RESEARCH OBJECTIVES The dissertation focuses on clarification of the effects of the insulating layer in multi-layer concrete pavement and the effects of ambient temperature conditions o
Trang 1MINISTRY OF TRANSPORT UNIVERSITY OF TRANSPORT AND
COMMUNICATIONS
PHAM DUY LINH
INVESTIGATION AND EVALUATION OF SOME FACTORS AFFECTING OPERATION QUALITY OF
OF HIGHWAYS AND AIPORTS IN VIETNAM’S
CONDITIONS
Department: Transport Engineering
Code: 9580205
Major: Highway and Urban Road Construction
SUMMARY OF TECHNICAL DOCTORAL
DISSERTATION
HANOI – 2021
Trang 2The Study completed in:
University of Transport and Communications
Science Instructor:
1 PhD Vu Duc Sy
University of Transport and Communications
2 Prof PhD Pham Cao Thang
Military Technical Academy
… : … day… month … year …
The dissertation can be looked up at:
- Vietnam National Library
Communications
Trang 3THE AUTHOR’S PUBLICATIONS
1 Pham Duy Linh; Prof.PhD Pham Cao Thang; PhD Vu Duc Sy: “Research on calculation method to convert operating vehicle axle flow in designing highway rigid pavement structure” Bridge & Highway Magazine no 9/2017;
2 Pham Duy Linh; Prof.PhD Pham Cao Thang; PhD Vu Duc Sy: Bridge & Highway Magazine no 10, 2017;
3 Hoang Long Nguyen, Cao Thang Pham, Duy Linh Pham, Tuan Anh Pham, Duc Phong Pham, and Binh Thai Pham: Designing of concrete pavement expansion joints based on climate conditions of Vietnam: De Gruyter-Journal of the Mechanical Behavior of Materials, 28th issue dated 1/10/2019, (Scopus magazine);
4 Pham Duy Linh; Prof PhD Pham Cao Thang; PhD Vu Duc Sy; PhD Luong Xuan Chieu; PhD Tran Nam Hung (2020): “Research on Field Experiments to determine temperature distribution in slab in Hanoi” Bridge & Highway Magaze June 2020;
5 Pham Duy Linh; Prof PhD Pham Cao Thang; PhD Vu Duc Sy: “Calculation Method of multi-layer concrete pavement, considering the effect by thickness of the insulating layer between the courses” Transport Magazine June 2020;
6 Pham Duy Linh; Prof PhD Pham Cao Thang; PhD Vu Duc Sy: ”Research on temperature Gradient and average temperature in , in Vietnamese climatic conditions” Tranport Magazine August 2020
Trang 41
PREFACE
I NECESSITY OF THE STUDIED ISSUE
With significant advantages, concrete pavement can be applied broadly as pavement structure for high-class roads, for roads in airports, and highways with high axle volume and heavy load lorries travelling on However, current procedures being applied in Vietnam are not quite compiled by Vietnamese authors, but based on reference to foreign standards which are suitable to foreign countries’ conditions To make the technical regulations in those procedures fit to specific conditions of Vietnam, it is necessary to carry out researches for adjustment, supplementation of some technical requirements to make them more
adaptable to Vietnam’s conditions Therefore, the topic “Investigation
and Evaluation of some Factors Affecting Operation Quality of Concrete Pavement of Highways and Airport in Vietnam’s Conditions”
is a necessary research which is meaningful both scientifically and practically
II RESEARCH OBJECTIVES
The dissertation focuses on clarification of the effects of the insulating layer in multi-layer concrete pavement and the effects of ambient temperature conditions on working of the concrete pavement of highways and airports in Vietnam’s conditions
III RESEARCH CONTENT
The dissertation concentrates on following issues:
1 Overview;
2 Calculation to evaluate effects of the insulating layer to distribution
of internal forces in concrete pavement courses;
3 Theoretical investigation combined with field experiment, determining temperature profile distributed by depth in concrete pavement;
4 Studying and calculation to determine temperature gradient and average temperature in concrete pavement by thickness and calculation of the necessity of expansion joint of concrete pavement slab row on highways, and airports;
5 Study and calculation of digitalized experiment, quantifying effects
of the insulating layer and ambient temperature on working of concrete pavement of highways and airports in climatic conditions of North Vietnam
IV SCIENTIFIC AND PRACTICAL SIGNIFICANCES OF THE DISSERTATION TOPIC
Scientific Significance:
Setting calculation approach to evaluate effects of thickness and strength
of the insulating layer on the performance of multi-layer concrete pavement
Based on theoretical study and field survey, experiments, the temperature profile distribution is determined by depth of the concrete pavement and temperature gradient in the slab by each different pavement thickness
Trang 5OVERVIEW OF CALCULATION OF MULTI-LAYER CHAPTER 1.
CONCRETE PAVEMENT UNDER IMPACT OF WHEEL LOAD AND AMBIENT TEMPERATURE
Chapter 1 introduces and analyses the work of multi-layer concrete pavement under the impact of wheel load and the ambient temperature as the basis for continuing the study in subsequent chapters
1.1 General Construction of Concrete Pavement
1.1.1 Typical Construction of Concrete Pavement
Concrete pavement has general construction comprised of the following:
Upper course concrete pavement ; insulating layer; base; Sub-base; soil embankment; joints
1.1.2 Reason of Damages Reducing Operation Quality of Concrete Pavement
Main reasons causing damage and deterioration of the concrete pavement include the following: Due to truck load: Due to climatic conditions: Operation, and construction conditions One thing worth notice is that the designing, especially designing of constructions are not quite suitable to operation conditions
In the dissertation, it focuses on studying some issues relating to the insulating layer and effects of the ambient temperature in the designing calculation, which may affect operation quality of concrete pavement of highways and the airport in Vietnam’s climatic conditions
1.2 Calculation of Multi-Layer Concrete Pavement
1.2.1 Calculation Methods According to Designing Procedures of Vietnam
1.2.1.1 Vietnam’s design calculation method according to 22 TCN
223-95 [2]: Design calculation method according to temporary regulation on
ordinary concrete pavement with connection joint in transport works construction QD 3230/2012 [1] :
In calculation, it is required that between the layers, insulating layer must
be bituminous macadam or compacted asphalt concrete, but the insulating layer is only considered in structural role
Trang 63
1.2.1.2 Design calculation method of multi-layer concrete pavement in
airport roads according to TCVN 10907-2015 [3]: The insulating layer is
specified to be 1-2 layers of oil canvas, or bituminous sand with thickness not over 5mm In calculation the assumption that the upper course’s
deflection is equal to that of the below course is acceptable
1.2.1.3 Some Researches Calculating Multi-Layer Concrete Payment in
Vietnam [10, 11, 15]
In [11], Prof.PhD Nguyen Van Lien has introduced calculation method for girder and one-layer, and multi-layer concrete slab under flexural stress on elastic ground by finite difference method (FDM) In calculation for multi-layer concrete pavement structure, only the assumption that there is no friction between the layers is acceptable, if there is really no friction between layers, the insulating layer is not arranged for surveying the effect of the insulating layer In 1995, Prof PhD Pham Huy Khang in his Technical Doctoral Dissertation[15], has suggested calculation method for multi-layer concrete pavement with different modulus (strongly bonded), had calculate conversion from multi-layer to one-layer course, featured by the conversion of multi-layer to one-layer with converted elastic modulus
The dissertation of M.Sc Nguyen Hong Minh (2007) [10]: In calculation, the assumption that the insulating layer is small in thickness, thus effects
of the insulating layer on redistribution of internal forces in layers
1.2.2 Design Calculation Methods for Two-Layer Concrete Pavement, with expansion joints in the world:
1.2.2.1 Calculation of concrete pavement by Westergaard
semi-experimental method [16, 39]:
In calculation, the rigid base does not participate in flexural strength
1.2.2.2 Design calculation method according to AASHTO [17, 18, 19,
20, 21, 22, 23, 24, 36, 37]:
Bending and tensile stress calculation programme of multi-layer concrete with assumed thickness of the insulating layer is insignificant, not affecting distribution of internal forces among layers
Then the bending and tensile stresses in layers is proportionate to stiffness of the layers
1.2.2.3 Mechanical Experimental of the US [33, 42, 45]
In designing the additional strengthening concrete pavement on the existing concrete pavement, it states that the insulating layer is from hot asphalt concrete with allowable thickness of not over 2 inch (~ 5cm) In calculation, it only plays the role of insulating layer,
1.2.2.4 According to US Federal Aviation Administration (FAA) [41, 43]
In the design, it is specified that the insulating layer by construction structure, in case it is asphalt concrete, the thickness is not over 2 inches (5cm)
Trang 74
1.2.2.5 According to calculation method in India’s Designing
Procedure: Similar to Westergaard method
1.2.2.6 According to rigid pavement designing procedure of China JTG
D40-2011 [78]
In calculation of additional strengthening concrete pavement on the existing concrete pavement, it is compulsory to use leveling layer combined with insulating layer from hot asphalt concrete, min thickness
is equal 4cm But it is only considered structural layer, in consideration, the effects of insulating layer is not taken into account
1.2.3 Some Software Packages calculating pavement structure on deformed base
Currently in the world there are several commercial applications that are able to solve the question of multi-layer construction structure on deformed base Each software package is built with its own strength in solving interaction questions In calculation, only the insulating layer is required according to construction structure, provided that the concrete layers are bonded, half-bonded or freely slippery , without taking into account the effects of the insulating layer on performance of the structure
1.2.4 General Comments:
In design calculation, designing procedures all use thin-sheet principle
In case calculation of 2-layer concrete pavement with insulating layer, but
in the calculation diagram, the insulating layer is only considered as a constructional layer However, in some procedures, the specified thickness of the insulating layer is relatively high In hot sunny temperature in Vietnam, some materials will have their strength decreased (elastic modulus) will cause large deformation, increasing surface deflection, causing redistribution of internal forces in layers of multi-layer concrete pavement This issue needs to be considered and clarified
1.3 Calculation of Concrete Pavement Under Effects of Ambient Temperature
1.3.1 Effects of Temperature on Concrete Pavement
1.3.1.1 Temperature Gradient and concrete pavement cambering due to
temperature gradient :
Due to temperature difference between concrete sub-layer by depth, layering can have different expansion When the surface temperature is higher than that in bottom of the pavement in hot summer days, the slab can be cambered , causing flexural stress at bottom of the pavement
Trang 85
Meanwhile, it is on contrary in case of deflection, the wheel load also cause bending and tensile stresses in the bottom of the pavement So the most disadvantage of the concrete pavement is that in hot summer days, the thermal stress magnitude depends on difference between the surface temperature and that of the bottom (temperature gradient ): ∆t=Tbm-Tđ
1.3.2 Temperature Gradient calculation method
1.3.2.1 Temperature Ambient calculation method according to Standard
No 22TCN 223-95 [2]:
In the process, the nearly true approx assumption acceptable is that the heat conduction line by pavement depth is linear to the unchanged rate of
0.84
1.3.2.2 Calculation Method of Gradient Temperature of the Concrete
Pavement according to Decision no 3230/QD-BGTVT [1]
It is specified in the procedure that the internal process by depth is linear with unit gradient (Tg, 0C/cm) in a concrete layer as constant in cement concrete for each Area;
1.3.2.3 Calculation Method of thermal stress, Cement Concrete
Pavement for airport roads according to TCVN 10907-2015 [3]
In the process, the flexural strength for the load is 70% of that of the Concrete, the remaining 30% is for thermal stress The distance of expansion joints is specified according to constructional structure s
1.3.2.4 The method of calculation of thermal stress of concrete
pavement taking into account American temperature’s effect (According
to AASHTO-1998 [21, 22])
In calculation, it is taken into account the effects of temperature on dimensions and work force of cement concrete applies some of experimental factors
1.3.2.5 Calculation of the Thermal Effects in the surface cement
concrete pavement slab according to Russian concrete pavement designing [52, 58, 65]
In calculation of temperature gradients between the surface and bottom of the slab It is accepted that the surface temperature fluctuates in finite space by Fourie law according to explanation
1.3.3 Regulation on Arrangement of Expansion Joint on Concrete Pavement
1.3.3.1 According to Regulation of Concrete Pavement Association US
[22, 25, 26, 27, 30, 31, 32, 34, 38, 40, 45]
The expansion joints are arranged according to constructional structure
On the main axis, in case of really crucial, it is possible to arrange expansion joints with distance of up to 500fit( ~ 150m)
Trang 96
The American Concrete Institute also specifies that expansion joints are only arranged in either of the below conditions
1.3.3.2 According to US Federal Aviation Administration [16, 18, 20]
The expansion joints are only arranged at intersections with neighbouring projects (runway with taxiways, taxiways with apron)
1.3.3.3 According to pavement designing procedure of India [28, 35]
It also states that expansion joints should be arranged the same as the US
1.3.3.4 According to pavement designing process of some other
countries [17, 34, 45]
[34] has stated practical experiments of Western World Countries (Belgium, Denmark, Dutch, Deutscheland), the expansion joint is only arranged at the approaches of the bridge, on curves, while on straight roads, if necessary, they are arranged at 30-60m interval (98-196ft) Fwa has suggested that with concrete pavement’s thickness of over 20cm, the distance between the expansion joints is 60m And thickness of the smaller concrete pavement for thickness of the concrete slab is equal or minus 20cm, taking the distances between the expansion joint of 40m
1.3.3.5 According to Concrete Pavement Designing Procedure by
Russia [52, 53, 55, 56, 62, 63, 65]
The distance between expansion joints, is specified based on construction structure included in specific table which is suitable to Russian’s climatic condition
1.3.3.6 According to Rigid Pavement Designing Process by China JTG
D40/2011 [78]
Only arrange expansion joint at intersection with other works, bridges on the road While in the general route, expansion joints are only arranged when it is really necessary according to calculations As such, arrangement of expansion joints on a highway is only according to constructional structure
1.3.3.7 Vietnam’s TCVN 10907/2015 specifies: [3]
The expansion joints, the expansion joints are classified by structure, at fixed distance for each region, with expansion joint structure being the typical design
1.3.3.8 Decision no 3230/2012 specifies arrangement of contraction
joints, expansion joints for concrete pavement slab rows[1]
The expansion joints are arranged depending on the constructional structure, depending on temperature at working hours, the Consultant may arrange some additional expansion joints, but the interval between the joints should not be over 12-15 times of the concrete pavement slab’s length
1.3.3.9 In TCVN 9345/2012 [4], The regulation on arrangement of
expansion joint in concrete pavement
Also arranging expansion joint provided that thermal expansion of the concrete pavement slab is ensured
Trang 107
1.3.3.10 Actual arrangement of expansion joints of concrete pavement
slab row in Vietnam
On concrete pavement of Vietnam, there are always expansion joints by structure However, actual condition of concrete pavement shows that the phenomena of heart shake rarely appear beside contraction joint but beside expansion joints in all North, South, Central Regions
1.3.4 In some other Works, Researches on temperature gradient and distance of contraction, expansion joints of cement concrete in Vietnam and the world
In the world there are some studies on temperature profile in concrete pavement and regulations on arrangement of concrete pavement’s expansion joint, it is remarkable that determination of average temperature in concrete pavement is by the formula:
1.3.5 General Comments
Based on overview of regulations of countries on calculation to determine the distance of expansion joints on concrete pavement, there are many differences, depending on conditions and regulations of each country In hot weather of Vietnam, it is required to study to apply experiences of nations in calculation of distance of expansion joints on concrete pavement to fit Vietnam’s conditions
1.4 Issues to be Studied and Clarified in Concrete Pavement Designing Calculation in Vietnam’s Condition
1.4.1 Effect of the insulating layer in multi-layer pavement
In case the insulating layer is asphalt concrete with high thickness, in hot weather of Vietnam, large deformation may happen, affecting performance and redistribution among concrete layers in multi-layer system This issue is to be studied to clarified
1.4.2 Calculation of temperature profile by depth of the slab with different thicknesses
So far, in the designing process according to QD 3230/2012 accepts the assumption that heat conduction line in the concrete slab is linear to
Trang 118
gradient, Tg, which is constant, it only depends on climatic conditions of each Region of Vietnam In deed, each climatic region, factor Tg ‘s value
is not a constant, but depends on thickness of the concrete pavement slab
On the other hand, currently in Vietnam, there is no research determining temperature gradient for concrete slab with high thickness such as airport road’s pavement (with h = 38-40cm)
1.4.3 Calculation of Necessity and Required Distance of Expansion Joints on Concrete Pavement in Vietnam’s Climatic Conditions
At present, design calculation of concrete pavement for highways and airports in Vietnam often chooses the solution of creating distance for expansion joints based on construction structure Actual operation shows that on the pavement there appear fractures on expansion joints This needs to be investigated and clarified
1.5 Studied Content of the Dissertation
The Candidate chooses the study direction for the Dissertation for issues
as mentioned in the Preface
EFFECTS OF INSULATING LAYER ON PERFORMANCE OF
MULTI-LAYER CONCRETE PAVEMENT
Chapter II consists of theoretical study aiming at building a method of investigation and calculation of effects of the insulating layer on operation quality when calculating the multi-layer concrete pavement structure in Vietnam’s conditions
2.1 Theoretical Bases for Calculating the Multi-Layer Concrete Pavement taking into account the Effects of the Insulating Layer
Flexural layers of multi-layer pavement can be arranged in construction structure to create one of the following: Bonded layers, directly contacting layers are half-bonded, or among the layers there is insulating layer
In case of arranging an insulating layer: In the calculation diagram [15,
19, 28, 69, 70], it is accepted that the insulating layer buffer is considered
as springed buffer (only compressive layer) between two flexural layers, one calculates concrete slab’s performance in three-layer diagram on equivalent base course, of which the cement concrete course and the rigid base course work following flexural diagram, while the insulating layer works following compressive diagram When bearing pressure transmitted down from the upper layer, the insulating layer is compressed, causing reflection back to the upper layer and pressure on the lower layer
Then, one writes differential equation for multi-layer pavement, in case of two-layer pavement having insulating layer, it is equation (2.6) with stiffness coefficient of the insulating layer is determined by formula (2.5):
Trang 12cl cl
∂
∂ +
∂
∂
∂ +
∂
∂
=
− +
∂
∂ +
∂
∂
∂ +
∂
∂
).
( )
2 (
);
, ( ) ( ) 2
(
2 1 2 0 4 2 4 2 2 2 4 4 2 4 2
2 1 4
4 2 2 1 4 4 4 1
w w C w C y
w y x
w x
w D
y x q w w C y
w y x
w x
w D
cl cl
(2.6)
2.2 Survey of Influence of Deformation of the Insulating Layer on Internal Force Distribution among Layers
2.2.1 When using small thickness insulating layer
When deflection of the insulating layer has minor value in designing processes, the hypothesis w1 = w2 = w is accepted Sum each side of the equation system, in case of two-layer concrete pavement in equation (2.6) Then the answer of the question of two-layer pavement is converted to one-layer pavement question’s answer, with stiffness equivalent to total stiffness of pavement layers De = D1 + D2
2.2.2 Calculation of Concrete Pavement
using Insulating Layer of High
Thickness
2.2.2.1 Building a calculation
programme for surveying deformation of
the insulating layer
In the dissertation, it is suggested to
evaluate through the answer of sets of
equations (2.6), of which the influence of
the insulating layer’s thickness and
strength on internal force distribution in
pavement layers through formula (2.5)
answered by FDM method through MLCP
flowchart programme as in Figure 2.5
2.2.2.2 Survey of Reliability of the
Proposed Calculating Method:
To survey the reliability of the
calculation method, the dissertation
consider to use the insulating layer
from bitumen - sand of 0.5cm
thickness as specified in in TCVN
10907-2015, BCH197-91 process
Calculation result of flexural stress in
the concrete pavement , compared to
the result calculated by two-layer
Calculation method
CP flexural , (VND)
Comparison
of methods
to the proposed method Proposed method 1.517 0.00%
Trang 1310
conforming to the cement concrete pavement calculation theory
2.2.3 Survey of Influence of the Insulating Layer of High thickness 2.2.3.1 Using insulating layer from bitumen - sand and SAMI
a Using insulating layer of Bitumen – sand
In calculation, only influence of
the insulating layer on internal
force of the layers: select the
insulating of bitumen, sand, the
insulating layer’s thickness varies
from 0,5 to 2 cm, showing the
result as in table 2.10:
Table 2.10: Survey result of influences of the thickness of the insulating on deflection and flexural stress inside the Concrete pavement
Insulating layer’s thickness Bitumen- sand,cm
Concrete pavement ‘s deflection ,mm
Flexural stress of cement concrete layer (Mpa)
Survey Result Remarks:
When increasing thickness of the isolating layer made of bitumen - sand, from 0.5cm to 2cm , insulating settlement also increases consequently It causes changes of redistribution of flexural stress in the layers, increasing significantly flexural stress of the upper layer(14.35%) and decrease flexural stress of the lower layer (26.54%), then most effect of the load will be born by the concrete pavement above
b Using SAMI insulating layer
In calculation, use SAMI insulating layer ,
replace the thickness of the insulating layer to
1.5 - 3cm, the results are as in table 2.16:
Survey Result Remark:
When increasing thickness of the isolating layer
made of SAMI, 1.5cm – 3cm insulating
settlement also increases consequently, It causes
changes of redistribution of flexural stress in the
layers, increasing significantly flexural stress of
the upper layer (6.97%), higher deflection
(2.89% ) Because SAMI material has higher
elastic modulus than that of sand bitumen, thus
when increasing the insulating layer’s thickness,
the influence degree of the insulating degree of
SAMI is smaller, compared to influence of
bitumen - sand material
Table 2.11: Calculation result
of surveying influence of SAMI insulating layer’s thickness on deflection and flexural stress
Insulating layer’s thickness Bitumen- sand,cm
Concrete pavement
‘s deflection ,mm
Flexural stress of cement concrete layer, Mpa