Rock Grouting: With Emphasis on Dam Sites

ISBN-13: 9783642510137 / Angielski / Miękka / 2012 / 428 str.

Friedrich-Karl Ewert; R. Phillips

Opis

Fifteen years have passed since I was working at a dam site super vising grouting work. That was not the first time that I had to car ry out engineering geological investigations for several similar projects, which always included testing programmes to find out the permeability of the rock, and often I was in charge of grouting work. It thus attracted my attention when this particular grouting programme did not run as intended: most of the grout holes took only very little grout It could not be the aim of the invested work simply to drill holes and fill them again without bringing about any further improvement. Fortunately, I had the chance to be en gaged in many other grouting programmes in the following years and used all these examples to analyse as thoroughly as possible the permeability of the rocks being treated in view of their grout ability. The more I studied, the stronger my conviction grew that our rules which had decided the grouting of rock for many de cades should be developed further, and therefore I occupied my self with contributing some ideas for a new basis to investigation and judgment of permeability of rock and for a more adequate application of this technology."

Spis treści

1 Introduction.- 2 Remarks on the Methodology of Preparation.- 3 Analysis of Completed Grouting Programmes.- 3.1 Preliminary Remarks.- 3.1.1 Selection of the Programmes; Data.- 3.1.2 Representation of Grouting Data.- 3.2 Description and Evaluation of the Programmes.- 3.2.1 Grouting Programmes in Folded Siltstone-Sandstone Alternations of the Westphalian Upper Carboniferous.- 3.2.1.1 The Grouting Programme at the Möhne Dam.- 3.2.1.2 The Aabach Dam Grouting Programme.- 3.2.2 Grouting Programmes in Buntsandstein.- 3.2.2.1 The Grouting Programme at the Haune Dam.- 3.2.2.2 The Antrift Dam Grouting Programme.- 3.2.2.3 The Twiste Dam Grouting Programme.- 3.2.2.4 Conclusions and Recommendations for Grouting Programmes in Buntsandstein and in Similar Rock Types.- 3.2.3 Grouting Programmes in Turonian Limestone of Southeastern Westphalia.- 3.2.3.1 Location, Geology, Hydraulic Routing.- 3.2.3.2 The Grouting Programme in Downtown Paderborn.- 3.2.3.3 The Grouting Programme for the Haxter Valley Bridge.- 3.2.4 The Tavera Dam Grouting Programme in Oligocene Conglomerate.- 3.3 Microscopical Studies.- 3.3.1 Purpose and Origin of Samples.- 3.3.2 Size of the Injectable Voids.- 3.3.3 The Process of Sedimentation, Separation and Drainage of the Excess Water.- 3.3.4 The Influence of the Grouting Pressure (Rock Fracturing).- 3.4 Generally Valid Conclusions from the Analysis of the Grouting Programmes.- 4 Discussion of the Conventional Investigation Methods for Determining Rock Permeability.- 4.1 Introduction.- 4.2 On the Execution, Evaluation and Interpretation of Water Pressure Tests.- 4.2.1 The Layout of the Tests.- 4.2.2 Testing Scheme.- 4.2.3 Several Aspects of the Practical Execution and Evaluation of Water Pressure Tests.- 4.2.3.1 The Pump.- 4.2.3.2 The Packer.- 4.2.3.3 Recording of Test Data.- 4.2.3.4 Evaluation of the Measured Data.- 4.3 Assessment of Current Investigation Methods for Rock Permeability.- 4.3.1 Water Pressure Tests and kf-Coefficient.- 4.3.2 On the Applicability of the Lugeon Criterion; Appropriate Impermeabilization Criteria.- 4.3.3 WPT Rates and the Appraisal of the Specific Rock Permeability.- 4.4 Conclusions.- 5 On Hydraulic Routing in Rock.- 5.1 Introduction.- 5.2 Methods of Researching the Hydraulic Routing in Rock.- 5.3 Influential Factors in the Development of Water Paths in Rock.- 5.4 Discontinuities as Prescribed Water Paths and Their Behaviour During Grouting.- 5.4.1 Preliminary Remarks.- 5.4.2 Bedding Planes.- 5.4.3 Joint Planes.- 5.4.4 Cleavage Planes.- 5.4.5 Faults.- 5.4.6 Dissolution Cavities.- 5.5 The Results of Field Investigations of the Hydraulic Routing.- 5.5.1 Hattelberg Tunnel.- 5.5.2 Oker-Grane Tunnel.- 5.5.3 Outcrops at the Aabach Dam Project.- 5 .5 .3 .1 Preliminary Remarks.- 5.5.3.2 Excavations at the Main Dam.- 5.5.3.3 Karbach Tunnel.- 5.5.3.4 Summary.- 5.5.4 Hydraulic Routing in the Buntsandstein.- 5.5.5 Hydraulic Routing of the Upper Turonian Limestone of Southeast Westphalia.- 5.5.6 Exploratory Addits for a Pump Storage Scheme in Taiwan.- 5.5.7 Outcrops at the Tavera Project.- 5.5.8 Other Indications Concerning Hydraulic Routing.- 5.6 Synopsis of the Percolation Behaviour in Rock.- 5.7 Remarks on Percolation Models and Calculation Methods in Rock Mechanics.- 6 Studies of the Relationship Between the Type of Hydraulic Routing, the Course of the Water Pressure Tests and Grouting Behaviour.- 6.1 Introduction.- 6.2 Tests Using Geologically Defined Models for the Hydraulic Routes Around the Boreholes.- 6.2.1 Prerequisites.- 6.2.2 Description of the Models, Arrangements of the Tests.- 6.2.3 Results of Simulated Water Pressure Tests.- 6.2.4 Results of Simulated Grouting Tests.- 6.3 Interpretation of Simulated Water Pressure Tests and Conclusions.- 6.3.1 Conclusions Concerning the Type of Hydraulic Routing: Direct or Indirect Communication.- 6.3.2 Conclusions Concerning the Size of the Routes in Relation to the Lugeon Criterion.- 6.3.3 Conclusions Concerning the Type of Water Paths Drawn from the Absorption Rates.- 6.3.4 Possibilities for Misinterpreting Water Pressure Tests.- 6.4 Interpretation of Simulated Grouting Tests and Conclusions.- 6.4.1 Required Pressures for Grouting Very Fine Routes, Rock-Type-Specific Groutability.- 6.4.2 The Parallel Grouting of Dissimilar Water Paths.- 6.4.3 Interplay Between Extension and Velocity of Grout Travel, Causes for Buildup of Pressure, Groutability and Grout Takes Dependent upon the Type of the Conductivity, Remaining Permeability.- 7 Practical Field Investigations on Permeability by Means of Water Pressure Tests.- 7.1 Introduction.- 7.2 Rock Fracturing Contingent upon Injection Pressure.- 7.3 Appropriate Maximum Pressures for Water Pressure Tests.- 7.4 The Factor “Time” in Conducting the Water Pressure Tests.- 7.5 Characteristic Water Pressure Tests for Determining the Permeability Behaviour of Different Rock Types.- 7.5.1 Classification of the Water Pressure Tests, “Basic Types”.- 7.5.2 Geological Conditions for the Basic Types of Water Pressure Tests.- 7.5.3 Discussion of Actual Test Diagrams.- 7.5.3.1 Water Pre.ssure Tests in Impermeable Rock (Group 1).- 7.5.3.2 Water Pressure Tests in Rock of Unchangeable Permeability (Group 2).- 7.5.3.3 Water Pressure Tests in Rock of Changeable Permeability (Group 3).- 7.5.3.4 Water Pressure Tests in Rock of Very Changeable Permeability (Group 4).- 7.5.3.5 Time-Dependent Fracturing Processes (P-Q-t-Diagrams).- 7.5.3.6 Conclusions: Catalogue of the Possible Rock Permeabilities Based on the Water Pressure Tests.- 7.6 Comparison of Rock Permeabilities Under the Conditions of Injection and Operation.- 7.7 Water Pressure Tests in Grouted Rocks for Controlling its Success.- 7.8 On the Definition of “Reference” Pressure.- 8 Practical Criteria for Determining Grouting Methods Considering Rock-Type-Specific Groutability.- 8.1 Introduction.- 8.2 Selection of Grouting Pressures in View of the Fracturing Behaviour.- 8.3 Assessing the Rock-Type-Specific Groutability.- 8.3.1 Orientation and Types of Separation Planes Related to the Specific Conditions for Grouting.- 8.3.2 Relationships Between WPT Rates and Grout Takes.- 8.3.3 The “Specific Absorption Rate” as an Indicator for Groutability.- 8.3.4 Mapping Separation Planes from Drill Cores and Their Representation.- 8.3.5 Conclusions Concerning Groutable Permeability and Grouting Pressure.- 8.4 Penetration or Displacement Grouting?.- 8.5 Comments on Setting W/C Ratios.- 8.6 Spacing of Grout Holes, Grouting in Series.- 8.7 Downstage or Upstage Grouting, Schematic or Adapted Execution, Accompanying Water Pressure Tests.- 8.8 Relationship Between the Type of Hydraulic Routing and the Remaining Permeability.- 8.9 Test Grouting.- 9 Practical Criteria for Determining the Tolerable Permeability.- 9.1 Introduction, Hydraulic Fundamentals, Depth of the Curtain, “Tolerable Permeability”.- 9.2 Estimating the Mean Permeability of the Rock for Determining Seepage Losses.- 9.2.1 Problem and Possible Solutions.- 9.2.2 Determining kf by a “Modified Well Method”.- 9.2.3 Determining kf on the Basis of a Coefficient of Infiltration.- 9.2.4 Estimating kf on the Basis of the Inclination of the Groundwater Table.- 9.3 Erodibility.- 9.4 Examples of the Possible Differences Between Groutable and Tolerable Permeabilities.- 9.5 Changes in Permeability and Groutability Due to Comparatively High Storage Levels.- 9.6 The Expenditures for Grouting Programmes Compared with the Degree of Impermeabilization.- 9.7 Summarizing Assessment of the Tolerable Permeability.- 9.8 The Expediency of a Control Gallery Considering Geological Setting and Rock-Type-Specific Groutability.- 9.9 Lateral Extension of the Grout Curtain, Systematic Groundwater Measurements Prior to the Construction of the Dam.- 9.10 Influence of the Type of the Project on the Tolerable Permeability.- 10 The Influence of the Local Geological Setting and the Grouting Measures on the Reduction of Uplift.- 10.1 Introduction.- 10.2 Example: Aabach Dam.- 10.3 Example: Antrift Dam.- 10.4 Example: Tavera Dam.- 10.5 Example: Twiste Dam.- 10.6 Conclusions Concerning the Reduction of the Uplift.- 11 Final Remarks: an Attempt at Guide-Lines.- 11.1 Hydrogeological Scope.- 11.2 Site Investigations by Geological Mapping, Core Drilling, Testing of Both Permeability and Groutability.- 11.3 Control Measures During Impoundment.