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MINISTRY OF EDUCATION AND TRAINING
UNIVERSITY OF TRANSPORT AND COMMUNICATIONS

DO VAN THAI

RESEARCH ON UTILIZATION OF WASTE ROCK AND SOIL IN
THE COAL MINES OF CAM PHA AREA, QUANH NINH FOR
AUTOMOBILE ROAD CONSTRUCTION

Discipline
Code
Major

: Transport Construction Engineering
: 9580205
: Automobile and urban road construction

SUMMARY OF TECHNICAL DOCTORAL THESIS

HA NOI – 2019



The study was completed at
University of Transport and Communications

Academic supervisors:
1. Assoc. Prof. Dr. Nguyen Huu Tri
Institute of Transport Science & Technology
2. Prof. Dr. Pham Huy Khang
University of Transport and Communications

Referee 1:
Referee 2:
Referee 3:

The thesis will be defended in front of the university-level
doctoral thesis judgement panel at the University of Transport and
Communications.
At…….. , dated …………………………. 2019

The thesis can be found at:
- Viet Nam National Library
- UTC Library – Information Centre


PUBLICATIONS BY THE AUTHOR
1. MSc. Doctoral Candidate Do Van Thai, Assoc. Prof. Dr. Nguyen
Huu Tri, Prof. Dr. Pham Huy Khang (2015), “Reseach on utilization
of waste rock and soil at the coal mines in Cam Pha, Quang Ninh and
possibility of using them in automobile road construction”, Transport
and Communications Science Journal, (9), pgs. 45-48.
2. MSc. Doctoral Candidate Do Van Thai, (2018), “Evaluation of
cracks on pavement using cement – reinforced aggregate of waste
rock and soil from Quang Ninh based coal mines and measures to
overcome”, Transport and Communications Science Journal, (4), pgs.
83-86.
3. MSc. Doctoral Candidate Do Van Thai, Assoc. Prof. Dr. Nguyen
Huu Tri, Prof. Dr. Pham Huy Khang (2018), “Experimental results of
utilization of cement-reinforced waste rock and soil from Quang Ninh
based coal mines for automobile pavement construction”, Transport
and Communications Science Journal, (9), pgs. 41-44.


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INTRODUCTION
1. Rationale for the study
To exploit and select 1m3 clean coal, in Quang Ninh they normally have to
remove 8 - 12m3 waste rock and soil. The volume of potential waste rock and
soil discharged from coal mining in Quang Ninh by the end of 2012 was approx.
3.7 billion m3 and is expected to increase by 1.9 billion m3 in the period 20132020. The path to the waste dumps is muddy in the rain and dusty in the Sun,
causing environmental pollution at an alarming level, landslides of waste rock
and soil being lurking, likely to bury construction works and cause disaster to
people.
Viet Nam Coal and Mineral Group has converged the waste dumps on one site.
The environmental pollution here has been improved somehow, yet it is still not
feasible to prevent consequences from the waste dumps formed from open coal
mining in Quang Ninh.
Initiated by the fact, the doctoral candidate has come up with and successfully
completed a study entitled “Research on utilization of waste rock and soil in
the coal mines of Cam Pha area, Quang Ninh for automobile road
construction”.
2. Aims of the study
Based on field survey, lab experiment and on-site testing, the researcher has
conducted analysis, evaluation and proposed possibility of utilizing waste rock
and soil from the coal mines in Cam Pha area, Quang Ninh for automobile road
construction.
3. Targets and scope of the study
Targets: The waste rock and soil at the coal mines in Cam Pha area, Quang
Ninh, with or without cement reinforcement to be used as materials in pavement
construction for automobile roads and rural roads.
Scope: The waste dump of Dong Cao Son (ĐCS) in Cam Pha area, Quang Ninh;
experimenting to determine physio-mechanical technical specifications of waste
rock and soil with and without cement reinforcement at coal mines; on-site
testing waste rock and soil as materials in pavement construction for automobile
roads.
4. Scientific and practical significance of the study
4.1 Scientific significance
Clarifying the scientific fundamentals and effectiveness of cement reinforcement
on 02 types of the aggregate proposed (A-ĐCS và AB-ĐCS).
Supplementing and finalizing the technology of construction and quality control
of cement-reinforced aggregate AB-ĐCS in automobile pavement construction.


2
Analyzing and proposing application in several structures of typical automobile
pavement using waste rock and soil at the coal mines in Cam Pha area, Quang
Ninh.
4.2 Practical significance
The study results have contributed to saving natural resources, protecting
environment and fully utilizing the local materials for automobile road
construction.
Having completed a technological production line from material production to
reinforced aggregate batching, leveling, spreading, compacting and quality
control, maintenance, reducing cracks in aggregate made of cement-reinforced
waste rock and soil in automobile pavement construction.
Having succeeded in building an experimental section with the pavement made
of waste rock and soil from Quang Ninh – based coal mines.
Having proposed several structures of typical pavement using the waste rock
and soil from coal mines, applicable to construction of automobile roads and
rural roads.
5. Structure of the thesis
The thesis includes the Introduction, four main chapters, the Conclusion and
Recommendation – Direction for further study; References and Appendices.
Chapter 1. OVERVIEW OF STUDIES ON UTILIZATION OF WASTE
ROCK AND SOIL FROM COAL MINES IN AUTOMOBILE ROAD
CONSTRUCTION
1.1 Overview on waste rock and soil from coal mines
1.1.1 Coal mining and the waste rock and soil from coal mines worldwide
Coal mining exerts serious impacts on the environment, including soil erosion,
landslide due to flooding, biological imbalance, environmental pollution (air,
water, soil) as well as land occupation for disposal sites.
All mining companies and corporations in the world strictly comply with the
government's regulations on the environment and must restore the original
environmental status and address some consequences on environment caused by
mineral exploitation, including coal mining.
1.1.2 Coal mining and the situation of waste rock and soil from the coal
mines in Quang Ninh
In the period of 2013 - 2020, the volume of waste rock and soil from the coal
mines in Quang Ninh is estimated to grow by approx. 1.9 bil m3. At pressent, the
largest waste dump in Cam Pha, Quang Ninh named Dong Cao Son (ĐCS) has a
capacity of 295 mil m3. In the period 2011 – 2015 alone, the volume of waste
rock and soil at Dong Cao Son waste dump was as much as 509.8 mil m3,


3
accounting for almost 83% of the total volume of waste rock and soil in Cam
Pha area as a whole.
1.1.3 Size and current situation of Dong Cao Son waste dump in Cam Pha,
Quang Ninh
Designed by the former USSR in 1980 with the total area of 280 ha, the
maximum elevation of the waste dump is at +255m with the capacity of 359.1
mil m3 and was intended to serve Cao Son mine only. Today, ĐCS waste dump
(Figure 1.4) is planned for waste disposal for the adjacent coal mines, too.
Super-heavy and super-load vehicles
constantly come and go one after
another to discharge here. The waste
rock and soil collected heaps up from
60m to 150m high, some places even
up to 250m above sea level.

Figure 1.4: The site of Dong Cao Son
waste dump as planned
The waste rock and soil from coal mines gathered at Dong Cao Son waste dump
are formed from rock blasting to remove the upper primary cover till the layer
adjacent to the near-ore area (coal basin). The waste rock here has low intensity,
low mechanical strength mixed with a small amount of soil from the surface of
the cover layer, which is estimated to account for about 10% of the total waste
material. Waste rock and soil has different particle sizes, varying from granular
to sandy, macadam, rocky and boulder types.

Figure 1.5: situation of waste rock and soil on Dông Cao Son waste dump
1.2 Overview on utilization of waste rock and soil in automobile road
construction
1.2.1 Study results and technical instructions overseas
Many countries in the world have put waste rock and soil into use and issued
technical standards associated with rock, waste rock, rock mixed with soil to
construct dams and pavement, including
- Technical instructions for automobile roads - Building embankment by South
Africa, 1982.
- US technical instructions
- Technical instructions by Transport Department, Washington, USA
- Technical requirements for waste rock and soil in embankment by the UK


4
- Instructions for utilization of waste rock in embankment in Australia
1.2.2 Initial study results and technical instructions in Viet Nam
In Viet Nam, the source of waste rock and soil from mining, rock production
and solid waste from dismantling or construction is tremendous. However, the
results from research on utilization of these waste materials in automobile road
construction are modest, especially in terms of experiment, testing and
evaluation.
1.2.2.1 Standards for automobile pavement construction related to waste
rock and soil
- Prior to 2005, several localities made use of waste rock and soil to build
automobile roads, but mainly out of their own will and without regard to
standards.

Figure 1.9: Pavement covered with multi sized rock or mixed rock
- Post 2005 by now, certain technical regulations for automobile pavement
construction related to waste rock and soil have been issued, such as
TCVN4054; TCN211-06; TCVN9436; TCN333-06.
- Recent studies and testing
a/ Testing: Building embankment with waste rock has not ever been recorded in
the existing standards, therefore, the Transport Ministry has conducted a trial
case to study and draw experiences on some routes, such as Ha Noi – Lao Cai
Motorway, Le Cong Thanh – Phu Ly – Ha Nam road.

Figure 1.11: Embankment of waste rock, Contract Pakage A8,
Ha Noi – Lao Cai Motorway

Figure 1.12: Embankment of waste rock,
National Highway 1A, section Phu Ly - Doan Vi Bridge


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b/ Some studies
1. Project “Handling and reusing solid waste in construction of road traffic
works” Code: MT 103005, Institute of Transport Science & Technology.
2. Ministerial-level study “Studying embankment of stones and embankment of
rock and soil in construction of roadbed and pavement in Viet Nam” Code:
124002, Institute of Transport Science & Technology.
3. Experimental study on waste rock and soil on Nam Khe Tam waste dump –
Postgraduate dissertation – Vũ Vinh, 2013.
4. Draft basic standards for “Studying embankment of stones and embankment
of rock and soil in construction of roadbed and pavement in Viet Nam”, 2018,
Institute of Transport Science & Technology
2- Standards for construction of automobile road foundation related to
waste rock and soil
- 22TCN 211-06; TCVN 8857:2011; TCVN 8859:2011; TCVN 8858:2011;
TCVN 10379:2014.
1.3 Summarizing, analyzing and proposing the content for research
- Overseas: Encouraging to utilize waste rock and soil for site clearance,
automobile embankment with extension of 500mm as much. At the same time,
the source of waste rock and soil can be used to produce macadam aggregate for
automobile road foundation.
- In land: Available projects, studies on waste rock and soil in coal mining in
Quang Ninh, but mainly focusing on site planning; Studies on mineral chemical
properties of waste rock and soil; on land properties; on production building
materials such as bricks and tiles; on ground leveling, construction of temporary
roads, permanent roads; on production of artificial sand, etc.
1.3.3 Analyzing and proposing the content for research
Research content
The research on theoretical fundamentals and lab-based experiments of
aggregate made of waste rock and soil has resulted in a proposal of cement
reinforcement; choice of reasonable binding ratio; analysis and evaluation of
reinforcement effectiveness and determination of the physio-mechanical
specifications of cement reinforced mixture used in calculation of design tested
on site; building a test section that uses waste rock and soil from coal mines in
pavement structure; proposing some typical structures; recommending
technology to produce aggregate materials; and finalizing the technology for
construction of aggregate made of waste soil and rock cement reinforced.
Research methods
Studying theories, analyzing scientific fundamentals of material utilzation in


6
automobile pavement construction; Studying lab-based experiments and on-site
testing; Employing synthetical and statistical approaches in designing tests and
processing lab results.
Chapter 2: STUDYING LAB-BASED EXPERIMENTS AND PROPOSING
TO UTILIZE WASTE ROCK AND SOIL FROM THE COAL MINES IN
CAM PHA, QUANG NINH AS MATERIALS FOR AUTOMOBILE
PAVEMENT CONSTRUCTION
2.1 Studying the scientific fundamentals of utilzation of rock and soil
reinforced with inorrganic binders in automobile pavement construction
2.1.1 General concept of material reinforcement
The physio-mechanical impact by crushing, mixing and compacting aggregates
enables close contact among the soil and rock particles as well as the added
substances. The physio-mechanical properties and compactedness have been
improved, increasing stability with water and limiting harmful effects in the
environment. However, the high reinforcement effect is only achieved with the
right bonding and the utilization rate suitable for soil groups or particle materials
to be reinforced. At the same time, the bonding agent must be evenly distributed
together with guaranteed compacting.
2.1.2. Formation of strength of soil reinforced with inorganic binders
Soil reinforcement of inorganic binders is a form of mixing soil with inorganic
binders and water at a certain ratio in the device or on site; then spreading and
compacting to the required compactedness to form the road foundation and
pavement. The strength of reinforced soil will increase over time to achieve the
required design strength, depending on the type of bonders used.
Formation of the strength and water stability of particle mixture reinforced with
inorganic binders depends heavily on the mineral composition of the particle
material, reinforcing method, and the reactions occuring on the contact surface
between the bonders and mineral materials and the ion exchange between them.
2.1.3 Formation of strength of material layers reinforced with cement
In the early stage, cement mixed in soil hydrated by water in the mixture will
create hydrated products, which turn solid to help create the intensity of the
mixture. In the next stage, there will be physio-chemical and chemical
interactions of fine aggregates in the mixture with hydrated cement products.
The results of those two processes create high-intensity crystalline structures for
cement reinforced mixtures. This intensity depends not only on cement grade,
ratio, type of cement but also on properties such as dispersion, particle
composition, mineral chemical composition, content of soluble salts, organic
humus content and pH in the reinforced material mixture. According to the


7
nature of cement, the process of forming strength of cement reinforced materials
also gradually takes place, mainly during the 28-day-old period.
2.2 Designing experiments and processing the data obtained
2.2.1 Designing experiments
Design of Experiments (DoE) includes selection of experiments, sample
planning, experiment performance and data collection, analysis and processing.
The general full factorial design employs Minitab 18 with reliability of 95%,
significance of α=5% within the framework of a study having a small number of
samples by Turkish method.
2.2.2 Calculation formula
For the xi sample set of n samples, average value x and standard deviation s ,
the average value is specified by the formula:

x
n

x

i 1

i

n

(2.1)
The standard deviation of the parameter to be controlled x is calculated by the
formula:

  x  x
n

s

i 1

2

i

n 1

(2.2)
With the number of samples n is ≤30, the denominator of the formula is (n-1)
whereas the population is n >30, (n-1) is replaced by n. For lab-based
experiments with a few samples, the denominator (n-1) is recommended.
The variance coefficient of the parameter under control is calculated by the
formula:
cv 

s
x

(2.3)
For a group or a set of samples, to evaluate the variation degree or precision, the
range (R) is often used as per the formula:
R  X max  X min

(2.4)
The confidence interval is identified as the range of values within which lies the
parameter with a corresponding probability. The lower bound of the confidence
interval is called the lower confidence limit. The upper bound of the confidence
interval is called the upper confidence limit. In quality control of pavement
construction, the confidence interval (CI) of ± 95% is usually taken.
xCI  x   

s
n

(2.5)


8
With xCI being the lower and upper bounds of the confidence interval
corresponding to the reliability R;   is the coefficient specified by t-test;  is the
allowable error   1  R , normally when R=95%, then =5%.
The typical value X dt of the variable X follows the standard distribution rule

calculated as: X dt  X  K .S
(2.6)
In which, coefficient K=1.645 corresponding to reliability R = 95%
2.2.3 Evaluating the number of samples in the sample group
Using Minitab 18 to reevaluate the number of samples by t-test, power=0,8

(coefficient   1  0,8  0, 2 ) and the significance degree =0,05 (Figure 2.5)
Power Curve for 1-Sample t Test
Power and sample size
1-Sample t-test
Average value = null (versus ≠ null)
The power calculated yields the average value =
null + variance α = 0.05. Supposing the
standard deviation degree is 1, the result is
Sample
Power
Difference
Difference
size
9
0.8

Figure 2.5: Analysis to select some samples
2.2.4 Eliminating foreign data and evaluating precision
Precision is the proximity of independent test results received under specified
conditions, demonstrating the experiment quality, ensuring the scientific
grounds for analysis to make conclusions and recommendations in the research.
2.3 Surveying, sampling and experimenting to determine the mechanical,
physical and chemical indexes of the waste rock and soil at Dong Cao Son
mine
2.3.1 Selecting representative waste dump
Dong Cao Son waste dump has the biggest capacity of estimatedly up to 295 mil
m3, seerving as the site to collect wate rock and soil from the open mines nearby
like Deo Nai, Cao Son, Coc Sau, Khe Cham II and Dong Da Mai, constituting
over 94% of the total volume of wate rock and soil in the entire area.
1.0

Sample
Size
9

0.8

Assumptions
α
0.05
StDev
1
Alternative


P o w er

0.6

0.4

0.2

0.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

Figure 2.6: Waste rock and soil at Dong Cao Son mine


9
2.3.2 General features of Dong Cao Son waste dump
The waste rock and soil at Dong Cao Son waste dump are mainly composed of
weathered rock (sandstone, siltstone, clay), having low mechanical strength
mixed with a small amount of soil from the surface of the cover layer, which is
estimated to account for about 10% of the total waste material. Waste rock and
soil has different granular sizes, varying from dirt to sand, macadam, rock and
bould (Figure 2.6).
2.3.3 Selecting representative samples
Survey, analysis and planning for sample selection were conducted cautiously
according to these criteria; First, samples should be typical for the entire waste
dump; Second, each sample collection should be adequate in quantity for all
experiments (classification and identification of particle composition; physiomechanical indexes and technical characteristics in road construction).

Figure 2.7: Sample collection at Dong Cao Son mine
2.3.4 Mineral chemical composition of wate rock and soil
Table 2.1: Mineral chemical composition of waste
rock and soil at Dong Cao Son mine
Average
Testing
Mineral chemical
Order
Norm
Unit
result
method
composition of wate
1
SiO2
%
77,12
rock and soil at ĐCS
2
Fe2O3
%
4,47
waste dump, Cam Pha
3
KMn
%
4,42
area, Quảng Ninh is
4
Al2O3
%
9,4
given in Table 2.1
TCVN
(Cited from the report at
5
TiO2
%
0,26
7131 the Annual Sciencitic
6
K2O
%
1,67
2002
Conference 2014/ISBN:
7
Na2O
%
0,16
(978-604-82-1388-06).
8
CaO
%
0,84
9
MgO
%
0,8
10
SO3
%
0,02
2.3.5 Identifying particle composition
The particle composition is classified into 2 groups:


10
Table 2.2: Volume by group at Dong Cao Son
Group A has sizes of more

Size in

than 50mm; group B has sizes
of 50mm or less.
The analysis result is given in
Table 2.2

Volume in %

mm

Group

Sample 1

Sample 2

A

>50

89,6

88,5

B

≤ 50

10,4

11,5

waste dump
Group of >50mm is subdivided into 3 grades: Grade a: >50100mm; Grade b:
>100 ÷ 150mm; and Grade c: >150mm. The analysis result of percentage by
volume of each particle grade in the total volume of Group A at ĐCS waste
dump is given in Table 2.3.
Table 2.3: Volume by grade at ĐCS waste dump (Group A)
Grade

Size in mm

Volume in %
Sample 1

Sample 2

a

> 150

50,6

57,2

b

> 100÷150

26,6

21,8

c

> 50100

22,8

21,0

Table 2.4: Particle composition of waste rock and
soil at ĐCS waste dump (Group B)
Seaving size in mm
Composition analysis of
particles of 50mm or
smaller follows TCVN
4198: 2015. The result is
given in Table 2.4.

Through seaving in %
Sample 1

Sample 2

50

99,17

100

25

86,2

84,42

9,5

64,32

60,54

4,75

51,2

46,91

2

26,85

33,41

0,425

11,31

13,68

0,075

3,84

5,06

Bottom
The summary of particle classification by size of waste rock and soil at ĐCS
waste dump is given in Table 2.5.


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Table 2.5: Summary of particle classification by size of waste rock and soil at
ĐCS waste dump
Result in %
Group
Grade
Size in mm
Sample 1
Sample 2
a
>150
45,3
50,7
b
>100÷150
23,8
19,3
A
c
20,5
18,5
>50100
50 ÷ 25
1,44
1,81
25 ÷ 9,5
2,27
2,77
9,5 ÷ 4,75
1,35
1,58
B
4,75 ÷ 2
2,54
1,57
2 ÷ 0,425
1,61
2,29
0,42 ÷ 0,075
0,77
1,00
< 0,075
0,4
0,59

Figure 2.7a: Classifying waste rock and soil by size at ĐCS waste dump
The particles above classified by size are recommended for two uses:
(i) Grinding Group A into aggregate of similar form as macadam, or (ii)
Grinding Group A, then mixed with Group B to produce aggregate Group AB.
2.3.6 Experimenting to determine basic indexes of waste rock and soil
The experiments were conducted on both representative samples Sample 1 and
Sample 2.
Table 2.6: List, volume, testing method
No of samples
Experimenting
Total
Order
Testing method
Sample
content
Sample 2 number
1
TCVN 75721
Rock intensity
9
9
18
10:2006
TCVN 7572–12:
2
LA Abrasion %
9
9
18
2006
3
Liquid limit %
9
9
18
TCVN 4197–1995
4

Plastic limit %
9
Standard
5
9
compaction
6
CBR
9
2.3.6.1. Experimenting rock intensity

9

18

TCVN 4197–1995

9

18

22TCN 333-06.

9

18

22TCN 332–06


12
The average result of typical intensity on two samples is 70.22 MPa.
2.3.6.2. Experimenting Los Angeles abrasion
The average result of LA abrasion on two samples is 38.59%.
2.3.6.3. Experimenting soil’s plasticity
The average result: Liquid limit is 29.65%; Plastic limit is 25.02%; Plastic index
is 4.63%.
2.4.6.4. Experimenting to determine CBR index
The average result of CBR is 61.40%.
2.3.7 Remarks and evaluation of experiments on waste rock and soil to be used
as materials for construction of roadbed and pavement
Some ways to utilize waste rock and soil for roadbed construction are proposed
as follows:
1. Directly use it for embankment of automobile roads
2. Directly use it for roadbed of automobile roads
3. For roadbed construction after cement reinforcement
2.4 Proposing to select waste rock and soil of the coal mines in Cam Pha area,
Quang Ninh as materials for automobile pavement construction
- Option 1: Using only materials of Group A to produce aggregate since the
required particle composition achieves Dmax as per TCVN 8859:2011, also Dmax= 31.5 as per TCVN 8858:2011 and naming it as “Aggregate A-ĐCS”.
- Option 2: Using all waste rock and soil of all sizes at ĐCS waste dump
produce aggregate “rock and soil mixture” and naming it as “Aggregate ABĐCS”.
2.4.1 Particle composition and physio-mechnical indexes of aggregate A-ĐCS
Table 2.10: Particle composition of aggregate A-ĐCS
Percentage % of through sieving
Size of sieving
square hole in
Aggregate
TCVN 8858:2011 TCVN 8859:2011
mm
A-ĐCS
Dmax= 31.5
Dmax= 25.0
37.5
100
100
100
31.5
95 ÷ 100
25.0
85
79 ÷ 90
79-90
19.0
78
67 ÷ 83
67-83
9.5
57
49 ÷ 64
49-64
4.75
40
34 ÷ 54
34-54
2.36
30
25 ÷ 40
25-40
0.425
17
12 ÷ 24
12-24
0.075
6
2 ÷ 12
2-12
- The CBR result of aggregate A-ĐCS is 67.98%; the experimented content of


13
elongated flat grains achieves 16%; the organic content is 0.5% and the amount
of sulfate salt is 0%.
- The experiment result of other indexes of aggregate A-ĐCS is given in Table
2.11.
Table 2.11: Some physio-mechanical indexes of aggregate A-ĐCS
Aggregate TCVN 8859:2011
Index
TCVN 8858:2011
A-ĐCS
Class I
Class II
Upper foundation
LA abrasion, %
38,59
≤ 35
≤ 40
≤ 35
CBR at compactedness
67,98
K98, submerged for 96
≥ 100

(61,40)
hours, %
Liquid limit (WL), %
29,65
≤ 25
≤ 35
Index of Plasticity (IP),
4,63
≤ 6
≤ 6
≤ 6
%
(5,34)
Amount of elongated flat
16
≤ 18
≤ 20
grains, %
0,5
Organic content, %
2
(0,9)
Amount of sulfate salt
0
0,25
Note: The values given in brackets are of aggregate AB-ĐCS
Remarks
Thus, aggregate A-ĐCS can be used directly for the lower layer of pavement of
all structures. In case of using it for the upper layer of pavement of automobile
roads, it is recommended to be reinforced with cement (presented below).
2.4.2 Particle composition and physio-mechanical indexes of aggregate ABĐCS
Table 2.12: Particle composition of aggregate AB-ĐCS
Size of
Amount of through sieving, %
sieving
Macadam
Macadam
Natural
Natural
square
Aggregate
aggregate,
aggregate,
aggregate
aggregate
hole in
AB-ĐCS
Dmax 37,5 Dmax 31,5
Class A
Class B
mm
50,0
100
100
37,5
95-100
100
100
100
95
31,5
95-100
90
25,0
79-90
75-95
85
19,0
58-78
67-83
78


14
9,5
39-59
49-64
30-65
40-75
57
4,75
24-39
34-54
25-55
30-60
45
2,36
15-30
25-40
15-40
20-45
37
(2,00)
0,425
7-19
12-24
8-20
15-30
23
0,075
2-12
2-12
2-8
5-15
12
The physio-mechanical indexes of aggregate AB-ĐCS are similar to those of
aggregate A-ĐCS as given in Table 2.11. Two indexes higher than those of
aggregate A-ĐCS are the index of plastic (IP=5,34%); the organic content
(0,9%); CBR value is lower compared to aggregate A-ĐCS (CBR=61,40%).
2.5 Studying aggregates A-ĐCS and AB-ĐCS cement reinforced to be used
as materials in automobile pavement structure
2.5.1 Briefing on requirements and content of research
1. Testing reinforcement for aggregate AB-ĐCS with cement as per rates 0%;
2%; 4%; 6%; 8% and 10%.
2. Testing reinforcement for aggregate A-ĐCS with cement as per 02 usual rates
4% and 6% (based on the testing result from aggregate AB-ĐCS cement
reinforced) to compare with aggregate AB-ĐCS cement reinforced.
3. Determining the technical specifications of aggregate AB-ĐCS cement
reinforced (at reasonable rates of cement) to refer to the requirements set in
TCVN 8858:2011 and apply in calculation of test pavement design.
4. Contrasting the technical specifications of both aggregates A-ĐCS and ABĐCS when both cement reinforced at 4% and 6% cement.
2.5.2 Experiment planning
2.5.3 Sample preparing and experiment conducting
2.5.4 Experiment result on aggregate A-ĐCS cement reinforced
The experiment results are summarized in Table 2.15.
Table 2.15: Summary of the average result of experiments on aggregate AĐCS cement reinforced
Cement content
4%
6%
5%
Sample
Rn
Rech
Rn
Rech
Edh
(Mpa)
(Mpa)
(Mpa)
(Mpa)
(Mpa)
Xtb
4,26
0,51
5,71
0,60
573
S
0,13
0,02
0,29
0,05
20,23
Xđt
4,04
0,47
5,23
0,52
539,72
2.5.5 Experiment result on aggregate AB-ĐCS cement reinforced
The experiment results are summarized in Table 2.16 and Table 2.17.


15
Table 2.16: Result of compressive strength at Day 14 with AB-ĐCS
reinforced
Compressive strength at Day14 (MPa)
Sample
2%
4%
6%
8%
Xtb
2,20
3,80
5,26
6,49
S
0,10
0,30
0,15
0,22
Xđt
2,03
3,31
5,01
6,12

Sample
Xtb
S
Xđt

cement

10%
7,45
0,27
6,99

Table 2.17: Result of split pressing strength at Day 14 and
Edh aggregate AB-ĐCS cement reinforced
Split pressing strength at Day14 (MPa)
E đh (MPa)
2%
4%
6%
8%
10%
6%
0,31
0,41
0,52
0,61
0,70
481
0,03
0,04
0,04
0,03
0,03
16,24
0,26
0,35
0,46
0,57
0,65
454,28
Biểu đồ cường độ ép chẻ ở 14 ngày Rech (MPa)

Biểu đồ cường độ nén ở 14 ngày Rn (MPa)

95% CI for the Mean

95% CI for the Mean
9

0.8
0.702222

8

7.44556

5.26111

5
3.80222

4

4
3.5
3

2.20222

0.522222

0.5

0.413333

0.45
0.4
0.35

0.4
0.306667

0.3
0.2

2
1.5

1
0

Rech (MPa)

0.6

6

3

0.612222

6.48889

7

Rn (MPa)

0.7

2

4

6

Tỷ lệ xi măng (%)

Individual standard deviations are used to calculate the intervals.

8

10

0.1
0.0

2

4

6

8

10

Tỷ lệ xi măng (%)
Individual standard deviations are used to calculate the intervals.

Figure 2.24: Chart of
Figure 2.25: Chart of split
compressive strength at
pressing strength at Day 14
Day 14 of AB-ĐCS
of AB-ĐCS
From the results of experiments and statistical data processing, two regression
equations of the relationship between Rn, Rech with rates of cement for
reinforcement (XM, %) 14 days old are developed.
Rn = 1,0880 + 0,6587 XM (applied to Day 14)
Rech = 0,2143 + 0,04950 XM (applied to Day 14))
These equations only prove right in the context of the sutdy with the cement
content ranging from 2% to 10%.
2.5.6 Comparing experiments Rn, Rech and aggregates A-ĐCS and AB-ĐCS
cement reinforced at rates 4% and 6%
a/ Analysis result of compressive strength Rn
b/ Analysis result of split pressing strength Rech
2.5.7 Comparing experiment results for elastic modulus of aggregates A-ĐCS
and AB-ĐCS cement reinforced
2.6 Remarks and conclusions of Chapter 2
- The waste rock and soil from ĐCS waste dump, Cam Pha, Quang Ninh stems


16
from coal mining, thus can be utilized in automobile road construction;
- Having determined the technical specifications of aggregates A-ĐCS and ABĐCS cement reinforced at the studied rates; having developed the regression
equations of compressive strength and split pressing strength of AB-ĐCS as per
rates of cement;
- Having proved that aggregate A-ĐCS cement reinforced has higher technical
indexes than those of aggregate AB-ĐCS reinforced with the same rates of
cement;
- With aggregate made of waste rock and soil from the coal mines in Cam Pha,
Quảng Ninh cement reinforced at 4 % or more, it is possible to construct
pavement of rural roads providing the upper layer has to be asphalated for
protection.
- Recommending reasonable rates of cement between 4% đến 6% to reinforce
the waste rock and soil from coal mines in Cam Pha, Quảng Ninh, depending on
the volume of the mixture.
- Proposing to use aggregate A-ĐCS and AB-ĐCS for the lower foundation of
the automobile pavement as per TCN 221-06 and TCN274-01; Proposing to use
aggregate A-ĐCS and AB-ĐCS cement reinforced for the upper foundation for
roads of Grade III and lower or the asphalated surface.
Chapter 3. FIELD TESTING ON PAVEMENT MADE OF CEMENT –
REINFORCED WASTE ROCK AND SOIL TAKEN FROM COAL
MINES IN CAM PHA, QUANG NINH
3.1 Designing the section for field testing
3.1.1 Briefing the content and requirements of the section for field testing
3.1.2 Selecting the location, site and geometric parameters of the section for
field testing
3.1.3 Structure of the pavement to be tested
3.2 Studying to produce aggregate from waste rock and soil
3.2.1 Exploiting, transporting and gathering materials
3.2.2 Producing test materials
3.3 Constructing pavement of the test section
3.3.1 Materials for embankment
3.3.2 Pavement addressing before embankment
3.3.3 Conducting embankment
3.3.4 Result from checking and accepting the pavement
From the pavement measurement Edh, the average value E0= 45.37MPa exceeds
the minimum value 40 MPa as regulated.


17
3.4 Constructing layers of pavement of the test section
3.4.1 Constructing the foundation of AB-ĐCS 18cm thick
1- Preparation

Figure 3.9: Framing for foundation construction
2- Transporting, leveling, spreading, compacting
Roughly leveling by a bulldozer, then
combining with a specialized bulldozer
to level aggregate. The levelling process
should ensure the vertical slope of 1%
and horizontal slope of 2% according to
the design document.
Figure 3.10: Gathering, leveling, spreading, compacting the lower foundation
layer
3- Result from checking and accepting
- Checking the geometric size of the foundation of the test section,
- Checking the compactedness on site,
conducted at the end of the compacting
process by the sand hopper as per
22TCN 346-06.
Figure 3.11: Checking compactedness
of the lower foundation layer
- Measuring the elastic modulus by
TCVN 8861:2011 of the road
foundation with hard pressed plates
Figure 3.12: Measuring Edh at 3
positions of the test foundation

Figure 3.13: Roughly measuring Edh at 3 positions of the test foundation
The average Edh on surface of the foundation made of aggregate AB-ĐCS
reaches 75.8MPa.


18
3.4.2 Constructing foundation from aggregate AB-ĐCS reinforced with 6%
cement 16cm thick
1- Producing materials for cement reinforcement
Employing the mixing method at the
commercial concrete batch plant of Branch 1,
Song Hong 6 JSC (address: Quan Tien, Hoi
Hop, Vinh Yên city, Vinh Phuc).
Figure 3.14: Monitoring and inspecting at
Song Hong 6 concrete batch plant
2- Constructing with aggregate AB-ĐCS cement reinforced

The whole process of leveling, spreading, compacting and finalizing the surface
is performed before the cement bonding (120 minutes).
3- Checking compactedness of aggregate AB-ĐCS cement reinforced
4- Completing and maintaining
3.5 Constructing asphalated macadam layer 3.5 cm thick with 4.5 kg/m2
3.5.1 Materials
- Macadam: Using macadam from Minh Quang quarry, Tam Dao, Vinh Phúc,
qualified by TCVN 8863:2011.
- Bitumen: Using Singaporean bitumen with the needle deflection of 60/70
abiding technical standards of hot asphalated surface.
3.5.2 Constructing asphalated layers
3.6 Testing and verifying the measure to restrict cracks in aggregate made
of rock and soil cement reinforced
3.6.1. Creating cracks in advance (fake gap)

Figure 3.18: Sketch of the site for the test section
3.6.2. Adjusting maintenance regulations
Phase 1: Maintenance is constantly performed by spraying water for
moisturizing for the first 72 hours while observing and monitoring crack
development on the surface of aggregate AB - ĐCS reinforced with cement.


19
Phase 2: After 03 days of maintenance by damping, a fake gap is then made and
measured. Development of initial cracks on the surface of aggregate AB – ĐCS
cement reinforced is observed. Maintenance has been performed by fully
covering the surface with acidic asphalt elmusion with density of 0.8 – 1.2 litre/
m2.

Figure 3.20: Phase 2 maintenance (emulsion spraying)
3.6.3 Measuring and observing the crack development
- Within the first 24 hours after construction,
- From 24 to 72 hours,
- After maintenance by asphalt emulsion
- Remarks and evaluation of causes and development of cracks
3.7 Observing and evaluating the pavement structure
3.7.1 Checking and accepting the pavement
3.7.2 Drilling samples for evaluation of the compressive strength and split
pressing strength
Drilling samples to test the cement reinforced layer at Days 7, 14 and 28 as per
TCVN 8858:2011.
- Result of compressive and tensile strength when split pressing the drilling
samples on site
Table 3.10: Result of the
Table 3.11: Result of the split
compressive strength of drilling pressing strength of drilling samples
samples on site
on site
Sample
Xtb
S
Xđt

Compressive strength
at Day (MPa)
7 ng 14 ng 28 ng
4,20
5,85
7,90
0,10
0,15
0,25
4,03
5,60
7,49

Sample
Xtb
S
Xđt

Split pressing strength
at Day (MPa)
7 ng
14ng
28ng
0,41
0,53
0,74
0,03
0,03
0,05
0,37
0,48
0,65

The compressive strength value of the drilling samples tested on site at Day 14
Rn = 5.85 Mpa > 5.26 Mpa of the lab-based experiment as presented in Chapter
2, thus the reinforced rock aggregate meets requirements on compressive
strength.
The average value of split pressing strength of the drilling samples tested on site
is 0.53 Mpa > 0.52 MPa of the lab-based experiment as presented in Chapter 2,
thus the drilling samples on site meets the technical requirements as regulated.
3.7.4 General remarks of the test section
The section lying in a school was commenced on 01/04/2017 and completed on
31/09/ 2017. Many heavy vehicles run on the section to serve construction of


20
works in the school.

Figure 3.29. Operational situation of the test section
For nearly 2 years of operation, the test section has been under constant
observation. There have been no signs of damage or cracks detected on the
surface. At the position of fake gaps, no cracks are visible on the asphalated
surface.
3.8 Remarks and conclusions of Chapter 3
1. The test section has satisfied the technical requirements specified in the
current standards for automobile road construction.
2. Aggregate AB-ĐCS made from the original waste rock and soil of Dong Cao
Son waste dump meets the requirements for the lower foundation of the
pavement, and when reinforced with cement, it is suitable for the foundation of
automobile roads and the surface for rural roads.
3. The solution of gap cutting for aggregate AB - ĐCS cement reinforced has
been tested and verified. The result shows that gap cutting does not bring about
visible effects, rather it weakens the strength of reinforcement materials and
wastes resources, so it is recommended to halt. Instead, more focus should be
put on proper maintenance to restrict cracks or shrinkage while emulsion
spraying is practised for protection and also for coverage of cracks due to
shrinkage present on the surface of the reinforcement layer.
Chapter 4. PROPOSING SEVERAL PAVEMENT STRUCTURES AND
APPLICATION SCOPE
4.1 Principles to propose pavement structures and the application scope
4.1.1 Principles to propose pavement structures: following the principles of
forming pavement structures; basing on actual designing and using the local
pavement structure, including in-situ material availability; construction
capability and maintenance conditions; construction investment costs as well as
environmental impact taken into account.
4.1.2 Application scope for pavement structure
- Non-reinforced aggregate made of waste rock and soil from coal mines can be
used for (i) material for embankment; (ii) the upper roadbed for roads of all
grades; (iii) the lower foundation for high-grade roads A1 as per 22TCN 211-06;


21
(iv) the upper foundation for roads A2 or B1 as per 22TCN 211-06.
- Cement-reinforced aggregate made of waste rock and soil from coal mines (4%
- 6% cement) can be used for (i) rural road pavement as per TCVN 10380:2014
with the surface asphalated or covered; (ii) the upper foundation for high-grade
roads A1, A2 as per 22TCN 211-06.
4.2 Selecting the method to design pavement structures
Designing pavement structures according to the current standards (22TCN21106 for soft surface; specified in Decision No 3230/QĐ-BGTVT for hard
surface). In case of applying AASHTO (in TCN 274-01), there should be
studies, experiments to determine appropriate parameters according to the
calculation model including coefficient ai, CBR index, effective elastic modulus
MR, etc.
4.3 Proposing pavement structures
From the study result, 8 pavement structures have been recommended, mainly
meaningful in terms of structure design. The layer thickness in the proposed
structure is for reference and has been carefully determined based on auditing
outcomes according to the actual input data of load, traffic flow, roadbed status,
etc.
4.3.1 Pavement structure for rural roads (including trans-district roads)
Structure 1: In order, the upper most layer is of cement concrete #30 Mpa 18 –
22cm thick; the flat layer is 1-3 cm thick; aggregate layer A-ĐCS reinforced
with 5% cement (or aggregate AB-ĐCS reinforced with 6% cement), 16-18cm
thick; aggregate AB-ĐCS (or A-Dong Cao Son) 14-18cm thick; the soil roadbed
is underneath. The design follows 3230/QĐ-BGTVT with the traffic flow
designed (Nn) of 100  200 vehicles/day&night, applicable for roads with heavy
vehicles (the axis is more than 6000 Kg) exceeding 10 %.
Structure 2. In order, compacted asphalt concrete 12.5, 4-5 cm thick;
compacted asphalt concrete 19, 6-7cm thick (if necesary for main roads);
aggregate A-ĐCS reinforced with 5% cement (or aggregate AB-ĐCS reinforced
with 6% cement), 14-18cm thick; aggregate AB-ĐCS (or A-ĐCS), 15-30cm
thick; the soil roadbed is underneath. The design follows 22TCN 211-06 or
22TCN 274-01, with the traffic flow designed (Nn) of 100  200
vehicles/day&night, applicable for roads with heavy vehicles (the axis is more
than 6000 Kg) not exceeding 10 %.
Structure 3. In order, 3 layers asphalated as per TCVN 8863:2011, 3-3,5cm
thick; aggregate A-ĐCS reinforced with 5% cement (or aggregate AB-ĐCS
reinforced with 6% cement), 14-18cm thick; aggregate A-ĐCS (or AB-ĐCS),
15-30cm thick; the soil roadbed is underneath. The design follows 22TCN 21106 or 22TCN 274-01, with the traffic flow designed (Nn) of 100  200
vehicles/day&night, applicable for roads with heavy vehicles (the axis is more
than 6000 Kg) not exceeding 10 %.
Structure 4. In order, cement concrete #25-30Mpa 18-20cm thick; the
seperation layer; aggregate A-ĐCS reinforced with 5% cement (or aggregate
AB-ĐCS reinforced with 6% cement), 16-18cm thick; aggregate A-ĐCS (or


22
AB-ĐCS), 15-18cm thick; the soil roadbed is underneath. The design follows
3230/QĐ-BGTVT, with the traffic flow designed (Nn) of 50  100
vehicles/day&night, applicable for roads with heavy vehicles (the axis is more
than 6000 Kg) not exceeding 10 %.
Structure 5. In order, cement concrete #25-30Mpa 18-20cm thick; seperation
layer; aggregate A-ĐCS reinforced with 5% cement (or aggregate AB-ĐCS
reinforced with 6% cement), 14-16cm thick; aggregate A-ĐCS (or AB-ĐCS),
14-16cm thick; the soil roadbed is underneath. The design follows 3230/QĐBGTVT, with the traffic flow designed (Nn) of < 50 vehicles/day&night,
applicable for roads with heavy vehicles (the axis is more than 6000 Kg) not
exceeding 10 %.
4.3.2 Pavement structure for ordinary automobile roads
Structure 6. In order, compacted asphalt concrete 12.5, 5-6cm thick; compacted
asphalt concrete 19, 7-8cm thick; aggregate A-ĐCS reinforced with 5% cement
(or aggregate AB-ĐCS reinforced with 6% cement), 15-20cm thick; aggregate
A-ĐCS (or AB-ĐCS), 16-35cm thick; the soil roadbed is underneath. For highgrade pavement A1, the design follows 22TCN 211-06 or 22TCN 274-01. The
elastic modulus is required at 140  160 Mpa.
Structure 7. In order, cement concrete # fr=4.5  5.0 Mpa, 20-25cm thick; the
seperation layer; aggregate A-ĐCS reinforced with 5% cement (or aggregate
AB-ĐCS reinforced with 6% cement), 16-25cm thick; aggregate AB-ĐCS (or
A-ĐCS), 15-30cm thick; the soil roadbed is underneath. The design follows
3230/QĐ-BGTVT, applicable for heavy vehicles or lighter.
4.3.3 Pavement structure for motorways, heavy-load roads
The structures apply to motorways, heavy-load roads (aggregate layers made of
waste rock and soil from coal mines serve as the lower foundation only).
Structure 8. In order, the roughing layer is of polymer asphalt concrete
12.5/SMA; polymer asphalt concrete 19, 6-7cm thick; layer ATB25, 8-10cm
thick; macadam aggregate Class 1 reinforced with 5% cement, 15 -18cm thick;
aggregate A-ĐCS reinforced with 5% cement (or aggregate AB-ĐCS reinforced
with 6% cement), 16-20cm thick; layer AB-ĐCS (or A-Đông Cao Sơn) 16-30cm
thick; the soil roadbed is underneath. For the high-grade pavement A1, the
design follows 22TCN 211-06 or 22TCN 274-01. The elastic modulus is
required at > 180 Mpa.
4.5 Calculating pavement structure
To verify various structures, it is recommended to calculate one typical structure
according to the design standards.
The audited structure is given in Table 4.17. For the high-grade pavement A1,
the design follows 22TCN 211-06 or 22TCN 274-01. The time for calculation
t=15 năm. The growth coefficient q=5%. The elastic modulus is required at 160
MPa. The reliability coefficient R=90%.
The calculation result as per 22TCN 211-06 achieves Ech=176.1 MPa > Kcđđv x
Eyc=1.1 x 160 = 176MPa, satisfying 3 standards of limitation.
The auditing result as per Decision No 3230/QĐ-BGTVT given in Table 4.18


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