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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: Assoc Prof Dr Nguyen Huu Tri Institute of Transport Science & Technology 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 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 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 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 INTRODUCTION Rationale for the study To exploit and select 1m3 clean coal, in Quang Ninh they normally have to remove - 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” 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 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 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 AB-ĐCS) Supplementing and finalizing the technology of construction and quality control of cement-reinforced aggregate AB-ĐCS in automobile pavement construction 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 Structure of the thesis The thesis includes the Introduction, four main chapters, the Conclusion and Recommendation – Direction for further study; References and Appendices Chapter 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, 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 - 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 b/ Some studies Project “Handling and reusing solid waste in construction of road traffic works” Code: MT 103005, Institute of Transport Science & Technology 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 Experimental study on waste rock and soil on Nam Khe Tam waste dump – Postgraduate dissertation – Vũ Vinh, 2013 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 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 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 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 (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) 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 Sample A >50 89,6 88,5 B ≤ 50 10,4 11,5 waste dump Group of >50mm is subdivided into 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 Sample 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 Sample 50 99,17 100 25 86,2 84,42 9,5 64,32 60,54 4,75 51,2 46,91 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 11 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 Sample 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 ÷ 2,54 1,57 ÷ 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 and Sample Table 2.6: List, volume, testing method No of samples Experimenting Total Order Testing method Sample content Sample number TCVN 75721 Rock intensity 9 18 10:2006 TCVN 7572–12: LA Abrasion % 9 18 2006 Liquid limit % 9 18 TCVN 4197–1995 Plastic limit % Standard compaction CBR 2.3.6.1 Experimenting rock intensity 18 TCVN 4197–1995 18 22TCN 333-06 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: Directly use it for embankment of automobile roads Directly use it for roadbed of automobile roads 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 ÷ 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 ≤ ≤ ≤ % (5,34) Amount of elongated flat 16 ≤ 18 ≤ 20 grains, % 0,5 Organic content, % (0,9) Amount of sulfate salt 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 Testing reinforcement for aggregate AB-ĐCS with cement as per rates 0%; 2%; 4%; 6%; 8% and 10% 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 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 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 14 ngày Rech (MPa) Biểu đồ cường độ nén 14 ngày Rn (MPa) 95% CI for the Mean 95% CI for the Mean 0.8 0.702222 7.44556 5.26111 3.80222 4 3.5 2.20222 0.522222 0.5 0.413333 0.45 0.4 0.35 0.4 0.306667 0.3 0.2 1.5 Rech (MPa) 0.6 0.612222 6.48889 Rn (MPa) 0.7 Tỷ lệ xi măng (%) Individual standard deviations are used to calculate the intervals 10 0.1 0.0 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 - 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 % 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 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 positions of the test foundation Figure 3.13: Roughly measuring Edh at 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 JSC (address: Quan Tien, Hoi Hop, Vinh Yên city, Vinh Phuc) Figure 3.14: Monitoring and inspecting at Song Hong 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 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) 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) 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 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 The test section has satisfied the technical requirements specified in the current standards for automobile road construction 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 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 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, 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 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 In order, 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 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 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 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 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 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 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 standards of limitation The auditing result as per Decision No 3230/QĐ-BGTVT given in Table 4.18 23 achieves high reliability 4.6 Technology for production of materials made from waste rock and soil in Cam Pha area, Quảng Ninh It is recommended to centrally produce materials on large-scale located right at Dong Cao Son waste dump for in-situ and commercial production 4.7 Technology for construction of pavemenent using Quang Ninh – based waste rock and soil 4.8 Remarks and conclusions of Chapter Having recommended pavement structures utilizing waste rock and soil from the coal mines in Cam Pha area, Quang Ninh, satisfying the technical requirements for construction of automobile roads and rural roads; Having identified the parameters of materials A-ĐCS and AB-ĐCS without reinforcement in Table 4.9 and with cement reinforcement in Table 4.16; Having proposed the technology to produce materials A-ĐCS and AB-Dong Cao Son (with and without cement reinforcement) for automobile road construction; concurently, contributed to perfecting the technology of cementreinforced aggregate production as per Decision No 3230/QĐ-BGTVT CONCLUSIONS AND RECOMMENDATIONS I The results achieved From the study results in lab and on site, it is ascertained that the waste rock and soil at ĐCS waste dump, Cam Pha area, Quang Ninh can be utilized for automobile road construction Based on the theories of aggregate, material reinforcement and lab-based experiments, 02 types of aggregate A-ĐCS and AB-ĐCS are proposed, which are made from the original waste rock and soil at Dong Cao Son waste dump, meeting the requirements as specified for macadam aggregate Class II (according to TCVN 8859:2011) and qualified to be cement reinforced for the foundation of automobile roads (according to TCVN 8858:2011) The experiements have helped determine the technical specifications of 02 types of aggregate A-ĐCS and AB-ĐCS cement reinforced at different rates and showed that the amount of cement for reinforcement ranging from 4% or more can be used for construction of the lower foundation for automobile roads of all grades and the upper foundation for roads of Grade III or lower, or the surface (asphalted) for high-grade A2 pavement or the surface of rural roads The results from obsering and evaluating the test section set up on site have demonstrated that - The structure of the test section pavement achieves Eyc = 110 Mpa, having in operation for nearly years under axial load of 10T No signs of deterioration have been detected so far - The technologies for production of cement reinforced aggregate AB – ĐCS 24 together with testing and verification of solutions for surace cracking treatment have been completed It is recommended to ensure proper maintenance and emulsion spraying on the surface as an appropriate solution The application scope has been put forward for pavement structures proposed to use waste rock and soil from the coal mines in Cam Pha area, Quang Ninh The technical specifications of types of aggregate A-ĐCS and AB-ĐCS reinforced with cement at studied rates have been determined The regression equation for relationship between compressive strength and split pressing strength has been developed for aggregate AB-ĐCS reinforced with 6% cement and time variable of 28 days II Recommendations It is recommended to use macadam aggregate made of cement-reinforced waste rock and soil from the coal mines in Cam Pha area, Quang Ninh for pavement of rural roads and foundation of various automobile roads Suitable cement rates of 4% - 6% depending on volumes of the mixture are recommended to reinforce the waste rock and soil from the coal mines in Cam Pha area, Quang Ninh Conducting fake gap cutting (cracks created in adance) and maintenance by asphalt emulsion for layer AB-ĐCS cement reinforced Depending on local circumstances, it is possible to adopt the production line for materials of waste rock and soil from coal mines using mini rock grinders together with manual work on site of material stocking yards It is also possible to install the large-scale production line for aggregate at Dong Cao Son waste dump, then supply to contract packages, aimed at specializing each work item III Shortcomings and limitations The study was merely tested on a section 100m long, under observation for nearly years of only A2 pavement structure, as a result, the conditions are not sufficient for evaluation of longervity of the test section pavement The thesis has not yet mentioned the eco-technical effectiveness of pavement utilizing waste rock and soil from the coal mines in Cam Pha area, Quang Ninh, compared with traditional materials The experimental results and proposals from the study are merely initial, requiring further observation and evaluation so that conclusions closer to reality could be made IV Direction for further study Testing on concrete pavement A1, cement concrete pavement made of waste rock and soil in Cam Pha area, Quang Ninh Continueing observation and evaluation of the test section in order to work out the rules of deterrioration, damage in reinforcement materials ... 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... mines in Cam Pha area, Quang Ninh for automobile road construction 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... 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