Tunnel Work Research Articles

Study of Tunnel Surface Parameterization of 3-D Laser Point Cloud Based on Harmonic Map

In the maintenance work of tunnels, images are often used to detect diseases, but collections of tunnel images are limited by the tunnel environment and working time. Three-dimensional laser scanning technology can acquire high-precision tunnel information efficiently, and the main problem to be solved by using this technology to collect tunnel inner wall images is the dimensionality reduction of the laser tunnel point cloud data. This letter proposes a tunnel surface parameterization algorithm based on a harmonic map, where a 3-D tunnel point cloud is used as a data source to reconstruct a triangle mesh model of the tunnel and then generate a harmonic map depth map of the tunnel inner wall on the triangle mesh. We can obtain the spatial distribution and position information of the appendages and detect whether there are cracks, water leakage, falling pieces, and other diseases by the depth images. The results of this study indicate that the proposed algorithm is suitable for tunnels of various shapes and has low area distortion, which can better avoid the loss of information during dimensionality reduction. Compared with other existing methods, the algorithm has higher efficiency and applicability.

Features of health disorders in miners employed at northern copper-nickel mines

The aim of the study was to assess the influence of different working conditions on the health of 1523 copper-nickel miners of the Kola High North. The low degree of mechanization of mining operations was established to be related to more higher levels of vibration, noise and physical overloads. The working in such conditions, when compared with high mining mechanization, leads to a decrease in the number of conditionally healthy workers (12% and 20.7%, p <0.001) an increase in the number of diseases in the one worker (2,94 ± 0,10 and 2.13 ± 0.07 cases, p <0,001), the increase of the risk of occupational diseases (OD) of the musculoskeletal (RR = 2.31) and nervous (RR = 2.07) systems, vibration disease (RR = 1.70), neuro-sensory hearing loss (RR = 1.90). Both at low and high degree of mechanization of mining operations the greatest risk of occupational diseases in noted in drifters (OR = 5.68), at that it was higher at hand mining than at mechanized mining (RR = 1.44). There was made a conclusion about the need to improve the complex of measures for the preservation of health in this group of workers, especially engaged in the performance of tunnel works.

Measurement and analysis of surface deformation after the sixth nuclear explosion in the Democratic People&amp;rsquo;s Republic of Korea using InSAR

We use the small baseline subset (SBAS) method and Sentinel-1B synthetic aperture radar data to obtain the cumulative surface deformation at highly coherent points and different times (12-d intervals from September 10, 2017 to June 1, 2018) following the sixth nuclear explosion conducted by the Democratic People’s Republic of Korea (DPRK). The study is conducted for a 17 km ×22 km area centered on the explosion. Measurement points are aggregated into 14 sets according to their spatial neighborhood. According to the average coherence of each point in the set, the point deformation is weighted and averaged to obtain the cumulative deformation of each set. The location of each set is also weighted and averaged according to the average coherence of each point in standing for all points in the set. The analysis and discussion in this paper are based on these 14 sets for 14 different regions. Results show that the deformation process in the thermal radiation aftereffect stage of the sixth nuclear test can be effectively observed using interferometric synthetic aperture radar. There was still surface uplift near the epicenter for ~10 d after the explosion, after which the surface began to sink. The sinking rate and total sinking amount varied by location. Meanwhile, the phenomenon of subsidence slowing or even the surface uplifting possibly due to the freeze–thaw cycle of water in underground rock in winter was observed. After May 24, 2018, deformation began to rise because the government of the DPRK bombed the entrance of the nuclear facilities. We indirectly demonstrate the reasonableness and consistency of the observation results via the coherence of high-resolution optical images, meteorological data, and interferograms for the area of the nuclear explosion. The spatial and temporal distributions of surface deformation and their causes are then modeled. The results of modeling analysis are as follows. (1) In the thermal radiation aftereffect stage of the DPRK’s sixth nuclear explosion, the surrounding rock softened under high temperature and high pressure, and the surrounding metamorphic rock then compressed under the action of its own gravity and began to sink. This time-varying process is fitted by a deformation prediction model based on the Weibull function, and four parameters—namely the acceleration factor of deformation, comprehensive influence factor of deformation, initial surface deformation, and prediction value of maximum deformation—are obtained. The average correlation coefficient of the fitting curve is about 0.97. Model fitting results show that the sinking deformation tended to stop around May 20. (2) A function model was proposed to analyze the genetic mechanism of surface deformation, where the thickness of the layer of metamorphic rock is taken as the independent variable and the maximum deformation is taken as the dependent variable. The thickness of the layer of metamorphic rock was calculated for explosion burial depths of 450 and 770 m. The vertical impact distance of the explosion from the epicenter was about 1800–2300 m while the deformation coefficient of the metamorphic rock was about 7×10−5–8×10−5. The statistical fitting degree R 2 is about 0.8 and the P value is close to zero. In conclusion, the scope of the impact of the explosion metamorphism is the intrinsic condition of deformation, and gravity is the driving force of surface subsidence in the explosion area. Differences in the deformation rate and amount in different geomorphological locations are due to different thicknesses of the compressible layer relating to the rock thickness and metamorphism. Such differences have directionality, possibly because the attenuation of high-temperature and high-pressure propagation in the direction of tunnel works is less than that in the direction of surrounding rock.

Fiber Bragg Grating (FBG) based magnetic extensometer for ground settlement monitoring

Monitoring for sub-surface settlement in deep excavation construction and tunneling works will provide an early indication of potential settlement or sinkhole formation at the ground surface. Currently, rod and magnetic extensometers may be used to monitor sub-surface settlement, with the latter most commonly used. In this paper, a novel Fiber Bragg Grating (FBG) based extensometer is proposed working on the magnetostatic interaction between a ring magnet and a disc magnet. The proposed FBG extensometer can be automated for continuous monitoring, as compared with the commonly used magnetic extensometer which monitors manually at prescribed intervals. Multiple units of FBG extensometer can be connected together and easily installed in a deep borehole. The number of FBG extensometer used is not limited by the borehole size, as compared with the rod extensometer where a maximum of 3 tips per borehole is typically specified. The proposed extensometer with current instrumentation gives a measurement range of 80 mm with a measurement resolution of 0.65 mm/με.

Geotechnical site investigation for tunneling and underground works by advanced passive surface wave survey

This study introduces crosscorrelation seismic interferometry, a new and feasible complimentary surface wave survey for geotechnical site investigation for tunneling and underground works. Crosscorrelation seismic interferometry uses ambient noise as source to estimate the green’s functions received by geophones. The proposed methodology is presented and demonstrated by three case studies in Singapore. The 1st case study demonstrates the workflow of the proposed method. Conventional active multichannel analysis of surface waves (MASW) and passive microtremor array measurement (MAM) have also been carried out on the same site. The comparison with classic active MASW shows that the dispersion curves and shear wave velocity profiles derived by crosscorrelation are more comparable and reasonable. With multiple signal classification (MUSIC) beamforming, the direction of arrival (DOA) of ambient noise field can be characterized. As the prerequisite of crosscorrelation method, with the known DOA, it also affords the opportunity to measure both Rayleigh and Love waves. The 2nd case study demonstrates that the polarization of shear wave velocities can be distinguished by the proposed method. The 3rd case study shows a feasible way to construct a 2D shear wave velocity profile. In short, with a simple linear array, fewer geophones, crosscorrelation is considered to be an attractive complement to the conventional MAM and MASW survey.

Control of EPB TBM tunneling parameters to mitigate the effects on Dambovita river structures

This paper presents an assessment of the impact of tunnelling of the M5 Metro line in Bucharest, and its associated risks on Dambovita river development located in the influence zone of tunnelling operation. During the metro performance the undercrossing of the hydraulic works related to the Dambovita River was required. The Dambovita River hydraulic development is made of 2 main components – the upper clean water channel and the sewage/drainage system cassette, placed below (the base slab of the channel representing the roof of the cassette). On the left river bank, the B0 collector is an old structure with uncertain technical condition Tunnelling in proximity of existing development introduces deformations in both structures and in turn induces additional axial and bending forces. In modern mechanized tunnelling, ground convergence is controlled through balancing the earth pressure at the tunnel face. Reducing ground deformation can consequently lower the additional deformations and forces and lessen the associated construction risk. In this paper, a detailed finite element modelling was performed to simulate the sequence of construction works. The model was calibrated based on the measured settlements behind the face. Based on model results the undercrossing area of influence is revealed. Recommendations regarding the tunnelling works are made in order to avoid any damages to the existing facilities.

M5 Metro Line Tunnelling Works and their Effect on the Hydraulic Structures of the Dambovita River

In order to carry out the M5 Metro line in Bucharest, the undercrossing of the hydraulic works related to the Dâmboviţa River was required. The common technology for the metro tunnels is the earth pressure balanced excavation (EPB – TBM), precasted segment lining and back-fill grouting to minimize the surface settlements. The Dâmbovita River hydraulic development is made of 2 main components – the upper clean water channel and the sewage/drainage system cassette, placed below (the base slab of the channel representing the roof of the cassette). To evaluate the structural effects of the undercrossing on the existing hydraulic structures, a 3D finite element model was created, to simulate the sequence of construction works. The model was calibrated based on the measured settlements, during the execution works of the metro tunnels before reaching the undercrossing section (a region with similar geotechnical properties). The calibrated parameters were the elastic modulus of the backfill grout at early hardening stages and the length of the grout, still being in “gel phase” (with no stiffness). The paper presents a brief description of the existing and the designed structures, as well as the steps followed to create and calibrate the mathematical model. Concerning the results, the undercrossing area of influence is revealed, by longitudinal and transversal effects expressed in induced displacements and stresses. Several considerations and recommendations regarding the tunnelling works are made in order to avoid any damages to the existing facilities.

Superabsorbent polymers to seal and heal cracks in cementitious materials

Superabsorbent polymers (SAPs) are promising admixtures to improve properties in cementitious materials. Not only useful to mitigate autogenous shrinkage and to increase the freeze-thaw resistance, SAP particles may enhance self-sealing and self-healing in cementitious materials. The self-sealing leads to a regain in water tightness and promoted autogenous healing may prove to be useful to limit repair works caused by concrete cracking. By providing sufficient building blocks for healing, limiting the crack width by means of synthetic microfibers and inducing water by means of SAPs, a smart cementitious material is obtained. This material can be an excellent material to use in future building applications such as tunnel works and ground-retaining structures. This paper gives an overview of the current status of the research on SAPs in cementitious materials to obtain sealing and healing.

The application of distributed optical strain sensing to measure the strain distribution of ground support members

A distributed optical strain-sensing technique is presented as a solution for measuring the strain distribution along ground support members used in tunnelling and mining works. The technique employs a Rayleigh optical frequency domain reflectometry technology, which measures strain at a spatial resolution of 0.65 mm along the length of a standard optical fiber. A rationale for selecting this technology as a potential monitoring technique for ground support elements over alternative commercially available technologies is discussed. The development of a technique to couple optical fiber sensors with rock bolt, umbrella arch, and cable bolt support members is also demonstrated. A robust laboratory investigation of such optically instrumented support members demonstrated the capability of the technique to capture the expected in situ support behaviour in the form of coaxial, lateral, and shear loading arrangements as would be anticipated in the field. Moreover, the micro-scale data obtained by this optical sensing technique are shown to provide unprecedented insight into the local/micro-scale geomechanistic complexities associated with the bearing capacity of ground support members, especially when compared with data obtained by discrete strain-sensing technologies.

Integrating geotechnical and SAR data for the monitoring of underground works in the Madrid urban area: Application of the Persistent Scatterer Interferometry technique

The Differential Interferometric Synthetic Aperture Radar (DInSAR) is a powerful deformation control technique for civil engineering applications. However, the performance definition and limitations of the technique in tunneling works are far from being standardized. This work presents a thorough validation effort of the applicability of the Persistent Scatterer Interferometry (PSI) technique to the Madrid’s M-30 tunneling works. A set of 26 Envisat images, covering from August 2003 to April 2008, were processed with two PSI techniques and the results were validated with on-ground measurements from leveling benchmarks and strips. The comparison of the deformations of more than 1500 control points has led to a global deformation difference of 2.6 mm RMS and 3.5 mm RMS with a coverage of the area of interest with persistent scatterers of 65% and 34% for the two PSI algorithms used. The limitations of the PSI technique when using SAR missions with low revisit time were shown. PSI has proven the potential to complement on ground monitoring techniques in tunneling works as soon as the limitations are overcome.

Stability Analysis and Case Study of Shallow Tunnel Using Pipe Roof Support

Pipe roof system is widely used in the shallow tunnel as the support system. Although the diameter of pipe roof is diversity, the pipe roof system of small diameter pipe roof and small spacing steel grating is widely adopted in China. The stability mechanism of that pipe roof system is to form shed-scaffold system. In that shed-scaffold system, the function of pipe roof is to form micro-soil-arch in overlying soils between the pipes and to transmit the excavation loads. The steel gratings are the main bearing structure. To form the shed-scaffold system effect, three stabilities, stability of soils between pipes, stability of tunnel working face and stability of tunnel foundation, should be satisfied simultaneously. On that basis, the collapse accidents of Tianhengshan highway tunnel and Haide highway tunnel in China are analyzed. It shows that the stability of tunnel foundation would be overlooked easily and causes even overall collapse. At last, the measures to improve the stability are proposed.

A Model for Vibration Monitoring of Immovable Art in Churches: Reflections on Monitoring as a Tool for Preventive Conservation

ABSTRACT During construction of a 6 km long railway tunnel close to historic churches in Stockholm, a preventive monitoring model was applied for ensembles of large-scale immovable ecclesiastical artworks. Construction work such as blasting and pile-driving took place during five years under or very close to these immovable works of art. In Sweden, risk assessment related to construction work is focused on risks associated with the building; meanwhile, there is no common approach for protecting the immovable historic works of art and architectural surfaces. This paper discusses how a preventive model for vibration monitoring on immovable artworks was developed and used as well as how the preventive purpose was perceived by different stakeholders during and after the tunnelling work. Experience from this project concludes that monitoring that includes uniform visual inspection becomes crucial for being able to protect the artworks. The concept of vibrations standards relying on fixed numbers of critical vibrations levels for mitigating the effects of vibration on immovable art can be questioned based on experiences from this project.

The use of tunnelling parameters and spoil characteristics to assess soil types: a case study from alluvial deposits at a pipejacking project site

Generally, when there are only a few boreholes present along a tunnel design alignment, geological understanding of the worksite may not be adequate and the ability to optimise the tunnelling parameters is limited. This lack of boreholes will cause an increased potential of geo-hazards during tunnelling works. This study proposes an alternative method to determine the major and other components of ground under such circumstances. Five factors, cutter wheel torque, sieve residue, flow rate of feedline, pressure in the feed and discharge lines and density of bentonite slurry, are adopted for determining the major and other ground components. Comparisons of the soil types based upon the results of grading and Atterberg limits tests on the spoil and soil samples, respectively, and those resulting from the proposed method indicate good consistency. The proposed method provides an opportunity for establishing a more comprehensive geological structure for refining the tunnelling parameters, reducing the potential of geo-hazards associated with the inappropriate tunnelling parameters.

Application of the NATM method in the road tunneling works in difficult geological conditions – The Carpathian flysch

The paper presents the characteristics of geological, geotechnical and construction conditions in the Laliki tunnel in Carpathian flysch. Until now, it is the only tunnel constructed there; yet, another one is underway, and several more are in the design stage in Poland and Slovakia. Therefore, the experience gained during construction of this tunnel using NATM method are extremely important from the point of view of further tunneling works. The analysis has shown that the flysch formation met in Laliki is different from e.g. in Greece which is better known from tunneling. The changes in geological and engineering conditions along the tunnel, mainly in dip of rock layers, approximately between 70 and 85°, and a varying lithology, led to diversification of the quality of the rock mass and its different evaluation on the design and tunnel execution stages. Changes observed in the rock mass quality have forced the contractor to apply a primary support with a higher load-bearing capacity, i.e. using micropile umbrella system, which was not planned before. The determined RMR, GSI and KF (Polish classification of the Carpathian flysch) rock mass quality indices shown significant discrepancies that proves high subjectivity of the methods in the condition of flysch formation. Simultaneously, the analysis has shown that KF classification can be applied in flysch rock mass successfully, together with RMR and GSI classifications.The paper also analyzes selected monitoring elements covering convergence measurements of the primary support and the surface subsidence. So called Squeezing Index SI, designed by Singh (based on Barton solution), was used to set the critical deformations. Also warning levels of tunnel stability loss proposed by Sakurai were implemented to predict the potential flysch rock mass deformations. The analysis shows the good correspondence between the rock mass propensity to deform and the applied support, however the support was not adjusted adequately to the ground conditions at some sections. It become apparent that in flysch the rock mass evaluation is not yet researched well and resolved. As a consequence of the wrong evaluation is a pronounced displacement contour and a need of additional support.The results of surface subsidence indicate that the high dip of the strata and the shallow tunnel depth (here – up to 35 m) are the major factors of the asymmetrical shape of the trough and the long-term deformations (6 years), even in the sections where the rock mass quality was evaluated high. The claystone content and steep dip of the strata are critical in this aspect, because they both lead to the shear displacements.The observations and experience gained during Laliki tunnel drivage are the basis for the designs of new tunnels in flysch rock mass in this part of Europe.

Deep excavation in urban areas – defects of surrounding buildings at various stages of construction

Deep excavation and tunnelling works in city centres always bring some risks to surrounding structures, especially in the case of old town centres, where the technical condition and structural stiffness of historical buildings is rather doubtful. When the new desired excavation depth goes deeper than the foundation of the surrounding buildings or when tunnelling works are conducted directly under them, the existing objects are subject to stress, vibrations and displacements imposed at almost every stage of building the new construction. The presented paper outlines, on the basis of the authors’ experience, the typical damages appearing during the supporting wall construction (sheet pile driving, piling and formation of diaphragm walls) and tunnelling works. Other damages appear due to soil mass unloading (caused by excavation stages) and horizontal loading during pre-stressing of struts or ground anchors. The selected case studies of steel sheet pile wall installation is given with regard to typical failures caused by an unplanned excavation and its impact on neighbouring structures.

Developing a Methodology for Determining Design and Operating Requirements for Contracting Tunnel Works

Directive 2004/54/EC [1] on minimum safety requirements for tunnels in the trans-European road network sets the bases for establishing an acceptable safety level for tunnel users across EU member states. Furthermore, many EU member states enforce stricter safety requirements for tunnels in their territory. The lack of a methodology for determining design and operating requirements for tunnels leads many times to an expensive over-design for tunnel works and thereafter operation and maintenance, throughout the tunnel lifetime without the expected increase in safety levels. In the present paper a methodology has been developed in order to assist all parties involved in contracting tunnel works to establish the optimum design and operating requirements. The methodology combines results of risk analysis with cost benefit analysis in different time periods throughout the tunnel design life. The results from implementing the aforementioned methodology include the optimum set of design and operating requirements for each tunnel under consideration. Concluding, the necessary contribution of each beneficiary to the funding of the different sets of design and operating requirements for certain time periods throughout tunnel lifetime, is soundly estimated and justified. The proposed methodology is an excellent tool since it can be used regardless of specific risk acceptance criteria.

Fort Wayne Tunnel Works - Successes And Lessons Learned In Bidding The Largest Single Project In City History

Fort Wayne Tunnel Works - Successes And Lessons Learned In Bidding The Largest Single Project In City History

Modelling and Analysis of the Excavation Phase by the Theory of Blocks Method of Tunnel 4 Kherrata Gorge, Algeria

The aim of our work is to check the stability during excavation tunnel work in the rock mass of Kherrata, connecting the cities of Bejaia to Setif. The characterization methods through the Q system (method of Barton), RMR (Bieniawski classification) allowed us to conclude that the quality of rock mass is average in limestone, and poor in fractured limestone. Then modelling of excavation phase using the theory of blocks method (Software UNWEDGE) with the parameters from the recommendations of classification allowed us to check stability and to finally conclude that the use of geomechanical classification and the theory of blocks can be considered reliable in preliminary design.

Development of holistic prognosis models using exploration techniques and seismic prediction

AbstractAs part of the Brenner Base Tunnel project, the currently running Tulfes‐Pfons construction lot includes a stretch of the exploratory tunnel (ET), which has a length of 15 km and is being bored by a gripper TBM. During this tunnelling work, a diverse and broad set of exploration techniques is being used. Although it is an exploratory tunnel, the tunnel is subject to the same constraints as a performance heading. The choice of exploration techniques was made with regard of the capability to smoothly integrate them into regular tunnelling in order to not create further downtime. The exploration techniques are useful for the current ET but also to produce a forecast for the subsequent main tunnels (MT). The geological investigation is undertaken by face and peripheral mapping as well as by percussion drilling ahead of the machine. The geotechnical exploration is carried out by analysing the TBM parameters and the system behaviour, and analysing the percussion drilling. The exploration concept is completed with the geophysical reflection seismic method. All these exploration methods have different sensitivities, exploration ranges and directions, strengths and weaknesses, so they complement one another. This paper assesses the exploration techniques based on the experience until now. A case study of one fault zone is presented to show how the different exploration methods interact and contribute to a holistic prognosis model.

Cover Picture: Geomechanics and Tunnelling 6/2017

AbstractDSI is supplying numerous supporting measures for the 9 km long NorthConnex Tunnel, one of Australia's longest road tunnels. The tight project schedule and continuous operation of the tunnelling work require an optimal supply chain, product management, planning and cooperation between the project teams and DSI Underground, Australia (see page 788–789)