Tóm tắt tiếng anh: Nghiên cứu ảnh hưởng của quá trình xây dựng đường hầm bằng tổ hợp khoan đào hầm (TBM) đến lún và các công trình trên bề mặt tại thành phố Hồ Chí Minh

Nghiên cứu ảnh hưởng của quá trình xây dựng đường hầm bằng tổ hợp khoan đào hầm (TBM) đến lún và các công trình trên bề mặt tại thành phố Hồ Chí Minh.Nghiên cứu ảnh hưởng của quá trình xây dựng đường hầm bằng tổ hợp khoan đào hầm (TBM) đến lún và các công trình trên bề mặt tại thành phố Hồ Chí Minh.Nghiên cứu ảnh hưởng của quá trình xây dựng đường hầm bằng tổ hợp khoan đào hầm (TBM) đến lún và các công trình trên bề mặt tại thành phố Hồ Chí Minh.Nghiên cứu ảnh hưởng của quá trình xây dựng đường hầm bằng tổ hợp khoan đào hầm (TBM) đến lún và các công trình trên bề mặt tại thành phố Hồ Chí Minh.Nghiên cứu ảnh hưởng của quá trình xây dựng đường hầm bằng tổ hợp khoan đào hầm (TBM) đến lún và các công trình trên bề mặt tại thành phố Hồ Chí Minh.Nghiên cứu ảnh hưởng của quá trình xây dựng đường hầm bằng tổ hợp khoan đào hầm (TBM) đến lún và các công trình trên bề mặt tại thành phố Hồ Chí Minh.Nghiên cứu ảnh hưởng của quá trình xây dựng đường hầm bằng tổ hợp khoan đào hầm (TBM) đến lún và các công trình trên bề mặt tại thành phố Hồ Chí Minh.Nghiên cứu ảnh hưởng của quá trình xây dựng đường hầm bằng tổ hợp khoan đào hầm (TBM) đến lún và các công trình trên bề mặt tại thành phố Hồ Chí Minh.Nghiên cứu ảnh hưởng của quá trình xây dựng đường hầm bằng tổ hợp khoan đào hầm (TBM) đến lún và các công trình trên bề mặt tại thành phố Hồ Chí Minh.Nghiên cứu ảnh hưởng của quá trình xây dựng đường hầm bằng tổ hợp khoan đào hầm (TBM) đến lún và các công trình trên bề mặt tại thành phố Hồ Chí Minh.

MINISTRY OF EDUCATION AND TRAINING

UNIVERSITY OF TRANSPORT AND COMMUNICATIONS

THACH BICH NGUYEN

EFFECT OF THE TUNNEL CONSTRUCTION PROCESS USING THE TUNNEL BORING MACHINE ON THE SETTLEMENT OF THE GROUND AND OTHER STRUCTURES IN HO CHI MINH CITY

SUMMARY OF DOCTOR OF THESIS

Hanoi – 2022

The work was completed at: University of Transport and Communications

Science Advisor 1:Assoc Prof Dr Nguyen Phuong Duy

Science Advisor 2:Prof Dr Tran Duc Nhiem

Thesis can be found at:

- The library of University of Transport and Communications;

- National library

is crowded, traffic is always overloaded, buildings on the ground are numerous and diversified with complex foundation structures…, then TBM method is the most suitable consideration Even though tunnel construction is implemented by TBM method, surface settlement which is potentially dangerous for buildings on ground cannot avoid The main cause is radial volume loss and volume loss of tunnel face Two big cities like Hanoi and Ho Chi Minh City have inconsistent planning characteristics; land reservation for traffic system is limited; many ancient architectural buildings need to be conserved; population is crowded; traffic is overloaded; types of buildings on ground are diversified and abundant Therefore; the current issue with a special concern is the investigation

of the influence of the tunnel construction for Metro system on the settlement and structural buildings on the ground, the behavior of the ground around the tunnel construction area, the factors affecting surface settlement, the influence boundary of settlement on structural buildings on the ground, and particularly, the estimation model for surface settlement should be developed when tunnel construction of Metro system by the TBM method is implemented in big cities in Vietnam

The thesis would like to propose the selected research content as follows: “ Effect of the tunnel

construction process using the Tunnel Boring Machine on the settlement of the ground and other structures in Ho Chi Minh city”

2 Research object

- The object of the investigation focuses on the phenomenon of surface settlement and the influence of settlement on buildings on the ground during the construction of metro tunnels in Ho Chi Minh city

3 Research scope

- The investigation focuses on the underground segment of Metro line from Ben Thanh Station

to Ba Son Station in the construction project of Metro line No 1 Ben Thanh - Suoi Tien, Ho Chi Minh city

4 Research Methodology

- The research methodology is the theoretical method based on the results of calculations according to the empirical formulas compared with the field monitoring results and comparison with results of the finite element analysis

5 Objectives of the thesis

- To develop a formula for calculation of Vloss in order to improve the finite element analysis method to analyze the influence of the Metro tunnel construction on settlement and buildings on the ground

- To propose equations for calculation of surface settlement values by empirical methods reflecting the ground settlement rules during the construction of Metro tunnels by the TBM method

in Ho Chi Minh city

6 Scientific and practical significance of the topic

The development of an empirical formula for calculation of the volume loss coefficient Vloss is considered a significant contribution in this field due to in previously published studies, although the problems of volume loss during construction the tunnel causing surface settlement were also mentioned, all were guidelines based on the field construction experiences without any published formula Simultaneously, with the calculated Vloss value, it will help to improve the finite element analysis method to evaluate the impact of Metro tunnel construction on buildings on the ground

2 The investigation’s results for the surface settlement in the thesis have been compared with the results calculated by experimental formulas which were published by the authors and those of the actual monitoring data at the construction project of Metro line No 1 Ben Thanh - Suoi Tien, from the Opera House station to the Ba Son station Based on that, formulas have been proposed to calculate surface settlement values by experimental methods reflecting the settlement rules of the ground during the construction of Metro tunnels by the TBMmethod in Ho Chi Minh City

The research’s results of the thesis are of great scientific significance and practical relevance when

in Vietnam, a series of Metro lines have been constructed in both Hanoi and Ho Chi Minh City The results of this study can be applied to the construction projects of the next Metro line in the

planning in Viet Nam

CHAPTER 1 OVERVIEW OF THE ISSUES RELATED TO THE TOPIC 1.1 Metro construction situation in the world and Vietnam

The first Metro line was built in England in 1863, so far about 80 cities around the world use the Metro system in public transport The largest Metro system in the world is in New York with a total length of 471km and 468 stations In Vietnam, the development planning for urban transport has approved by the government, accordingly, Hanoi is going to build a Metro system with 8 lines and Ho Chi Minh City is going to build system with 6 lines

1.2 Construction of metro tunnels using TBM technology and arising problems

1.2.1 The generation and development of TBM technology

The Shield Tunneling Method is a mechanized construction method that uses shields to excavate underground tunnels A tunneling shield consists of a protective metal cylinder and trailing support mechanisms which can both support geostatic pressure and move ahead in stratum The tunnel boring machine complex (TBM) performs the entire tunnel construction cycle from excavating the tunnel, supporting, transporting soil and rock out and assembling the tunnel-ring unit The first idea

of constructing by a shield was proposed by a French engineer, Brunel in 1818 derived from the image of the shell of the shipworm Between 1825 and 1843, Brunel used the tunneling shield to excavate the Thame Tunnel which is the first tunnel was constructed by this method with a total length of 458m So far from 1818, thousands of types of tunneling shields have been researched and manufactured in many countries and this method has also widely been applied in underground constructions in urban areas

In practice, mechanized tunneling shields (MS), semi-mechanized tunneling shields (PMS) and non-mechanized tunneling shields (NMS) Mechanized tunneling shields are divided into earth pressure balance shields mining shields with equal pressure on the digging mirror and mining shields without equal pressure on the digging mirror (MS) The excavator shield has equal pressure

on the digging mirror depending on the type of material creating pressure in the digging mirror, divided into 4 types: with clay mortar solution (MS-S) (Bentonite Slurry Shield- BS Shield or Hydroshield), with excavated soil (MS-E) (Earth Pressure Baland Shield) (this type is divided into two: only MS-E soil and injected into the soil with clay solution or MS-ED powder), by compressed air ( MS-A) (Compressed Air Shield – CA Shield) and mixed type (MS-M) (Mixshield)

1.2.3 Arising Problems

3

1.2.3.1 Ground settlement during tunnel construction by TBM

In tunnel construction by the tunneling shield method in soft and saturated clay stratums, deformation of the ground is generated along the tunnel axis In general, the deformation can be divided into 3 phases: The ground pushes up and subsides in front of the shield, subsides during construction and subsides due to consolidation

Figure 1.1: General deformation law of the ground 1.2.3.2 The settlement phenomenon caused by underground buildings has been recorded

- Surface settlement of the ground during the construction of the city subway line München (Munich), Germany, 1994

- Tunnel collapse during subway tunnel construction in Taipei, Taiwan, 1994/1995

- Tunnel collapse of the subway tunnel (MRT) Singapore 2004

- Sinkhole formed in Tannery Road due to Bengaluru subway construction

- Partial collapse of a highway during construction of a new subway line in Sao Paulo, Brazil, February 1, 2022

1.3 Investigations and evaluations of the influence from metro tunnel construction on the buildings on the ground

1.3.1 Influence of tunnel and Metro construction on buildings on the ground

In general, the different types of structures will be affected by settlement troughs in different ways

As experience, masonry structures will be affected the deformation equal to the deformation of the ground where they are erected The same occurrence to the majority of buildings placed on single foundations

In contrast, the current advanced buildings made of reinforced concrete with strengthened stiffness will be affected smaller horizontal deformation than the deformation of the ground The bending stiffness of these structures is the reason of their reductive deformation compared to the deformation of the ground, especially, these cases usually occurs on buildings placed on strip foundations or raft foundations

The greater the stiffness of the structure, the greater the shear resistance and this is reason of tilting deformation rather than warped deformation This feature depends on the height of the building (number of floors), the number of drilled holes and the type of buildings (concrete walls or beams

or pillars, etc.)

4

Figure 1.2: Types of influence of settlement funnel on buildings on the ground [01]

In 1974, Burland & Wroth [02] showed that the signs to recognize and determine the deformation

of the buildings are very abundant They have proposed 9 parameters based on which the deformation of the structural buildings can be defined

1.3.2 Classification of failures on the adjacent buildings due to surface settlement

The degree of failure on the structural buildings near the tunneling area, especially masonry structures, is often random rather than deterministic Therefore, the method used to investigate the failures of the structural buildings is introduction of limit thresholds When a certain feature of the building violates one of these thresholds, the engineer will rely on that and evaluate its damage level According to Burland et al (1977) [03], failures of structural buildings near the tunnel construction area can be classified into three main categories:

Failure on architectural aspect can be observed by the naked eye;

Function failures may lead to malfunctions in operation and use;

Structural destructions can influence on the stability of the buildings

Figure 1.3 Modeling a building as an elastic beam and defining relative deflections (Burland and

Wroth, 1975)

1.3.3 Monitoring the displacement of the foundation of high-rise buildings during the construction

of foundations and basements

According to JGJ 120 - 99 [04], the monitoring content during the excavation process includes: monitoring the horizontal displacement of the supporting structures; deformation of underground pipelines and surrounding structural buildings; underground water level; internal forces in piles and walls; tension forces in the ground; longitudinal force in the strut; deformation of vertical columns; the settlement according to the depth of the soil layers and the emergence of the ground on the bottom of the foundation pit; horizontal pressure on the surface of the supporting structures

1.3.4 Analyzing and evaluating the monitoring data for displacement of foundations and basements

of high-rise buildings

In deformation monitoring of foundation and basement of high-rise building, the research orientation usually focuses on the increase of the accurate degree and reliability of the monitoring values and analyses monitoring data to control the potential troubles to internal and adjacent buildings P.Erik Mikkelsen (2003) investigated and analyzed the monitoring data to increase the accurate degree of the measurement of horizontal displacement by Inclinometer [05] On the basis

of the monitoring data of 530 constructions, Christian Moormann (2004) proposed the warning and limit thresholds of horizontal displacements of walls and vertical displacements of the ground in the vicinity of excavated hole that these thresholds are applied to control and prevent possible failure on the buildings near excavated hole

The actual construction incident of the deep foundation pit is analyzed based on the monitoring results predicted prior to the basement construction and promptly added during happening of the incident The incident control method is quite proactive based to the scientific analysis of information from monitoring [53] Richard N Hwang, Za-Chieh Moh and C H Wang (2007) have shown that fluctuations in the bottom point of Inclinometer tubes are inevitable, even when the bottom of the pipe is installed in a gravel bed In measuring the horizontal displacement by applying

5 the bottom point of the tube as the reference point can be misleading Points at the top of the guide tube that need to be tracked for reading, can be calibrated accordingly [06] A.Rahman, M.Taha (2005), Inclinometers are good tools to measure and monitor the horizontal deformation of soil due

to excavation and backfill However, the guide tube used must be deep enough to get reliable results For this reason Inclinometers guide pipes installed inside diaphragm walls must be installed

at least to the end of the wall depth or even deeper It is recommended to install Inclinometers in order to perform more accurate analytical models of the displacement parameters of the soil outside

of the retaining wall or for better design standards [04]

1.3.5 Domestic investigations in deformation and settlement of urban buildings around Metro construction area

In 1985, there was standard TCVN 3972:1985 "Geodetic working in construction" [08] which mentioned the deformation monitoring of buildings Since then, there have been many scientific investigations at the whole levels, a number of research theses and dissertations on construction deformation monitoring to complete the working of construction monitoring to meet the monitoring requirements for the specific projects

Investigation the method and regulation of deformation monitoring for buildings:

The technological regulation of the deformation and displacement monitoring of the building was performed by Tran Khanh (1991) in the report of the branch project of the nation-level project 46A-05-01 [09]

Investigation the grid design and processing of construction deformation monitoring data

In order to the deformation monitoring grid to meet the accuracy and time requirements, the monitoring grid system should have an optimal design As regard to optimal design for the monitoring grid, there was mentions in Quang Phuc Nguyen’s work (2006) This work fully presented the characteristics of the design of the construction deformation monitoring grid system and the research results on the optimal design of the construction deformation monitoring grid by computer The effectivity and simplicity for the optimal design of deformation monitoring grids by computers were also presented in many investigations [10]

1.4 Conclusion of chapter 1

The tunnel construction for Metro lines by TBM method is suitable and effective in big cities with crowded population, complex and diversified architecture like Hanoi and Ho Chi Minh city Although the advanced construction technology has been applied, the negative influence on entity

on the ground like surface deformation and settlement in construction is inevitable This significantly effects on the existing buildings on the ground Therefore, investigations for estimating, evaluating and controlling surface settlement due to tunnel construction of Metro lines are imperative issue which investors, contractors and managers should specially consider

CHAPTER 2 THEORETICAL BASIC TO ESTIMATE GROUND SETTLEMENT

DURING TUNNEL CONSTRUCTION 2.1 Analysis and prediction of ground subsidence by theoretical methods

Some authors develop analytical methods, extrapolate from semi-empirical formulas and combine

all the factors to generalize the ground deformation calculation formula.:

2.1.1 Sagaseta (1987), Verruijt và Booker (1996), Gonzalez và Sagaseta (2001)

Sagaseta (1987) [11] presents a generalized solution in unconsolidated, undrained, isotropic and homogeneous soils The soil is modeled as a linear elastic material with virtual image technology and the resulting semi-elastic space to calculate the surface soil displacement The volume of undrained soil loss at a finite depth of infinite space is estimated to be due to volume reduction when tunneling ignoring the action of the soil on the surface, provided that it is incompressible and transferred radial position has axial symmetry

6 Verruijt and Booker (1996) [12] present an analytical method for tunneling in homogeneous elastic space, using the approximation method suggested by Sagaseta (1987)

Verruijt and Booker (1996) [12] present an analytical method for tunneling in homogeneous elastic space, using the approximation method suggested by Sagaseta (1987)

2.1.2.Lee et al (1987), Rowe và Lee (1992)

Lo and Rowe (1982) and Rowe et al (1983) [13] introduced the gap factor causing volume loss with the strength and strain relationship between elastic and plastic states, which is the gap between hole diameter and tunnel cover

This gap is corrected by Lee et al (1992) as follows.:

2.1.3.Loganathan và Poulos (1998)

Loganathan and Poulos (1998) [14] modified Veruijt and Booker's method by incorporating actual boundary conditions An oval was introduced at the top of the tunnel because volume loss occurs

at different stages during tunneling

2.2 Analysis and assessment of settlement according to empirical and semi-empirical methods

2.2.1 Methods of empirical research Macklin and Field (1999):

Macklin and Field (1999) [15] based on actual data with a 2.8 m diameter tunnel in London clay show the changing relationship between secondary earth pressure and surface settlement

deformation with tunneling speed In this case, up to 70% of the ground surface settlement deformation at the perpendicular section occurred when the tail of the excavated shield was passed, during shell installation and grouting VL is determined as a percentage of the total tunnel cross-sectional area

V

D





Macklin (1999) [16], Mair (1981) [17], and O'Reilly (1988) [18], combining historical and

experimental results from centrifugation experiments suggested a method of loss prediction volume in both clay and vegetation This theory uses the concept of stability coefficient: Call the stability coefficient: N (the concept of Broms and Bennermark (1967)): [19]

,

The most common empirical method to predict surface settlement is based on the Gaussian distribution Peck (1969) [21], and Schmidt (1974) [22] assume that the shape of the settlement funnel is similar to that of the Gaussian normal distribution curve

By statistical analysis based on actual observations, they have shown that this is a reasonable method to model the subsidence funnel shape caused by the tunneling process

Basic Equation:

S = Smax exp

In there:

- S is the surface settlement according to theoretical calculation;

- is the maximum surface settlement (above the tunnel axis);

- x is the horizontal distance from the center of the tunnel to the point to calculate

settlement;

- i is the standard deviation of the settlement curve (distance from the inflection point

of the settlement chute to the center of the tunnel shaft), also known as the settlement

width parameter

2 2

2

x i

.( ) 2

2, 5.

L

D V S

i





7

-

Figure 2.1: Gaussian curve for horizontal settlement and soil loss Vl

Then different authors have based on actual observed data to give formulas for calculating Smax

in Table 2.1

Peck (1969)

Based on actual observation data

Atkinson & Potts (1979) [24]

Based on actual observed data and model test results

There are many authors, based on the results of field observations, have proposed formulas to determine the value of i in order to adjust Peck's original formula to suit each specific condition of the works

Peck (1969)

: n=0,8 ÷1,0

Based on actual observation data

Atkinson & Potts (1979) for loose sandy soil i = 0,25(Z0 + R) Based on actual observed data and model test results

New & O’Reilly (1982)

i = 0,43Z 0 + 1,1 for consolidated soil

i = 0,28Z 0 – 0,1 for unconsolidated soil

Based on actual tunnel monitoring data in the UK

2.2.4 Chow's semi-empirical research method (1994) [30]

This method investigates vertical settlement at a point located at the distance from the

2

max

( ) 2

2, 5.

L

D V S

2, 5.

L

D V S

L D V S

L

D V S

i





n O

R Z R

n O

R

Z R



n O

R

Z R



2 max

1.252V R L S

i



2 max

2 8

L

V D S

i





8 concentrated load position in an elastic semi-space (this concentrated load is modeled as a load line running along the tunnel center axis due to the process of digging earth blocks inside the tunnel) The land surface settlement displacement is then calculated according to the formula:

2.2.5 Mair and Taylor's semi-empirical research method (1993)

Mair and Taylor [32] studied to compare with the solutions of approximate formulas (empirical formulas) of the underlying deformation of the ground Specifically, the two men gave formulas for spherical and cylindrical pore shapes: and

Comment:

The experimental and semi-empirical research direction provides numerical formulas that allow us

to quickly and easily estimate the level of settlement influence caused by the tunneling construction process.However, these methods do not consider the interaction effects as well as the behavior characteristics of the soil

A typical example of this method is Peck's publication in 1969 The scientists then continued

to develop and refine Peck's formula based on actual monitoring data of works in different countries, in order to better suit the specific conditions of each country

The empirical methods and empirical data are mostly based on the empty surface hypothesis

“Green field”, in other words, the existence of construction works as well as its load influence affect the deformation behavior of the ground and surface settlement, displacement of ground structures caused during construction cellar is not considered

2.3 Analyze and evaluate surface settlement based on numerical model and using finite element method

General concept of finite element method The finite element method is a numerical method for solving problems described by partial differential equations with specific boundary conditions Mathematically, the finite element method is used to approximate the problem of partial differential equations and integral equations The basis of this method is to discretize the complex continuous domains of problem Continuity domains are divided into several subdomains (elements) These domains are linked together at the nodes On this subdomain, the variant form

is equivalent to the problem that is approximately solved based on approximation functions on each element, satisfying the boundary condition along with balance and continuity between the elements

Comment:

The problem of surface settlement during the construction of tunnels in the city, especially metro tunnels, is an extremely complex interaction problem and can be effectively solved with numerical methods The advantage of the mathematical method in modeling ground settlement analysis problems is that it is possible to consider the reciprocal impact between ground settlement caused

by metro tunnel construction and existing works on the ground ground, can be analyzed according

to the construction sequence of each project along with the development of commercial software makes the analysis of this problem by the method of mathematical analysis become more and more popular However, the results of the analytical problem by this method depend a lot on the input data Including the volume loss coefficient Vloss However, there are not many studies analyzing this quantity and most of them assume this value according to construction experience

2.4 Conclusion of chapter 2

Through an overview study of methods to assess surface settlement due to tunnel construction by TBM, we have summarized three main research directions: Theoretical research, experimental and semi-empirical research, and numerical model and using finite element method

The direction of finite element research applies the development of science and technology to model and consider more related factors such as interaction effects, or construction technical factors

N u

s D e

s D e

D G r



9 during the construction process The problem of surface settlement during the construction of tunnels in the city, especially metro lines, is an extremely complex interaction problem and can only be solved effectively with numerical methods However, the results of the analytical problem

by this method depend a lot on the input data, including the volume loss coefficient Vloss which is usually taken under the assumption

Typical for the experimental method is Peck's publication in 1969 After that, scientists continued

to develop and adjust Peck's formula based on actual observation data of works in different countries Since then, the current urgent issue is to study and survey the monitoring data of actual works in Vietnam in order to adjust the formula to suit Vietnam's conditions in order to build forecasting and forecasting tools analysis of surface subsidence during the construction of underground Metro lines in Vietnam

CHAPTER 3 OBSERVATION-COMPARING THE RESULTS OF OBSERVATION WITH THEORY

CALCULATION RESULTS 3.1 General introduction about the construction project of metro line No 1 Ben Thanh - Suoi Tien, Ho Chi Minh City

In 2013, according to the adjustment of traffic planning in 2007, the urban railway system has had significant changes: Specifically, by 2030, Ho Chi Minh City is going to have 8 Metro lines

Metro Line 1 Ben Thanh - Suoi Tien

Route: Ben Thanh (at Quach Thi Trang Square) – Le Loi – Nguyen Sieu – Ngo Van Nam – Ton Duc Thang – Ba Son – Nguyen Huu Canh – Van Thanh – Dien Bien Phu – Saigon Bridge – Hanoi Highway

Total length: about 19.7 km (2.6 km underground and 17.1 km overhead) Number of stations: 14 (3 underground stations and 11 elevated stations) The connection between the Opera House station and Ba Son 2 station is 02 single tunnels, reinforced concrete structure, inner diameter 6.05m, outer diameter 6.65m, construction technology is using TBM excavator

3.2 Construction process of underground lines and monitoring of surface settlement and deformation of urban works on the surface

3.2.1 The importance of monitoring

3.2.2 Purpose and content of monitoring work

3.2.3 Principles of monitoring system design

3.2.4 Monitoring contents

The necessity and importance of measuring the displacement of the ground and the ground above the roof is determined depending on the depth of the tunnel relative to the ground

Distance between measuring points: In the longitudinal direction of the tunnel from 5÷10m (when

h < D), 10÷20m (when D ≤ h ≤ 2D) and 20÷50m (when h > 2D); Horizontal tunnel from 3÷5m

Figure 3.1: Layout diagram of ground displacement measuring device in the vertical

and horizontal direction of the tunnel

Monitoring for neighboring buildings and structures: Mainly monitoring surface settlement affecting neighboring houses and structures, monitoring elevation changes, location changes, and changes cracks, of neighboring houses and public works before and after tunneling

3.3 Monitoring and monitoring results

10

3.3.1 The layout diagram of settlement monitoring points along the underground Metro line

constructed according to TBM

Figure 3.2 The layout of settlement monitoring measuring point [120]

3.3.2 Results of settlement monitoring

Because there is only one drilling machine, when drilling the East tunnel (the lower tunnel) from

Ba Son Station to the Opera House Station first, then the West tunnel (the upper tunnel) is drilled The monitoring results used in this document are the results obtained up to the time of completion

of an East tunnel This tunnel is located on the left side of the Saigon River from the direction of

Ba Son Station to the Opera House Station

Figure 3.3 Surface settlement measurement results along the Metro

Figure 3.4: Survey results of some settlement measurement data at the cross-section

3.4 Analysis of ground settlement according to theory and comparison with observation results

3.4.1 Compare the results of surface settlement calculation according to the theoretical

formulas and the actual monitoring results in the field

The thesis applies Peck's 1969 formula with three cases corresponding to three cases of

calculating i: n=0.8; 0.9 and 1.0

The thesis applies the formula of New & O'Reilly (1982) based on actual monitoring data in the

UK, and proposes a formula with two cases corresponding to two cases of calculation of i

Case 1: i = 0,43Z0+1,1

Case 2: i = 0,28Z0 – 0,1

The thesis applies the formula of Mair (1993) based on actual observation data and centrifugation experiment

The thesis applies the formula of Attewell (1977); of Clough & Schmidt (1981) and of Atkinson

& Potts (1979) and the actual monitoring results in the field

After comparing the results of field observations with the theoretical calculation results proposed

by Peck 1969 and the next 8 proposals of the above authors, we can see that the largest settlement

at the heart The observed tunnels in HCMC are usually smaller than the theoretical maximum settlement values

11 With the comparison results from 30 typical cross-sections we studied, the error between the calculated results and the observed data is shown in Table 3.6

Table 3.6: Average error of maximum settlement between calculated and observed results

Theory Error

( Peck1)

Error ( Peck2)

Error ( Peck3)

Error ( New OReilly1)

Error ( New Oreilly2)

Error ( Mair)

Error (Attewell)

Error ( Clough)

Error (Atkinson)

Figure 3.5 Graphs comparing surface settlement between observation

and theoretical calculation

it is necessary to have studies to propose adjustments to Peck's formula to be more suitable for

specific conditions in Vietnam

CHAPTER 4 DEVELOPMENT OF RESEARCH GROUND SETLEMENT AND ESTABLISHMENT

OF EXPERIENCE FORMULATIONS 4.1 Proposed formula for calculating volume loss coefficient Vloss

4.1.1 Concept of volume loss coefficient VL

VL is the volume loss coefficient: This factor considers the volume loss when installing the tunnel shell compared to the excavation process using the TBM technology Specifically, these losses include

- Volume loss of excavated mirror surface (Vf),

- Volume loss of around digging shield (Vs),

- Volume loss at the tail of the shield (Vt)

However, this coefficient even Peck's formula does not suggest any specific calculation formula Therefore, this coefficient is often estimated in the calculations And the subsequent studies also only adjusted the coefficients i or Smax without studying and proposing the exact formula for calculating VL The above studies have not mentioned the technical factors in construction and the geological conditions that the tunnel will go through

4.1.2 Analysis of correlations between Vloss volume loss coefficient and characteristic factors

4.1.2.1 Investigate the influence of volume loss coefficient on pumped grout pressure