Underground Vault Research Articles

Restoring Predevelopment Hydrology with Smart Stormwater Controls in Aiken, South Carolina

For decades, large quantities of stormwater runoff from the City of Aiken flowed at destructive velocities (exceeding 5 ft/s) into the Sand River, deeply eroding the channel in the downstream Hitchcock Woods. From 1990 to 2015, the City of Aiken commissioned several consultants to produce over a dozen studies to investigate viable solutions for the destructive erosion. Upon the recommendation from a collaborative Stormwater Task Force, the City of Aiken approved a stormwater implementation plan in 2018 which recommended 20 capital improvement projects sized to capture 58 ac-ft of stormwater in order to restore the river’s predevelopment hydrology, with a goal of reducing stormwater velocities in the Sand River to reflect design considerations in the National Engineering Handbook (between 2.0 ft/s for fine sand channels and 4.0 ft/s for coarse sand channels). In November 2023, the City of Aiken completed construction on two underground detention vaults with a total storage volume of 25 ac-ft. These vaults were designed to capture stormwater runoff before it enters Hitchcock Woods and infiltrate as much stormwater runoff as possible; any additional stormwater will be released at a reduced flow rate compared to existing conditions. The 10-year, 24-hour storm event was selected to size the vaults because it was an achievable metric given numerous constraints such as available land, impacts to existing infrastructure and environmental resources, and available funding. The 10-year event also corresponded to typical stormwater requirements for new development. The vaults utilized the largest height, 15 feet, available for precast underground storage vaults in the marketplace. In addition to providing stormwater management below ground, a new public park was constructed on top of the buried vaults to be used as a gateway between the Hitchcock Woods and the City of Aiken.

Multiscale Characterization of E-Glass/Epoxy Composite Exposed to Extreme Environmental Conditions

Fiber-reinforced polymer matrix composites continue to attract scientific and industrial interest since they offer superior strength-, stiffness-, and toughness-to-weight ratios. The research herein characterizes two sets of E-Glass/Epoxy composite skins: stressed and unstressed. The stressed samples were previously installed in an underground power distribution vault and were exposed to fire while the unstressed composite skins were newly fabricated and never-deployed samples. The mechanical, morphological, and elemental composition of the samples were methodically studied using a dynamic mechanical analyzer, a scanning electron microscope (SEM), and an x-ray diffractometer, respectively. Sandwich composite panels consisting of E-glass/Epoxy skin and balsa wood core were originally received, and the balsa wood was removed before any further investigations. Skin-only specimens with dimensions of ~12.5 mm wide, ~70 mm long, and ~6 mm thick were tested in a Dynamic Mechanical Analyzer in a dual-cantilever beam configuration at 5 Hz and 10 Hz from room temperature to 210 °C. Micrographic analysis using the SEM indicated a slight change in morphology due to the fire event but confirmed the effectiveness of the fire-retardant agents in quickly suppressing the fire. Accompanying Fourier transform infrared and energy dispersive X-ray spectroscopy studies corroborated the mechanical and morphological results. Finally, X-ray diffraction showed that the fire event consumed the surface level fire-retardant and the structural attributes of the E-Glass/Epoxy remained mainly intact. The results suggest the panels can continue field deployment, even after short fire incident.

Application of a combined precast and in-situ-cast construction method for large-span underground vaults

Exploitation of large underground space calls for innovative structures and construction methods. In this paper, a combined precast and in-situ-cast method for construction of large-span underground vaults is proposed. It was applied to an engineering example in the form of the vault of the Wuzhong Road Metro Station in Shanghai. This vault consists of 56 elements. Construction of an element involves the following steps. Firstly, upper ribbed arch segments are precast in a factory. After hardening, they are transported to the site and then assembled to three-hinged arches. The latter serve as a permanent formwork. Then, steel cages are made, followed by in-situ casting of concrete. As the concrete hardens, an integral arch, representing an element of the vault, is obtained. It carries the dead load of the covering soil and the overload on top of it. Structural analysis of this example is based on transfer relations, representing analytical solutions of the linear theory of slender circular arches. From the viewpoint of engineering practice and computational analysis, the advantages of the combined precast and in-situ-cast method over the in-situ-cast method are as follows: (i) the construction period is shortened by 50%, (ii) a fair-faced concrete surface of the vault is produced, rendering decoration work superfluous, and (iii) the maximum bending moment of an element of the studied vault is reduced by 40%.

Creep analysis of E‐glass/vinyl‐ester laminated composites for underground vault structures

AbstractCreep is eminent in fiber reinforced polymer matrix composite materials given the susceptibility of polymers to constant loading. The response of polymer matrix composites used in retrofitting vital infrastructure to long‐term flexural loadings is investigated to elucidate the effect of creep. The experimental approach consisted of first establishing a benchmark of the quasi‐statically tested flexural properties. A fresh set of samples were then flexural tested for an extended period. Failure was determined to be strain‐driven in both quasi‐static and long‐term testing conditions. The mechanical properties were found to be insensitive to the strain rate (in the low strain regime), while being mildly sensitive to creep loading. The flexural response also showed dependence on the historic creep loading. The creep strain was successfully fitted into Baily‐Norton power law, which allowed for forecasting the creep life based on the critical strain failure criteria. The overall results explicate the interrelation between long‐term loading and fidelity of composites‐based infrastructures.

Application of settlement monitoring of underground excavation station vault based on inverted rule method

In the urban rail transit engineering, there is a great risk in the underground excavation construction of the existing railway station, and the monitoring accuracy of the underground excavation construction is very high. Taking station A of a project as the research object, combined with the construction situation and the structural characteristics of the station, this paper discusses the influencing factors of the vault settlement monitoring in the undercut section of the existing metro station, and formulates the vault settlement monitoring scheme in the undercut section. The feasibility of the method is verified by setting up two sets of independent elevation system and adopting the method of setting up a single station to measure the inverted ruler, and then the error control measures are given. The results show that the method can meet the accuracy requirements of the vault settlement monitoring in the underground excavation section of metro station. This method can provide some technical reference for the similar monitoring project of underground subway station.

Structural analysis of earth construction’s vaults: Case of underground tombs of Chogha Zanbil

The 3300-year-old Chogha Zanbil is the largest and best-preserved five levelled pyramidal earth ziggurat outside Mesopotamia, which was inscribed on UNESCO’s World Heritage List. Underground tombs of Chogha Zanbil are accepted as outstanding instances in Iran and consist of vaults, which are built with special methods by Elamite architects. In this context, the main purpose of this paper is to contribute to sustain the outstanding universal value of the Chogha Zanbil. For that purpose, this paper puts forward a structural analyse of the vaults of five Chogha Zanbil underground tombs, which were built inside the ground by brick, lime mortar, plaster and bitumen materials. Data for underground tombs and vaults were collected upon field observations and literature study. SAP software was used to determine the way the forces are transmitted through the vaults, the conditions of bending moments, the shear forces. As a result, it has been observed that the bending in the vaults turns into pressure force that is perfectly resisted by bricks. In conclusion, it was ascertained that the vaults of the Chogha Zanbil underground tombs were built with the right techniques at that time, so that the vaults still have solid behaviour after thousands of years and remained completely healthy to this day.

Structural analysis of earth construction’s vaults: Case of underground tombs of Chogha Zanbil

The 3300-year-old Chogha Zanbil is the largest and best-preserved five levelled pyramidal earth ziggurat outside Mesopotamia, which was inscribed on UNESCO’s World Heritage List. Underground tombs of Chogha Zanbil are accepted as outstanding instances in Iran and consist of vaults, which are built with special methods by Elamite architects. In this context, the main purpose of this paper is to contribute to sustain the outstanding universal value of the Chogha Zanbil. For that purpose, this paper puts forward a structural analyse of the vaults of five Chogha Zanbil underground tombs, which were built inside the ground by brick, lime mortar, plaster and bitumen materials. Data for underground tombs and vaults were collected upon field observations and literature study. Finite-element methodology was used for structural analysis and SAP software was utilized to determine the way the forces are transmitted through the vaults, the conditions of bending moments, the shear forces. As a result, it has been observed that the bending in the vaults turns into pressure force that is perfectly resisted by bricks. In conclusion, it was ascertained that the vaults of the Chogha Zanbil underground tombs were built with the right techniques at that time, so that the vaults still have solid behaviour after thousands of years and remained completely healthy to this day.

Understanding cementitious backfill interactions with groundwater components

Many concepts for the disposal of intermediate-level radioactive waste specify the emplacement of waste packages in underground vaults backfilled with cementitious material. The cementitious backfill performs a number of functions including maintaining alkaline conditions and providing a high sorption capacity for radionuclides. In the UK, the Nirex Reference Vault Backfill (NRVB) has been developed for such a role. To improve our understanding of its long-term performance, a detailed programme was undertaken to investigate interactions of the NRVB with selected groundwater components using sodium sulphate and magnesium chloride solutions.Experiments using the selected solutions were performed under conditions of constant flow, over timescales of up to 860 days. Elemental composition and pH of the egressing eluent were determined throughout the experiments. At the end of the experiments, detailed solid analyses were performed on samples from various locations in the NRVB using a wide range of techniques. In the sodium sulphate experiment, sulphate attack resulted in the formation of ettringite, thaumasite and gypsum. For the magnesium chloride case, the results were dependent on the concentration of the magnesium in the ingressing solution. At higher concentration, precipitation of brucite at the upstream surface of the NRVB led to clogging and termination of the experiment after about one month. At lower concentration, no such clogging occurred, despite almost all the ingressing magnesium being removed by the NRVB over timescales of more than two years. For both systems, high pH values of the eluent were maintained over the full periods studied; for the sodium sulphate experiment the final pH was 12.7 (after 180 sample volumes) and for the low concentration magnesium chloride case pH 11.5 (after 749 sample volumes).A “top-down” modelling approach was applied to interpret the results, involving solution equilibration with the NRVB represented by a simple set of mineral phases. Further processes were modelled only where they improved the overall fits. The resulting models were considered to be simple while maintaining consistency with the major features of the experimental data sets. This has helped to provide mechanistic interpretations of the evolution of NRVB, based on relatively simple sets of secondary mineral phases, early kinetic control of mineral dissolution and diffusion-restricted release of portlandite at longer times.

The Problem of Lighting in Underground Domes, Vaults, and Tunnel-Like Structures of Antiquity; An Application to the Sustainability of Prominent Asian Heritage (India, Korea, China)

Lighting in heritage is complex because of the forms intervening in it. The historical evolution of cultures has not been analytical and therefore, the shapes involved differ greatly from the cuboids typically found in 21st century architecture. As a vector, light inevitably attaches to surface sources. In this research, we focused on 3D curved geometries. Following a different trail to radiative transfer by virtue of detailed knowledge of the spatiality of volumes, we present new expressions, previously undefined in the literature, that are derived from a combination of surfaces that we have found in many archaeological sites around Asia. In the discussion, we start from the particularities of spherical surfaces where a normal vector has to pass through the center. By means of easy calculations, we deducted innovative laws. These in turn, allowed us to formulate several new expressions for configuration factors based on the adroit use of spherical fragments. The method easily extends to organic shapes that are often contained in the sustainable architecture of the past. The method finishes with suitable algorithms to assess the reflections in such curved forms. Finally, we implemented the results in our creative software. In this way, we enhanced the sustainable paradigms for heritage structures in Asia that we present as a conclusion of the article.

Effect of elevated operating temperature on the dynamic mechanical performance of E-glass/epoxy composite

The construction industry has seen a proliferation of continuous and discontinuous fiber-reinforced polymer composites due to their high strength-to-weight and stiffness-to-weight ratios while being resilience to harsh environmental and operating conditions. This paper reports a comparative experimental investigation of field-deployed E-glass/Epoxy composite panels with those freshly manufactured to elucidate the effect of deployment conditions on the performance of these panels. Samples extracted from underground vault after power-line explosion due to arcing fault were examined using optical and atomic force microscopes to assess the extent of the damage. The samples were also characterized using a dynamic mechanical analyzer to explain the change in the properties post-explosion quantitatively. Microscopy investigations show no significant change in morphology or topography of the panels as well as the absence of failure modes such as delamination, fiber-failure or core-failure. Nonetheless, surface contaminations due to service conditions were found to exaggerate the surface burn marks despite the fire retardation properties of the composite panels. The dynamic mechanical properties of the panels were found to change as a function of temperature and loading frequency slightly. A shift in transition temperatures (Tβ and Tg) was found to be within a few degrees Celsius. The storage modulus was reduced by 21%, while the overall complex modulus remained relatively constant when comparing fresh and field-deployed samples. A frequency and temperature dependent model was used to fit the dynamic data and found to provide insights into the microstructure evolution of the polymer matrix.

A new efficient error control algorithm for wireless sensor networks in smart grid

Error detection and correction is an important issue in the design and maintenance of a smart grid communication network to provide reliable communication between sender and receiver. Various error-control coding techniques are employed to reduce bit error rates (BER) in wireless sensor networks (WSNs). The performance of these techniques is also compared and evaluated to find the most suitable technique for WSNs. This is the first study to compare the most efficient coding techniques in the smart grid environment, and it suggests a new error correction algorithm based on this comparison result. Therefore, this article first examines and compares two forward error control (FEC) coding techniques such as Bose-Chaudhuri-Hochquenghem code (BCH) and Reed Solomon code (RS) with various modulation methods including frequency shift keying (FSK), offset quadrature phase-shift keying (OQPSK), and differential phase shift keying (DPSK) in a 500 kV line-of-sight (LoS) substation smart grid environment. Second, as a result of this comparison, a new adaptive error control (AEC) algorithm is proposed. Adaptive error control adaptively changes error correction code (ECC) based on the channel behavior that is observed through the packet error rate (PER) in the recent previous transmissions. The link-quality-aware capacitated minimum hop spanning tree (LQ-CMST) algorithm and the multi-channel scheduling algorithm are used for data transmission over the log-normal channel. Therefore, the performance of compared coding techniques and AEC are also evaluated when multiple channels are used during transmission. Further, AEC is compared with static RS and without-FEC methods based on performance metrics such as the throughput, BER, and delay in different smart grid environments, e.g., 500 kV Substation (LoS), underground network transformer vaults (UTV) (LoS), and main power control room (MPR) (LoS). Our simulation results indicate that the proposed AEC algorithm achieves better performances than all those techniques.

MONSTER FROM THE VAULT: A NEW FINDING OF ONE OF THE LARGEST EUROPEAN LEECH TROCHETA HASKONIS GROSSER, 2000 FROM BOSNIA AND HERZEGOVINA

One extremely large leech specimen of Trocheta haskonis Grosser, 2000, reaching almost 190 mm when contracted, was collected in an underground vault constructed out of concrete in the village Prijakovci in the north-western part of Bosnia and Herzegovina. This finding indicates that one of the largest European leech species can colonize also small artificial habitats like a utility vaults, possible also subway tunnels and storm drains.

Evaluating Performance of Wireless Sensor Network in Realistic Smart Grid Environment

Wireless Sensor Networks (WSNs) is a strong candidate for smart grid applications, such as advanced metering infrastructure, demand response management, dynamic pricing, load control, electricity fraud detection, fault diagnostics, substation monitoring and control as well as automation of various elements of the power grid. The realization of these applications directly depends on efficiency of communication facilities among power grid elements. However, the harsh power grid environmental conditions with obstacles, noise, interference, and fading pose great challenges to reliability of these facilities to monitor and control the power grid. The purpose of this paper is to evaluate performance of WSNs in different power grid environments such as 500 kv substations, main power control room, and underground network transformer vaults. The power grid environments are modeled using a log-normal shadowing path loss model channel with realistic parameters. The network is simulated and performance is evaluated using packet delivery ratio, communication delay, and energy consumption. The simulation results have revealed that different environments have considerable impacts on performance of WSNs which make it suitable for most applications that need low data rate with low reliability requirements.

Performance Analysis of ZigBee in Beacon Enabled and Beacon-less Network for Smart Grid Environments

Background: Wireless sensor networks play very important role in the realization of Smart Grids having low cost and multi-functional sensor nodes to monitor the critical parameters of smart grid components. Its various applications are home automation, real time pricing, power outages, load control and security monitoring. It contains different harsh environments like 500 kV outdoor substation, main power control room and underground transformer vaults which are very difficult to access and monitor for a human being during an operational power grid. The communication in it constitutes of different type of traffic distinguished by exclusive attributes in terms of the data profile and latency requirement. Keywords: Wireless sensor network (WSN), IEEE 802.15.4, beacon, ZigBee, smart grid, QualNet 6.1.

Repeatability of Testing a Small Broadband Sensor in the Albuquerque Seismological Laboratory Underground Vault

Abstract Variability in seismic instrumentation performance plays a fundamental role in our ability to carry out experiments in observational seismology. Many such experiments rely on the assumed performance of various seismic sensors as well as on methods to isolate the sensors from nonseismic noise sources. We look at the repeatability of estimating the self‐noise, midband sensitivity, and the relative orientation by comparing three collocated Nanometrics Trillium Compact sensors. To estimate the repeatability, we conduct a total of 15 trials in which one sensor is repeatedly reinstalled, alongside two undisturbed sensors. We find that we are able to estimate the midband sensitivity with an error of no greater than 0.04% with a 99th percentile confidence, assuming a standard normal distribution. We also find that we are able to estimate mean sensor self‐noise to within ±5.6 dB with a 99th percentile confidence in the 30–100‐s‐period band. Finally, we find our relative orientation errors have a mean difference in orientation of 0.0171° from the reference, but our trials have a standard deviation of 0.78°. Electronic Supplement: Table of dates of the trials used as well as Q – Q plots for the statistics collected from the sensor tests.

Characterizing Local Variability in Long‐Period Horizontal Tilt Noise

ABSTRACT Horizontal seismic data are dominated by atmospherically induced tilt noise at long periods (i.e., 30 s and greater). Tilt noise limits our ability to use horizontal data for sensitive seismological studies such as observing free earth modes. To better understand the local spatial variability of long‐period horizontal noise, we observe horizontal noise during quiet time periods in the Albuquerque Seismological Laboratory (ASL) underground vault using four small‐aperture array configurations. Each array comprises eight Streckeisen STS‐2 broadband seismometers. We analyze the spectral content of the data using power spectral density and magnitude‐squared coherence ( γ 2 ‐coherence). Our results show a high degree of spatial variability and frequency dependence in the long‐period horizontal wavefield. The variable nature of long‐period horizontal noise in the ASL vault suggests that it might be highly local in nature and not easily characterized by simple physical models when overall noise levels are low, making it difficult to identify locations in the vault with lower horizontal noise. This variability could be limiting our ability to apply coherence analysis for estimating horizontal sensor self‐noise and could also complicate various indirect methods for removing long‐period horizontal noise (e.g., collocated rotational sensor or microbarograph).

Performance Analysis of IEEE 802.15.4 in Different NLOS Environments of Smart Grids

Background: In smart grids mainly there are two types of communications based on the paths travelled by the received signals. These are line of sight (LOS) communication and non-line of sight (NLOS) communication. These communication models are formed because of different harsh environments like 500 kV outdoor substations, main power control room and underground transformer vaults which are very difficult to access and monitor for a human being during an operational power grid. In the recent research, the network lifetime has been evaluated with respect to the arrival rate, distance and duty cycle for LOS and NLOS communication. Methods:The systematic analysis is performed to characterize the aptness of the cluster tree topology of ZigBee based wireless sensor networks in the monitoring of non-line of sight regions having different shadowing channel properties in the smart grids. Results: The performance is evaluated by thoroughly analyzing the average end-to-end delay with respect to the packet interval, throughput, energy consumption, packet reception rate and network lifetime with respect to the packet size. The simulations are performed on QualNet 6.1 simulator. The objective of this work is to determine the influence of packet interval, packet size and different NLOS environments on the performance of ZigBee based wireless sensor network deployed in smart grids and to give prominence to this field for further exploration. Conclusion: The simulation results illustrate that huge errors in packet reception and variable link capacity in complex environments of the smart grid spectrum gives rise to many challenges in the reliability of ZigBee based wireless communications in smart grids. The design and implementation of efficient algorithms and protocols to reduce the collisions and interference can be considered for the future work. Keywords: Smart grid, Wireless sensor network, Shadowing parameters, Cluster tree topology, QualNet 6.1.

Noise Reduction in Long‐Period Seismograms by Way of Array Summing

Long‐period (>100 s period) seismic data can often be dominated by instrumental noise as well as local site noise. When multiple collocated sensors are installed at a single site, it is possible to improve the overall station noise levels by applying stacking methods to their traces. We look at the noise reduction in long‐period seismic data by applying the time–frequency phase‐weighted stacking method of Schimmel and Gallart (2007) as well as the phase‐weighted stacking (PWS) method of Schimmel and Paulssen (1997) to four collocated broadband sensors installed in the quiet Albuquerque Seismological Laboratory underground vault. We show that such stacking methods can improve vertical noise levels by as much as 10 dB over the mean background noise levels at 400 s period, suggesting that greater improvements could be achieved with an array involving multiple sensors. We also apply this method to reduce local incoherent noise on horizontal seismic records of the 2 March 2016 M w 7.8 Sumatra earthquake, where the incoherent noise levels at very long periods are similar in amplitude to the earthquake signal. To maximize the coherency, we apply the PWS method to horizontal data where relative azimuths between collocated sensors are estimated and compared with a simpler linear stack with no azimuthal rotation. Such methods could help reduce noise levels at various seismic stations where multiple high‐quality sensors have been deployed. Such small arrays may also provide a solution to improving long‐period noise levels at Global Seismographic Network stations.

The effect of ore roasting on arsenic oxidation state and solid phase speciation in gold mine tailings

Metallurgical pretreatment of As-bearing ores involves oxidation of sulphides (most often As-bearing pyrite, arsenopyrite or enargite) resulting in complex oxidized As-bearing products. We have evaluated roasting pretreatment of arsenic-bearing ores in a broad context and related this to the specific operations at the Giant mine, Yellowknife, NWT, Canada, which roasted arsenopyrite (FeAsS)-rich gold ore concentrates during 50 years of operations. A large portion of the As was collected and stored in underground vaults as As 2 O 3 dust; however, some of the As was also released with tailings which contain concentrations between 1000 to 5000 ppm. Powder X-ray diffraction (XRD) and sequential extractions have been completed on samples of mill products and various ages of tailings at the Giant mine. These data along with petrographic and synchrotron μXRD and μX-ray absorption near-edge spectroscopy (μXANES) indicate that the largely oxidized roaster products (calcine) and electrostatic precipitator (ESP) dust host most of the As in the tailings with a lesser component of sulphide arsenic. The fine-grained nature of these oxidized products has led to hydraulic sorting within the tailings impounds and dispersal to downstream creek and lake sediments.

Laboratory and Field Evaluations of Mosquiron® 0.12CRD, a New Formulation of Novaluron, Against Culex Mosquitoes.

Laboratory and field evaluations were conducted to assess the activity and efficacy of Mosquiron® 0.12CRD, a new formulation containing 0.12% novaluron, against immature Culex mosquitoes. In laboratory bioassays, this formulation was highly active against Culex quinquefasciatus as indicated by low inhibition of emergence (IE) values (IE50 and IE90). When Mosquiron 0.12CRD was applied at 1 briquet per underground stormwater vault, counts of late instars showed a significant reduction on day 28 posttreatment. When the late instars and pupae collected from Mosquiron-treated water were brought back to the laboratory for posttreatment observation, emergence inhibition was >90% on day 7. When the late instars from a laboratory colony of Cx. quinquefasciatus were exposed to the Mosquiron-treated water, 99% and 95% emergence inhibition was noted on day 7 and day 14, respectively. When Mosquiron 0.12CRD was applied at 11 briquets per vault, significant reductions of larval populations were encountered on days 7 and 35 posttreatment for early instars, and on days 14, 21, and 35 posttreatment for late instars. Laboratory observation of late instars and pupae sampled from the treated vault water showed nearly complete emergence inhibition from day 7 to day 28 posttreatment. A similar trend was observed in laboratory-reared late instars of Cx. quinquefasciatus when exposed to the treated water. Preliminary evaluations indicated that Mosquiron 0.12CRD is a useful new tool to control Culex mosquitoes breeding in persistent sources.