Dissertation summary: Research on characteristics of Quaternary sediments and the relations to land subsidence in the West area of Hanoi

Research objectives: To elucidate of characteristics of lithological composition, physicalmechanical 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.

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: Assoc Prof Dr Do Minh Duc 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 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” The objective of the thesis To elucidate of characteristics of lithological composition, physicalmechanical 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 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, 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 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) + 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 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 (sub-profile types 1.2, 1.3 and 1.4) and profile type by the water table was lowered Ground collapse occurred in areas distribution in profile types and by extraction underground water unreasonable and combination with the fractured limestone layer, underground karts 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 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 The layout of the thesis Preface - Chapter Overview of research and natural conditions, economic and social in the West area of Hanoi - Chapter Methodology and Research Methods - Chapter Characteristics of Quaternary sediments in the West area of Hanoi -Chapter The relationship between Quaternary sediment and land subsidence, ground collapse Conclusions and Recommendations CHAPTER 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 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 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 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 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 (bmQ21-2hh) 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 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 (T23sb) 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 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 11 - Part 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 (aQ12-3 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 (Q13 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; Sk = 1.2-1,45, medium selectivity SPT test: N30=1634, the density of sand γs=2,66g/cm3; 3.2.2 Flat plain deposit Clay, silty clay with patchy color The mineral composition of clay is kaolinite and hydromica, composition chemical include SiO2 (50-70%), Al2O3 (15-23%), Fe2O3 (2-5%), TiO2 (0.5-1.8%) Environmental Indicators: pH =7; Kt = 0,28 In Quoc Oai district, composition of particles size: clay from 30% to 75%; silt from 11% to 34% and sand from 7% to 20% Parameter of grain size: Md=0,015-0,005mm; Sk=0,5-0.7; S0 = 3,1-5,5 In Chuong My district: composition size: clay 39% - 51%; silt: 35%-43% and sand: 27,4-31,7% Parameter of grain size: Md=0,007-0,020mm; So=3,29-4,43; Sk = 0,670,86 In My Duc district: composition of particles size of clay 39,5% - 12 57,5%; silt: 38,5%-45,8% and sand: 8%-14,7% Parameter of grain size: Md=0,007-0,014mm; So=3,46-4,21; Sk = 0,55-0,75 3.3 Hai Hung formation 3.3.1 Alluvial - marine deposit (amQ2 hh)(?) Fine sand, gray-brown, gray, narrow distribution in Can Huu, Ngoc My communes; Quoc Oai town (Quoc Oai district) and Bot Xuyen, Hop Tien communes (My Duc district) Composition of particles size: sand 94-99%, the rest are small grit Parameter of grain size: Md=0,358-0,372mm; Sk=1.1-1.12; So=1.27-1.45 SPT test: N30=12-23; density of sand: γs=2.652.67g/cm3; friction angle: αwet=280-300; αdry=330-34030’; void ratio: emin=0.702-0.735; emax= 1.023-1.085 3.3.2 Bog - marine deposit (bmQ21-2 hh) Clay-silty, clay-sand contained organic dark gray Composition of particles size: sand 19%-43.5%; silt 18%-34%; clay 34.5%-61.5% Parameter of grain size: Md=0,01-0,070mm; So=3,2-3,6; Sk=0.8-1.1 Sediments distributed in center of Quoc Oai and neighboring areas as Dong Quang, Thach Than, Ngoc My, Tan Phu communes, in Dong Son, Thuong Vuc, Dong Phu communes (Chuong My) and widely in My Duc district 3.3.3 Marine deposit (mQ21-2 hh) Green-gray clay, gray-yellow The mineral composition of clay is kaolinite hydromica-monmoriolit or hydromica-kaolinite-chlorite Parameter of grain size: Md = 0,005-0,01mm; So=2,3-2,5 Environmental indicators: pH=7-8, Kt=1,03-1,06, Fe+2S/Corg=0,25-0,5 The chemical composition: SiO2:54,9%; Al203:18%; Fe203:5,27%; Ti02:0,78% and others 10,12% The composition of particles: sand 20-29,5%; silt 21-28.5% and clay 4258.5%[33] SPT test: N30 = 6-12, stiff clay 3.3.4 Alluvial - bog deposit Narrow distribution, dispersed in coastal areas of the delta, small thickness The composition: silt-clay, clay, silt, sand-clay with organics 13 3.4 Thai Binh formation (aQ23 tb) 3.4.1 River chanel deposit Fine sand grained, brown-yellow, gray yellow In My Duc district, the composition of particles: sand 82,2-94,3% silt 4%-12,8%; clay 2%-5%, parameters grain size: Md=0,128-0,224mm; So=1,8- 2,53; Sk=1,15-1,35 In Quoc Oai district, the composition of particles: sand 71.6-90.73%; silt 6,3%-21,8%; clay 3%-7%; grain size parameters: Md=1,4 -0,231mm; So = 1,65-1,85; Sk=0,97-1,15 Composition of mainly quartz sand (80%-85%), small grit and mica, medium selectivity 3.4.2 Flat plain deposit Clay, silty clay and sand brown, yellow-brown, yellow-gray, browngray The mineral composition include kaolinite clay, hydromica,chlorite In Quoc Oai district, components grai size: clay 31,5%-72,5%; silt 32%-55%; sand 0,6%-7,4% and the parameters of grain size: Md =0,005-0,013mm; So=2,6-3,8; Sk =0,73-0.92 In My Duc district, components grain size: clay 30%-45%; silt 39,5%-59,7%, sand 2,4%-10% and parameters of grain size: Md=0,0045-0,015mm; So=3,0-3,75; Sk =0,87-0,95 3.5 The profile types of Quaternary sediments in West area of Hanoi 3.5.1 Purpose and principle to division of profile types of Quaternary sediment Principle to division: The profile types are division based on the stratigraphy of Quaternary sediments formation in research area The sub-profile types sections are division based on the features of the sediments 3.5.2 The profile types of sedimentary and distribution in spatial 3.5.2.1 Profile type - Sub-profile type 1.1:distribution in Can Huu, Liep Tuyet (Quoc Oai) - Sub-profile type 1.2: distribution in SongDay bridge and some places along the Thang Long avenue - Sub-profile type 1.3: distribution in East of Chuc Son town - Sub-profile type 1.4: distribution in An Thuong commune, Hoai Duc 14 Mặt cắt điển hình kiểu a(f) Q 2³ tb Phụ kiểu 1.1 Phụ kiểu 1.2 Phụ kiểu 1.3 Phụ kiểu 1.4 a(c)Q 2³ tb aQ 2³ tb bmQ2 ¹-² hh amQ 2¹-² hh a(f)Q ³ vp a(f) Q 2³ tb amQ 2¹-² hh a(f) Q ³ tb a(f) Q 2³ tb bmQ 2¹-² hh bmQ 2¹-² hh amQ 2¹-² hh a(c)Q 1³ vp a(f)Q 1³ vp ap,a(f) Q ²-³hn apQ ²-³hn apQ ²-³hn aQ ²-³hn aQ ²-³hn P2 nv P nv P nv P2 nv P2 nv bmQ 2¹-² hh a(f)Q ³ vp a(c)Q 1³ vp Figure 3.26 Profile type and sub-types of sedimentary 3.5.2.2 Profile type Mặt cắt điển hình kiểu Phụ kiểu 2.1 Phụ kiểu 2.2 Phụ kiểu 2.3 Phụ kiểu 2.4 a(f)Q 1³ vp a(c)Q ³ vp a(f)Q 1³ vp a(f)Q ³ vp apQ ²-³hn apQ ²-³hn apQ ²-³hn a(c)Q 1³ vp T2a dg P2 nv/ T 2a dg T 2a dg P2 nv a(f)Q 1³ vp T2a dg Figure 3.27 Profile type and sub-types of sedimentary - Sub-profile type 2.1: distribution in junction area from hilly, mountainous to the plains in western Quoc Oai district, Mieu Mon - Sub-profile type 2.2: distribution discontinuous in Hoang Van Thu, Thong Nhat, Dai Yen communes and a part of Phu Nghia commune (Chuong My) - Sub-profile type 2.3: distribution with narrow, discontinuous in Dinh To village, Ngoc Liep commune (Quoc Oai district) and a part of Phu Nghia commune (Chuong My district) - Sub-profile type 2.4: distribution of a strip stretching from Quoc Oai town to Dai Dong commune, Chuong My district 3.5.2.3 Profile type - Sub-profile type 3.1: distribution in Yen Noi village, Dong Quang commune, Quoc Oai district 15 - Sub-profile type 3.2: distribution of Quoc Oai town and neighboring area as Dong Quang, Thach Than communes, Western Quoc Oai urban area (Quoc Oai district) and My Thanh, An My, An Tien, Bot Xuyen, Phu Lien, Phu Luu Te, Xuy Xa communes (My Duc district) - Sub-profile type 3.3: distribution in Le Thanh, Xuy Xa communes, My Duc district Phu Chinh village - Hoa Chinh commune, Chuong My district and Giang Soi village, Dong Tien commune, Ung Hoa district Mặt cắt điển hình kiểu a(f)Q 2³ tb Phụ kiểu 3.1 Phụ kiểu3.2 Phụ kiểu 3.3 a(f)Q 2³ tb a(f)Q ³ tb Phụ kiểu 3.4 Phụ kiểu 3.5 a(c)Q ³ tb mQ ¹-² hh bmQ 2¹-² hh amQ 2¹-² hh a(c)Q 2³ tb a(f)Q 1³ vp bmQ 2¹-² hh bmQ 2¹-² hh bmQ 2¹-² hh aQ 2³ tb bmQ 2¹-² hh a(c)Q 1³ vp a(c)Q ³ vp a(f)Q ³ vp a(f)Q 1³ vp bmQ2 ¹-² hh a(f)Q ³ vp T 2a dg T2a dg T2a dg T2a dg mQ ¹-² hh a(c)Q 2³ tb mQ ¹-² hh T2a dg T2a dg Figure 3.28 Profile type and sub-types of sedimentary - Sub-profile type 3.4: distribution in SongDay bridge area (route Do Xa – Quan Son) and some parts of the Xuy Xa, Le Thanh communes (My Duc district), Western Quoc Oai urban area (Quoc Oai district ) - Sub-profile type 3.5: distribution in South of Dai Nghia town and neighboring areas (Ung Hoa district ) 3.5.2.4 Profile type - Sub-profile type 4.1: widely distribution in delta fringe of West Quoc Oai, Chuong My districts and partly in Dong Tam commune, My Duc district - Sub-profile type 4.2: widely distributed in Quoc Oai, Chuong My districts - Sub-profile type 4.3: distributed in Van Con commune of Hoai Duc district, in East-Northeast of Quoc Oai district 16 - Sub-profile type 4.4: distributed in an Phu commune (Quoc Oai district), Van Con, An Thuong communes (Hoai Duc district) - Sub-profile type 4.5: distribution in Tan Phu and Dai Thanh communes (Quoc Oai district) Mặt cắt điển hình kiểu Phụ kiểu 4.1 Phụ kiểu 4.2 Phụ kiểu 4.3 Phụ kiểu 4.4 Phụ kiểu 4.5 a(f)Q2 ³ tb a(c)Q 2³ tb aQ 2³ tb a(f)Q1 ³ vp a(f)Q 2³ tb a(f)Q 1³ vp a(f)Q 2³ tb a(f)Q 2³ tb a(f)Q ³ tb a(c)Q 1³ vp a(c)Q 1³ vp ap, a(f)Q ²-³hn apQ ²-³hn aQ1³ vp aQ 1³ vp aQ ²-³hn aQ ²-³hn T2 a dg T 2a dg P nv P2 nv P2 nv P nv a(c)Q 1³ vp Figure 3.29 Profile type and sub-types of sedimentary CHAPTER RELATIONSHIP BETWEEN QUATERNARY SEDIMENT WITH LAND SUBSIDENCE, GROUND COLLAPSE 4.1 Features of land subsidence in the West area of Hanoi 4.1.1 Current situation Estimated of land subsidence in Hanoi by interferometry technology from february 2007 to June 2008 shows that some regions of the Hanoi, including some place in Western areas being subsidence from 3cm to 9cm Figure 4.2a Cracks extending on old walls and concrete roads in East hamlet, Phu My village, Ngoc My commune, Quoc Oai district Figure 4.2b Cracks expanding on old walls in the Xuan Coc hamlet, Phu My village, Ngoc My commune, Quoc Oai district Results survey on status of old house with low loading, brick foundation in Ngoc My, Thach Than communes (Quoc Oai district) shows that most of 17 these houses have been cracked Cracks appeared around from 2008 to the present Calculation of settlement results Độ lún hạ thấp mực nước ngầm thời điểm năm 2008 S (cm) 10.3 12 11 9.6 10 8.8 CHÚ GIẢI aQ ³ tb Sét màu xám nâu, vàng nhạt, dẻo mềm Cát hạt nhỏ mịn màu aQ ³ tb xám nâu, xám vàng 21.5 Sét, màu xám xanh, xám mQ ¹-²hh vàng, dẻo cứng Sét, bột lẫn hữu màu bmQ ¹- ²hh xám, xám đen, dẻo chảy aQ 1³ vp Sét loang lổ bị laterit hóa, dẻo cứng Cát hạt thơ vừa màu xám vàng, chặt vừa MNN năm 2000=2.5-3m Cao độ (m) aQ 1³ vp 10 4.2 7.6 8.5 4.7 6.3 11.8 22m 20 -20 aQ 2³tb 2.1 28.3 34.7 1.2 7.6 6.2 11.7 bmQ 2¹ -²hh 5.2 8.2 11.7 6.0 20 36m 39.3 P2 nv 45.8 HKBT-CS 47 HKBT-CS46 HKBT-CS 50 8.61 5.96 6.18 6.2 bmQ 2¹- ²hh 18.3 19.5 20.5 21.2 aQ1³ vp -40 HKC-CS04 2.5 11.2 12.0 15 20 3.0 42.3 43.5 58 HKC -CS05 8.7 45.5 44.1 47.4 HKCCS06 HKCCS07 8.6 8.5 Khu ĐT Tây Quốc Oai(TT Quốc Oai) 53 45.4 47.2 aQ 1³ vp bmQ 2¹- ²hh aQ 2³ tb 15m MNN năm 2013 10 25 35 P nv aQ1³ vp 24.5 31 40 43 P2 nv 39 QO -02 QO -01 YN4 YN1 7.5 8.36 8.1 5.0 xã Thạch Thán, Ngọc Mỹ Yên Nội, Đồng Quang, Quốc Oai 1000 2000 m Figure 4.11 Land subsidence in Quoc Oai town and neighboring areas (2008) 4.1.2 The causes of land subsidence 4.1.2.1 Current situation of exploitation groundwater The mainly water source to serve life activity and productions from wells Currently, many wells of the populations, organs and wells in the industrial zones exploit water in limestone The cones lowered of groundwater level located in Quoc Oai town and neighboring areas as Thach Than, Ngoc My communes and Dai Nghia town The cones lowered of water level coincides with area has the soft soil layer 4.1.2.2 The cause of land subsidence When groundwater level was lowered lead to change stresses in soil, pore water pressure drops, and effective stress (stress caused subsidence) increases to make deformation of ground and sunk down 18 Lún - hồi phục biến dạng đàn hồi Lún không hồi phục vĩnh viến biến dạng không hồi phục Tầng chứa nước Tầng cách nước (sét, sét pha) Sự nén chặt hệ thống nước ngầm tập trung tầng cách nước Mực nước Các hạt cốt đất giới hạn lấp đầy nước ngầm lỗ rỗng Sự xếp làm chặt lại tầng cách nước với giảm độ lỗ rỗng lượng nước tích trữ lỗ rỗng Thời gian Suy giảm lâu dài mực nước theo chu kỳ bơm hút nước ngầm Figure 4:19 Inelastic deformation of aquifer 4.1.3 Relationship between Quaternary sediments with land subsidence For sedimentary in profile type : included four sub-profile types - Sub-profile type 1.1 without soft soil layer, less affected by land subsidence -Sub-profile types 1.2; 1.3 and 1.4, has soft soil layer, affected by land subsidence when the water table is lowered and depending on the thickness of the soft soil layer For sedimentary in profile type 2: included four sub-profile types, without soft soil layer, less affected by land subsidence For sedimentary in profile type 3: included five sub-profile types, the soft soil layer thickness varying from 10m to more than 20m, high affected by land subsidence, especially uneven settlement For sedimentary in profile type included five sub-profile types, without soft soil layer, less affected by land subsidence 4.2 Features of ground collapse in the West area of Hanoi 4.2.1 The current status of ground - collapse From 2006 to present, in the West area of Hanoi has happened series of ground collapse during drilling wells 19 Typical location of ground collapse as Yen Noi village, Dong Quang commune, km16, provincial 419 Quoc Oai town; Hamlet16, Ang Ha village, Le Thanh commune and Team 6, Thuong village, Xuy Xa commune (My Duc district) In the first months of 2014 have occurred three points of ground collapse at Le Xa village, Le Thanh commune, My Duc district and in Yen Son, Liep Tuyet communes (Quoc Oai) 4.2.2 The causes of ground collapse General features of the ground collapse as follows: - The ground collapse occurs only when human impacts (drilling) - The geological section has fine sand layer and soft soil layer - Limestone layer beneath was cracked (high fractures), somewhere has karstic caves underground The nature of the ground collapse is due to fine-grained, and soft soil layer were washed out and creating voids in the soil and destroy layers cover above of the voids Cracks (or underground karstic) act as path and stores contained fine-grained material from above moved down 4.2.3 Relationship between Quaternary sediment to ground collapse x.Yên Sơn, Quốc Oai TT Quốc Oai aQ 2³ tb 13.5 20 x.Xuy Xá Mỹ Đức x.Lê Thanh, Mỹ Đức 7.0 12.5 aQ ³ tb 11 12.5 bmQ 2¹- ²hh x Hợp Tiến Mỹ Đức mQ 2¹- ²hh 10 13.7 18.7 18.5 26.5 28 30.5 aQ 1³ vp aQ 1³ vp 40 44 P2 nv 48 ¹- h ²h 12 43 P nv aQ 1³ vp T2a dg 35 48 Chú giải Q bm 8.5 21.6 24 25 38 aQ 2³ tb 4.0 4.0 10 amQ 2¹- ²hh Yên Nội, Đ.Quang Quốc Oai 39.3 40.8 38.8 39.7 karst 47.5 60 k arst23.3 26.5 karst 34 karst T2 a dg 43.6 46.7 60 Sét, sét pha màu xám nâu, vàng nhạt, dẻo mềm - dẻo cứng Sét m àu xám xanh, loang xám vàng, dẻo cứng, Sét, sét pha, bùn sét pha lẫn vật chất hữu màu xám, xám đen Sét loang lổ bị laterit hóa, dẻo cứng - nửa cứng Cát mịn màu xám, xám nâu, xám ghi Đá vôi màu xám, xám sáng nứt nẻ, đơi nơi có hang karst ngầm Fig 4:27 Combine stratigraphic at ground collapse positions in Western Hanoi 20 Most of the positions occurred ground collapse has fine sand layer and soft soil layer in the geological sections (Fig4.27), bedrock beneath are limestone, high fractured, cracked, some places have underground karstic 4.5 Warning and proposed prevention solutions land subsidence, ground collapse 4.5.1 Forecasts land subsidence Results calculation of land subsidence in 2008, forecast to 2020 and final settlement were integrated on the geological section Độ lún hạ thấp mực nước ngầm thời điểm năm 2008 S (cm) 10.3 12 11 9.6 10 8.8 Dự báo độ lún hạ thấp mực nước ngầm đến năm 2020 5.2 S (cm) 13 14 16 13 21.5 1512 14 CHÚ GIẢI aQ 2³ tb Sét màu xám nâu, vàng nhạt, dẻo mềm Cát hạt nhỏ mịn màu aQ2 ³ tb xám nâu, xám vàng Sét, màu xám xanh, xám mQ2 ¹-²hh vàng, dẻo cứng Sét, b ột lẫn hữu màu b mQ ¹ -²h h xám, xám đen, dẻo chảy 32 Dự báo độ lún cuối thời gian lún hạ thấp mực nước ngầm aQ1 ³ vp Sét loang lổ bị laterit hóa, dẻo cứng aQ1 ³ vp Cát hạt thơ vừa màu xám vàng, chặt vừa 8.2 18 45.5 (năm) mQ ¹-²hh aQ2 ³tb Cao độ (m) 70 10 4.2 7.6 8.5 4.7 6.3 11.8 20 28.3 34.7 b mQ2¹ - ² hh 5.2 8.2 11.7 6.0 3.0 20 20 19.5 20.5 aQ1 ³ vp P2 nv HKB T-CS47 HKB T-CS46 HKB T-CS50 6.18 6.2 58 42.3 8.7 45.5 44.1 47.4 HKCCS06 8.6 HKCCS07 8.5 Khu Đ T m ới Tây Q uốc Oai(TT Quốc Oai) 53 MNN năm 20 00=2.5-3m 2.5 bmQ ¹-²hh 18.3 21.2 36m 39.3 43.5 HKC - CS05 145 11.2 12.0 15 45.8 5.96 7.6 11.7 6.2 -40 HKC -C S04 8.61 48 152 1.2 2.1 22m -20 45 39 45.4 47.2 bmQ 2¹ - ²hh aQ2 ³ tb 15m MNN năm 2013 10 25 aQ1 ³ vp 35 P nv QO -02 QO -01 7.5 8.36 xã Thạch Thán, Ngọc Mỹ aQ1 ³ vp 24.5 31 40 43 P nv 39 YN4 YN1 8.1 5.0 Y ên N ội, Đồng Quang, Quốc Oai 1000 2000 m Figure 4.30 Section forecast land subsidence due to groundwater extraction from Quoc Oai town to Dong Quang commune 4.3.2 Warning risk of ground – collapse - Areas with high risk of ground collapse occurred in profile type (subprofile types 1.1 and 1.4) and profile type (sub profile types 3.2 and 3.4) - Areas with high risk of ground collapse occurred in profile types has soft soil in sub-profile types 1.2 and 1.3 and sub-profile types 3.1, 3.3 and 3.5 - The remaining areas of profile types and has no soft soil or fine sand layers, less likely to occur ground collapse 4.3.3.Proposed solutions to prevent land subsidence and ground collapse Limiting exploitation of underground water, construct of the water treatment plant and ensures high quality provide sufficient flow for domestic service and manufacturing sector is essential and urgent 21 Encourage peoples not to arbitrarily drilling In case of drilling well for short-term, they have to apply reasonable engineering science drilling, with the assistance of the specialized agencies 52 26 54 56 58 th¹ch 24 60 62 64 66 68 q.ba đ ình 70 72 74 76 78 80 82 84 86 q cầ u TÔđƠẳ Ê T1o tlT£½È PR£È ½ thÊt 4.2 PR£È Ð 88 26 giÊy P2 nv CƠ PÊẳ ắ Ô q đ ống ®a 24 T1o tl T£½È 3.4 22 2.1 2.1 2.3 T1o tl T£½È £ 4.3 ap Q 18 2.3 2.3 2.1 TÔơƠẳ Ê ỉõTÊẳ é PÔểắ aQ29 tb 1.4 TÊéẩ Ô TÊéẩ Ê PÔểắ 18 Hà đ ÔN G 4.2 4.5 2.2 2.1 a p Q 18 -9h n 2.1 2.4 16 PÔểắ T1o tl TÊéẩ Ô 4.2 than h 1.3 14 trì 2.1 TÊéẩ Ê 2.1 2.4 12 TÊẵẩ £ 12 c h − ¬4.2 n g mü 2.1 TÔơƠẳ Ê aQ ẻẳ Ô 10 2.2 than h oai TÔơƠẳ Ê TÔắ Ô 08 q h o n g TÔắ Ê 14 10 22 20 2.1 TÊéẩ Ô TÔơƠẳ Ê TÊéẩ Ê TÊéẩ Ê aQ ẻẳ Ê aQ29 tb 4.4 3.1 4.2 TÔơƠẳ Ê 16 xu â n TÊéẩ Ô TÊéẩ 3.2 q u 1.1 ốc oai 2.1 q hoài đứ c 2.4 2.3 TÊéẩ Ô 20 q hai bà trng 4.4 PRÊẩ ẵ TÔđƠẳ Ê 2.2 4.1 TÔắ Ô TÔẩ ẻ 08 2.4 2.2 06 06 3.4 TÔẩ ẻ 04 T1o tl Hò a 00 bì nh TÊéẩ Ô 02 dpQ TÊẵẩ Ô TÊẵẩ Ê 2.1 02 TÔẩ ẻ 00 TÔắ Ô 1.1-1.4 Khu vực bị bị lún 3.1-3.5 có nguy xảy lún mặt đất TÔắ Ô Khu vực có nguy xảy lún mặt đất Khu vực có nguy 4.1-4.5 xảy lún mặt đất 3.3 94 98 3.2 2.1-2.4 96 04 TÔắ Ô 4.1 4.2 Chú giải 98 th ờn g tí n 96 TÔắ Ô TÔắ Ê TÔắ Ô 94 3.3 92 TÔắ Ô Khu vực núi đá 92 3.2 3.4 mỹ đứ c 90 T2_3 sb1 Phơ hƯ tÇng d−íi - hƯ tầng Sông Bôi T2 T2nt nt Hệ tầng Nậm Thẳm T2 a dg Hệ tầng Đồng Giao T1 vn2 Hệ tầng Viên Nam Phụ hệ tầng TÔắ Ô ứng 3.5 90 hòA 88 88 aQ29 tb TÊẵẩ Ơ 86 82 86 TÔắ Ê TÔắ Ô 84 TÔắ Ô 3.5 84 TÔắ Ô Q Ô TÔắ TÔắ Ô Q 82 TÔơƠẳ Ô T1 vn1 Phụ hệ tầng dới 80 TÔơƠẳ Ê TÔắ Ô Q T1 o tl Hệ tầng Tân Lạc P2 nv Hệ tầng Na Vang 3.5 80 TÔắ Ô TÔắ Ô TÔắ Ê pQ 78 78 76 76 Đứt gãy 74 TÔắ Ô Tỷ lệ 1:50.000 Hà 1c m đồ 500m thực tế 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82 na m 84 86 Figure 4:32 The prediction map of risk on land subsidence in the West area of Hanoi 74 88 mai 22 Figure 4.34 The warning map of risk on ground collapse in the West area of Hanoi Encourage and require the implementation of strategies to use water saving Some of measures necessary to apply include: - Management of the investigation, geological survey, hydrogeology more stringent, fully assess the distribution characteristics of underground karst 23 - For construction: compliance with standards and processes in karst areas - Upon detection of karst cave must have the appropriate remedial For the high loading constructions, applied solutions pile foundation Avoid karstic caves cases are not detected during the survey, but reappears when construction and strict management of different human activities impact on the ground in those areas at high risk of land subsidence CONCLUSIONS AND RECOMMENDATIONS From the research results of the thesis, some conclusions are referred as follows: The Quaternary sediments in the West area of Hanoi includes 10 sequences - Alluvial-proluvi sediments (apQ12-3 hn) and alluvial channel (a (c) Q12-3 hn) of Hanoi formation; - Alluvial channel (a(c)Q13 vp) and alluvial flat plain (a(f) Q13vp) of Vinh Phuc formation; - Alluvial-marine (amQ21 hh), bog-marine (bmQ21-2 hh), marine (mQ21-2 hh) and alluvial-bog (abQ21-2 hh) of Hai Hung Formation; - Alluvial channel (a(c)Q23tb) and flat plain (a(f)Q23tb) of Thai Binh formation Quaternary sediments in the West area of Hanoi is divided into four profile types with 18 sub-profile types The profile types and with the participation of the soft soil layer, high risk occurring subsidence and ground collapse The profile types and without the participation of the soft soil layer, less effected to land subsidence and ground collapse Land subsidence occurred in places with soft soil layer in the geological sections (distribution of sedimentary with profile types and 3) and the effects of lowering water tables In Quoc Oai town and adjacent, the water table was lowered to 35.5-36.5 m depth At the time in 2007- 2008 the 24 ground surface in this area subsidence 8.8-10cm and forecast to 2020 land subsidence will be 12-15cm The average settlement rate about 0.5-1cm/year In Dai Nghia town (My Duc district) and adjacent, the water table was lowered to 7-16m depth Forecast to 2020, land subsidence about cm to 15cm Land subsidence, ground collapse occurred in Quoc Oai district and My Duc district closely related to the characteristics of Quaternary sediments and only occurs in the area has distribution of sediment in profile types of and and influenced from human activities (exploitation of groundwater) Ground collapse occurred in areas has fine sand, soft soil layer and the technology of drilling not reasonably made material sediments in fine sand layer moves into the fissures, underground karst leads to destroying ground and creating sinkholes The fissures and underground karst in limestone as same as path and domain contained materials are destroyed before being transported by underground flow 5.The high-risk areas of subsidence and ground collapse in the West area of Hanoi is Ngoc My, Thach Than communes, Quoc Oai town (Quoc Oai district) and Le Thanh, Xuy Xa, Hop Tien communes, Dai Nghia town (My Duc district) Recommendation: - Additional detailed study of the distribution of underground karst, especially in areas with high risk of land subsidence and ground collapse - Restricting exploitation of underground water, increasing the use of surface water to replace - For constructions, the necessary research and provide solutions appropriate to the building foundation to limit risks of land subsidence, ground collapse - Setting up of monitoring stations groundwater and land subsidence in the Western area of Hanoi 25 LIST OF PUBLICATION RELATED TO THESIS Do Minh Duc, Dang Quang Khang, Nguyen Van Binh, Vu Van Loi, Pham Truong Sinh, Pham Hong Duc, Nguyen Ngoc Truc (2012), "Mechanism of sinkhole formation in underground limestone karstics area ( A case study of Natum area, Backan province)”, ScientificTechnical Journal of Mining and geology No 38/4-2012 pp 16-24 Nguyen Van Binh, Vu Van Loi (2012)"A study on soft soil formations in relation to land surface subsidence in the My Duc district, Hanoi city”, Vietnam Geotechnical Journal No-2012 pp 57-67 Binh.N.V, Duc D.M (2012),"An analysis of land subsidence in the West area of Hanoi city", Proceesding of the International Workshop-Hue Geo- Engineering 2012, pp.191-198 Nguyen Van Binh, Do Minh Duc (2013)"Land subsidence and its effects to stability of buildings in the West Hanoi City", Proceeding of International Symposium Hanoi Geo-engineering 2013, pp 41- 46 Nguyen Van Binh (2014),“Analyzing and evaluating affect of geotechnical properties and distribution of soft soil layer on land subsidence in Western area of Hanoi city” Journal of Science on Natural Resources and Environment No 02-2014 ISSN 0866-7608, pp76-84 Nguyen Van Binh, Do Minh Duc (2014), “Characteristics of soft soil foundation and the Relation to Land subsidence and Sinkhole in the Western Area of Hanoi City“ VNU Journal of Science Vol 30, No 2S,2014 pp175-184 ... topic: Research on characteristics of Quaternary sediments and the relations to land subsidence in the West area of Hanoi The objective of the thesis To elucidate of characteristics of lithological... 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... 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