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Showing posts with label Construction. Show all posts
Showing posts with label Construction. Show all posts
  • Internet of Things (IoT) in Tunnel Monitoring for the Construction Phase

    Safety has historically been one of the most critical challenges faced by the 

    tunnelling industry, especially given that half of all construction projects still use 

    manual data readings – which is both risky and costly – or cables, which can be 

    expensive and inconvenient, especially with regards to stopping traffic – meaning 

    that in tunneling projects the laying down of cables leads to projects having to be 

    put on hold. In contrast, wireless systems increase efficiency and reduce costs, 

    making the monitoring process easier through introducing automation. 

    Companies no longer need to think about how they’re going to take readings. The 

    automatic, remote monitoring process makes the workplace safer and improves 

    compliance with industry regulations and standards. The experts on this webinar 

    explore how wireless monitoring can be used to enhance risk management and 

    improve instrumentation and monitoring in tunneling projects, helping operators 

    to tackle the safety challenge head-on.

    Real-time insights for active risk-management

    Active risk-management based on real-time information in tunneling projects can only be implemented through IoT wireless monitoring. David notes that “wireless technology is nothing new in the geotechnical and construction industries, however the wireless radios and systems that have been around for the last 20 years are not optimized for the challenges of technical monitoring”.

    Modern systems using new IoT technologies for technical monitoring have advanced things considerably – giving operators greater control over how much data they are collecting from each sensor and when. Not every wireless monitoring system covers all bases. According to David, truly effective systems should have three main characteristics:

    • Wireless-ness
    • Long-range signal
    • Low-power consumption
    In civil engineering, the ability to continuously transmit data over large distances without having to use physical infrastructure (such as cables) or risk batteries failing, is key to effective instrumentation and monitoring. Wireless signals need to be able to reach long distances underground and go through walls as thick as 4m in urban buildings or manholes. “They also need to be low maintenance and durable – having to replace batteries, for instance, means excavation downtime and putting workers lives at risk”, David points out. For genuinely automated readings, data nodes need to be able to be configured easily and to be connected to gateways without constant maintenance.

    Wireless monitoring to eliminate potential incidents

    In Christina’s experience, wireless monitoring is increasingly popular for tunneling projects:
    “Many of the challenges present in tunneling projects could be significantly reduced with a wireless, real-time monitoring system because the latter allows tunnel excavation operators to respond earlier to potentially negative situations, permitting operations to be adjusted accordingly and remedial actions reduced in the long-run”.

    This, in turn, reduces the downtime of excavation works, which saves major costs, giving wireless monitoring systems almost a guaranteed return on investment as, in the end, their total cost is minimal compared to the cost of remedial actions and system downtime. With this type of system, the direct costs of installation and maintenance of other wired or technically complex systems are significantly reduced.

    Four elements are needed in order to adopt an IoT wireless monitoring system:


    1. An internal IoT champion
    2. A total end-to-end wireless monitoring system – an advanced IoT wireless monitoring system which captures all sensor data used in your project
    3. Devices such as data nodes
    4. A proof of concept initial test phase to make sure that all the hardware and software can be carefully tested and adjusted according to actual conditions

    Real-life tunneling projects

    Based on his experience working on the LA Metro Purple Line 2 Project, Dr. Oyenuga highlights the advantages of using low-power, wireless, real-time monitoring for this kind of tunneling project: “A lot of tunnel projects have a mishmash of systems. They could use 3 or 4 systems because operators feel like they have to use a specific system for a certain type of sensor. On our project, for the first time, we are using an integrated, automated data acquisition system. We are using this system for pretty much everything – it’s being used for every single monitoring sensor we’re deploying.”

    Dealing with risks effectively

    Tunneling excavation project operators’ principal pain points are typically occupational health and safety hazards, alongside the need to comply with strict and costly insurance regulations, and the need to carry out constant monitoring without incurring too much expense. Specific challenges in this sector include the dispersion of critical points that need to be monitored across a large area, a continually changing construction environment, and, if using sensors placed on cables, the need to make adjustments to those cables at every stage of the project. The way to deal with these challenges most efficiently and precisely is through aggregating real-time information, which accurately describes the performance state of the tunneling project and can be used by decision-makers to implement the most appropriate action, and instigating proactive risk-management approaches with alarm thresholds and response plans. One of the only ways to do this is through implementing an IoT wireless monitoring system, which is low-power, low-maintenance, durable, compatible with different types of sensors and monitoring software, and continuously gathers data in real-time.

    What’s next for the tunneling industry?

    The future of tunneling is in IoT – a technology that offers operators the opportunity to generate greater efficiency through digitizing their operations. The type of real-time operational management currently enabled by wireless monitoring solutions will eventually allow for the creation of digital twins. These “videogame” models of the tunneling site will allow operators to plan ahead for any possible incidents and implement actions to prevent them first virtually, and then literally, improving the efficiency of their operations and reducing the risks of tunneling significantly.

    Authors

    • Christina Lafuente: Geotechnical Engineer and Project Management Consultant for several TBM tunneling projects in Spain and the US.

    • Dr. Dots Oyenuga: Geotechnical and tunneling expert with over 40 years of experience in geotechnical and tunneling instrumentation.

    • David Gomez: Expert on wireless monitoring in geotechnical contexts and Industrial Engineer with over 7 years of experience helping industrial companies to transform their operations through IoT technologies in the US.:



    (Source: https://blog.worldsensing.com/construction/digitizingtunnelmonitoring/ )


    Tunnel Construction Monitoring: How IoT Wireless Systems Diminish Risks in Construction Projects


    A recent survey conducted by software company TrackVia revealed that 47% of construction managers still use manual methods to collect important project information. The construction sector is a slow adopter of new technologies: although automated data, often enabled through wireless monitoring systems, can make operations more efficient, save costs and reduce risks, the industry remains hesitant to implement novel approaches.

    Tunneling projects are one of the most high-risk geotechnical construction sites. Being able to monitor the stability of surrounding structures and underground excavations in real-time is essential to keeping risk-potential low. Operators who rely on manual readings are working with out-of-date information and therefore make partly blind decisions. This poses major risks as potential incidents cannot be detected easily. Despite great advances in instrumentation and monitoring, loss of life of workers and the public due to incidents during tunnel construction projects is still a great threat. The level of risk can be significantly reduced with advanced Internet of Things (IoT) technology.

    IoT technology for real-time monitoring

    One approach to replace manual readings is to deploy a wireless monitoring system. While “wireless” is not a new concept, working with a system which runs on IoT technology is. IoT monitoring doesn’t rely on 3G or Wi-Fi but on low-power wide area (LPWA) networks such as Sigfox and LoRa, which increases data accuracy and reliability. With IoT wireless monitoring systems, sensors, such as multi-point borehole extensometers, used in a construction project can be connected to wireless data nodes, which transmit the sensor data via gateways to on-site servers. This allows operators to track operations in real time.

    Metro projects in North America using IoT wireless monitoring

    In North America, some of the biggest metro extension projects such as the Purple Line Rail Link in Washington D.C., the Purple Line Extension in Los Angeles and the Toronto Subway Project, are using IoT wireless monitoring in order to ensure their risk-management systems are reliable and accurate. This kind of monitoring enables operators in these cities to carry out remote, real-time monitoring of in-ground sensors such as piezometers, extensometers, and inclinometers. They are even able to gather data from sensors placed across metallic manholes because the sensors are installed in boreholes drilled into the pavement. Operators can gather data on the stability of the tunnels in a non-intrusive way, through data units that are connected to the sensors inside the manholes, installed at the mouth of the boreholes. These wireless data units are also able to consistently transmit data without requiring traffic cuts to collect readings sporadically. Sporadic readings collected manually are not enough to understand the behavior of a tunnel or excavation station – both in terms of ringing the alarm should something go wrong in the moment, and continuously monitoring the situation to pick up on trends and prepare for any future incidents.

    These metro construction projects use Loadsensing to remotely monitor the tunnel excavation, because IoT wireless monitoring systems like this offer a variety of benefits, such as:

    Long-range, low-power geotechnical monitoring

    Systems running on IoT LPWA networks such as Sigfox and LoRa offer increased data accuracy and reliability. They enable operators to remotely collect and transmit data over long distances (depending on the use case over up to nine miles) without needing much power. The systems are usually battery-powered and can last up to eight years, making them easy to maintain.

    Cables, which are still often used in tunnel construction projects, as opposed to wireless approaches, are vulnerable to physical damage, surrounding structures are affected by soil movements induced by tunneling, and design assumptions need to be verified to check that performance is as predicted. Extend cable and cable protection can be used to centralize the data acquisition in traditional data-loggers, but they require much more time for installation, are expensive and are sometimes perceived to be an eyesore. It is also difficult to place cables in hard-to-reach areas, and they are vulnerable to damage over time.

    Increased data availability

    Within a tunnel, the most interesting data corresponds to the first few days after the excavation. Data gathered manually during this period contains a lot of hidden, or uninterpretable, information, since it cannot follow events exactly as they happened. When systems are based on IoT technology and run on LoRa, this technology enables 157 dB maximum link budget (151 dB in Europe), a metric used to define the quality of the data transmission. Paired with advanced data nodes, which in some cases are highly sensitive (down to -137 dBm) and have a transmission of +20dBm (+14 dBm in Europe), construction projects can ensure efficient communications in conditions where other data reading systems or approaches fail.

    This table shows a comparison of some of the wireless options available in the geotechnical monitoring market today:

    WirelessFrequencyNetwork typePowerData rateSensitivityRange**
    SmartMesh2.4 GHzMeshMedium250 kbps-95 dBm40-150 m
    XBee

    sub 1 GHz

    902-928 MHz

    868 MHz Europe

    Star/

    Mesh

    Medium10 kbps-110 dBm150-400 m
    LoRa used by Loadsensing902-928 MHz

     

    868 MHz Europe

    StarLow5469 bps SF7

     

    537 bps SF11

    -137 dBm

    node

     

    -141 dBm

    gateway

    2-15 km

    Table 1. Performance of available wireless geotechnical monitoring systems. **Range considered for typical installation on site and with standard antenna.

    Due to its long-range, low-power and sensitivity levels, systems like Loadsensing are the most suitable for tunneling projects. The constant aggregation of data from sensors located within and outside the construction area allows for a long-term picture of events to emerge, enabling operators to plan ahead with a more evidence-based approach. Sampling rates are high (with more data), so, even though tunneling is often a slow process, operators can see exactly what is happening over time, while also being warned of any deviations in ground stability, pore water pressure etc. In a station, it is very useful to see the evolution of all the parameters at each phase of excavation. It is then possible to implement remedial actions if something is wrong – for example excessive horizontal displacement, or overload of the ground anchors. This is particularly useful for the control of shotcrete curing, where initial readings can be collected, and pressure cells depressurized accordingly.

    Minimal maintenance

    Having to regularly replace or maintain a monitoring system requires putting workers at greater risk, and decreases reliability and overall safety as there is a constant possibility that the system might go down suddenly and with it all risk-management operations too. This threatens lives.

    Systems that employ low-power, wireless hardware have high durability and adaptability and are thus a good option because they require much less upkeep and are adjusted to specific environmental conditions, making their fallibility less significant. This applies to the sensors as much as the network and the software. Long-range, low-power wireless technologies, such as LoRaWan, used by IoT networks worldwide, are the most reliable option. Adaptability in the wireless data units, with operating frequency bands that are adjustable to each territory requirement is also key. It is additionally useful for wireless monitoring solutions to be compatible with multiple types of sensors. This means that no hardware needs to be replaced gratuitously, again putting lives at risk and stalling operations, even if it is produced by a different company to the one providing the wireless monitoring network and software.

    RELATED: Satellite Monitoring for the Grand Paris Express

    Typically, in tunneling projects, a mesh network is installed, which tends to be more vulnerable due to the existence of critical paths where the density of nodes is not enough to balance the network. In other words, if some of the nodes are damaged or unavailable, other parts of the network are majorly affected. Star topology networks are a good alternative here because the loss of one of the nodes does not have an impact on the rest of the network, making the whole system more resilient and reliable.

    Monitoring of surrounding tunnel areas

    Monitoring the stability of the surrounding ground structures and buildings during a tunnel excavation with tiltmeters, settlement systems or crack meters is a crucial risk-management area in geotechnical construction projects. One of the major concerns for contractors and designers in a tunneling project is the potential nuisance caused to local residents by noise or ground movements. Wireless nodes can be a very useful measuring tool for this when placed on buildings or boreholes surrounding the excavation area. By using these nodes, it is possible to collect readings from tiltmeters, liquid settlement gauges and other types of measurement tools installed in the basements of the buildings, or via nodes placed at the mouth of the borehole in a manhole. These readings can then be transmitted to a gateway installed on top of the building, with no need for constant upkeep or manual readings. Importantly, the evaluation of the data collected and transmitted by geotechnical sensors through these wireless nodes not only increases the safety level of the project, but also reduces the nuisance often caused to locals by soil movements induced by tunneling.

    With wireless monitoring systems, operators can monitor not only the direct excavation area but also the surroundings, giving them access to real-time data that can alert them when something goes wrong, allowing them to sound the alarm immediately and halt operations in order to prevent, for instance, a nearby building from becoming unstable and therefore unsafe.

    Flexibility and durability

    To withstand the harsh working conditions of tunneling construction sites, devices used to measure the situation onsite need to be highly durable. Wireless data nodes are specifically designed to be installed in tough environments. In comparison, cables tend to be a lot more vulnerable to damage. Durability is key to ensuring that minimal maintenance is required: operators need to make sure the units they want to deploy are IP67 certified and tested from -40 to +176 F, making them highly robust and protected in any scenario. Hardware durability is essential for effective risk-management because data needs to be constantly gathered to ensure that operators know exactly what is happening in the tunnel at any given moment. Any interruption to this data-aggregation through equipment failure therefore increases risks greatly.

    Flexibility is also important. Sensors can give operators flexibility in their monitoring because once installed, they facilitate the easy deployment of data-loggers. Wireless nodes are very moveable, meaning that they can be easily removed if another kind of construction activity needs to be carried out in the same location, for example waterproofing or installing the final tunnel lining. Flexibility and durability of wireless monitoring systems are thus key to ensuring that data aggregation, crucial to risk-management, can be carried out constantly, while also cutting operational costs, as equipment rarely needs to be maintained or replaced.

    The future of tunneling?

    In the past, the loss of human life was not an uncommon part of tunnel construction projects; today, this is no longer acceptable, and this is largely down to technological advances based on the Internet of Things that have made risk-management easier and much more accurate. The next frontier of risk-management in instrumentation and monitoring for tunneling projects is probably real-time data assimilation into a computational model of the project. This will enhance the quality of the information available and allow operators to make educated, evidence-based decisions while tunneling.

    In the future, we will see operations becoming digitized through operational intelligence (OI). When a wireless monitoring system is connected to advanced IoT software, such as an OI solution, operators can integrate sensor data, other data sources, assets, teams as well as existing systems into one overarching system, in order to make centralized, data-informed decisions. Through constantly receiving updated project insights, operators can access information and KPIs allowing them to predict events and “try out” solutions in the software, before implementing them in real-life. As such, digitizing construction projects with smart sensors not only enables operators to track how operations are going in real time, but it also allows companies to predict what is needed next by displaying real, planned and projected production needs. Wireless monitoring technologies will thus continue to give tunneling construction operators the power to protect not only their workforce and local residents, but also their critical assets too.

    About the author

    Juan PĂ©rez is a Geotechnical Engineer and Product Owner of the globally recognized wireless monitoring system, Loadsensing. Juan has a background in geotechnical and structural instrumentation and has been leading the product development of wireless monitoring at IoT pioneer Worldsensing since 2013.

    (Source: https://tunnelingonline.com/tunnel-construction-monitoring-iot-wireless-systems-diminish-risks-construction-projects/)
  • Emerging Technologies in Tunnel Construction

    The tunnel construction market is one of constant evolution – and sometimes revolution. Dating back to ancient civilizations through today’s modern marvels, designers and constructors have kept pace with the needs of society by applying new technology to an ancient craft. The 19th century saw the advent of subaqueous tunnels (Thames Tunnel) and drill-and-blast tunnels (Hoosac Tunnel), that changed the way we travel, while the 20th century ushered in a whole new era of underground construction with the introduction of Tunnel Boring Machines.

    Today, we are seeing TBMs that are dealing with a broader range of ground conditions, with larger diameters and under greater pressures. These machines are opening doors for projects that may not have been feasible in the past, improving the quality of our infrastructure and contributing to a sustainable urban environment.

    To get a sense of the impact of technology in today’s tunnel construction market and where it is headed, we talked with HNTB’s Mike Wongkaew and Tony Bauer. Specifically, the topics of large-diameter TBM tunneling, hyperloop and tunnel lining design were discussed.

    Anthony Bauer, PE, is HNTB Corp.’s national tunnel practice operations manager-West. He is based in Los Angeles and supports tunneling projects throughout the West Coast and nationally. Bauer’s high-profile, complex underground project expertise includes working with clients such as Virgin Hyperloop One, Valley Transportation Authority, California High-Speed Rail, London Underground, Sound Transit (Seattle), Washington Metro and others.

    Mike Wongkaew, Ph.D., PE, SE, PMPMike Wongkaew, Ph.D., PE, SE, PMP, is HNTB Corp.’s national tunnel practice lead-Northwest and associate vice president. He is based in Bellevue, Washington, and oversees all tunneling work on the Sound Transit West Seattle and Ballard Link Extension Project, as well as projects across the nation. Previously, he served as chief tunnel engineer for research and development of an innovative underground transportation system.

    TBM: There has been a trend toward large bore tunnels internationally and we are now seeing it in the United States – Seattle, San Jose, Miami, Hampton Roads. Why are owners becoming more receptive to the idea of using large-diameter TBMs?
    Wongkaew: With increasing numbers of successful projects and the availability of experienced suppliers, contractors and consultants internationally and in the United States, owners begin to feel more comfortable with large bore and consider it among the feasible alternatives that could address their infrastructure needs. Large bore also provides several unique advantages over twin bores.

    TBM: What are the challenges associated with building and using large-bore TBMs?
    Wongkaew: From the designer’s perspective, portal site constraints and logistics are key physical challenges for building large bore tunnels. Access to the site for TBM and material delivery, power requirements, muck processing (especially for slurry TBM) and hauling requirements are important factors that must be considered in portal area planning. Additional challenges include exponential increase in cutterhead torque requirements, increased cutting tool wear and replacement, large variation of pressure across the tunnel face and large perimeter of the annular gap between the excavated diameter and the lining extrados. The last two challenges must be well managed to mitigate the risk of settlement impacts.

    Challenges for using large bore TBM include increased tunnel profile depth at the portal to address the buoyancy effect and under existing infrastructures to manage settlement impact risk, and increased minimum alignment radius to accommodate TBM articulation and lining installation. An additional challenge, although this could be viewed as opportunity, is optimization of the space utilization within the large bore as void spaces may require additional ventilation and fire and life safety consideration.

    TBM: What technological improvements have been made to increase the practicality of large TBMs
    Wongkaew: Improvements are continuing to be made to address some of technical challenges discussed above. For example, TBM manufacturers have developed methods for replacing cutting tools under atmospheric pressure, improving mixing of the muck within the chamber, addressing abrupt or large change in the face pressure across the height of the chamber, backfilling and lubricating the shield gap, and for rapidly filling the annular gap between the liner and the excavated ground. These improvements, among many others, mitigate several key risks of large TBM tunneling and demonstrate how TBM’s advanced controls add to the machine’s ability to control the ground settlement impacts on large bore projects.

    TBM: What are the advantages of large bores vs. twin bores?
    Wongkaew: There are several advantages of large bores. For example, WSDOT and the City of Seattle saw the benefits of reducing the SR 99 tunnel project footprint as compared to two smaller bores and reducing the surface impacts and disruption as compared to surface and elevated alternatives. For mass transit projects, VTA in San Jose and another transit agency in the Pacific Northwest began exploring a large bore option because of its ability to accommodate two tracks and station platform(s) inside the bore. This would reduce the need for cut-and-cover station construction including impacts on streets, traffic and utilities which can be very disruptive to communities and businesses situated within dense urban areas. The continuous space within the large bore also increases flexibility in locating stations and helps identifying station locations and track crossovers readily along the tunnel alignment, which enhances user experience and operational reliability.

    TBM: How does a single large bore compare to twin bore when it comes to cost of construction? Cost of maintenance?
    Wongkaew: The cost of tunnel construction is higher for large bore compared to twin bores as the TBM cost, tunnel liner and muck handling and disposal costs are greater; however, for many projects tunneling is not the only major cost items. For underground mass transit projects in urban centers, as an example, the increased cost of large bore tunneling would be offset by the reduction in station and crossover construction, right of way acquisition, and surface disruption mitigation costs, adding to an overall project schedule reliability. It is difficult to provide a generalized conclusion as each project is unique, but for several projects that HNTB have been involved with, the large bore can be cost competitive to twin bore when all cost aspect of the project is thoroughly analyzed.

    We do not yet have enough case histories of life cycle costs, but similar tradeoffs could be foreseen. Large bores would have more and larger elements to be maintained; however, inspection and maintenance access in large bores would be easier and less impeded by space constrains and generally feasible during revenue service hours for large parts of the tunnel structure.

    TBM: What are some of the safety considerations of large bore tunnels?
    Wongkaew: The larger cross section of large bores means larger volume of air will need to be ventilated during construction, normal operating condition and emergency (this aspect could be controlled by guideway cross-section area control). Heightened attention is also needed in the areas of fall protection, ladders and stairs, scaffolding, hoisting and conveyors, etc., for the construction of sizable interior structures inside the large bores. Large bore also increases the importance of face pressure control, muck volume balancing, shield gap grouting and annular gap grouting for ground movement and settlement risk management.

    TBM: How do you see the future of large bore tunneling in the US and internationally? Will it continue to grow?
    Wongkaew: We expect the demand for large bores to continue to grow as the technology matures and owners find innovative ways to utilize the large underground space.

    TBM: What are some areas that perhaps can be improved on to increase the effectiveness of large TBMs?
    Wongkaew: Muck handling and ring erection continue to be two slow steps in the mining cycle that limit the production rate of TBM tunneling.

    TBM: What is the current status of hyperloop development in the US and internationally? Are we close to building routes?
    Bauer: Hyperloop is an emerging technology that is still in the early development phases; however, it is closer to reality than many believe. There are several projects in various stages of development within the United States – St. Louis to Kansas City and the Colorado Front Range being the most prominent.

    Obviously, there is no operating commercial hyperloop system to use as a precedent. Therefore, the challenge for each of these projects will be to demonstrate to government agencies that the technology has achieved a level of technical maturity sufficient to justify the investment of public funds. If they cannot demonstrate this level of development, the hyperloop companies will be compelled to rely on private financing or government grants to build the first systems.

    TBM: Tunneling is not necessarily needed for hyperloop. What do you envision as the role of tunneling in hyperloop development? What impact will it have on the tunneling industry?
    Bauer: The physics of high-speed travel – whether with a hyperloop, high-speed train, or airplane – require straight routes to maintain acceleration forces which are tolerable to passengers. Passenger hyperloop systems would likely connect densely populated cities and there are not many transportation corridors available to build a new transportation network. The practicalities of designing the infrastructure for hyperloop in an urban setting will necessitate going underground. The tunneling industry should encourage the development of hyperloop systems because it will result in more underground construction all around.

    TBM: What special considerations would be needed for tunneling for hyperloop vs. typical water or transportation tunnels?
    Bauer: Current construction and design practices can be used for hyperloop tunnels. If the industry can continue to mechanize, standardize and automate the tunnel construction methods with the goal of driving costs lower, this can unlock other projects which have previously been considered uneconomical.

    TBM: What advantages does tunneling have for hyperloop development vs. surface or aerial alignments?
    Bauer: Using tunneling for hyperloop infrastructure will lead to simpler alignments, faster speeds, shorter travel times, and less disruption to the communities around the project.

    TBM: What areas of tunneling are ripe for improvement?
    Wongkaew: In the near term, I would like to see more research into fiber reinforcing. Steel fibers have been used in segments for quite some time. However, we could use more research to ensure fibers are consistently and uniformly distributed in the precast segments. Macrosynthetic fibers may help in this regard as we will get more fiber count for the same cost. However, we need more case history and research done to confirm the performance of macrosynthetic fiber reinforced segments for this technology to be widely accepted.

    We also would like to see TBM technologies that can deal with manmade steel obstruction such as steel piles and tieback ground anchors. These are growing problem for TBM tunneling in dense urban areas.

    TBM: A lot of talk recently has focused on the construction cost of tunneling, as well as production rates. What can we do to make tunneling less expensive? How can we increase production?
    Wongkaew: Muck handling and disposal continue to be a major cost factor for TBM tunneling. We applaud the effort by Elon Musk and others to find ways to reuse the muck.

    Ring erection is another step in the mining process that takes time and human intervention. We expect to see more innovation in this area including the use of boltless segments that could simplify automation of ring erection.

    TBM: What are some of the issues related to liner design? Speed to produce? Ease of installation? Cost? Performance?
    Wongkaew: Corner spalling of lining segments remains an issue that has not been fully eradicated. It is challenging to provide proper reinforcing in the corners. The use of steel fiber reinforcement is helping but only when proper distribution of fibers is achieved. We would benefit from more research and best practice guidance on how to ensure proper distribution of fibers in the lining segments.

    I also personally would like to see more standardization of tunnel lining segment as the sizes, thickness and details of the segments now vary from project to project often unnecessarily. The bridge industry developed standard precast girder sections quite some time ago and everyone in the ecosystem has benefited from it, including owners, contractors, precasters and designers. Standardization has the potential to reduce the cost and improve the quality of lining segments.

    TBM: How have liner designs changed to allow tunneling under high pressure (Lake Mead, Delaware Aqueduct)?
    Wongkaew: Most of the challenges are in the TBM tunneling process, e.g. advance grouting to reduce permeability and inflow, maintaining suitable active face support, muck conditioning and hyperbaric intervention. The liner design approach itself has not changed significantly to allow tunneling under high pressure. Suitable gaskets for high pressure application have been available for quite some time. The tunnel liners need to be designed for the concentrated reaction forces from the compressed gaskets and for the relatively high external ground loads. Some projects opted for the use of double gaskets for redundancy.

    TBM: How have liner designs changed to allow tunneling in seismic areas?
    Wongkaew: We see more utilization of advanced methods of analysis, such as nonlinear time history analysis and three-dimensional analysis, to increase our understanding of the seismic load effects in the liner and how the liner would behave during seismic events. We also see increased use of double gaskets or combination gasket (EPDM and hydrophilic) in seismic areas to provide redundancy.

    Traditionally, gaskets have been tested under static condition. For SR 99 tunnel in Seattle, the gasket was also tested under dynamic loading-unloading condition to better understand the potential adverse memory effect of the gasket material and to confirm water tightness under seismic condition. For Istanbul, special rings and expansion joint details were provided at geologic transitions between rock and soft ground in addition to the interfaces with stiffer cut and cover structures.





    Ref.: https://tunnelingonline.com/emerging-technologies-in-tunnel-construction/

  • ANG INDIA TECHNOLOGIES (AIT) IS AN ENGINEERING, CONSTRUCTION & CONSULTANCY ORGANIZATION

     



    ANG INDIA TECHNOLOGIES (AIT) IS AN ENGINEERING, CONSTRUCTION & CONSULTANCY ORGANIZATION

    Ang India Technologies is a premier engineering, construction & consultancy organization established in the year 2009 with its corporate office in Navi Mumbai. It's engaged in empowering nation's infrastructural developments. We believe in AIT tagline, "Right Solutions Value Additions".

    Ang India Technologies provides technical and consultancy services to various organization in India and abroad. For capacity building of human resources in the area of highway Engineering to undertake and execute roads and runway projects, Institute has the competence to organize National & International Training Programmes continuing education courses since its inception to disseminate the R&D finding to the masses.

    Ang India Technologies is engaged in carrying out research and development projects on design, construction and maintenance of roads, bridges. tunnels, runways, traffic and transportation planning, management of roads in different terrains, material testings, geotechnical investigations, improvement of marginal materials, utilization of industrial waste in road construction, landslide control, ground improvements environmental pollution, road traffic safety and analysis & design, wind, fatigue, corrosion studies, performance monitoring/evaluation, service life assessment and rehabilitation of highway & railway bridges.

    WHAT WE DO

    We've been developing corporate tailored services for clients for 12 years.

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    For enquiries you can contact us in several different ways. Contact details are below.

    Ang India Technologies

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