Groundwater Lowering in Construction A Practical Guide to Dewatering, Second Edition

Linking theory and application in a way that is clear and understandable, Groundwater Lowering in Construction: A Practical Guide to Dewatering, Second Edition uses the authors’ extensive engineering experience to offer practical guidance on the planning, design, and implementation of groundwater control systems under real conditions. Discover engineering methods that can help you improve working conditions, increase project viability, and reduce excavation costs. In the decade since publication of this book’s first edition, groundwater lowering and dewatering activities have been increasingly integrated into the wider ground engineering schemes on major excavations to help provide stable and workable conditions for construction below groundwater level. Consequently, many engineering ventures now require a more in-depth assessment of potential environmental impacts of dewatering and groundwater control, and this book details the latest best practices to evaluate and address them. Includes New Chapters Covering: Cutoff methods used for groundwater exclusion Issues associated with permanent or long-term groundwater control systems Groundwater control technologies used on contaminated sites Methods needed to understand, predict, and mitigate potential environmental impacts of groundwater control works Updated to reflect the crucial technological and application advances shaping construction processes, this book contains valuable direction that can give you a true competitive advantage in the planning and execution of temporary and permanent dewatering works. The authors cover cutting-edge methods and key subjects, such as the history of dewatering, working on contaminated sites, site investigation techniques, and operation and maintenance issues, including health, safety, and legal aspects. Written for practising engineers and geologists as well as postgraduate engineering students, this updated manual on design and practice provides numerous case histories and extensive references to enhance understanding.

Groundwater lowering: A personal view, P.Cashman Structure of the rest of the book History of groundwater theory and practice Earliest times to the sixteenth century Renaissance period to the nineteenth century Progress from a qualitative to a quantitative science Later theoretical developments Groundwater modeling Early dewatering technology in Britain Practical publications Groundwater and permeability Hydrology and hydrogeology Permeability and groundwater flow Aquifers, aquitards, and aquicludes Flow to wells Aquifers and geological structure Aquifer boundaries Using geological structure to advantage Groundwater chemistry Groundwater effects on the stability of excavations Groundwater control—the objectives Groundwater, effective stress, and instability Large-scale instability caused by groundwater Slope instability Base instability Localized groundwater problems Excavations in rock Surface water problems Effect of climate and weather Methods for control of surface water and groundwater Control of surface water Methods of groundwater control Exclusion methods Dewatering methods Groundwater control for tunnels and shafts Use of pumping and exclusion methods in combination Site investigation for groundwater lowering Purpose of site investigation Planning of site investigations Stages of site investigation Determination of ground profile Determination of groundwater conditions Determination of permeability Design of groundwater lowering systems What is design? Design approach Development of a conceptual model Expectations of accuracy Selection of method and geometry Estimation of steady-state discharge flow rate Specification of well yield and spacing Other considerations Numerical modeling Sump pumping Applications of sump pumping Pumping of surface water runoff Pumping sumps Drainage of side slopes of an excavation Sump pumping of small excavations Sump pumping problems Disposal of water from sump pumping operations Case history: Sump pumping of large excavation Wellpoint systems Which system: Wellpoints or deep wells? What is a wellpoint system? Wellpoint installation techniques Spacing of wellpoints and drawdown times Sealed vacuum wellpoint system Wellpoint pumping equipment Wellpoint installations for trench excavations Wellpointing for wide excavations Wellpointing for deeper excavations Case history: Derwent outlet channel, Northumberland Deep well systems Deep well installations Design of wells for groundwater lowering Constructing deep wells Drilling of well boreholes Installation of well materials Well development Installation and operation of deep well pumps Vacuum deep well installations Shallow well installations Case history: Tees barrage, Stockton-on-Tees Other dewatering systems Ejectors Horizontal wellpoints Horizontal wells Pressure relief wells Collector wells Siphon drains Electro-osmosis Artificial recharge systems Dewatering and groundwater control technologies used for the control or remediation of contaminated groundwater Methods for the exclusion of groundwater Principal methods for groundwater exclusion Geometries of exclusion applications Steel sheet piling Vibrated beam walls Slurry trench walls Concrete diaphragm walls Bored pile walls Grout barriers Mix-in-place barriers Artificial ground freezing Pumps for groundwater lowering duties Wellpoint pumps Jetting pumps Sump pumps Pumps for deep wells Sizing of pumps and pipework Permanent groundwater control systems Types of permanent groundwater control systems Objectives of permanent groundwater control systems Design issues for permanent groundwater control systems Practical issues for permanent groundwater control systems Opportunities associated with permanent groundwater control systems Case history: Govan underground tunnel, Glasgow Environmental impacts from groundwater control Why are impacts from groundwater control of concern? Potential environmental impacts from groundwater control Impacts from groundwater abstraction Impacts from groundwater pathways Impacts from groundwater barriers Impacts from discharge flows to the groundwater environment Impacts from discharge flows to the surface water environment Assessment of potential environmental impacts Monitoring and maintenance of groundwater lowering systems Need for monitoring Monitoring of water levels Monitoring of discharge flow rate Other parameters that may be monitored Data-logging systems Mechanical factors and automation Backfilling and sealing of wells on completion Encrustation, biofouling, and corrosion Fault finding and problem solving Safety, contracts, and environmental regulation Health and safety Contracts for groundwater control works The future—a personal perspective by Toby Roberts Applications and techniques Communication and monitoring technology Numerical modeling Regulation Where do we go from here? Next generation of dewatering practitioners Appendix 1: Estimation of permeability from laboratory data—Loudon method Appendix 2: Execution and analysis of variable head permeability tests in boreholes Appendix 3: Execution of well pumping tests Appendix 4: Design examples Appendix 5: Estimation of flow rate using V-notch weirs List of notation Glossary List of conversion factors References

Prior to his death in 1996, Pat Cashman was the leading British exponent of groundwater control for his generation. For more than 40 years, during the growth of soil mechanics into the practice of geotechnical engineering, Pat was responsible—through the organisations he ran, and later as a consultant—for maintaining a practical and straightforward approach to the art of groundwater control. Dr. Martin Preene is a highly experienced geotechnical engineer specializing in groundwater engineering and hydrogeology. Martin has more than 25 years of experience working with contractors and consultants on the design and implementation of dewatering and groundwater control systems. He has worked on major engineering projects around the world, including power stations, road and railway tunnels, dry docks, and open-pit mines. He is widely published on dewatering and groundwater engineering, including papers and industry guidance documents. Dr. Preene is currently a principal at Golder Associates in the UK.