Tóm tắt Luận án Research on characteristics of quaternary sediments and the relations to land subsidence in the west area of Hanoi

The West Hanoi (formerly Hatay province) was merged into Hanoi since 2008, this area in the process of urbanization at high speed. Geological characteristics in this area considered complex, the limestone layer widely distributed, high fractured and somewhere has underground karst. The Quaternary sediments include many kind and difference in ages, origin, composition, physical - mechanical properties. Especially, existence of the soft soil layer has thickness and distribution irregular.

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MINISTRY OF EDUCATION AND TRAINING VIETNAM ACADEMY OF SCIENCE AND TECHNOLOGY GRADUATE UNIVERSITY OF SCIENCE AND TECHNOLOGY NGUYEN VAN BINH RESEARCH ON CHARACTERISTICS OF QUATERNARY SEDIMENTS AND THE RELATIONS TO LAND SUBSIDENCE IN THE WEST AREA OF HANOI Speciality: Geology Code: 62 44 02 01 SUMMARY OF GEOLOGY DOCTORAL THESIS HA NOI, 2015 The thesis was completed at: Graduate University of Science and Technology, Vietnam Academy of Science And Technology Scientific Supervisors: 1. Assoc. Prof. Dr. Do Minh Duc 2. Assoc. Prof. Dr. Doan Dinh Lam Reviewer 1: Dr. Do Van Nhuan Reviewer 2: Assoc. Prof. Dr. Nguyen Huy Phuong Reviewer 3: Assoc. Prof. Dr. Pham Quy Nhan This thesis is going to be defended at the council of doctorate thesis examiners of Graduate University at:.................................................... ............hour, day ......., month...year 2015. Thesis can be found at: - National Library, Hanoi - Library of Vietnam Academy of Science and Technology - Library of Graduate University of Science and Technology 1 PREFACE The West Hanoi (formerly Hatay province) was merged into Hanoi since 2008, this area in the process of urbanization at high speed. Geological characteristics in this area considered complex, the limestone layer widely distributed, high fractured and somewhere has underground karst. The Quaternary sediments include many kind and difference in ages, origin, composition, physical - mechanical properties. Especially, existence of the soft soil layer has thickness and distribution irregular. From 2007 to present, in some places as Ngoc My, Thach Than communes (Quoc Oai district) appeared many cracks on the walls of old constructions with low loading capacity and these cracks are expanding. Research results identified that the surface in this area being subsidence, expressions of land subsidence complex and unpredictable. In additions, some geological hazards have been occurred with damages and destroy constructions. Land subsidence and ground collapse occurred for many reasons and related to Quaternary sediment (lithological composition, physical - mechanical properties, distribution) and groundwater. However, the detail researches of them in the West area of Hanoi not very much. Therefore, PhD student has chosen the topic: “Research on characteristics of Quaternary sediments and the relations to land subsidence in the West area of Hanoi”. 1. The objective of the thesis To elucidate of characteristics of lithological composition, physical- mechanical properties and distribution of Quaternary sediments, the relationships between sediment characteristics, especially, the soft soil layers in the West Hanoi to land subsidence and ground collapse; then to propose prevention measures for sustainable development of infrastructure. 2 2. Object and scope of the study : The Quaternary sediments in the West area of Hanoi and its relation with land subsidence. In the thesis, land subsidence is considered the deformation of the surface by two forms: First: ground subsidence is the deformation of soil foundation due to the change effective stress leads to compaction of the soil when the water table lowered. Thesis research on a large scale ground subsidence (regional), not analysis in a specific location of construction. Second: ground collapse due to human activities creates voids in the soil (the exploitation of underground water) and natural voids relatively close to the surface (karst) leads to the collapse of soil and forming sinkholes. The study scope includes Quoc Oai, Chuong My and My Duc districts, 3. Research contents - Characteristics on lithological, physical - mechanical properties and the distribution of Quaternary sediments in the West area of Hanoi. - The relationship between Quaternary sediment to land subsidence hazards in the West area of Hanoi. - Proposed solutions to preventing land subsidence and ground collapse, serve for development of infrastructure sustainable. 4. Database of the thesis + The reports geotechnical investigation in the study area including 431 boreholes, depth from 7-50 meter; 1272 samples, 1778 of standard penetration test (SPT) and 47 of vane test. + The theme "Research the potential geological hazards related to the process of urbanization in the West area of Hanoi" in Hanoi University of Natural Resources and Environment. PhD student as main responsible person, acceptances 2013. + Topic "Research geohazards ground subsidence and propose solutions to handle at Km16, provincial road 419 of Quoc Oai town, Hanoi" by the Vietnam Institute of Geosciences and Mineral Resources (2009). 3 + Project "Mitigation of Geohazards in Vietnam" by Vietnam National University (VNU) and the Norwegian Geotechnical Institute (NGI). + The reports on the survey results and determined the cause of ground collapse and execute fillings material for sinkholes in Hamlet 16, village Ang Ha, Le Thanh commune and Team6, Thuong village, Xuy Xa commune, My Duc district. 5. Defending issues Issue 1: Quaternary sediments in the West area of Hanoi is divided into four profile types with 18 sub-profile types based on sediment characteristics, age, origin and distribution. Issue 2: Land subsidence and ground collapse in the West area of Hanoi took place with local nature. Land subsidence occurred in areas distribution of sediment in profile type 1 (sub-profile types 1.2, 1.3 and 1.4) and profile type 3 by the water table was lowered. Ground collapse occurred in areas distribution in profile types 1 and 3 by extraction underground water unreasonable and combination with the fractured limestone layer, underground karts. 6. The new scientific finding of the thesis - Base on association of sediment characteristics and physical-mechanical properties of soils; determine the scope and depth distribution of Quaternary sediments in the West area of Hanoi. - Determination of profile types and sub-profile types of Quaternary sediments and their spatial distribution in the West area of Hanoi. - Clarification of causes on local land subsidence and surface ground collapse in the relations to Quaternary sediments, especially the soft soil layers in the West area of Hanoi. - Zonation of the areas with potential risk of land subsidence hazard in relations to the Quaternary sediment profiles, karstic distribution in the West area of Hanoi. 4 7. The scientific significance and practice of thesis Scientific significance: characteristics and the distribution of Quaternary sediments in the West area of Hanoi and its relations to the land subsidence, ground collapse in this area are clarified. Determining the cause of land subsidence and ground collapse. Practice significance: results of research to explain the causes, mechanisms of formation and development of land subsidence, define the areas with a high risk of land subsidence, raising warnings on human activities inducing the occurrence of land subsidence, which helps to outline rational land use and sustainable development of infrastructure 8. The layout of the thesis Preface - Chapter 1. Overview of research and natural conditions, economic and social in the West area of Hanoi - Chapter 2. Methodology and Research Methods - Chapter 3. Characteristics of Quaternary sediments in the West area of Hanoi. -Chapter 4. The relationship between Quaternary sediment and land subsidence, ground collapse Conclusions and Recommendations CHAPTER 1 OVERVIEW OF THE RESEARCH AND CONDITIONS OF NATURAL, ECONOMIC AND SOCIAL IN THE WEST AREA OF HANOI 1.1. Historical of geological research 1.1.1. Period before 1975 The geological study primarily serves for exploration and mining. Studies of sediment little attention. After 1965, there is some research is published. 1.1.2. Period after 1975 so far After 1975, there are many researches of Quaternary sediments comprehensively published. The North Vietnam Geological Mapping 5 Division finished geological mapping group Ha Dong-Hoa Binh(1988) and Hanoi map group (1994), scale 1:50 000. Quaternary sediments in the West area of Hanoi divided into four formations: Hanoi, Vinh Phuc, Hai Hung and Thai Binh. Also, the Geology Division, Geological Corps number 6, 29, 79, 51, 54 and 64 have made mining exploration, mineral occurrences, exploration, observation and exploitation underground water. 1.2. Overview of researches on land subsidence and its relation with Quaternary sediments 1.2.1. The researches around the world According to Winslow and Wood, for the fine-grained material saturated with water, the amount of subsidence is equivalent to the amount of losing pore space by compaction. Poland and Davis determined the cause of land subsidence included: 1)loadings at the land surface; 2)vibratory near the land surface; 3)the compaction by irrigation and agricultural production; 4) the dehydration and shrinkage of sediment; 5)oxidation of organic materials; 6) lowering of the groundwater level; 7) pressure drop. According to Leake S. A, in case the aquifer sandwiched the layers (or clay- silty clay lenses), when the pressure in the aquifer was lowered lead to increased of strain compression for the aquitard and making them compact (thinner) and is regarded as the subsidence of the land surface, the process of settlement is irreversible. Amin. A and Bankher. K gave different reasons cause ground subsidence in Saudi Arabia. In addition to natural causes, the authors suggest that cause land subsidence occurs due to excessive exploitation of ground water from deep aquifers. In Shanghai city (China), the Quaternary sediments thickness of 300m. Land subsidence in Shanghai was first reported in 1921 with the average rate about 21cm/year. In 1965, the total settlement in Shanghai about 6 2,63m. Chai JC et al, Xiao-Qing Shi concluded: the consolidation of the clay layer, clay mud contributes approximately 80% of total subsidence. Bangkok capital of Thailand in Chao Phraya delta. Geological section in here includes 8 aquifer composed of sand with gravel sandwiched with clay, soft soils located near the land surface with an average of 14m thickness. Since 1969, the phenomenon of land subsidence more attention when there are many indicators to be monitored in Bangkok and get the attention of many scientists. According to Nutalaya (1989), the most powerful of land subsidence in Bangkok over the period 1933-1987 approximately 1,60m and by 2002 the settlement was 2,05m In India, Sahu and Sikdar studied the geological features in the Kolkata city and swamps area in Eastern Kolkata, West Bengal. Quaternary sediment in this area included clay, mud and sand layers. Calculation results show that amount of land subsidence varying from 1,12mm to 43,8mm/year, average of 13,53mm/year. Estimates, amount of land subsidence corresponding with 1m lowered hydraulic pressure about 1,79 cm to 10 cm, average of 3,28 cm. 1.2.2. The researches in Vietnam In Vietnam, land subsidence phenomenon happens quite universal in Hanoi, Ho Chi Minh city, Hai Phong, Can Tho, Ca Mau and some provinces, cities in Mekong river delta 1.2.2.1. In Hanoi and Ho Chi Minh city In Hanoi, land subsidence has been warning by scientists from the 80s of 20 century. Many authors have published results of researches on land subsidence in Hanoi (old) such as Nguyen Kim Cuong (1995);Tran Trong Hue et al (1995, 1996); Doan The Tuong (1999); Tran Van Hoang and Bui T. Bao Anh (2000); Pham Quy Nhan (2004); Tran Manh Lieu (2005); Tran Manh Lieu and Doan The Tuong (2006); Tran Van Tu; Dang.V Khac...etc. 7 In Ho Chi Minh city, since 1992 (the first year of land subsidence monitoring through satellite images) to 2011, has recorded 17/24 districts was sinking from 20 cm to 50cm. Subsidence increasing and proportional to speed of urbanization 1.2.3. The researches in the West area of Hanoi 1.2.3.1. Research overview Vietnam National University (VNU) and Norwegian Geotechnical Institute (NGI) carried out the project "Mitigation of GeoHazards in Vietnam". One of the tasks of the project is research the phenomenon of land subsidence in Hanoi. The Geophysics Technology JSC; Vietnam Institute of Geosciences and Mineral Resources; Divison of Water Resources Planing and Investigation for the North of Vietnam researches some topics about land subsidence, ground collapse in My Ducm, Quoc Oai district. The positions was collapse has fine sand and soft soil layers (bmQ2 1-2 hh) with considerable thickness. Nguyen Van Binh et al researched engineering-geological and geohazard related potential the process of urbanization in the West area of Hanoi (Quoc Oai and vicinity areas), analyze the effective of soft soil layers, groundwater exploitation and relationship with land subsidence. Most of researches show that the risk of land subsidence occurred in areas distribution of soft soil layer, especially when they are distributed above aquifers and within the influence of the water table was lowered. 1.2.3.2. General comment a, About the research issue on Quaternary sediment: - The depth studied of sediment within 20m depth - The detail division on the scope and depth distribution of sediments with different composition of the lithological is limited. - Relationship of Quaternary sedimentary with bedrock, especially with to fractured limestone and underground karts have not been clarified. 8 b. About the studies of geological hazards related to Quaternary sediments in the process of urbanization Most of theme, research projects primarily focus on geohazards assessment of status events such as landslides, river erosion. The researches on land subsidence occurred in Quoc Oai and My Duc district mainly to assess the status and treatment of complications, the causes of geohazards have not yet been elucidated. 1.3. Natural conditions and socioeconomic in the West area of Hanoi 1.3.1. Topography - Geomorphology feature: 1.3.1.1. Topography feature: includes lower mountain, hill and plain 1.3.1.2. Geomorphology feature: includes erode and accumulation terrains. 1.3.2. Geological and structural feature 1.3.2.1. The geological formations before Quaternary. The geological formations before Quaternary from Paleozoic to Mezozoi include geological formations in order from old to recent as follows: Na Vang (P2 nv); Yen Duyet (P2 yd); Vien Nam; Tan Lac (T1o tl); Đong Giao (T2 dg); Nam Tham (T2 nt) and Song Boi (T2 3 sb) 1.3.2.2. The Quaternary: Quaternary sediments in the West area of Hanoi including four formations: Hanoi, Vinh Phuc, Hai Hung and Thai Binh. 1.3.3. Hydro-geological feature in the West area of Hanoi. Ground water in the West area of Hanoi exist two kind include: water in the pore of the unconsolidated Quaternary sediments and water in fissures, karst in limestone of Dong Giao and NaVang formations. CHAPTER 2. BASIC OF THEORETICS AND RESEARCH METHODOLOGY 2.1. Basic theoretics Oscillation of sea level to the formation and distribution of sediments: The correlation between speed of sediment deposit, tectonics and sea level fluctuation plays a key role during the formation and development of deltaic. 9 Figure 2.2. Facies transition diagram from the mountains to the delta [22] Transfer of facies in the West area of Hanoi are outlined in the diagram: proluvi→ mountainous and highland river → plain river → plain delta Figure 2.3. The distribution of depositional environments in spatial [22] Quaternary sediments in the West area of Hanoi formed in the context of closely related with the oscillations of the sea level, river activities and interaction between river and the sea. Research the features of Quaternary sediments and relationship with land subsidence needed have to integrate the features of sediment and the physical-mechanical properties of soil and Assessment of the status of human activities to natural conditions, and needs a suitable method comprises: the methodological to research on D e lu v i P ro lu v i A lu v i D e l ta M o u n ta in o u s r iv e r M id lan d r iv e r R iv e r p la in D e l ta p la in D e l ta f ro n t P ro d e l ta S e a l e v e l a t h ig h tid e S e a l e v e l a t lo w tid e C h a n e l la g I n te r tid a l are a S an d rid g e e s tu a ry w e a th e rin g c ru s t B e d ro ck Lu tích (Proluvi) (P) TiÒn ch©u thæ (delta front) ĐBCT (delta plain) al (hå mãng ngùa) ac A + + + + + + + + + + + + am 3 am 3 am2 am 1 am 1 ac am 2 am 2 Àaf (b ·i bå i)a c (lßn g s«n g) afaf (Prodelta) §ång b»ng (a ) 3 S«ng miÒn Trung du S«ng miÒn nói 10 characteristics of Quaternary sediments (lithological composition, distribution and relationships in spatial), Experimental methods of physical and mechanical properties of the sediments and the methods of calculation and forecasting. 2.2. The research methodology Systems of research methods used include: field survey method; Geophysical methods; Drilling and sampling methods; Grain size analysis methods; Analysis of mineral composition; Experimental methods of physical and mechanical properties; Analysis on indicators of environmental method; Interferometry technology InSAR method; Data processing method; Kriging interpolation method; Forecasting land subsidence method. CHAPTER 3. FEATURES OF QUATERNARY SEDIMENT IN THE WEST AREA OF HANOI Quaternary sediments in the Western area of Hanoi includes four formations: Hanoi, Vinh Phuc, Hai Hung and Thai Binh. 3.1. Hanoi formation (Q1 2-3 hn) 3.1.1. Alluvial- proluvi deposit (apQ1 2-3 hn) Aluvi-proluvi deposit of Hanoi Formation consists of 3 parts: - Part 1. Cobbles, pebbles, polymictic minerals, multi colors mixed with gravel, sand and silt, lightning yellow, yellow-brown. Composition of mainly quartz pebbles (50%), mafic volcanic rocks (30%). In addition, composition of sediment contained sandy-siltstone, tuffaceous, size from 5 -15cm. Composition of pebbles and gravel in some places up to 70%; sand 20-25%, clay, silty 5-10%. - Part 2. Sand and silty, lightning yellow, russet contain quartz grit. Composition mainly of quartz sand, silica, sharp, irregular, contain small grit. The thickness of sediment from 7.5m to> 20m. Composition of particles size: sand 50-75%; gravel 5-20%; clay, silt 5-10%. Parameter of grain size: Md=0,33-0,4mm; Ro= 0,12-0,2; So= 3,3-4,5. SPT test: N=20- 25. 11 - Part 3. Clay, silty yellowish brown, brownish red, contained many laterite grit on surface layer. Composition of particles size: clay 45-53,4%, silty 19%-22,8%, sand: 15%-21% and gravel from 3,1% to 5,5%. The parameters of grain size: Md = 0,0055mm; Sk=0,21-0,3; S0=3,02 – 4,15. Environmental indicators: pH=6,6, Kt=0,24. SPT test: N30=17- 42, in near surface bedrock N30=30-50 to N30 = 60-70. 3.1.2. River chanel deposit (aQ1 2-3 hn) Pebbles, gravel, sand grey-yellow, light grey, multi mineral, gray, cobbles size from 2cm to 10cm. Composition of sediment include: cobbles 51,4%-60%, gravel 15,5% - 20,4%, sand 18-27%. SPT test: N30=50/7cm. 3.2. Vinh Phuc formation (Q1 3 vp). 3.2.1. River chanel deposit Sand, sand with silt, gray yellow, gray blue, light gray, somewhere sandwiched lens of small grit. The mineral of sand is quartz 70-80%, pieces of grit, less mica. Composition of particles size: sand 65.9%-71,7%, silty 25,1%-27,1% gravel 1,3-7,5%. Parameter of grain size: Md= 0,28 - 0,42mm; So=2,5-3,2; S
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