Escalator Tunnels Research Articles

Reduction of additional pressure from ground construction on the subway escalator tunnel

The study considered options for reducing the additional pressure from the construction of a single-storey building on the underground structures of a deep shallow metro station. In the 3D formulation, the efficiency of the unloading «bridge» over the escalator tunnel was evaluated by the finite element method. It was found that the stiffer the grillage plate of the unloading «bridge», the more effectively the additional pressure from the building is transferred to the soils below the bottom of the escalator tunnel. However, in this case it is impossible to completely eliminate the additional pressure. In this regard, the option of creating an underground floor was considered. In this case, the weight of the selected from the excavation soil compensates the load from the building. The required depth of the basement floor was determined analytically, calculations were performed in characteristic sections on 2D models, and the operation of all structures in combination was considered on a general 3D model. Based on the results of the study, a rational algorithm was proposed for calculating the additional pressure from ground construction on underground subway structures.

Substantiation of the Escalator Tunnel Construction Technology Based on the Results of Field Research

Purpose. The authors aim to substantiate a new technology for the construction of an escalator tunnel in Ukraine based on the results of field studies performed as part of surveying measurements during the construction of the inclined run of the Dnipro metro. Methodology. The article analyzes the main technology of the escalator tunnel construction, which was based on the development of an inclined working from top to bottom with preliminary preparation of the massif by means of artificial soil freezing. Several cases of application of the bottom-up escalator tunnel construction method using the New Austrian Tunneling Method (NATM), which is successfully used in metro of other countries, are considered. The main principle of the method is that a shotcrete system is used as a temporary (primary) support, and a reinforcement system with monolithic concrete is used as a permanent support. Findings. The authors analyzed the peculiarities of the escalator tunnel excavation of the Dnipro metro by the Turkish company «Limak» in 2017–2018. It was noted that the excavation was carried out from the bottom up in conditions of strong rock (plagiogranite) using drilling and blasting operations. The characteristic results of field studies during drilling and blasting operations in the process of developing the calotte are analyzed. On the basis of these data, it is possible to trace the tendency to the appearance of minor overburden during sinking. The value of the deformed state (displacement of the contour of the designed casing) is within the normative limits, which indicates the effective use of these works within the framework of NATM. It is proved that in the conditions of military operations, the technology of building an escalator tunnel from the bottom up is a guarantee of the safety of workers and equipment. Originality. The results of the scientific work presented in the article make it possible to determine the level of deformed state during the excavation of the escalator tunnel of the Dnipro metro in hard rocks. During the field studies, the dependences of deformation of plagiogranite in the inclined bore were obtained. Practical value. An alternative technology for the construction of a bottom-up escalator tunnel based on NATM with the provision of normative deformation of the surrounding rock mass is substantiated.

JUSTIFICATION OF THE CHOICE OF THE CALCULATION MODEL OF THE ESCALATOR TUNNEL IN FLAT AND SPATIAL SETTINGS

Purpose. To perform an analysis of analytical and numerical methods of mathematical modeling of an escalator tunnel. To identify the main characteristics and differences of methods based on flat or spatial settings. To justify the choice of the calculation model of the escalator tunnel and its setting. To justify the choice of the calculation model of the escalator tunnel and its construction. Methodology. To achieve the goal, a number of analytical methods based on a flat (2D) setting (Gap method, Volume loss control method, Convergence-confinement method) were analyzed. Approaches in numerical methods, in particular in the method of finite elements, which have successfully applied flat setting, are considered. The spatial (3D) setting in the finite element method is also analyzed. Analysis of a numerical experiment based on 3D models shows that the three-dimensional structure forces interpretation decisions that are not taken into account in the cross-section, that is, in the two-dimensional model. Findings. Finite-element models of the escalator tunnel were developed in flat and spatial settings, and the 2D model with a thickness of 1 m repeated the conditions of the 3D model in its middle part. The obtained parameters of the stress-strain state were subjected to comparative analysis. It was found that the values of the norms of horizontal and vertical stresses in the fragment of the 3D model (middle) and in the 2D model differ by 3.2 and 7.2 %, respectively. Originality. Based on the results of the justification of the choice of the calculation model of the escalator tunnel, it was proved that the use of 2D models is adequate for the system of interaction of the escalator tunnel with the surrounding massif. This statement is evidenced by the almost identical distribution of stresses and strains in finite-element models in flat and spatial settings. Practical value. In the course of research, it has been proven that the flat finite-element model of the escalator tunnel is adequate for the given task, provided that it is used in several characteristic sections of the escalator tunnel, that is, the creation of a number of models in 2D, which allows considering its position along the length of the calculated tunnel.

Calculation-theoretical justification of the compensation grouting parameters for the metropolitan railway protection from sedimentary deformations

An increase in the volume and scale of underground space development, including the construction of metropolitan railway facilities in large cities, is accompanied by a significant impact on the surrounding urban development, which requires the development and implementation of a set of special measures to protect buildings and structures from excess deformations. At the same time, numerous above-ground and underground structures are involved in the area of influence of the construction, including existing metropolitan railway facilities, as well as residential buildings and above-ground transport facilities. Сurrently, one of the most effective methods that provide reliable facilities protection from sedimentary deformations is the compensation grouting method. The article outlines the theoretical foundations for the use of compensation grouting technology to protect buildings and structures from excess sedimentary deformations during the construction of transport infrastructure facilities in dense urban areas. A mathematical model has been developed that corresponds to the actual geometry of the computational area of the metropolitan railway lobby with a soil base, the actual physical and mechanical characteristics of the materials of its structures, and the soil mass. The article presents the computer modeling results, with its help determined volumes, pressure, sequence, and injection sites. Based on calculated data, the duration of the special solution compensatory injection was determined to maintain a stable position of the foundations of the metropolitan railway escalator tunnels by forming the calculated stress-strain state of the soil mass at the ground slab base of the structure to provide a given preventive lift, the dependences of the lift deformations on pressure and the grouting volumes of special mixtures were established. Based on the obtained data, a procedure was developed for the production of work to maintain the planned-altitude position of metropolitan railway facilities at all construction stages and operation of the multifunctional complex.

Uphill excavation of an escalator barrel between operational underground platforms

A new underground triple escalator has been provided at Bank Station in London as part of a major capacity upgrade project. Unusually, the inclined escalator tunnel was excavated uphill rather than downhill due to restricted access. Using a sprayed-concrete lining and no pilot tunnel, it was a first in the UK for a triple escalator. The new escalator intercepted several existing structures which had to be backfilled and then broken out, some just 0.5 m from operational Tube lines. This paper sets out design considerations, construction sequence decisions and operational risk management, and discusses the existing assets’ response to uphill tunnelling based on a comprehensive monitoring scheme.

The comparative analysis of the stress-strain state of the support of the escalator tunnel constructed in weak soils by the NATM

The construction of underground objects of the subway is always associated with building of structures connecting the surface. For subways, such structures are escalator tunnels. During the construction of the Dnipro Metro, these underground structures are built using a new technology that forms a multilayered support. This technology is the New Austrian tunneling method. A special feature of its application under the conditions of the Dnipro city is the existence of weak rocks in the upper part of the escalator tunnel. To ensure their stability, various special operational techniques are used that impact the rock massif. The basic techniques include artificial freezing, which was the dominant strengthening technology, and chemical strengthening (cementation), which is more consistent with the New Austrian tunneling method. To elucidate the effectiveness of the two strengthening techniques, a finite-element model of the Dnipro Metro escalator tunnel has been built. The numerical calculation of two variants for the strengthening of weak soils yielded results for a comparative analysis of the stress-strain state. The result of the comparative analysis is the conclusion of greater cementation efficiency when strengthening weak soils of the massif in which the escalator tunnel is constructed using New Austrian tunneling method.

ON ONE METHOD FOR CALCULATING THE STRESS-DEFORMED STATE OF ESCALATOR TUNNELS

In the article, based on the finite element method, the main stages of the study of free oscillations are given, since the separation of normal coordinates in the system of differential equations of vibrations of structures is possible only with constant global stiffness and damping matrices of the system. The method of calculating the stress-strain state of the subway escalator tunnel structure under the influence of both constant and seismic loads, as well as with a special combination of loads, is given in order to scientifically substantiate the design and construction of its lining made of monolithic reinforced concrete in Almaty, which allows, in general, to obtain significant economic efficiency compared with the traditional method of lining made of cast-iron tubing. A comparative analysis of the stress-strain state of the lining is performed from the main combination of loads, seismic impact and a special combination of operational loads. The authors proposed a finite element design scheme of the lining and the surrounding soil massif. The analysis of the distribution of vertical displacements in the tunnel lining is carried out on the basis of the application of the dynamic theory of seismic resistance for building structures of special responsibility.

Deformations assessment during subway escalator tunnels construction by the method of artificial freezing of soil for the stage of ice wall formation

The work is devoted to the study of the processes of displacement and deformation of the surface during the escalator tunnels construction of the subway by the method of artificial freezing of soils. The features of the construction and freezing technology, the rocks characteristics in which the escalator tunnels made are considered. The data of specially organized, full-scale surveying observations of deformations on the earth surface are presented. The main factors influencing deformation processes in the frozen strata of a layered inhomogeneous rock mass with inclined tunneling are determined, the complexity of the predictive task and the need to simplify the design scheme are shown. The work is focused on the assessment of the least studied geomechanical processes of soil heaving-uplifts and deformations during the periods of active and passive freezing stages. When studying the displacements processes of the earth surface and rock mass, the finite element method and analysis of the obtained data using field observations of displacements were used. A simplified calculation scheme is proposed for modeling, which allows taking into account the uneven influence of frozen rocks of an inhomogeneous layered rock mass with a large inclined tunneling. The satisfactory convergence of the data of field surveying observations on the earth surface and the results of modeling geomechanical processes for the period of active and passive freezing stages is shown. The proposed calculation scheme is recommended for the prediction of deformation at the stages of underground construction, characterized by the development of the most dangerous tensile deformations of buildings and structures on the surface.

COMPARATIVE ANALYSIS OF NATM CONSTRUCTION TECHNOLOGIES OF DNIPRO METRO ESCALATOR TUNNEL

Purpose. On the basis of the comparative analysis to carry out a substantiation of the most expedient and rational way of strengthening of a weak massif during a construction of Dnipro metro escalator tunnels by NATM. Methodology. To achieve this goal, an analysis of construction technologies in weak soils was conducted. The most used technologies are Forepoling Umbrella System (FUS), artificial ground freezing and chemical cementation. The peculiarities of carrying out each of the technologies for the conditions of inclined production were analyzed. It is determined how each of the technologies is applied to escalator tunnels and implements the strengthening of weak soil. Findings. The advantages and disadvantages of three technologies for fixing weak soil around the escalator tunnel are identified. Based on comparative analysis, it was found that the only technology that provides increased strength parameters of loamy soils, characteristic for the upper part of the escalator tunnel of the Dnipro metro, is the technology of chemical strengthening (cementation). In some cases, if necessary, short sections of sloping course, characterized by particularly weak soil, can be supported by several pipes, without creating a continuous leading mount. The results of the analysis are the basis for further substantiation of cementation, which creates a multilayer system "reinforced soil massif – temporary fastening – permanent lining". Originality. Based on the results of comparative analysis of three technologies for escalator tunnel construction by NATM, it is proved that the use of cementation not only increases the strength of the soil during drilling, but also further in operation serves as an additional element of the multilayer system "reinforced soil massif – temporary fastening – permanent lining". Practical value. In the course of research, the substantiation of cementation as the most rational and effective technology of strengthening of the surrounding weak massif at construction of the Dnipro metro was carried out.

Field data analysis in construction of escalator tunnels at Obvodny Kanal and Admiralteyskaya Stations of the Saint-Petersburg Metro using tunnel boring machine

Field data analysis in construction of escalator tunnels at Obvodny Kanal and Admiralteyskaya Stations of the Saint-Petersburg Metro using tunnel boring machine

Analysis of the mathematical modelling results of displacements and deformations induced by the construction of the escalator tunnel of "Mining Institute” station in Saint Petersburg

The article presents the results of mathematical modelling of geomechanical processes that occur during the construction of an escalator tunnel using EPB TBM at the «Mining Institute» station in Saint Petersburg. A numerical model was built using the finite element method implemented in «Plaxis 3D» software. Hardening soil model was used for modelling of soil massif. The analysis of the distribution of displacements and deformations in the main cross-sections of the displacement trough is performed. Issues of assessing the harmful effects of underground construction on undermined buildings and structures are considered. Based on the research, we can conclude that the construction of a tunnel is safe for undermined buildings with strict tunnelling technologies compliance.

Analysis of escalator tunnels deformations, when exposed to soils freezing

The presented work studies deformation processes of escalator tunnels support lining constructed by means of soils freezing in difficult engineering and geological conditions. The features of construction technology are considered. The features of the freezing effects during the active, passive stage of freezing and during the natural thawing of soils are considered. The data of the long-term arch support monitoring, as well as the earth’s surface is presented. The non-standard nature of geomechanical processes, in particular the support lifting during the construction of the escalator tunnel is revealed. Methods of mathematical statistics and error theory were used to process and analyze data of field observations at surface and array displacements and deformations. According to survey observations on a few escalator tunnels in Saint-Petersburg underground the correlation form shown is increased in horizontal diameter of the rings and reduce the vertical dependence of the sedimentation casing from subsidence of the earth’s surface. The data also reveals that with increasing development depth, despite the increase in vertical load, the deformation of the lining is reduced, which is associated with physical and mechanical properties of the array.

Геотехнические исследования при сооружении эскалаторных тоннелей

Геотехнические исследования при сооружении эскалаторных тоннелей

New Method of Surface Settlement Prediction for Saint-petersburg Metro Escalator Tunnels Excavated by EPB TBM

The article describes a new technology of escalator tunnel construction using earth pressure balance tunnel-boring machines (EPB TBM) in complex geological conditions of St. Petersburg soils. The results of field surveying observations of settlements and strain calculations arisen from the construction of the escalator tunnels of the St. Petersburg metro “Obvodny kanal”, “Admiralteyskaya”, “Spasskaya” stations are presented. It is established that the evolving strain can be dangerous for undermining buildings and structures. The method of escalator tunnel construction numerical modeling based on the finite element method is used to evaluate the qualitative relations of the geomechanical processes. A new method of surface settlement prediction is based on the results of complex processing of field data and results of construction numerical modeling. This method involves determination of the following characteristics of the displacement process: the position of the point of the maximum settlement in a subsidence trough, the size of a subsidence trough, the value of the maximum settlement, distribution of displacements and strains in the trough. The developed method for calculation of the settlements was tested on Saint-Petersburg metro escalator tunnels. Comparison of results for predicted and observed data indicate the reliability of the developed settlement and deformation prediction method in the construction of the escalator tunnels using the TBM in St. Petersburg.

Preservation of Urban Historic Centers

The subway construction in St. Petersburg is a very important challenge for the development of the city. The existing stations are dramatically deficient, especially in the city's bedroom suburbs. The end stations are overloaded, and parallel subway lines have to be built to relieve the available ones. The subway in St. Petersburg is mainly a deep-level one, as stable water-free rocks (Proterozoic clays) are at depths of over 40 m. Located higher are unstable aqueous sand-clay Quaternary varieties prone to frost heave, and parent Upper Vendian clays, characterized by fissures and sandstone interbeds of varying thickness. But even at significant bore depths, ground surface movements occur on large areas covering several hectares of the city's territory. The current technology of construction of subway station hubs and inclined escalator tunnels lead to significant deformations of the overlying rock and of buildings and structures erected on it, sometimes resulting in loss of structural strength and full decommissioning of buildings. The rehousing of dangerous buildings and their repair require sizeable funds and time for reconditioning of the buildings. This is especially intolerable for subway construction in the historic center of the city when memorial buildings and samples of architecture are subjected to total destruction. For instance, during the construction of the exit to the Griboyedov Canal from Nevsky Prospekt Station, one half of a historic building was dismantled, and for the construction of the surface concourse of Admiralteiskaya Station, an available house had to be totally pulled down, with a new one having similar facades erected in its place later. Therefore, extremely important is development and implementation of proposals to prevent intolerable deformations of existing buildings and structures in the construction of the subway and other underground facilities in the central districts of St. Petersburg. To solve the problem of ground surface deformation, an integrated approach is needed, comprising low-subsidence sinking techniques with parallel geotechnical monitoring including monitoring of low-depth displacements of the surrounding rocks, both in the vertical and horizontal plane.

Evaluation of jet grouting efficiency as means of minimizing of the harmful effect of escalator tunnel construction

The article describes the escalator tunnel construction using tunnel boring machines in St. Petersburg. To reduce the harmful effects of underground construction on the Earth's surface in the mouth of the tunnel technology is used jet grouting rock mass. Based on the analysis of field data of the earth surface subsidence and rock strata proved the effectiveness of the jet grouting technology. Subsidence of the surface and within the grouting area, are approximately null. The fact that the development of subsidence occurs mainly outside the zone of jet grouting soil is shown. A method of reducing subsidence by grouting additional unstable rocks in the massif, which will reduce the harmful effects of underground construction for an massif and the earth's surface, is offered. To assess the efficiency of the proposed method, a numerical modeling based on the finite element method is carried out. According to the modeling results it is revealed that the proposed method will reduce the subsidence at the surface by 2-3 times.

Specific Features of Calculating Underground Structures Erected with Use of Freezing Method

The article regards the problems arising in building the underground structures and, in particular, escalator tunnels under the built-up areas. In case of a thick mass of weak water-saturated soil such tunnels are frequently made with the use of freezing method. The purpose of this article consists in evaluating influence of the established and degrading ice structures on soils deformations and objects contacting with them. It is offered to assess this influence using the finite elements method contemplating a consecutive solution of temperature tasks and the tasks of stress and strain state of soil in time in 3D erection. The article describes briefly the formula part and specific features of calculating temperatures and deformations of soils. By way of example a calculation of defrosting deformations around an inclined tunnel for one of the deep-laid subway stations in Saint-Petersburg has been made. The data of performed calculation are closely approximated to the full-scale measurements.

Evaluation of ground freezing data from the Naples subway

The method of artificial ground freezing was employed to ensure stability and waterproofing of the platform and escalator tunnels in the Università station of the Naples underground. The paper presents the temperature histories monitored within the ground during the freezing process. Furthermore, the importance of the mineralogical composition of the ground is discussed and it is shown that the temperatures monitored can be interpreted numerically using the ‘Freeze' code, a thermo-hydraulic software developed at the ETH Zurich. The influence of important parameters, such as the spacing between the freeze pipes, the thermal conductivity of the ground and the time–development of cooling temperatures in the freeze pipes, is investigated and critically discussed in order to gain a better understanding of the thermal behaviour of the ground during artificial freezing with liquid nitrogen. ‘Freeze' software is a powerful tool for analysing field data for cases involving non-constant temperatures within freeze pipes.

Observations of ground and structure movements for compensation grouting during tunnel construction at Waterloo station

A new escalator tunnel and associated passageways have been constructed at Waterloo station in London, passing only a few metres beneath two sensitive masonry structures. Compensation grouting was undertaken in the ground between the tunnels and the overlying structures to limit settlements to acceptably small levels. This comprised injections of grout during tunnelling in response to detailed observations of ground and structure movements. The observational method was used in the control of the compensation grouting operations. This was achieved by comparison of field observations with defined limits of acceptable behaviour, and by planned contingencies in the event that these limits were approached. The extensive instrumentation installed to monitor the movements of the ground and the structures during tunnelling is described. Details are given of the performance of the instrumentation, of the measurements made and of the interpretation of the observations required to evaluate the soil-structure interaction behaviour. The specified requirements for compensation grouting and a summary of the grouting operations are presented. Settlements of the structures due to tunnelling were restricted to less than 15 mm. The relatively novel technique of compensation grouting has proved very successful in limiting settlements. Un nouveau tunnel d'escalator et les couloirs associés ont été construits à la gare de Waterloo, à Londres. Ils passent quelques mètres seulement au dessous de deux structures de maçonnerie particulièrement sensibles. Un coulis compensateur a été injecté dans le terrain entre les tunnels et les structures sus-jacentes pour limiter le tassement à des valeurs faibles acceptables. Ceci consiste à injecter du coulis lors du percement du tunnel en fonction d'observations minutieuses de mise en mouvement du terrain ou des structures. La méthode d'observation a été utilisée pour contrôler la mise en place du coulis compensateur. Ceci a été réalisé en comparant les observations de terrain à des limites définies de comportement acceptable, et en parant à l'imprévu au cas où ces limites seraient approchées. On décrit l'instrumentation mise en place pour enregistrer à la fois les mouvements du terrain et ceux des structures. On détaille les performances de cette instrumentation, les mesures réalisées et l'interprétation des observations permettant d'évaluer l'interaction sol-structure. On présente également les conditions requises et le résumé des opérations de mise en place du coulis compensateur. Le tassement des structures dû au tunnel a été inférieur à 15 mm. La technique du coulis compensateur s'est donc révélée efficace pour limiter les tassements.

Poling pile hood protects building against settlement : Tindle, A Tunn Tunnlg, V11, N9, November 1979, P34–37

Protection against settlement of a 100-year-old building became necessary during the construction of an escalator tunnel for the Tyne and Wear rapid transit system in the U. K. The method selected, described in the article, involved the construction of a parabolic arch of poling piles over the escalator shaft to form a shield while tunnelling proceeded.