INFLUENCE OF ENGINEERING PROPERTIES OF THE SOIL, GEOLOGICAL AND HYDROMETEROLOGY FACTORS ON FAILURES AND DISTRESS OF EARTH DAMS IN NORTH-EASTERN NIGERIA BY UMARU, Ahmadu Babayi (Matric. No; 109913) B. Eng. (Maiduguri), M. Sc. (Ibadan) MNIAE, MNSE, R.ENGR. (COREN) A thesis in the Department of AGRICULTURAL AND ENVIRONMENTAL ENGINEERING Submitted to the Faculty of Technology in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY of the UNIVERSITY OF IBADAN December, 2014 i CERTIFICATION I certify that this work was carried out by Mr. Umaru Ahmadu Babayi in the Department of Agricultural and Environmental Engineering. Faculty of Technology, University of Ibadan, Ibadan. Nigeria. ------------------------------------------------------------- (Supervisor) A.Y. Sangodoyin, B.Sc. Agric. Engrg. (Ibadan) M.Sc. Water Res. Tech.,Ph.D. Civil Engrg. (Birmingham) MASABE, MNIAE, MIWES, MNSE, NPOM Professor of Water Resources and Environmental Engineering Department of Agricultural and Environmental Engineering University of Ibadan, Ibadan, Nigeria . ii ABSTRACT Earth dam failures could result in the loss of lives, damage to properties, health, environmental and social problems. Distressed dams cost a lot of resources and inconveniences to remediate. There is paucity of data on failures and distresses of many earth dams located in the north-eastern part of Nigeria. This study was designed to determine the geological, hydrometeorological, engineering factors and soil properties responsible for the failures and distresses of earth dams. A total of 42 randomly selected earth dams spread across various geologic formations and constructed with different soil materials in north-eastern Nigeria were studied. Data were obtained on failure modes, design and construction features, operation and maintenance, dam safety instrumentations and operations using the Association of State Dam Safety Officials method. Geological and hydrometeorological data related to dam failures, distresses and functionality were obtained from Upper Benue River Basin Development Authority, States Ministries of Water Resources and Nigerian Meteorological Agency. Soil samples collected were analysed for specific gravity (Gs), particle size distribution, Atterberg limits, compaction, California Bearing Ratio (CBR), permeability, triaxial compression and consolidation tests according to BS1377. The results were analysed using descriptive statistics. The proportions (%) of failed, distressed, uncompleted and functional dams were 27, 12, 12 and 49 respectively. The failure modes were; seepage (5%), piping (8%), structural (1%), hydraulic (50%) and a combination of two or more modes in a complex manner (36%). The main causes of failure were inadequate maintenance (71%), lapses in design (9%) and poor construction (15%). On the Basement complex formations, 62, 27 and 11% of the dams were functional, failed and distressed respectively. All the dams on Gombe sandstones and Pindiga formations are functional. The status of the dams were affected by peak monthly total rainfall iii (327.1–478.8mm) where 75% of the failures and distresses occurred due to high runoff, erosion, siltation and overtopping, while 20% of the failures occurred due to excessive water loss as influenced by peak monthly total evaporation ranging from 354.6-409.7mm coupled with relatively high temperatures (39–43oC). Soil groups for constructing the earth dams in the study area ranged from poorly graded sands to silty/clayey sands. Seventy-nine percent of the failed and distressed dams have embankment materials with Coefficient of uniformity of less than 5. Sixty- five percent of failed and distressed dams have Plasticity Index of 0-7. Eighty percent of functional dams have highly compacted soils with maximum dry density ranging from 1.84 to 2.01Mg/m3. High permeability ranging from 0.018 to 0.110 m/day influenced 33% of dam failures. Consolidation tests showed a settlement of 1.18mm and 2.29mm for functional and failed dam respectively. The Gs (2.41-2.70) and CBR values (11-46%) as well as cohesion (35- 215kN/m2) and angle of internal friction (3-18o) influenced particular incidents without a trend. Geologic formations, weather conditions, lapses in design, poor construction, maintenance, operation and poor soil characteristics influenced the status of earth dams in north- eastern Nigeria. Grouting, soil stabilisation, use of rock ripraps, impervious blankets and maintenance scheduling are suggested to minimise failures and ameliorate distresses. Keywords: Earth dam, Failure modes, Soil properties, Hydrometeorology, Geologic formation Words count: 497 iv ACKNOWLEDGEMENTS My profound thanks go to Allah Subhanahu wa Ta’ala, Who made it possible for me to embark on the journerny towards achieving a Doctoral Degree in the Premier University. I am grateful to my able supervisor, Professor A.Y. Sangodoyin, who assisted and guided me throughout the period of this research work. His high accessibility, constructive criticism and concern, in spite of his tight schedules are highly appreciated. My thanks also goes to Professors E.B. Lucas, J.C. Igbeka, M.A. Onilude, K. Ogedengbe, E.A. Ajav O.A. Raji, A.I Bamgboye, J.A. Tanko and F.A. Adeniji, Drs. Y.A Mijinyawa, A.K Aremu, and the entire staff of Agricultural and Environmental Engineering Department, University of Ibadan, for their contribution in one way or the other towards the realization of this work. My sincere gratitude goes to Dr. A. I. Oke of the Department of Civil Engineering Obafemi Awolowo University Ile-Ife, Nigeria for his useful suggestions, advice and guidance towards the success of this work. The support given to me by Engr. (Dr.) Babagana Umara from the beginning up to the end is highly appreciated. I wish to thank Engrs. Babaji, Modu, Aderibigbe, Oluniyi, Adeniran and the entire staff of the Department of Dams, Irrigation and Drainage, Federal Ministry of Agriculture and Water Resources Abuja for their cooperation and willingness to assist towards the success of this work. I really appreciate the encouragement and support given to me by Engrs. S. M. Naibi A. B. Pella and B. N. Pius of the Upper Benue River Basin Development Authority, Yola. My heartfelt gratitude goes to Engr. S.Y. Umar the Coordinator of Civil Engineering programme, Mal. Abdllahi and Alh. H. Y. Sade of Soil Mechanics Laboratory, Abubakar Tafawa Balewa University (ATBU), Bauchi. These people assisted very well in the course of the Laboratory work. v Many thanks also go to Mal. A. A. Chinade, Engr. Muh’d Tela, Alh. Arabi, Mal. Ahmed Baba, Alh. Yusufu, Engr. A. Kojoli, Mal. Ahmed Musa, Mal. Bashir Barhama who really made my stay a memorable one in Bauchi. I appreciate the contributions of Drs. D. N. Adewole, T. Ewemoje, Omoniyi, F. Owofadeju, O. O. Adefison and Mr. M. O. Omobowale. I say thanks for your assistance and accommodative nature. I wish to thank Dr. Ja’afaru Inuwa, Dr. Augustine A. Ndaghu, Dr. Colman Tizhe Vandi, Dr. Ade, Dr. Marie Octavie and Dr. Alfa for making my stay an enjoyable one in the Tafawa Balewa Postgraduate Hall, University of Ibadan. More grease to your elbows. To Alhaji Abubakar Usman Borkono, Yusuf Usman Borkono, Umaru Usman Borkono, Nuhu Aliyu Modibbo, Alhaji Abubakar Makinta and Adamu Garba Adamu; I say thank you a million for making my stay enjoyable at Abuja. I am very grateful to my father Alhaji Umaru Babayi and Dr. A. Abba who encouraged me to pursue a Doctoral Degree. I want to thank the authorities of the Modibbo Adama University of Technology (MAUTECH), Yola for giving me a Full-time study fellowship to pursue a PhD Degree programme in the University of Ibadan, Nigeria. The support and understanding shown to me by my seniors, colleagues and the entire staff of the Department of Agricultural and Environmental Engineering, Modibbo Adama University of Technology cannot be over emphasized. I thank you all. The support and understanding given to me by my wife Hawwa and children Al- amin, Fatimah, Aishat and Muhammad Sani is highly appreciated and well noted. vi DEDICATION This report is dedicated to my late grandfather Modibbo Suleimanu Gombi vii ACCRONYMS AND ABBREVATIONS Symbol Meaning GW Well graded gravels GP Poorly graded gravels GM Silty gravels GC Clayey gravels SW Well graded sands SP Poorly graded sands SM Silty sands SC Clayey sands ML Inorganic silts with low plasticity CL Inorganic clays of low plasticity OL Organic silts with low plasticity MH Inorganic silts with high plasticity CH Inorganic clays with high plasticity OH Organic clays with high plasticity Pt Peat and highly organic soils I Medium plasticity(clay) or compressibility(silt) R.C. Rolled Compacted U/P Upstream slope D/S Downstream slope HE Homogeneous Embankment ZE Zoned Embankment C Cohesion Ф Angle of Internal friction viii TABLE OF CONTENTS Page Title page i Certification ii Abstract iii Acknowledgements v Dedication vii Acronyms and abbreviations viii CHAPTER ONE INTRODUCTION 1.1 Dams in general 1 1.2 Evidence of earth dams failure around the world 3 1.3 Evidence of earth dams failure in Nigeria 5 1.3.1 Shiroro dam 6 1.3.2 Ojirami dam 6 1.3.3 Tiga and Challawa dams 6 1.3.4 Shiroro dam 6 1.3.5 Obudu dam 7 1.3.6 Igabi dam 7 1.3.7 Alau dam Maiduguri 8 1.4 Statement of problem 9 1.5 Aims and Objectives 9 1.6 Justification 10 ix 1.8 Expected contribution to knowledge 10 CHAPTER TWO REVIEW OF LITERATURE 2.1 History of dams 12 2.2 Classification of dams 14 2.3 Earth dams 18 2.4 Dam failures in general 26 2.5 Modes of dam failures 37 2.6 Dams in Nigeria 39