The Pennsylvania State University The Graduate School College of Engineering THE EXPANSIVE EFFECTS OF CONCENTRATED PYRITIC ZONES IN SHALES OF THE MARCELLUS FORMATION A Dissertation in Civil Engineering by Shad E. Hoover © 2008 Shad E. Hoover Submitted in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy May 2008 The dissertation of Shad E. Hoover was reviewed and approved* by the following: Mian C. Wang Professor of Civil and Environmental Engineering Dissertation Adviser Chair of Committee Brian A. Dempsey Professor of Civil and Environmental Engineering Angelica M. Palomino Assistant Professor of Civil and Environmental Engineering Susan Trolier-McKinstry Professor of Ceramic Science and Engineering David Lehmann Professional Geologist – Environmental Resources Management Special Member Peggy A. Johnson Professor of Civil and Environmental Engineering Head of the Department of Civil and Environmental Engineering *Signatures are on file in the Graduate School. ii ABSTRACT Expansive pyritic shales have caused untold amounts of damage to civil infrastructure throughout the world. The traditional characterization of potentially expansive pyritic shales only considers the presence of finely disseminated microscopic pyrite and references to case histories. The research presented in this paper shows that concentrated pyritic zones can have a significant impact on establishing microenvironments that are conducive to the production of heave inducing sulfates. Oxidation tests are conducted in a laboratory environment to assess the potential to form heave inducing sulfates through swell measurements and geochemical markers. Simple swell modeling is simulated with the PHREEQC geochemical computer program and a regression analysis of shale with significant gypsum infilling verifies calcite and pyrite concentrations. A detailed case history of micropile underpinning over expansive pyritic shales highlights the challenges associated with extensive structural remediation. The O2 diffusion controlled oxidation process in calcareous shales with finely disseminated pyrite is impractically slow under intense conditions and does not adequately explain how gypsum infilling can occur over time periods of less than a decade. Geochemical laboratory testing and theoretical modeling suggest that an acidic or low pH environment is not possible with a significant presence of calcite with zones of availability. Gypsum is most likely to crystallize in a low pH environment when highly oxidative conditions are present. The research shows that microenvironments within highly concentrated pyritic zones more adequately explain the acidic conditions necessary that lead to accelerated oxidation. Acidic capillary pore water, which is not subject to flushing by a fluctuating or flowing water table through the vadose zone, iii influences the calcareous microfractures and discontinuities resulting in the crystallization of sulfates. iv TABLE OF CONTENTS LIST OF TABLES .................................................................................................. viii LIST OF FIGURES ..................................................................................................x LIST OF MATHGRAMS ....................................................................................... xvi ACKNOWLEDGEMENTS ................................................................................... xvii Chapter 1. INTRODUCTION ..................................................................................1 1.1 General ...................................................................................................1 1.2 Microenvironmental Considerations ......................................................3 1.3 Thesis Organization ...............................................................................5 Chapter 2. LITERATURE REVIEW .......................................................................8 2.1 Introduction ............................................................................................8 2.2 Pyritic Bedrock Geology.......................................................................10 2.3 Pyrite Oxidation and Sulfate Precipitation Chemistry ..........................15 2.4 Weathering of Pyritic Shales ................................................................20 2.5 Identification of Potentially Expansive Pyritic Shales ..........................21 2.6 Pyritic Sulfur Identification Techniques ...............................................22 2.6.1 Munsell Color Guidelines ......................................................23 2.6.2 Static Laboratory Testing Techniques ...................................24 2.6.3 Kinetic Laboratory Testing Techniques .................................26 2.7 Laboratory Testing Methods – Swell Test ............................................27 2.8 Remnant Stresses and Horizontal Fracturing ........................................28 Chapter 3. CHEMICAL AND PHYSICAL EXPLANATIONS ............................32 3.1 Introduction ...........................................................................................32 3.2 Materials and Methods ..........................................................................33 3.2.1 Experiments Using 30% H2O2 ...............................................33 3.2.2 Experiments Using 10% H2O2 ...............................................34 3.3 Results ...................................................................................................36 3.3.1 Experiments Using 30% H2O2 ...............................................36 3.3.2 Experiments Using 10% H2O2 ...............................................39 3.4 Microscopic Observations ....................................................................41 3.5 Conclusions ...........................................................................................43 Chapter 4. PHREEQC HYDROGEOCHEMICAL TRANSPORT MODEL .........45 4.1 Introduction ...........................................................................................45 4.2 Irreversible Reaction Model .................................................................46 4.2.1 Introduction ............................................................................46 4.3 Input Parameters ...................................................................................48 4.3.1 First Run (0.1% S2 and 5% CaCO3 ........................................48 4.3.2 Second Run (0.5% S2 and 5% CaCO3 ...................................48 v 4.3.3 Third Run (Concentrated FeS2 and 5% CaCO3 .....................48 4.4 Results ...................................................................................................49 4.4.1 Moles in Assemblage and Volume Change ...........................49 4.4.2 Swell Model ...........................................................................51 4.5 Conclusions ...........................................................................................53 Chapter 5. EMPIRICAL REGRESSION MODEL ................................................59 5.1 Introduction ...........................................................................................59 5.2 Observational Data ................................................................................59 5.3 Experimental Data ................................................................................65 5.3.1 Image Analysis.......................................................................65 5.3.2 Measurements ........................................................................68 5.4 Regression Analysis ..............................................................................69 5.5 Conclusions ...........................................................................................70 Chapter 6. GEOTECHNICAL LABORATORY STUDIES ..................................75 6.1 Introduction ...........................................................................................75 6.2 Materials and Methods ..........................................................................76 6.2.1 Controlled Experiments with Bacterial Oxidation .................76 6.2.1.1 Bacterial Preparation Procedure .............................76 6.2.1.2 Swell Experiment Procedure ...................................78 6.2.2 Swell Experiments Using Kinetic Oxidation Techniques .....81 6.2.2.1 Swell Experiments Procedure .................................81 6.3 Results ...................................................................................................87 6.3.1 Controlled Experiments with Bacterial Oxidation .................87 6.3.2 Swell Experiments Using Kinetic Oxidation Techniques .....89 6.4 Conclusions ...........................................................................................96 6.4.1 Controlled Experiments with Bacterial Oxidation .................96 6.4.2 Swell Experiments Using Kinetic Oxidation Techniques .....97 Chapter 7. CASE HISTORY: MICROPILE UNDERPINNING OVER EXPANSIVE PYRITIC SHALES .......................................................100 7.1 Introduction ..........................................................................................100 7.2 Shale Expansion History ......................................................................105 7.3 Field and Laboratory Investigations ....................................................106 7.3.1 Field Investigation ................................................................106 7.3.2 Laboratory Testing ................................................................109