Urban Underground Engineering Research Articles

Experimental Study on the Effect of Environmental Water on the Mechanical Properties and Deterioration Process of Underground Engineering Masonry Mortar

Urban underground engineering is generally buried at a shallow depth and suffers long-term environmental water effects such as rainfall, rivers, underground pipeline leakage, and groundwater. The mechanical properties of the structures are affected by constant deterioration, which seriously hinders the safe, healthy, and sustainable development of the city. On the basis of on-site investigation of civil defense engineering, this article simulates the water environment conditions of mortar in underground engineering in the laboratory and conducts manual sample preparation in the laboratory. Then, water, H2CO3, NaCl, and Na2CO3 solution or wet–dry cycles are used to corrode the sample, respectively. A uniaxial compression test, Brazilian splitting test, analyses of the acoustic emission signals and electromagnetic signals, and magnetic imaging testing are performed, respectively. The results show that an increase in the action time of environmental water leads to a gradual increase in the uniaxial compressive strength, tensile strength, and elastic modulus of cement mortar, but it will decrease over a long period of time. Different environmental water components can also lead to a different performance of soaked mortar. The uniaxial compressive strength R, tensile strength σt, and elastic modulus E of mortar samples exhibit values in different solutions in the order of H2CO3 solution < NaCl solution < Na2CO3 solution < water. A moderate solution soak time can enhance the mechanical properties of the mortar, but this effect decreases at long time scales. The effect of wet–dry cycles on the mechanical properties and degradation process of mortar is significant. With the increase in wet–dry cycles, the porosity of mortar continuously increases. The cumulative ringing count, energy, amplitude, and impact number of acoustic emission signals always increase when the samples are loaded to failure. The uniaxial compressive strength, tensile strength, and elastic modulus first increase and then decrease. The experimental results lay the foundation for further investigating the performance changes in mortar under complex water environments in underground engineering.

Behavior of Horizontal-Directional Drilling for Multi-Pilot Heading Pretreating Blind Spots in Pipe Jacking Construction

The application of non-excavation construction technology, such as the pipe jacking method, has obvious advantages in building urban underground space engineering projects, which can effectively reduce the occupation of ground surfaces and the migration of obstacles above or below the ground. However, pipe jacking machines with a rectangular cross-section can easily encounter great difficulty due to the significantly increased jacking resistance while it is jacked in hard rock strata, which are often influenced by large blind spots on the working face of pipe jacking machines with a rectangular cross-section. The aforementioned blind spots belong to areas that cannot be cut by the cutter heads due to the circular cutterhead and rectangular outer frame of pipe jacking machines with a rectangular cross-section. Therefore, the effective pretreatment of the aforementioned blind spots should be implemented prior to operating pipe jacking machines with a rectangular cross-section in hard rock strata. This paper presents a case study of employing horizontal-directional drilling as a multi-pilot heading pretreatment for breaking large blind spots on the working face of pipe jacking machines with a rectangular cross-section, which was implemented prior to operating a pipe jacking machine with a rectangular cross-section in shallow buried rock strata. In particular, this multi-pilot heading pretreatment is expected to be used to safely construct a rectangular comprehensive pipe gallery using pipe jacking machines with a rectangular cross-section in shallow buried rock strata and when passing underneath existing light rail lines, which can effectively save the precious land resources required for sustainable development. The study was implemented by employing a numerical simulation, focusing on the safety of the adjacent existing light rail line and the stability of the surrounding rocks, which are influenced by the variation in the distribution positions and sizes of the drilling holes used when implementing the horizontal-directional drilling. The results demonstrate that the horizontal-directional drilling applied for the multi-pilot heading pretreatment could effectively break the blind spots on the working face of the pipe jacking machine with a rectangular cross-section, in which the safety of the adjacent existing infrastructure was significantly influenced by the distribution positions and sizes of the drilling holes used when implementing the horizontal-directional drilling. This study can provide a reference for carrying out pipe jacking construction using pipe jacking machines with a rectangular cross-section, in which horizontal-directional drilling is employed as the multi-pilot heading pretreatment for breaking the large blind spots on the working face. Moreover, the distribution positions and sizes of the drilling holes used when implementing the horizontal-directional drilling could be appropriately optimized by utilizing the method of numerical analysis. Meanwhile, the study is also expected to eliminate the hazards of safely running the aforementioned adjacent existing light rail line during implementing the multi-pilot heading pretreatment of horizontal-directional drilling.

Three-Dimensional Inversion Algorithm with A Footprint Computational Domain for Underground Engineering

Granite bodies pose a common geohazard in urban underground engineering. The GEM-2 system, employing small coils as transmitter and receiver (Tx-Rx), has gained widespread adoption for efficiently and non-invasively delineating low resistivity targets with 1D results in the near-surface. In this paper, we propose a 3D inversion algorithm based on the footprint-guided compact finite element method and Gauss-Newton optimization to accurately delineate the 3D structure of granite boulders. To demonstrate the effectiveness of our 3D inversion method, we conducted a GEM-2 test survey in a scenario featuring a granite boulder. The inversion results exhibit superior horizontal resolution compared to the current 1D inversion methods. The three-dimensional contour of the boulder is clearly depicted by areas of relatively high resistance, showcasing the capability of our inversion algorithm.

Generalized complex variable analysis of shallow tunneling through multi-layered ground

The mechanical analysis of shallow tunnels crossing multiple ground layers is a common problem in urban underground engineering. Since the tunnel boundary intersects multiple ground layers, the challenges of mixed boundary value problem for composite boundary and the conformal mapping of irregular banding computational domain are faced in solving the multi-boundary problem. For this, a new solution strategy regarding the generalized complex variable method to calculate the mechanical responses of the multi-layered ground is proposed. The research object is divided into two independent objects including the complete multi-layered ground without tunnel and the complete tunnel boundary. Firstly, the mechanical responses of the complete multi-layered ground are solved through the superposition of multiple single-boundary contributions. Subsequently, the virtual boundary circle and its corresponding analytic functions are introduced in analyzing the tunnel boundary contribution. Finally, the solution for the stress and displacement field of the multi-layered ground is modified by superimposing the contribution of the virtual boundary circle, so that all the given boundary conditions are satisfied. The self-consistency and accuracy of the proposed method are validated by several examples. The characteristics of the displacement propagation of typical multi-layered ground patterns are analyzed based on the analytical solution. The proposed method can be used to analyze the mechanical responses of multi-layered ground with arbitrary intersections between the tunnel and ground boundaries.

Detection and Monitoring Technique in Urban Underground Space Engineering – A Review

Detection and Monitoring Technique in Urban Underground Space Engineering – A Review

Approximate analytical solution of tunneling‐induced responses of a soil–foundation system using contact mechanics

AbstractEstimating the tunneling‐induced responses of a soil–foundation system is crucial for safety control in urban underground engineering. In existing analytical research, the soil–foundation interaction is considered based on the Winkler soil model, with minimal focus on the continuum soil model. Hence, in this study, based on the continuum soil model, an approximate analytical solution is derived to predict the tunneling‐induced responses of a soil–foundation system considering the contact effect, where an approximation by replacing the surface of the complex variable solution for an elastic half‐plane with a tunnel with the mathematical expression of Sagaseta's ground loss settlement formula is adopted. A new strategy is proposed to optimize the derivation process, where the normal contact pressure after tunnel excavation is directly determined using the contact mechanics, and the proposed solution is obtained using the superposition principle. Subsequently, the approximation is proven to be accurate when the ratio of the buried depth to the tunnel radius is greater than 2.00. The proposed solution meets the given conditions and is in good agreement with numerical results, which verify the correctness of analytical solution. Furthermore, a parametric study is performed to investigate the influences of the key parameters on the mechanical responses. The results indicate that the proposed solution can quantitatively describe the nonlinear contact characteristics in the soil–foundation system; the contact effect is found to contribute to the discontinuous displacement and stress concentration when subjected to the significant effects of tunnel excavation.

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.

The extended range phase shift method for broadband surface wave dispersion measurement from ambient noise and its application in ore deposit characterization

Surface wave tomography using seismic ambient noise has been applied widely in subsurface characterization, the depth of which ranges from a few meters in urban underground engineering to tens of kilometers in delineation of crustal heterogeneities. Currently, multichannel analysis of surface waves with active and passive sources together with some similar techniques has been widely applied to obtain fine near-surface structures. However, it is still difficult to retrieve accurate dispersion curves at low frequencies with those methods to constrain structures at greater depths. To better retrieve surface wave dispersion data at lower frequencies using ambient noise data acquired by dense linear arrays, we use the extended range phase shift (ERPS) method, which can extract broadband dispersions from the ambient noise crosscorrelation functions (CFs). A broadband dispersion curve is obtained by merging a dispersion curve of medium-to-high frequencies with a dispersion curve of low-to-medium frequencies measured using receivers with different combinations, whereas both curves reflect the local property of the subsurface structure under a subarray with a relatively small aperture. Thus, the horizontal resolution of the inverted models is not compromised, whereas the inverted depth is improved considerably. We first perform a synthetic test to validate the ERPS method, and then apply the method in characterizing the Woxi polymetallic deposit in Hunan, China, where eight 10 km linear arrays using 467 seismic nodes were deployed to record ambient noise. The dispersion data within 0.5–10 Hz are extracted from the CFs using ERPS and then used to invert for the [Formula: see text] models down to at least 2 km. The inverted structures are found to be consistent with the previous geologic studies and known structures from underground mining, and the proposed passive-source imaging method is considered to be economical and practical for ore deposit explorations.

Analytical Solution on Ground Deformation Caused by Parallel Construction of Rectangular Pipe Jacking

Pipe jacking has been widely used in urban underground engineering construction in recent years. Prediction of ground deformation caused by pipe jacking is particularly important for the safety of construction. With regard to the densely arranged pipes used in the pipe roof structure method, an analytical model of stratum disturbance caused by jacking of parallel rectangular pipes is proposed on the basis of Mindlin’s displacement solution and the stochastic medium theory. The influencing factors such as soil loss, additional thrust on the excavation face, friction between pipe jacking machine and soil, friction between subsequent pipes and soil, and the grouting pressure were comprehensively considered. Then, a 3D numerical simulation and a case study were conducted. The results showed consistent agreement with the analytical solution, and the proposed method can take into account the asymmetry of surface settlement curve induced by construction. A discussion of the ground deformation law shows that the proposed approach can reasonably predict the ground deformation and provide a reference for relevant pipe jacking construction.

Foundation Treatment in Urban Underground Engineering Using Big Data Analysis for Smart City Applications

A core element of the sustainable approach to global living quality improvement can now become the intensive and organized usage of underground space. There is a growing interest in underground building and growth worldwide. The reduced consumption of electricity, effective preservation of green land, sustainable wastewater and sewage treatment, efficient reverse degradation of the urban environment, and reliable critical infrastructure management can improve the quality of life. At the same time, technological innovations such as artificial intelligence (AI), cloud computing (CC), the internet of things (IoT), and big data analytics (BDA) play a significant role in improved quality of life. Hence, this study aims to integrate the technological innovations in urban underground engineering to ensure a high quality of life. Thus, this study uses big data analytics to carry out the status quo of foundation treatment and proposes a conceptual framework named the BDA with IoT on urban underground engineering (BI0T-UUE). This framework connects hidden features with various high-level sensing sources and practical predictive model characterization to lower building costs, productive infrastructure management, preparedness for disasters, and modern community smart services. The IoT integration gives an optimum opportunity to work towards the functionality of ‘‘digital doubles’’ of secret infrastructure, both economical and scalable, with the increasing sophistication and tooling of the underworld. The simulation analysis ensures the highest efficiency and cost-effectiveness of the underground engineering with a value of 96.54% and 97.46%.

Analysis on the Status Quo and Construction Problems of Domestic Urban Civil Air Defense Engineering System in China

As the urbanization process in developing countries continues to accelerate, although my country has achieved significant results in planning and construction, there are still many problems. For example, the rate of urban green space decreases with the continuous increase of urban buildings. Therefore, the domestic urban underground civil air defence Engineering construction is in a very important position at this stage, and our development goals must be shifted from above ground to underground. This article analyzes the general situation of the domestic civil air defence engineering system, expounds on the current situation and existing problems of my country's urban civil air defence engineering system, which has an important influence on the development of my country's cities. Functional departments must take into account the various functions of civil air defence projects and put people's safety first. At the same time, firefighters should also improve their professionalism, leadership and organizational skills, and evacuate people when encountering danger and arrange for them to take refuge in designated locations. The technicians in the relevant departments in the city need to use scientific and technological means to mix the urban network system in series and parallel so that the various structures of the urban network system are unified and interact with each other. When a disaster strikes, it can protect the safety of the people and reduce the economic loss of the city. Reduce to the lowest level to maximize benefits.

Space-Time Effect Prediction of Blasting Vibration Based on Intelligent Automatic Blasting Vibration Monitoring System

The vibration produced by blasting excavation in urban underground engineering has a significant influence on the surrounding environment, and the strength of vibration intensity involves many influencing factors. In order to predict the space-time effects of blasting vibration more accurately, an automatic intelligent monitoring system is constructed based on the rough set fuzzy neural network blasting vibration characteristic parameter prediction model and the network blasting vibrator (TC-6850). By setting up the regional monitoring network of monitoring points, the obtained monitoring data are analyzed. An artificial intelligence model is used to predict the influence of stratum condition, excavation hole, and high-rise building on blasting vibration velocity and frequency propagation. The results show that the artificial intelligence prediction model based on a rough set fuzzy neural network can accurately reflect the formation attenuation effect, hollow effect, and building amplification effect of blasting vibration by effectively fuzzing and standardizing the influencing factors. The propagation of blasting vibration in a soil–rock composite stratum is closely related to the surrounding rock conditions with a noticeable elastic modulus effect. The hollow effect is regional, which has a significant influence on the surrounding ground and buildings. Besides, the blasting vibration of the excavated area is stronger than that of the unexcavated area. The propagation of blasting vibration on high-rise buildings was complicated, of which the peak vibration velocity is maximum at the lower level of the building and decreased with the rise of the floor gradually. The whip sheath effect appears at the top floor, which is related to the blasting vibration frequency and the building’s natural vibration frequency.

Identification of core risk factors and risk diffusion effect of urban underground engineering in China: A social network analysis

Risk assessment plays an important role in urban underground engineering construction. Although the traditional risk assessment methods can quantitatively evaluate the risk of engineering project, they have limited capabilities in identifying the most influential risks and analyzing development mechanism of risks. Based on this, a novel risk analysis method is proposed to identify the core risk factors and analyze the risk diffusion effect of risk factors. Then, according to the characteristics of strong correlation of risk factors, a network of risk factors for urban underground engineering in China was constructed from multi-dimensional perspectives such as technology, organization management, environment and human factors in the whole life cycle. Furthermore, the core risk factors and the risk diffusion effect of risk factors are analyzed based on this novel method for urban underground engineering in China. The research results show that R1 (Unreasonable personnel arrangement of safety management organization), R4 (No regular inspection and supervision mechanism), R6 (Weak safety awareness of the personnel), and R12 (Unreasonable construction technology) are core risk factors of urban underground engineering, among which R1 and R4 have strong risk diffusion effects. Last, the accidents of subway construction from 2017 to 2019 in China were collected to verify the research results. The validation shows that the conclusions obtained in this study are in accordance with the results of accident case analysis. The research provides a new research idea of risk management and is helpful to target and manage the risk factors for project managers.

Mathematical model and calculation of safety and stability evaluation of underground space engineering by TOPSIS and analytic hierarchy process

The development of economy promotes the development of urbanization, and the power of urban space engineering, so the stability research of urban underground space engineering is very important. Although the existing evaluation models can consider a single form of underground space safety problems, they seldom consider the uncertainty of cross-blending of multiple information types within a certain interval, and cannot continuously express the quantitative results of the suitability assessment of urban underground space. This paper takes an underground tunnel in China as the research background, calculates the weight of the selected construction stability index through the analytic hierarchy process, and finally evaluates the stability of different sections of the project by TOPSIS method, and draws the corresponding conclusions.

Numerical analysis on surface settlement in parallel rectangular pipe jacking construction

In recent years, rectangular pipe jacking technology has been gradually applied in urban underground engineering. Based on a parallel rectangular pipe jacking project, a three-dimensional finite element model is established for numerical analysis, and the surface settlement caused by rectangular pipe jacking construction is studied. The research shows that the pipe jacking construction has the most obvious impact on the soil above the pipe jacking axis, and when the clear distance between parallel rectangular pipe is 1D (D indicates the pipe inner width), the main influence range of pipe jacking construction on soil mass is about 1D along the longitudinal direction of pipe jacking. With the increase of parallel rectangular pipe distance, the surface settlement trough becomes wider and the maximum surface settlement decreases. The main influence range of parallel rectangular pipe jacking construction at the outside of the pipe jacking is about 1D~1.37D along the lateral direction. When the pipe distance is greater than 2D, the interaction between parallel pipe jacking is weak, and the influence range at the outside of pipe jacking is almost the same as that of single pipe jacking construction. The research results can provide a reference for the design and construction of similar pipe jacking projects.

Research on New Technology Development of Urban Underground Engineering Construction

Research on New Technology Development of Urban Underground Engineering Construction

Constructing 3D geological models based on large-scale geological maps

Abstract The construction of 3D geological models based on geological maps is a subject worthy of study. The construction of geological interfaces is the key process of 3D geological modeling. It is hard to build the bottom interfaces of quaternary strata only using boundaries in large-scale geological maps. Moreover, it is impossible to construct bedrock geological interfaces through sparse occurrence data in large-scale geological maps. To address the above-mentioned two difficulties, we integrated two key algorithms into a new 3D modeling workflow. The buffer algorithm was used to construct virtual thickness contours of quaternary strata. The Inverse Distance Weighted (IDW) algorithm was applied to occurrence interpolation. Using a regional geological map of a city in southern China, the effectiveness of our workflow was verified. The complex spatial geometry of quaternary bottom interfaces was described in detail through boundaries buffer. The extension trends of bedrock geological interfaces were reasonably constraint by occurrence interpolation. The 3D geological model constructed by our workflow accords with the semantic relationship of tectonics. Through the model, the complex spatial structure of urban shallow strata can be displayed stereoscopically. It can provide auxiliary basis for decision-making of urban underground engineering.

Undergraduate program for Urban Underground Space Engineering in China: Exploration and practice

In light of the rapid development of underground spaces in China and the intense demands of professionals for underground space, the Ministry of Education of the People’s Republic of China has permitted the offering of the urban underground space engineering professional degree program in universities since 2001. This professional degree has now been established in more than 80 universities across China. In this study, the authors have analyzed and discussed the background, history, disciplinary source, learning goals, curricula, and core courses of this profession in great depth. The authors hope that our findings shall contribute to the advancement and development of global efforts to train professionals in urban underground space engineering, promote the development of this profession, and improve the quality of professional cultivation efforts in this field, which in turn drives the scientific development and utilization of underground spaces.

Practice and Teaching Reform of Engineering Geology for Urban Underground Space Engineering1

Engineering geology is an important compulsory professional basis course for the urban underground space engineering. Its teaching hours is a few but rich in content. This course pays equal attention to theory and practice, whose teaching is difficult and endowed with challenging. In order to adapt to the deep, large and especial construction for urban underground space engineering, we must reform the practice and teaching system of engineering geology. The reformed course is closely combining with the construction practice of underground engineering and reflecting the latest academic achievements. We strengthen the practice and open teaching, focus on training students’ innovation ability and innovative thinking in the teaching process.

Application of Artificial Ground Freezing Technology in Modern Urban Underground Engineering

Based on typical water-rich sandy gravel strata in Beijing, in order to explore the application of the artificial ground freezing method (AGF) in urban large-scale underground engineering, the formation and development of freezing body were analyzed when multirow freezing pipes were working together, and the group effect exhibited during the freezing process was also revealed in this paper. On this basis, the basin-shaped freezing method (BFM) is put forward as an application of AGF used in underground engineering. BFM structure consists of two parts: the frozen curtain (basin wall) around the excavation scope and the horizontal frozen body (basin bottom) at the bottom of the station. Physical model test and numerical simulation were conducted to study temperature field expansion of BFM under two different conditions. The results show the following: (1) The group effect refers to the cooling effect of different freezing pipes influencing each other during freezing process. Under the condition of still water, the group effect expands the freezing area, and it shows the gradual development of freezing from back water surface to front water surface under seepage condition. (2) BFM can effectively play the role of water proofing, and although different parts of basin structure show different frozen order under different conditions, both basin wall and basin bottom can form an effective thickness during the freezing process.