Geotechnical properties on the Holocene sediments. in Giongtrom - Bentre Province. Presenter: Truong Tieu Bao

Transcription

1 Geotechnical properties on the Holocene sediments in Giongtrom - Bentre Province Presenter: Truong Tieu Bao February 16 th, 2017

2 Contents I. INTRODUCTION II. METHODS CONCLUSION III. RESULTS - DISCUSSION

3 Contents I. INTRODUCTION II. METHODS CONCLUSION III. RESULTS - DISCUSSION

4 I. INTRODUCTION. Fig.1 Location of Bentre Province and Map of Mekong River Delta

5 AIMS OF THE STUDY Geotechnical properties of Holocene sediments Relationship (Geotechnical properties characteristics of sedimentary facies)

6 II. Methods. Assessment in engineering geology Collecting researches Geotechnical properties of Holocene sediments in M.K delta [10,11,15] Testing Sedimentary Characteristics: The BT2 core [5,6,9] Field investigations On site (CPTu,SPT) In lab Fig.2: Tests on site a. CPTu b. SPT

7 CPTu The CPTU method works by pushing an instrumented cone into the ground at a constant rate continuously to measure: + cone resistance q C + sleeve friction f S + pore pressure u Figure 3: a 15 ton thrust rig with anchors Figure4: Some other CPTU trucks ( 20 tonnes in push capacity)

8 III. Results - Discussion. BT2 Fig 5: Location of the BT2 borehole in Giồng Trôm - Bến Tre ( citation: Nguyen et al., 2000)

9 III.1. Results on site of the BT2 borehole q t = kpa f s = 9-42 kpa u 2 = ,5 Kpa OCR tb =1.4 Fig 6 : Results on site of the BT2 borehole

10 III.1. Results on site of the BT2 borehole u2= Kpa OCR tb = q t = kpa fs = 9-60 kpa Fig 6 : Results on site of the BT2 borehole

11 III.1. Results on site of the BT2 borehole q t = f s = 2-48kPa u 2 = OCR tb =1-2 Fig 6 : Results on site of the BT2 borehole

12 III.1. Results on site of the BT2 borehole q tmax = 6386 kpa fs = 55kPa Fig 6 : Results on site of the BT2 borehole

13 III.2. Results in lab of the BT2 borehole. Fig 7: Results in lab of the BT2 borehole

14 III.3. Discussion. Connect the geotechnical properties with the sedimentary facies. Fig.8 : Result of connecting the geotechnical properties with the sedimentary facies

15 III.4. Estimating the defomable foudation loaded by road. Vertical stress Loading stress Determine deformable area by load of road Settlement of a Single Infinite Layer Total settlement

16 III.4. Estimating the defomable foudation loaded by road. sand percentage

17 Conclusion: Each sedimentary facies is also presented by the particular geotechnical properties correlated the hydrodynamic conditons and formative environment. Facies Sedimentary Characteristics Mechanic Behaviour Bay and Prodelta Delta front Tidal flat Sand dune -Clay, silty clay, liquid state Unifomity: high hydro-dynamic is high The grain size increases in upward direction. - Complicated in structure hydrodynamic is quite high Clayey sand and sandy clay are arranged rhythmicly, consist of a little organic influences of tidal changes hydro-dynamic is high Sand: coarse to fine, Unifomity: high Simple :q t, f s, u 2 linear in depth SPT low N=2, R tc =0,38-0,48 kg/cm 2 Varied: presentation of q t, f s, u 2 alternation of material is frequent, N=2 R tc =0,5-0,775 kg/cm 2 Varied: the values q t, f s, u 2 have got the shape like a saw tooth in overall plot, N=3-4 R tc =0,32-0,38 kg/cm 2 Simple: the values from CPTu quite high q max = 6386 kpa, f smax =55kPa

18 References Vietnamese documents: [1] Đỗ Bằng, Bùi Anh Định, Vũ Công Ngữ (1995), Bài tập Cơ học đất, NXB Giáo dục, Hà Nội. [2] Cục Thống Kê tỉnh Bến Tre (2013), Niên Giám Thống Kê 2012 [3] Nguyễn Văn Lập (2004), Tướng trầm tích và sự phát triển của tam giác châu sông Cửu Long giai đoạn Pleistocen muộn Holocen ở đồng bằng sông Cửu Long, Hội thảo khoa học nghiên cứu cơ bản trong lĩnh vực các khoa học về Trái đất phục vụ phát triển bền vững kinh tế và xã hội khu vực Nam bộ (12/2004), tr [4] Tạ Thị Kim Oanh, Nguyễn Văn Lập (2000), Diatom chỉ thị môi trường trầm tích và dao động mực nước biển trong Pleistocene muộn - Holocene, Tạp chí Các khoa học về Trái Đất, (số 22), trang [5] Tạ Thị Kim Oanh, Nguyễn Văn Lập (2002), Trầm tích Pleistocene muộn Holocene và sự phát triển của tam giác châu sông Cửu Long ở Bến Tre, Tạp chí Các khoa học về Trái Đất, (số 24/2), trang [6] Trần Văn Việt (2002), Cẩm nang địa kỹ thuật, NXB Xây dựng. English documents: [7] Braja M. Das,2002, Principles of Geotechnical Engineering, Califonia State University, Sacramento. [8] V.L. Nguyen, T.K.O. Ta, M. Tateishi, 2000, Late Holocene depositional environments and coastal evolution of the Mekong River Delta, Southern Vietnam, Journal of Asian Earth Sciences, (18), p

19 References [9] Ta, T.K.O., Nguyen, V.L., Tateishi, M., Kobayashi, I., Saito, Y. T. Nakamura, Sediment facies and Late Holocene progradation of the Mekong River Delta in Bentre Province, southern Vietnam: an example of evolution a tide-dominated to a tide- and wave-dominateed delta, Sedimentary Geology 152, p [10] Truong, M.H., et al., 2010, Reconstructing sedimentary environments of MR1 core and investigating facies geotechnical properties through the piezocone penentration test in the late Pleistocene Holocene periods in the Mekong River Delta, VNU Journal of Science, Earth Science, vol 26-1, p [11] Truong,.M.H., Nguyen, V.L., Ta, T.K.O., Takemura, J., 2011, Changes in late Pleistocene-Holocene sedimentary facies of the Mekong River Delta and the influence of sedimentary environment on geotechnical engineering properties, Elsevier, Engineering Geology, Vol. 122, paper Website. [12] [13] [14] [15] [16]

20 Future study