistency check identifies considerable uncertainties in the density of the V-bearing phases as the most likely reason to explain remaining discrepancies between measured and calculated V values.

Oct 14, 2023

By Robert Kimutis, Heather Dougherty, Eric Watkins

Gas wells have often intersected mining resources, but unconventional shale well drilling has more recently challenged mines to balance the risk of interaction due to higher pressures and larger quantities of gas. Full extraction mining, such as the longwall method, induces ground movement that may influence the casings if wells are drilled within the mining area. The possibility of a casing shear would lead to the risk of unplanned gas migration into the mine. This has the potential to quickly overcome the ventilation system and reach the explosive range which, if ignited, can have catastrophic consequences on the health and safety of underground workers. The utilization of network software to model mine ventilation is a common practice in the mining industry as a predictive tool for planning and monitoring and can assist with a well breach scenario over a large mining area. This work focuses on a well breach in between two longwall panels after second panel mining with gas entering primarily through the gobs of the adjacent longwall panels. Applying the network software Ventsim, a gob zone and ventilation network were created to better understand the distribution of gas within the mine and the limitations and effectiveness of a ventilation system. The model shows both a transient flow simulation and steady state concentrations throughout the mine ventilation system. Using a standard Pittsburgh coal seam longwall ventilation scheme, we find that the system can dilute a significant inflow of up to 700 cfm of methane.

Oct 12, 2023

By Kasimcan Koruk, Julian M. Ortiz

Building a geological model is important in resource estimation, as it defines the extent of domains for estimation. Geological models are built by assigning a domain to the samples, based on logging of different features related to lithology, alteration, and mineralization. Then, the extent of these domains is determined using geometric or geostatistical tools. However, these models should account for uncertainty, since the actual extent of these domains is not known and must be extrapolated from the labelled samples. With the availability of geochemical datasets and machine learning techniques, employing multiple variables to build resource models should be considered. This article proposes a two-step machine learning approach with an ensemble implementation to define geological domains and their uncertainties. First, an unsupervised binary clustering method labels the geochemical samples into two domains. These labelled samples are used to inform a geological domain model built by support vector classification. This application is repeated with subsets of variables and subsets of samples, leading to an ensemble learning method. Weak models are produced with each subset of samples and variables, and combined to devise a stronger learner. The final model accounts for uncertainties thanks to the ensemble implementation. The proposed workflow is demonstrated on a dataset from a porphyry copper deposit, applied hierarchically to define four domains. Performance is comparable with traditional methods, but provides the advantage of allowing domain knowledge in the selection of the variables, and generates domain boundaries that can be controlled in terms of their continuity and smoothness.

Oct 11, 2023

By D. Odendaal, S. Bharat, R. D. Cromarty

The aim of this investigation was to determine the effect of high-temperature heat treatment on the electrical resistivity of charcoal. Samples of two different wood types (eucalyptus and black wattle) were pyrolised in a retort at a temperature of 700°C and the resulting charcoals heat-treated in an induction furnace at temperatures from 800°C to 1800°C and residence times from 60 to 120 minutes. After cooling, the resistivities of the samples were measured at room temperature using the four-point probe technique. It was found that as the heat treatment temperature increased the electrical resistivity of the charcoal decreased, approaching an asymptotic value at higher temperatures. Longer residence times decreased the resistivity, but this effect was not pronounced.

Oct 3, 2023

By D. Stone, M. Le Roux, Q. P. Campbell, M. Fofana

Float-and-sink analysis is widely used in the coal industry to obtain washability data, yielding important information about beneficiation potential and performance. This method is associated with health and environmental problems, and research into alternative densimetric methods is important. The RhoVol is a new technology developed by De Beers Group Technology South Africa (DebTech) for the image-based generation of densimetric data from ores. The analysis is done on a per-particle basis, within a size range of +3 mm –8 mm. In this paper we compare the established methods used for the float-and-sink analysis of coal with a new method using RhoVol. The aim of the study was to determine the validity of the information obtained from the RhoVol analyser by performing comparative densimetric analysis on three different coal samples. The results showed that the RhoVol method was more rapid, safe, and precise, but tended to consistently underestimate the density of the coal sample, probably due to varying coal porosity.

Oct 3, 2023

By A. K. Raji, M. O. Ojumu

Robotic subsea dredging crawlers are dynamically and remotely controlled vehicles that are used for deep sea mining and recovery operations. These exploration machines are released from a mother ship and move around on the ocean floor using tracks. Current ocean crawlers such as the MK3 ROST are hydraulically powered. In this paper we develop a scaled-down model for simulating and performing static loading analysis of an electrically powered robotic subsea dredging crawler (EPRSDC). The modeling, simulation, and analysis were carried out using modelling software from Solidworks. The structural frame was assembled using the Tetrix max robotics kit. The kit’s structural components were produced from 1050 aircraft-grade aluminum. The results were used in optimizing and for considering other materials, and the to identify specific areas to be reinforced in future crawler designs.

Oct 3, 2023