Urban Underground Construction Research Articles

An integrated risk and productivity assessment model for public–private partnership projects using fuzzy inference system

Infrastructural projects based on public–private partnership (PPP) schemes usually struggle with large amounts of resources. Given such projects’ relatively long lifetime, it is expected to encounter a wide range of risks when executing them. This implies that increasing productivity based on cost, time, and quality goals requires accurately identifying and assessing risks in these projects. This study aims at risk assessment and analysing productivity in PPP projects based on an integrated analysis method. To this end, first, library studies are utilized to identify the most significant risks by surveying the PPP-based urban underground construction projects. Expert opinions and the fuzzy Delphi (FD) technique are then employed in three stages to identify 48 secondary risk factors. By identifying the sources of these secondary risk factors, we identify five primary risk dimensions: government, financing, operation, constructability, and organization-related risks. A questionnaire is distributed to acquire experts’ opinions and screen the most critical risks by integrating FD with fuzzy failure mode and effects analysis (FFMEA). Results showed that, in total, 23 secondary risk factors in the five primary risk dimensions exhibited risk priority number (RPNNormalized) values above 0.5, indicating their relatively more critical impacts. In the next phase, a multi-stage fuzzy inference system is designed to evaluate the impacts of critical risks on the productivity of PPP projects. Output results of the inference system indicated very high, high, and medium impacts of the risks on the overall productivity of the PPP projects in terms of time, cost, and quality, respectively.

Geotechnical challenges and innovations in urban underground construction – The Klang Valley Mass Rapid Transit project

AbstractThe Klang Valley Mass Rapid Transit (KVMRT) project involves the construction of an urban passenger transport system, i.e., Mass Rapid Transit (MRT) system, together with the existing urban rail network, will form the backbone of the public transport system in the Greater Kuala Lumpur/Klang Valley region in Malaysia. The first MRT line implemented is the 47 km Kajang Line, of which 9.5 km is underground tunnels with seven underground stations. Construction of the line began on 8 July 2011 and achieved the full line opening on 17 July 2017. The second MRT line―Putrajaya Line―began fully operations on 16 March 2023, stretches from Sungai Buloh to Serdang and ends at Putrajaya for a length of 57.7 km, of which 13.5 km is underground tunnels with 10 new underground stations. Like all other metro underground stations/tunnels designed as part of the urban city, the KVMRT underground construction faces challenges from a technical (engineering design and construction) as well as social (environmental and land related) point of view. Needless to say, underground construction in Klang Valley is intensified with the inherent geotechnical challenges presented by complex ground conditions ranging from hard granite, heterogeneous Kenny Hill formation and extreme karstic limestone with fully developed weathered profiles to soft recent deposits including alluvium and mine tailing that is under‐consolidated in places due to past mining activities. The development of this large‐scale infrastructure project has not only opened up tremendous works and new frontier for tunnelling and geotechnical engineering in Malaysia, but it also provided a wealth of information of unique geotechnical challenges/accomplishments as well as technology breakthrough and design innovation in underground engineering. This article discusses some aspects of geotechnical challenges and interesting lessons learnt as well as numerous innovations embedded into this highly complex urban underground construction project.

Experimental and Numerical Studies on Splitting Fracture of Rocks Using Different Bit Heads

A hydraulic splitting method was recently developed to reduce the generation of noise and vibration in urban underground construction. However, research on optimizing the method considering the shape of the hydraulic splitting machine or the rock type has yet to be conducted sufficiently. Herein, experimental and numerical investigations were conducted to identify the crushing performance of six types of bit heads on three kinds of rocks (granite, marble, and sandstone). The uniaxial and triaxial compressive test, Brazilian test, and semicircular bend (SCB) test were conducted to investigate the physical properties of the rocks. Simultaneously, the splitting fracture of the rocks was investigated depending on the shape of the bit head. The test results showed that the failure of the specimens was controlled by the tensile strength of the rock, while the failure mode was governed by the type of the bit heads. Based on the test results, a damage-plasticity model was used to simulate the failure test by introducing double damage variables. Consequently, the numerical simulations effectually replicated the failure modes of the splitting fracture of the rock samples by the different bit heads.

Research on Ground Surface Settlement of Curved Pipe Jacking Based on Numerical Simulation

The construction disturbance caused by pipe jacking is an index that must be strictly controlled in the project. With the wide application of curved pipe jacking in urban underground construction, predicting its ground surface settlement characteristics has become an increasingly important research topic. Based on finite element numerical simulation, a three-dimensional model of curved pipe jacking was established to simulate the construction stage. Compared with the straight pipe jacking, the normal component of jacking force is set in the outer tunnel of the curved pipe jacking to simulate the extrusion of the outer soil caused by the corner of the pipe joint, and the surface settlement characteristics of the curved pipe jacking are explored by changing the pressure value. The research results show that the surface settlement of the curved pipe jacking conforms to the normal distribution as a whole. Compared with the linear pipe jacking, the surface settlement is not symmetrical about the design axis of the tunnel. With the increase of the pressure outside the tunnel, the maximum settlement value of the surface and the difference between the two sides of the axis increase. Compared with the Peck formula, the width of the settling tank of the curved pipe jacking is larger, the convergence rate outside the width of the settling tank is slower, and the settlement trend is more in line with the Verruijt formula. The calculation formula is modified by axis offset distance and ovalization coefficient and modified formula can better reflect the measured engineering data. The research results can provide guidance and reference for the prediction and control of surface settlement of curved pipe jacking.

Leakage Analysis and Hazardous Boundary Determination of Buried Gas Pipeline Considering Underground Adjacent Confined Space

Urban underground construction projects are intertwined vertically and horizontally, and adjacent confined spaces such as water supply and drainage pipelines, side ditches and underground canals may exist near buried gas pipelines. Once the buried gas pipeline leaks, the gas will diffuse into the confined space through the soil and even enter the residential room by the confined space, which brings serious potential safety hazards. In this paper, the underground adjacent confined space hazardous boundary (HB) of underground gas pipeline leakage was defined, the distribution properties of gas leakage diffusion flow field were analyzed by numerical simulation and the distribution law of gas entering the confined space was studied. Using the least-squares method and multiple regression theory, the gas concentration prediction model in the adjacent confined space of buried gas pipeline leakage was established, the HB calculation model was further deduced, and the HB drawing board was drawn. The results showed that in the initial stages, the internal and external pressure and velocity distribution of the pipeline near the leakage hole were unstable, reaching a stable state after 60 s, and then the reverse flow occurred in the pipeline downstream of the leak hole. Reducing the minimum construction distance between the buried gas pipeline and the confined space improved the gas distribution concentration in the confined space. When the minimum construction distance increased from 3 m to 9 m, the gas concentration distribution decreased from 90.21% to 0.88%. Meanwhile, increasing the pipeline pressure and leakage diameter enhanced the gas concentration distribution in the confined space. The HB calculation model and HB drawing board realize the rapid determination of the HB between buried gas pipeline and confined space and offer a more reasonable basis for the design of gas pipeline safe distance in urban underground engineering construction.

Analysis of mechanized tunneling parameters to determine the overcutting characteristics

Tunneling in urban conditions requires costly measures, in order to ensure the safety of existing buildings. On average, there are up to 17–20 buildings per 1 km of Moscow Subway Lines under construction. Analysis and comparison of geotechnical monitoring data and results of geotechnical estimations for underground construction using cut-and-cover and tunneling methods in conditions of high-density urban area shows an unsatisfactory correlation between estimated and actual data. This can be described in the following way: insufficient geotechnical survey data; discrepancy between the accepted estimation model and the actual behavior of soil under load; insufficient qualification of the construction workers; and overcutting. The study was aimed at solving the urgent scientific and engineering problem of determining the characteristics of overcutting during mechanized tunnel boring. At the first stage, the investigations were aimed at identifying the key reasons and factors which determine the quantitative parameters of overcutting in urban underground construction by tunneling. These factors include the following: mismatch between the cutting diameter and the outer lining diameter; displacement of the soil mass in front of the face; incomplete grouting of voids beyond the lining; incomplete filling of beyond-shield voids with clay mortar or slow-curing grouting mortar or no filling at all; and human factor (low qualifications of personnel). The overcutting coefficient was determined on the basis of the proposed empirical dependence of its values with regard to the depth of tunneling. The experimental data allowed the depth dependence of the overcutting coefficient for different tunneling depths to be defined, as well as for tunnel diameters from 4 to 10 meters in the case of mechanized tunnel boring machine (TBM) using the earth pressure balanced tunneling method. The practical importance of the studies consists in determining the range of the empirical overcutting coefficient variation from 0.5 % (for TBMs with nominal diameter of 10 m) up to 5 % (for TBMs with nominal diameter of 4 m). The development of organizational measures and justification of process solutions, aimed at ensuring the safety of the existing buildings in conjunction with the scientific and technical support of underground construction has led to a shortening of tunneling time between the Okskaya and Nizhegorodskaya stations of Nekrasovskaya Line of Moscow Subway by about six months. It has also provided savings of about 2.5 billion rubles.

Analysis of four shield-driven tunnels with complex spatial relations in a clay stratum

The tunnelling-induced ground settlement is a key concern during urban underground construction. This paper examined the ground settlement caused by multi-line tunnelling with earth pressure balance shield in the clay stratum in Tianjin, China. Laboratory tests are conducted to determine the soil parameters used in the modified Cam-Clay model. The real-data numerical simulation achieves a good agreement with in-situ monitoring data. The influence zone partition of multi-line tunnel construction is obtained and then used to evaluate the safety risks. An improved Peck formula is proposed based on the combination of superposition, overlapping and grouting effects. The parameter ranges are calibrated by means of statistical and numerical analysis. This study provides a reliable reference and practical tool for design and construction of multiple tunnels in a clay stratum.

A new method for predicting the friction resistance in rectangular pipe-jacking

In rectangular pipe-jacking, excessive friction force resulting from the pipe-soil interaction is the dominant factor hindering its further application in long-distance, larger-section, and deep-buried scenarios in urban underground construction. These complex scenes are the frontiers and key issues that need to be developed in this method. To this effect, this paper aims to investigate the pipe-soil interaction and improve the prediction accuracy of the friction force in rectangular pipe-jacking. The widely used friction force solutions were examined based on the actual monitoring data via two field cases in Japan. The reasons for the current overestimation of the friction resistance in rectangular pipe jacking were discussed. To avoid the prediction deviation in the empirical and theoretical formulas, a new pipe-soil contact model for rectangular pipe-jacking was proposed for friction force prediction under the lubricant applied condition. Further, a numerical simulation was conducted using the finite element method to verify the proposed model. Combining the numerical results and field data, the developed model was preliminarily proved and it could provide the prediction accuracy of friction force within 5.5% in the greater Tokyo area. The results suggest that the improved friction force prediction could provide a reference for future designs of long-distance rectangular pipe-jacking.

Demonstration and Analysis of Urban Traffic Tunnel Expansion Project Adjacent to Buildings

With the increasing number of urban underground construction projects, the evaluation of the influence of tunnel expansion on building foundation is one of the important factors to be considered in the project. In this paper, the deformation of the upper structure and the deformation pattern of the upper structure were analyzed, and the two-dimensional finite element model was built based on the case of Chongqing Jiefangbei Underground Ring Road Expansion Project Scheme. Comparative analysis of the deformation and changes in stress of the two tunnel expansion construction schemes of full-frame support and bolt suspension was performed, and the safety, rationality and feasibility of the bolt suspension scheme was confirmed through project safety analysis. It is hoped that this paper will serve as a reference for similar projects in the safety control technology of tunnel construction process.

Strategy of Underground Construction Planning Based on Cognitive Modeling Methodology

Strategy to planning urban underground construction is considered as a tool for sustainable development concept for megapolises. The cognitive methodology, which is viewed as a decision-making process regarding behavior of complex systems in desirable future, is proposed for evaluating prospects of urban underground construction. Introducing disturbances to the vertices, the decision-maker is looking for the answer to the question: “What will happen if ...?” The conducted studies using this methodology allowed to propose a number of scenarios for assessing advisability of underground construction, considering highlighted groups of geological and technogenic factors, uncertainties of various nature and risk factor groups. The employed technique is a new tool for evaluating various risks, likelihoods of negative scenarios and related additional expenses, as early as a pre-project stage of underground construction.

Risk control system for the construction of urban underground structures

Complex development of dense urban underground space puts forward a number of requirements that must be taken into account when planning, designing and building, because underground structures under construction and in operation are high-risk areas and, in the event of an accident, pose a serious danger to the people in them. The purpose of the risk control system for the construction and operation of underground structures in megacities is to ensure the successful functioning of urban systems in conditions of risk and uncertainty. In the event of an emergency, the implementation of risk control measures should ensure that the adverse impact caused by accidental events on the successful operation of megacity facilities is minimized. The article considers the functional risk control system in urban underground construction, presents an analysis and classification of risk-forming factors that affect the environmental and technological safety of urban underground space development. Qualitative and quantitative indicators of risk development were identified. The main requirements and principles of forming a risk control system for the development of urban underground space are formulated.

Experimental and numerical investigation of gas diffusion under an urban underground construction

• Built 10 m full-scaled utility tunnel mockup for experimental research. • Evaluated different air supply diffuser models and turbulence models. • Qualitative and quantitative comparisons for model performances. Rapid increase of urban underground constructions has a great consideration of underground environment safety and how to expel toxic gasses out of tunnels effectively. The utility tunnel is a typical urban tunnel construction with multiple underground pipelines including gas pipelines, and it is necessary to investigate characteristic of gas diffusion and monitor gas leakage to ensure tunnel safety. In this study, the experimental measurements of airflow and gas distributions were conducted in a 10 m full-scaled utility tunnel mockup, and gas diffusion characteristic was also investigated. Numerical simulation of utility tunnel leakage was also conducted by computational fluid dynamics (CFD). Different turbulence models and different air supply diffuser models were compared via the experimental results based on visualization and the relative root-mean-square error (RRMSE) index, which quantitated the difference between the numerical and experimental results. The results showed that the standard k − ε turbulence model and random air opening model could provide better results than other models. According to the experimental data analysis, it was necessary to consider the optimization of monitoring detector arrangements in actual utility tunnels. This study provided basic experimental data and the validated numerical model for the leakage source identification and underground tunnels simulation research.

Review of cutting-edge sensing technologies for urban underground construction

An accurate understanding of infrastructure performance is beneficial for averting potentially severe accidents during construction because the increasing development of urban underground resources presents certain challenges. Cutting-edge sensing technologies offer intriguing solutions to assess conditions and monitor structural health. Depending on the characteristics of underground construction, fibre optics, photogrammetric, and other advanced sensing technologies are introduced. Such techniques have become commercially available and address the construction features and monitoring objectives of urban underground engineering with high-precision, automation, high-frequency, and high-resolution capabilities. This review summarises these technologies using examples to facilitate the selection of appropriate sensing technologies for upcoming projects.

3D geological modeling and engineering properties of shallow superficial deposits: A case study in Beijing, China

Three-dimensional (3D) geological modeling has been developed in recent decades to overcome the complex nature of shallow superficial deposits in urban areas as a result of urbanized advancement. To meet the requirements of 3D geological models in the urban underground space construction in Beijing City, we constructed a coupled 3D model of geological sequences setting up to 50 m from the surface, and geotechnical properties of subsoils in Beijing for the first time via Creatar Xmodeling software. The modeling relies on 107 intersecting cross-sections and the horizons-to-solids approach aims to provide an insight into related modeling projects, especially in a complicated alluvial environment. In this paper, we described detailed modeling procedures, exhibited the outputs from the 3D model (combined geological units, cross-sections or fence diagrams, and properties presented in the form of horizontal distribution maps), and analyzed typical engineering properties of silty clay and clay units. The achieved 3D attributed model provides geologists an effective method to visualize the property characteristics of each layer and the potential connections between them, thereby to predict underground conditions and to reduce risks in geotechnical engineering processes such as urban underground constructions.

Face Stability Analysis for a Shield Tunnel in Anisotropic Sands

Abstract Shield tunnels are widely used in urban underground construction. The stability of the tunnel face has become a crucial issue in shield tunneling. In this paper, the anisotropy of friction...

Assessment of the Twin-Tunnel Interaction Mechanism in Kenny Hill Formation Using Contraction Ratio Method

Volume loss during tunneling excavation leads to ground deformation, which can damage adjacent surfaces or subsurface structures. Thus, tunnel design with proper estimation of ground deformation and realistic geotechnical simulation is essential for large-scale urban underground construction. In this study, subsurface characterization of the tunnel excavation section in Kenny Hill Formation (KHF) was conducted to develop 3D ground model and tunnel-filtered models and obtain ground sections through the spatial interpolation of borehole data using the Inverse Distance Weighting (IDW) method. Six greenfield ground sections were selected by using the tunnel-filtered model’s configuration of tunnels and available tunneling-induced ground movement data. Conceptual models for finite element modeling were developed based on soil profiles, and the corresponding soil parameters were determined from ground sections. The strength and stiffness parameters of the Hardening Soil (HS) model were established using data from site investigation, in situ and laboratory tests, and empirical correlations with standard penetration test. The effectiveness of empirical correlations was determined through back analysis of twin-tunnel excavation in 2D finite element analysis using the contraction method and verified with monitored ground movement data. The numerical back-analyzed results of twin-tunnel excavation simulation using HS parameters obtained from a selected empirical correlation showed good agreement with construction-monitored ground movements. The application range of the values of contraction ratio was from 0.3 to 0.95%.

On the uniaxial compression strength of frozen gravelly soils

Frozen gravelly soils are often encountered in both cold regions engineering and urban underground constructions by artificial freezing method. This work takes a gravelly sand in Beijing as the basic material. Gravel grains of 10–20 mm in size are obtained and mixed with sand grains at certain ratios and then saturated frozen samples are prepared. Uniaxial compression test is used to study the uniaxial compression strength (UCS) of the material under 3 temperatures and 3 strain rates. Together with 4 gravel contents, 36 combinations are investigated. Test results show that stress-strain curves generally demonstrate strain-softening manner, with different strain energy dependent upon temperature and strain rate on the one hand, and on gravel content upon the other hand. An inclination of approximately 55° to 58° is found for the failure surface. UCS is obtained from all tests for analysis. It is found that the UCS of frozen gravelly soil increases with the decrease of temperature and the increase of strain rate. Generally accepted empirical relationships for fined-grained frozen soils are still applicable with the correlation coefficient of very close to 1. Gravel content plays another important role in the UCS of frozen gravel soil. UCS is found to decrease significantly with the increase of gravel content at high strain rate. At relatively low strain rates however, influence of gravel content on UCS turns out to be complicated. Mechanism of the mechanical performance of the sand-gravel-ice system is proposed in terms of gravel contents, ice contents as well as strain rate.

EVALUATING CONSTRUCTION SITES FOR UNDERGROUND PARKING LOTS USING MODIFIED MORPHOLOGICAL ANALYSIS METHOD

Purpose. Development and testing of a model that formalizes and supports decision-making process regarding the appropriateness of using territory (geological environment) for urban underground construction. Methodology. Modified morphological analysis of urbanized territories, expert evaluation method. Findings. A morphological model as a tool set for evaluating construction sites for underground construction was tested; the morphological tables were constructed; the expert estimate scales for alternative values of construction site parameters were justified; the cross-consistency matrices of influence factors and parameter alternatives were evaluated; evaluation of two sites in Kyiv for construction of underground parking lots was performed using the developed model. Originality. For the first time a morphological model of territorial development for underground city planning that combines the influence of structural and functional factors with impact of geological environment, was designed and tested on real construction sites in Kyiv; the modified morphological analysis method was applied for risk estimation of urban development of underground space; systemic characteristics of urban territories were obtained, which show the favorability of a site for underground construction of a parking lot. Practical value. Evaluating the prospect of underground construction on the pre-project stage, capabilities for risk management of urban underground city space development, diminishing the potential for project flaws caused by neglecting certain factors or specifics of a geological environment and technogenic impacts, convenient form of information generation as tables, charts or graphs.

Occupational exposure to radon for underground tourist routes in Poland: Doses to lung and the risk of developing lung cancer.

Radon concentrations for 31 Polish underground tourist routes were analyzed. The equivalent dose to the lung, the effective dose and the relative risk were calculated for employees of the analyzed routes on the grounds of information on radon concentrations, work time, etc. The relative risk for lung cancers was calculated using the Biological Effects of Ionizing Radiation (BEIR) VI Committee model. Equivalent doses to the lungs of workers were determined using the coefficients calculated by the Kendall and Smith. The conversion coefficient proposed by the International Atomic Energy Agency (IAEA) in the report No. 33 was used for estimating the effective doses. In 13 routes, the effective dose was found to be above 1 mSv/year, and in 3 routes, it exceeded 6 mSv/year. For 5 routes, the equivalent dose to lungs was higher than 100 mSv/year, and in 1 case it was as high as 490 mSv/year. In 22.6% of underground workplaces the risk of developing lung cancer among employees was about 2 times higher than that for the general population, and for 1 tourist route it was about 5 times higher. The geometric mean of the relative risk of lung cancer for all workers of underground tourist routes was 1.73 (95% confidence interval (CI): 1.6-1.87). Routes were divided into: caves, mines, post-military underground constructions and urban underground constructions. The difference between levels of the relative risk of developing lung cancer for all types of underground tourist routes was not found to be significant. If we include the professional group of the employees of underground tourist routes into the group of occupational exposure, the number of persons who are included in the Category A due to occupational exposure may increase by about 3/4. The professional group of the employees of underground tourist routes should be monitored for their exposure to radon. Int J Occup Med Environ Health 2017;30(5):687-694.

Leveling vs. InSAR in urban underground construction monitoring: Pros and cons. Case of la sagrera railway station (Barcelona, Spain)

Monitoring is required when dewatering underground construction sites to anticipate unexpected events and preserve nearby existing structures and/or buildings. The most accurate and widespread monitoring method to measure displacements is leveling, a point-like surveying technique that typically allows for tens of discrete in situ sub-millimeter measures per squared kilometer. Another emerging technique for mapping soil deformation is the interferometric synthetic aperture radar (InSAR) method, which is based on SAR images acquired from orbiting satellites. This remote sensing technique can provide better spatial point density than leveling, more extensive spatial coverage and lower-cost acquisitions. This paper analyses, compares and discusses leveling and advanced multi-temporal InSAR measurements when they are used to measure the soil deformation induced by the dewatering associated with underground constructions in urban areas. This comparison, which has not been considered in previous works, is of paramount importance to ascertain the most suitable technique (or combination of techniques) in these contexts. To do so, an experiment was performed in the future railway station of La Sagrera, Barcelona (Spain), in which leveling and advanced multi-temporal InSAR were used to quantify ground deformation by dewatering. The results showed that soil displacements measured by leveling and InSAR were not always consistent. In the context of soil deformation measurements produced by dewatering in urban areas, InSAR measurements appear to be more accurate for investigating soil deformation, whereas leveling was more appropriate for quantifying the real impact on the nearby buildings.