RESEARCH ON METHOD FOR GEODETIC MONITORING, ANALYZING FOUNDATION AND BASEMENT DEFORMATION OF HIGH RISE BUILDINGS IN THE CONSTRUCTION PERIOD

TRAN NGOC DONG RESEARCH ON METHOD FOR GEODETIC MONITORING, ANALYZING FOUNDATION AND BASEMENT DEFORMATION OF HIGH-RISE BUILDINGS IN THE CONSTRUCTION PERIOD Study field: Geodesy and mappi

TRAN NGOC DONG

RESEARCH ON METHOD FOR GEODETIC MONITORING, ANALYZING FOUNDATION AND BASEMENT DEFORMATION OF HIGH-RISE BUILDINGS IN THE CONSTRUCTION PERIOD

Study field: Geodesy and mapping Code: 62520503

SUMMARY OF ENGINEERING DOCTORAL DISSERTATION

Hanoi - 2014

Engineering surveying, of Surveying Faculty, Hanoi University of Mining and Geology

Scientific Supervisors: Assoc Prof Dr Tran Khanh

Hanoi university of Mining and Geology

Examiner 1: Dr Duong Chi Cong

VietNam Institute of Geodesy and cartography

Examiner 2: Dr Nguyen Van Van

Association of Geodesy, Maps and Remote Sensing of Vietnam

Examiner 3: Dr Vu Van Dong

Defense Mapping Agency of VietNam - General Staff

The dissertation will be defended at the University examination Council at the Hanoi University of Mining and Geology, at… h,

……… 2014

This dissertation can be referenced at the National library or at the library

of the Hanoi University of Mining and Geology

INTRODUCTION

1 The importance of dissertation

Recently, when excavating holes for constructing the foundation and basement

of a high-rise building, many adjacent works have confronted heavy breakdowns, which caused many economic losses and concern in society Those weaknesses are mainly caused by monitoring and analyzing impacts that are not conducted in time of the process of constructing the foundation and basement

The issue on monitoring, analyzing the deformation of foundation and basement

of a high-rise building in the construction period becomes urgent However, until now, this issue has not been paid crucial attention to There has not had any careful, comprehensive research and proposed technical solution Thus, researching the method of monitoring, analyzing foundation and basement deformation of a high-rise

building in the construction period is very necessary This contributes to ensuring safety

for not only the entire building but also adjacent buildings, people and normal activities

of the residents

2 Purpose, object and scope of research

- The dissertation aims at contributing to developing and finalizing the method of monitoring, analyzing deformation, evaluating and modeling the displacement process

of the foundation and basement of the high-rise building in the construction period

- Object of research is: the method of monitoring, analyzing deformation of foundation and basement of high-rise buildings in Vietnam

- Scope of research of the dissertation consists of: Researching the method of surveying, using sensing to monitor the deformation of foundation and basement of the high-rise buildings; Researching the combination of method of surveying and using sensing to increase the quality and effectiveness of monitoring the deformation

of the foundation and basement; Analyzing, evaluating and modeling the displacement process of the foundation and diaphragm wall of the high-rise buildings

in the period of constructing the foundation and basement

3 Contents of research

1- Researching the combination of method of surveying and using sensingto monitor the settlement of the foundation and displacement of the diaphragm wall of the high-rise buildings in the period of constructing the foundation and basement

2- Researching the application of the automatic monitoring system for monitoring the displacement of the diaphragm wall continuously

3- Building the displacement model; Analyzing, evaluating and predicting the displacement of the foundation and diaphragm wall of the high-rise buildings

4- Developing the software for analyzing the deformation of the foundation and basement of the high-rise buildings

4 Method of research

Method of research consists of statistics, analysis, experiment, comparison, informatics application and mathematical method

5 Scientific and practical meaning of the Dissertation

Scientific meaning: The Dissertation contributes to developing and finalizing the

method of monitoring, analyzing deformation and modeling the displacement process

of the foundation and basement of high-rise buildings in the construction period

Practical meaning: The research results of the Dissertation could be applied for

monitoring, analyzing, evaluating and predicting the foundation and basement of high-rise buildings in the construction period and adjacent buildings

6 Theoretical points to be defended

- First theoretical point: The solution in combining the surveying method and method

of using sensing as proposed in the Dissertation allows increasing the effectiveness of monitoring the deformation of foundation and diaphragm wall of high-rise buildings

- Second theoretical point: The work deformation model that is developed based on

the monitored data allows evaluating settlement as well as displacement of the foundation and diaphragm wall of high-rise buildings chronologically, in space and evaluating the dependence between deformation and its agent

7 New points of the Dissertation

1- The Dissertation suggests the solution in combining the surveying method and method of using sensing as proposed in the Dissertation allows increasing the effectiveness of monitoring the deformation of foundation and diaphragm wall of high-rise buildings

2- The Dissertation suggests developing the models on displacement of the foundation and diaphragm wall of high-rise buildings chronologically, in space and evaluating the dependence between deformation and its agents

3- The Dissertation suggests developing the software for analyzing foundation and basement deformation of high-rise buildings

8 Structure and contents of the Dissertation

Apart from Preface, Conclusion, the Dissertation is represented in five Chapters with more than 130 pages of interpretations, figures and charts

Chapter 1 OVERVIEW ABOUT MONITORING THE DEFORMATION OF THE FOUNDATION AND BASEMENT OF HIGH-RISE BUILDINGS IN THE CONSTRUCTION PERIOD

1.1 Overview of foreign research works

1 - Monitoring the displacement of the foundation of high-rise buildings in the construction period of foundation and basement

- Determining monitoring scope [82]

- Monitoring method: Surveying and using sensing [46], [47], [48], [49], [52], [53], [54]

2 - Analyzing and evaluating the results on monitoring the displacement of the foundation and basement of the high-rise buildings [47], [50], [53], [60], [62]

3 – Automation of monitoring and processing data [51], [55], [57], [58], [61], [63]

1.2 Overview of domestic research works

- Researching and analyzing the work deformation [18], [19], [29], [32]

- Researching the application of informatics into processing the work deformation monitoring data [8], [21], [29]

2 - Deployment of monitoring the building foundation in reality

There have been research works [1] in monitoring the foundation of the high-rise buildings Some of these works have become the National Standards such as [34], [35], [37], [38]

- Determining monitoring scope [36]

- Monitoring method: Surveying and using sensing

1.3 General evaluation of the research situation

1 - In general, the researches on this field in the world have some points that have not been suitable to the conditions in Vietnam (weak soil, mixed buildings, construction elements, etc.)

2 - In Vietnam, the used modern devices and technologies are mainly imported Vietnam has not manufactured the specialized measurement devices for monitoring the work deformation

1.4 Weaknesses and research orientations in the Dissertation

At present, the method of surveying and using sensing for monitoring the deformation of the foundation and basement of the high-rise buildings are still separate from each other Thus, research on combination of the surveying and sensor-used method to increase the quality and effectiveness of monitoring the deformation

of the foundation of the high-rise buildings is necessary

Researching the application of the automatic monitoring system into monitoring the displacement of the diaphragm wall of the high-rise buildings continuously to contribute to preventing the accidents that could occur in executing holes is necessary

At present, the monitoring process in this period are just for data collection only without specific analyses and evaluations of the effects of the hole excavating process

on the adjacent works Therefore, it is necessary to research, analyze the monitoring data and developing the model on displacement of the foundation and diaphragm wall

to control the accidents that could occur to the work and adjacent works

Chapter 2 MONITORING THE SETTLEMENT OF THE FOUNDATION

CONTRUCTION PERIOD

2.1 Technical requirements on monitoring the settlement in the process of building the foundation and basement of the high-rise buildings

2.1.1 Causes of settlement in the process of executing the foundation and basement

In the process of excavating holes for constructing the foundation and basement, when some soil volume is taken, the stress status will be changed This leads to deformation of the soil block surrounding the excavated holes Soil will displace to the excavated holes The displacement extent depends on the quality of the support structure, soil type, distance as well as location and load of the adjacent work The combination of these displacements will make the ground surface adjacent to the excavated holes settle If this affected area has works, these works will be deformed

2.1.2 Settlement monitoring contents in the foundation and basement construction process

- To monitor settlement of the ground surface; to monitor settlement in line with depth of soil layers surrounding the excavated holes

- To monitor settlement of adjacent works

- To monitor settlement of emerging of the foundation pit (ignite of the excavated hole bottom)

- According to [35], measuring and determining the work settlement should be performed immediately after the foundation is built completely When constructing the basement, the work has had load Thus, it is necessary to monitor the settlement

of the work immediately in this period

2.1.3 Determination of the settlement monitoring area in the foundation and basement construction process

If the design does not indicate the area that should be monitored settlement, we could calculate this affecting area using estimating formulas of the soil mechanics theory Accordingly, the affecting scope of the soil surrounding the excavated hole is estimated by formula [80]:

o o

2.1.4.1 Requirements on accuracy in settlement monitoring

Method 1: To base on the predicted settlement value (provided by the designing

unit) to determine the requirement on monitoring accuracy

Method 2 It is possible to use the settlement measurement grades in Vietnamese

Standard 9360:2012 [35] to monitor the settlement of the foundation of the high-rise buildings Under this Standard, measuring the settlement is divided into three levels: level I, level II and level III

2.1.4.2 Settlement monitoring cycle

Settlement monitoring cycle in the foundation and basement construction process is determined based on the construction progress

2.2 Monitoring the settlement of the foundation of the high-rise buildings in the foundation and basement construction period by the surveying method

2.2.1 Structure of landmark for monitoring the settlement of the foundation and basement of the high-rise buildings

2.2.2 Designing the monitoring network system

The system of settlement monitoring height network is designed with two levels: basic height network and monitoring network

2.2.3 Monitoring settlement of the ground base surrouding the foundaiton pit

Height of the point of monitoring the settlement of the ground base surrounding the foundation pit should be measured by the high geometric measurement method with accuracy in accordance with settlement measure level III

2.2.4 Monitoring settlement of the works adjacent to the excavated holes

Measuring the settlement of the adjacent works (residents’ houses,

steel-enforced concrete works) should be conducted with accuracy in accordance with settlement measure level II

2.2.5 Monitoring emerging of the foundation pit

Height of the point of monitoring the emerging deformation of the foundation pit should be measured by the high geometric measurement method with accuracy in accordance with settlement measure level III

2.2.6 Monitoring the settlement of the main work in the basement construction process

In nature, monitoring the settlement of the main work means monitoring the settlement of the diaphragm wall (basement wall) and internal parts of the diaphragm wall (column, partition, lifter wall, etc.) Accuracy in measuring the settlement of the main work should follow the accuracy of measuring the settlement level II

2.2.7 Processing the settlement monitoring data of the foundation of the high-rise buildings in the foundation and basement construction period

2.2.7.1 Analysis of stability of basic height mark

Standard on stability of basic height mark:

2.2.7.2 Calculation of adjustment of the settlement monitoring height network

2.2.7.3 Calculation of work settlement parameter

2.2.8 Comment on monitoring the settlement of the foundation of the high-rise buildings by the surveying method

The surveying method has the advantage of high accuracy, giving absolute settlement value The disadvantage of this method is that in order to monitor settlement of the soil layers in line with their depths (monitoring settlements of the foundation soil layers), it is required to execute separate monitoring marks Thus, the installation takes huge effort and each depth needs to be monitored requires a separate boring hole for installing mark

2.3 Monitoring the settlement of the foundation of high-rise buildings in the construction period using sensing

2.3.1 Structure of magnetic extensometer system

Magnetic extensometer is a specialized device for monitoring settlement in compliance with the magnetic induction principle The magnetic extensometer system consists of: guide pipe, standard magnet, spider magnet, plate magnet, meter wire and magnetic probe

Figure 2.9 Measuring settlement by magnetic

The settlement value of the monitoring point is determined by comparising its heights in two various measurement cycles

2.3.4 Accuracy in measuring settlement by magnetic extensometer method

According to Document [14], settlement square error is determined by magnetic

extensometer technology achieving size (5 8) mm

2.3.5 Example on measuring settlement of the work foundation by magnetic extensometer

2.3.6 Comment on monitoring settlement of the foundation of high-rise buildings

by sensing

The method of using sensing (magnetic extensometer) has the advantage that it permits arranging many monitoring marks for various depths at each boring hole The disadvantage of this method is that it takes the point at the pipe bottom as benchmark Thus, it is required that the bottom of the guide pipe to be anchored into stable rock layer lying at depth (not be settled) If this rock layer locates too deeply, it will be difficult for installing and it is not economical for boring deeply On the other hand, it

is impossible to evaluate the stability of the reference point in each monitoring cycle Therefore, if the reference point is settled, then the settlement value obtained at the settlement measuring table will not reflect the settlement of the monitored soil layers accurately

2.4 Solution in combining the method of surveying and using sensing for monitoring the settlement of the foundation of high-rise buildings

To overcome the disadvantage of the method of surveying and using sensing, this Dissertation suggests combining these two methods together to monitor the

2.3.2 Installation method

Guide pipe with spider is

installed in boring hole and

arranged in sequence as shown in

method, point at the pipe bottom

is taken as benchmark and height

of the monitoring point is

determined as follows (Figure 2.9)

Magnetic probe

Plate magnetSpider magnet Datum magnetFilling soil

settlement of the soil layers and emerging of the foundation pit The combining process is executed as follows:

2.4.1 Bottom of the guide pipe is anchored into a stable rock layer

Closing error of monitoring settlement by magnetic extensometer ( ) is calculated by the following formula:

Δ = S§T - ST§ (2.19)

In formula (2.19): SĐT - settlement of pipe top (Point A - Figure 2.9) measured by magnetic extensometer; STĐ - settlement of pipe top measured by surveying method Distributing the closing error ( ) for the measuring points at the depth in line with the principle of direct proportion to the distance from the pipe bottom to the measuring point will be able to determine the settlement values at the settlement measuring tables with increased accuracy (formula 2.20)

Δi

S : settlement of Poin Pi measured by magnetic extensometer;

2.4.2 Bottom of the guide pipe is anchored into an unstable rock layer

For this case, the value ( ) that is obtained using formula (2.19) could be considered as the settlement of the reference point at the pipe bottom At that time, adjust the value ( ) for the measuring points at the depth by following formula:

2.4.3 Example on measuring the foundation settlement by the method of surveying and magnetic extensometer

2.4.3.1 Example in case bottom of the guide pipe is anchored into a stable rock layer 2.4.3.2 Example in case bottom of the guide pipe is anchored into an unstable rock layer

2.4.4 Comments on monitoring settlement of the foundation of high-rise buildings by combing the method of surveying and using sensing

The solution in combining the method of surveying and using sensing (magnetic extensometer) for monitoring the settlement of the foundation of high-rise buildings have the following meanings:

- To increase the accuracy in measuring settlement at the settlement monitoring tables (in case bottom of the guide pipe is anchored into a stable rock layer)

- To permit taking the point at the pipe top as benchmark for determining settlement at the settlement monitoring tables So, in this case, the guide pipe should not be anchored into the stable rock layer; it is only necessary to install the guide pipe

to the depth of the soil layer that needs monitoring settlement Thus, it will be more convenient for constructing and installing the guide pipe, allowing increasing the effectiveness of monitoring the settlement of the foundation of high-rise buildings

Chapter 3 MONITORING DISPLACEMENT OF THE DIAPHRAGM WAL

OF THE HIGH-RISE BUILDINGS IN THE FOUNDATION AND BASEMENT CONSTRUCTION PERIOD

3.1 Technical requirements on monitoring displacement of the diaphragm wall

of high-rise buildings

3.1.1 Some general concepts of constructing the foundation and basement of high-rise buildings

3.1.1.1 Measures in constructing the basement of high-rise buildings

3.1.1.2 Measures in obstructing soil for excavating hole in the foundation and basement construction process

3.1.1.3 Diaphragm wall of high-rise buildings

3.1.2 Causes of displacement and deformation of the diaphragm wall

In the process of excavating holes for constructing the foundation and basement, when some soil volume is taken, the stress status will be changed This leads to deformation of the soil block surrounding the excavated holes Soil will displace to the excavated holes, which could make the diaphragm wall displace

3.1.3 Purpose of monitoring displacement of the diaphragm wall

Monitoring displacement of the diaphragm wall is aimed at determining displacement and deformation extent; researching to find the cause of displacement and deformation of the diaphragm wall; thereby, taking the measure for treating, preventing the accident occurring to the work and adjacent works

3.1.4 Requirements on accuracy and cycle of monitoring displacement of the diaphragm wall

3.1.4.1 Requirement on monitoring accuracy

Method 1: Based on the predicted displacement value (provided by the

designing unit) to determine the requirement on monitoring accuracy

Method 2: It is possible to use the displacement measurement levels in

Vietnamese Standard TCVN 9399:2012 “Buildings and civil structures - Measuring

horizontal displacement by surveying method” [38] to monitor the displacement of

diaphragm wall

3.1.4.2 Cycle of monitoring displacement of the diaphragm wall

Monitoring cycle depends on the construction progress of the excavated hole

3.2 Monitoring displacement of the diaphragm wall by the surveying method

3.2.1 Designing structure and distributing benchmark for monitoring displacement of the diaphragm wall

3.2.2 Designing the network system for monitoring displacement of the diaphragm wall

The system of monitoring displacement network of the diaphragm wall is designed with two levels: basic and monitoring level The requirement on errors in determining the placement for the network levels is determined by the following formulas:

- For basic network:

- For monitoring network:

In formulas (3.3) and (3.4): mq - required accuracy for displacement monitoring; k -

accuracy decrease coefficient between two network levels ( k = 2÷3)

3.2.3 Monitoring displacement of the diaphragm wall by angle-side measuring network

3.2.3.1 Triangle method

3.2.3.2 Polygon method

3.2.3.3 Synodic method

3.2.4 Monitoring displacement of the diaphragm wall by the standard method

3.2.5 Monitoring displacement of the diaphragm wall by the automatic monitoring system

3.2.5.1 Introduction of the automatic monitoring system

3.2.5.2 Automatic monitoring of displacement of the diaphragm wall by Total Station 3.2.5.3 Software for processing the monitoring data automatically

3.2.6 Processing the data of monitoring displacement of the diaphragm wall

3.2.6.1 Analysis and evaluation of stabibility of the benchmarks in monitoring displacement of the diaphragm wall

Like monitoring the settlement, the stability standard of the basic control point is:

In formula (3.7): qi - displacement of the basic control point in the

current cycle in comparison with the first cycle; mq - requirement on accuracy in displacement determination; t: coefficient for determining standard of limit error (t = 2÷3); k - accuracy attenuation coefficient between network levels (k = 2÷3)

3.2.6.2 Adjustment of the monitoring network

3.2.7 Calculation of displacement parameter of the diaphragm wall

3.2.7.1 Calculation of local displacement parameters

3.2.7.2 Graphic representation of displacement of the diaphragm wall

3.2.8 Proposal for processing the data of the automatic monitoring system when monitoring more than one station

In nature, the automatic

monitoring method using Total

Station from one station is to measure

pole coordinate and does not have

residual measurement value

Therefore, its reliability is not high

and could lead to mistake To

increase the residual value of the

measurement value, it is necessary to

apply the surveying method from two

or more stations at the same time Figure 3.20 Graph on monitoring more than

one station automatically

To determine the most reliable coordinate of the monitoring points, it is necessary to adjust the coordinates of the monitoring points The process of calculating and processing data is conducted as follows:

From Figure 3.20, the coordinates of the monitoring points are determined as follows:

δδ

(0) (0)

3.3 Monitoring displacement of the diaphragm wall using Inclinometer

3.3.1 Inclinometer structure

Inclinometer is a specialized device for monitoring displacement in line with depth The structure of this device consists of four main components: guide pipe; probe; signaling cable; reading device

3.3.2 Principle on measuring the displacement using Inclinometer

Measuring the displacement using Inclinometer is to measure indirectly the displacement of the object that need be monitored through the displacement of the guide pipe (figure 3.22, 3.23)

Figure 3.22 Conventional directions in monitoring using Inclinometer

Figure 3.23 Calculation diagram on measuring displacement using Inclinometer

Calculation method in measuring displacement using Inclinometer is to take the bottom of the measuring cylinder as basis for determining the displacements at the upper measurement locations; thus, the bottom of the measuring cylinder must not be displaced

On figure 3.23, lateral deviation for each measurement location by one axis is determined by the following formula:

In which: di - lateral deviation between two adjacent measurement points by one axis; L - measurement distance between two adjacent points; θi- angle of inclination

in comparison with vertical direction of ith point

Lateral deviation value of any point by one axis is total measurement value from the cylinder bottom to that point (figure 3.23); this value is called the

accumulative one (d) and calculated by following formula:

Axis A

Axis B