Investigation of Liquid Limit of Kamloops Silt by Soft-Base Casagrande Apparatus
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Investigation of Liquid Limit of Kamloops Silt by Soft-base Casagrande Apparatus and British Drop-Cone Penetrometer by Alan Zhong Lu A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF BACHELOR OF APPLIED SCIENCE in THE FACULTY OF APPLIED SCIENCE (Geological Engineering) This thesis conforms to the required standard ……………………………………….. Dr. R. Jonathan Fannin THE UNIVERSITY OF BRITISH COLUMBIA (Vancouver) MAY 2010 © Alan Zhong Lu, 2010 2010 Investigation of Liquid Limit of Kamloops Silt by Soft-base Casagrande Apparatus and British Drop-Cone Penetrometer Alan Zhong Lu The University of British Columbia 4/9/2010 ABSTRACT This study was to investigate the liquid limit of Kamloops silt using two world-wide popular testing apparatus: Casagrande device and British style Drop-Cone penetrometer. The testing with Casagrande device was conducted by a group of soil mechanics students in accordance with ASTM D423-61T (1961); the testing with British style Drop-Cone penetrometer was performed by two senior undergraduate engineering students in accordance with BS 1377 (1975). The liquid limit of Kamloops silt was found to be approximately 23%. The results obtained by both apparatus agreed to each other quite well, so these two testing methods can be alternative of each other. However, using Drop-Cone penetrometer required less experience of the operator and yielded results more easily and quickly than using Casagrande device. This paper also introduced the concept and the significance of Atterberg Limits, and summarized the development of Casagrande method by Arthur Casagrande and the evolution of Drop-Cone penetrating method. ii TABLE OF CONTENTS Page Abstracts ………………………………………………………………………. ii Table of Contents …………………………………………………………….... iii List of Figures …………………………………………………………………. v Acknowledgment ………………………………………………………………. vi 1.0 Introduction ………………………………………………………………… 1 1.1 Introduction ……………………………………………………………. 1 1.2 Research Hypothesis …………………………………………………… 1 2.0 Study Area ……………………………………….......................................... 2 2.1 Geological History …………………………………………………….. 2 2.2 Current Climate ……………………………………………………….. 4 2.3 Description of Kamloops Silt …………………………………………. 5 3.0 Literature Review ………………………………………………………….. 6 3.1 Atterberg Limits ……………………………………………………….. 6 3.2 An Invention of Arthur Casagrande …………………………………… 8 3.3 Fall-Cone Method ……………………………………………………… 10 4.0 Testing Methods …………………………………………………………….. 12 4.1 Casagrande Method ……………………………………………………. 12 4.1.1 Apparatus Setup ……………………………………………….. 12 4.1.2 Testing Procedures……………………………………………… 13 4.1.3 Acquisition of Results …………………………………………. 13 iii 4.2 Fall-Cone Method ……………………………………………………… 14 4.2.1 Apparatus Setup ……………………………………………….. 14 4.2.2 Testing Procedures …………………………………………….. 14 4.2.3 Acquisition of Results …………………………………………. 15 5.0 Results ………………………………………………………………………. 16 5.1 Casagrande Method …………………………………………………….. 16 5.2 Fall-Cone Method ……………………………………………………… 18 6.0 Conclusion ………………………………………………………………….. 21 6.1 Liquid Limit of Kamloops Silt …………………………………………. 21 6.2 Agreement of Results by Casagrande Method and Fall-Cone Method …. 21 7.0 Recommendations for Further Work ……………………………………….… 22 Appendix A: Data of Drop-Cone Penetration Test ………………………………. 23 Appendix B: Data of Casagrande Test …………………………………………… 27 Appendix C: Sample Calculation for Water Content ……………………………. 31 List of References ……………………………………………………………….. 32 iv LIST OF FIGURES Figure 1: Map of Kamloops Silt Bluffs …………………………………………. 2 Figure 2: Photographof Kamloops Silt Bluffs …………………………………... 3 Figure 3: Illustrative Drawing of Stratigraphy of Kamloops Silt Bluffs ………... 4 Figure 4: Four Phases of Soil-Water Mixture …………………………………… 7 Figure 5: Schematic Drawing of Casagrande Liquid Limit Device …………….. 9 Figure 6: Sketch of British Style Drop-Cone Penetrometer …………………….. 11 Figure 7: Trendlines of Thirty-nine Sets of Data Obtained by Casagrande Method ……………………………………………….. 17 Figure 8: Distribution of Liquid Limit of Kamloops Silt Obtained by Casagrande Method ……………………………………………….. 18 Figure 9: Trendlines of Thirty Sets of Data Obtained by Drop-Cone Method for Liquid Limit of Kamloops Silt ……………………………………. 19 Figure 10: Distribution of Liquid Limit of Kamloops Silt Obtained by Drop-Cone Method ……………………………………………….. 20 v ACKNOWLEDGEMENT I am grateful to Dr. R. Jonathan Fannin and Dr. Mahdi Taiebat of the University of British Columbia, who spent significant amount of time providing invaluable advice regarding their experience in this study and guiding qualitative thesis writing. I am also thankful to Ms. Emilie Lapointe who helped me gather the testing data of Casagrande method. Lastly, I appreciate the kindness of CIVL 210 students at the University of British Columbia, who share their testing data with me. vi 1.0 Introduction 1.1 Introduction The liquid limit of fine-grained soil is the lowest water content when the soil-water mixture starts to behave like a viscous fluid and flows by its own weight (Nagaraj, 1993). It is a factor used in the classification of fine-grained soils, and it also relates to their engineering properties. Casagrande device and Drop-cone penetrometer are the two methods world-widely adopted in practice to determine the liquid limit of fine-grained soils. Since 1910s, engineers and scientists have performed both tests on numerous soil samples, and the results by both methods agree with each other in general. This paper describes the process of determining the liquid limit of Kamloops Silts using a soft base Casagrande device and a British style Drop-cone penetrometer, and then compares the two methods in terms of the accuracy of results, ease of operation, and sources of errors. 1.2 Research Hypothesis This paper is to evaluate the liquid limit of Kamloops Silts and to assess the consistency of the results obtained by both Casagrande Method and Drop-Cone Method. 1 2.0 Area Study 2.1 Geological History Kamloops Silt Bluffs are distributed along the south bank of Thompson River, east of the City of Kamloops, British Columbia. Figure 1 shows the distribution of Kamloops Silt Bluffs which are alternatively named as Valleyview Silt Bluffs and Dallas Silt Bluffs and highlighted in green color. With the reference of NAD83 grid, the coordinates of the approximately 10-kilometer-long belt of silt bluffs are in Zone 10, 690000-701500 E, 5617000 N (NAD 83). Figure 1: Map of Kamloops Silt Bluffs (GCC) During the last deglaciation in late Wisconsinan (Roberts & Cummingham, 1992), in the process of ice receding, an ice tongue was trapped in Thompson Valley and was separated into eastern and western lobes that retreated apart each other. In the valley, 2 lakes were formed by melted glaciers and enclosed by ice-dams. After these ice-dammed lakes were drained out, the glacial till was exposed. During the same period of time, maximum erosion, transportation, and deposition derived much of the lacustrine silts from the glacial till that was deposited on the uplands next to the Thompson Valley (Lum, 1979). The formation of Kamloops Silt Bluffs are presented in the photograph (Figure 2) and drawing (Figure 3) below. Kamloops Silt Bluffs Figure 2: Photograph of Kamloops Silt Bluffs (Roberts & Cummingham, 1992) 3 Figure 3: Illustrative Drawing of Stratigraphy of Kamloops Silt Bluffs (Roberts & Cummingham, 1992) 2.2 Current Climate at Kamloops Kamloops, situated on the east side of the Rocky Mountains (rain shadow location), is in a semi-arid climate. The annual hours of sunshine are approximately 2000. The average annual precipitation is 256.5 mm, of which 174.8 mm is rainfall (BC Wildfire Management). The temperature changes significantly from season to season; the winter is usually mild and short, and the summer is prevailing hot and dry. According to the Department of Environment Canada, the mean temperature in January maintains around – 6.1°C for most of time, with occasional colder period of – 29°C and a historic extreme of – 38.3°C; the mean temperature in July stays about 20.8°C, with several days of 38°C and a historic extreme of 41.7°C. 4 2.3 Description of Kamloops Silt The soil sample was obtained from the Kamloops Silt Bluffs at Thompson River in Kamloops, British Columbia. A piece of uncrushed, air-dried soil sample exhibited light grey-beige colour, fair hardness, cohesiveness, and slight stratification. The crushed Kamloops silts were fine-grained inorganic soil with slight earthy smell. Based on a sieve (#3) and hydrometer analysis performed by UBC undergraduate students under the supervision of professor and graduate students, Kamloops Silts consisted of about 4% of sand, 89% of silt, and 7% of clay. 10% of particles had sizes less than 0.0027mm; 60% of particles were smaller than 0.0092mm. By MIT classification, Kamloops silt was classified as uniform clayey silt (Lum, 1979). A scanning electron microscope (Etec Autoscan Scanning Electron Microscope) study and a microprobe (Ortec Multichannel Analyser, Model 6200) study were also performed by Lum (1979) at the University of British Columbia campus. The mineralogy of soil particles were identified, such as mica, feldspar, and montmorillonite. Key elements were Si, Al, Fe, Ca, Mg, and Na, listed in the order of decreasing peak intensity observed in photomicrographs. Siliceous diatoms (a common species in freshwater lakes) scattered throughout the samples were also observed (Lum, 1979). This observation coincided with the theory that Kamloops silts were lacustrine silts exposed after ice-dammed lakes drained.