Engineering Group Working Party Report

Transcription

1 GEOLOGICAL SOCIETY ENGINEERING GEOLOGY SPECIAL PUBLICATION NO. 25 Hot Deserts: Engineering, Geology and Geomorphology Engineering Group Working Party Report EDITED BY M. J. WALKER Consultant, Berkshire, UK 2012 Published by The Geological Society London

2 Contents Foreword Members of the Working Party xv xvi Chapter 1 Introduction Deserts Definitions Scope of this report: hot deserts Engineering significance of the hot desert environment Major sand dunes Dissected terrain Indurated horizons (duricrusts) Metastable soils Karst Stone pavements Salinity The Working Party Membership Objectives Structure of the report: contents 5 References 6 Chapter 2 Desert environments Defining deserts Distribution of the world's deserts Causes of aridity Atmospheric stability Continentality Orographic influences Cold ocean currents High reflectivity (albedo) of desert surfaces Factors acting in combination Controls on the diversity of desert environments Geological controls Climatic controls Temperature and humidity regimes Precipitation regimes Wind regimes Groundwater controls Past climate change in deserts Challenges facing desert environments 25 References 29 Chapter 3 Processes and landforms in deserts Weathering 33

3 viii CONTENTS Weathering processes Insolation Frost weathering Wetting and drying weathering Salt weathering Salt types and occurrence Mechanical effects Chemical effects Weathering products and rates Chemical weathering Weathering by lichens and algae Solution processes and limestone: karst Landforms and features produced by weathering Tafoni Amphitheatres, alveoles and pits Rock varnish Case hardening Duricrusts Calcrete (a form of duricrust) Silcrete duricrust Ferricrete (a form of duricrust) Gypsum enrichment and gypcrete (a form of duricrust) Near-surface nitrate enrichment Wind, sand and dust Aeolian processes Wind and wind regimes Definition and characteristics Global air-mass movements Diurnal wind variations Local wind variations Wind erosion, transport and deposition Desert surface characteristics The sand-dust system Grain entrainment and transport Grain deposition and bedform development Aeolian landforms Aeolian bedform classification Free dunes Impeded dunes Erosional features Wind-related hazards Fluvial geomorphology Water in deserts Desert hydrology Vegetation Climate 60

4 CONTENTS ix High-magnitude spatially localized storms Aridity and drought Overland flow Channelized ephemeral stream flow Flow regime High sediment loads and channel scour Subsurface water Natural pipes and'piping' Karst Capillary rise Fluvial landforms Rills and gullies Ephemeral stream channels Alluvial fans Pediments Playas Hazards associated with fluvial processes Flash floods Channel changes under flood conditions Sedimentation Hydrocompaction/'collapsing' soils Subsurface water, salts and aggressive ground Aggressive ground conditions Features of arid saltlands Factors affecting salt accumulation The coastal environment: sabkha Inland saline environments: playas Groundwater chemistry The solubility of minerals in coastal water and groundwater The influence of the carrier soils: chromatography Conclusions 89 References 89 Chapter 4 Hazards and the desert ground model Desert hazards Existing desert ground models An Earth systems model for desert landscape classification Structural and volcanic landforms Weathering landforms Erosional landforms Depositional landforms Conclusions and recommendations 138 References '42 Chapter 5 Soil and rock description and characteristics Hot deserts surfaces and soils Relationship of rock and soil types to the desert model Bare and/or patinated rock 144

5 X CONTENTS Weathered in situ rock and soil mantles Transported soils: fluvial/coastal Transported soils: aeolian Duricrusts Salt-enriched soils Existing soil and rock characterization and classification schemes Introduction Generic soil and rock classification and description Hot desert specific soil characterization and classification schemes Hot desert specific rock/duricrust characterization and classification schemes Recommended method for hot desert soil and rock characterization and classification 154 References 156 Chapter 6 Desk study, remote sensing, geographical information systems and field evaluation The value of desk study and field evaluation Themes for this chapter The approach to and scope of desk study and field evaluation Stages of investigation The engineering geological model Terrain evaluation Uncertainties Desk studies Field evaluation Risk registers and logs Desk study Planning and undertaking desk studies Sources of information Reporting desk studies Remote sensing Image processing and mapping Remote-sensing applications Geological mapping Geomorphological surveys Geoecological surveys Sources and costs of remotely sensed data Data costs (at 2010 prices, unless stated otherwise) Field evaluation Field reconnaissance Field mapping Geographical information systems (GIS) and data management GIS data organization Effective use of GIS Review of GIS applications Thematic mapping Geohazard assessment Flash flooding Unstable ground 183

6 CONTENTS xi Water resources Corridor or site selection Land-cover changes Reporting of the Stage I investigations (desk studies and field evaluations) Case histories Bahrain Surface Materials Resource Survey Terrain Technical objectives Work done, results and key lessons learnt In Salah Gas Project (pipelines), Algeria Terrain Technical objectives Work done, results and key lessons learnt Expansion of Suez city, Egypt Terrain Technical objectives Work done, results and key lessons learnt In Salah Gas Project (facility sites), Algeria Terrain Technical objectives Work done, results and key lessons learnt 194 Appendix to Chapter 6: remote sensing and GIS Internet links 195 6A.1. Satellite remote sensing 195 6A.2. Radar remote sensing 196 6A.3. Aerial photography 196 6A.4. Airborne multispectral and hyperspectral sensors 196 6A.5. LiDAR remote sensing 196 References 197 Chapter 7 Ground investigation, testing and interpretation of results Ground investigation methods Planning Trial pits and trenches Soft-ground boring Rotary drilling Diagraphy Cone penetration testing Geophysics Sampling Geotechnical sampling Sampling aggregate sources In situ and laboratory testing Review of investigation techniques for individual environments Zone I: uplands Zone II: footslopes and fans Zone III: plains Zone IV: base level plains 7.5. Interpretation of results and reporting

7 xii CONTENTS 7.6. Ground investigation during construction Scope of investigation during construction Examples of application to hot deserts Records of investigation during construction 233 Appendix to Chapter 7: laboratory and in situ testing procedures 233 7A. 1. National Standards bureaux 240 7A.2. National research bodies 243 References 255 Chapter 8 Engineering behaviour of desert soils Mechanics of sands Background Compression Shearing and critical states Application to engineering design Moisture in desert soils Mechanics of partially saturated soils Background Types of suction The soil-water retention curve Stress variables for partially saturated soils Behaviour of partially saturated soils in compression Shear strength and stiffness of partially saturated soils Recent constitutive models Dry soils Potentially collapsible soils Identification Methods of estimating settlement Expansive clays Identification Methods of estimating heave Salts Occurrence and characteristics Precipitation of salts Change in hydration Cementing Dissolution Mechanics of cemented soils Soils from sabkha and salina environments 294 References 296 Chapter 9 Materials for construction in deserts Engineering materials in the desert environment Effects of the desert environment on source materials Rock for engineering purposes Location, extraction and processing of large blocks Dimension and cladding stone Armourstone 307

8 CONTENTS xiii 9.3. Sand, gravel and crashed rock aggregates Location, extraction and processing Natural sands and gravels as aggregate Aggregate source evaluation Aggregate processing Crushed rock and duricrusts as aggregate Materials for road construction Sources of materials Unpaved 'dirt' roads Use of duricrusts and marginal materials Bituminous paving materials Concrete and mortars Aggregates: requirements and specifications Cement and cementious materials Reinforcement Sand-lime bricks and blocks Storage of materials Traditional materials for building construction Natural local building materials Soil types: availability and evaluation Brick-making materials Construction and demolition wastes Types of material Utilization of demolition waste Regulatory framework Sources of water and water quality Water requirements Sources of water 340 References 342 Chapter 10 Engineering design and construction Earthworks Excavatability of desert materials Slope stability Excavation support Construction of fills Placing and compacting fills Salts in fill materials Reinforced soil Foundations General considerations Rock subgrades Collapsible soils Expansive soils Dissolution and salt heave Piled foundations Protection of buried concrete 356

9 xiv CONTENTS Roads and pipelines Route selection Subgrade Pavements Salt damage to pavements Unsurfaced and temporary roads Pipelines Coastal development Coastal development in desert areas Dredging Reclamation Shore protection Marine environment Flooding and erosion Prediction of runoff and channel flow Erosion Design approaches to mitigate flood and erosion hazard Groundwater changes due to urbanization and development Wind-blown sand and dust Sand and dust hazards Sand transport Control of drifting sand Trapping sand Enhancement of transportation Reduction of sand supply Deflection of moving sand Moving dunes Removal of dunes Dissipation of the dunes Immobilization of dunes Control of wind-blown dust Concrete structures Influence of climate and geology Mixing and placing concrete Concrete durability Traditional construction Environmental protection and sustainability 389 References 390 Glossary of some engineering and geological terms 393 Index 411