Geological Environment and Engineering Properties of Caliche in the Tucson Area, Tucson, Arizona
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Geological environment and engineering properties of caliche in the Tucson area, Tucson, Arizona Item Type text; Thesis-Reproduction (electronic); maps Authors Cooley, Donald B., 1937- Publisher The University of Arizona. Rights Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author. Download date 26/09/2021 19:56:34 Link to Item http://hdl.handle.net/10150/551826 GEOLOGICAL ENVIRONMENT AND ENGINEERING PROPERTIES OF CALICHE IN THE TUCSON AREA, TUCSON, ARIZONA by Donald B. Cooley A Thesis Submitted to the Faculty of the DEPARTMENT OF GEOLOGY In Partial Fulfillment of the Requirements For the Degree of MASTER OF SCIENCE In the Graduate College THE UNIVERSITY OF ARIZONA 19 6 6 STATEMENT BY AUTHOR This thesis has been submitted in partial fulfillment of requirements for an advanced degree at The University of Arizona and is deposited in the University Library to be made available to borrowers under rules of the Library. Brief quotations from this thesis are allowable without special permission, provided that accurate acknowledgment of source is made. Requests for per mission for extended quotation from or reproduction of this manuscript in whole or in part may be granted by the head of the major department or the Dean of the Graduate College when in his Judgment the proposed use of the material is in the interests of scholarship. In all other instances, however, permission must be obtained from the author. SIGNED! 'f APPROVAL BY THESIS DIRECTOR This thesis has been approved on the date shown below; Date Professor of Mining and Engineering Geology AKNOWLEDGMENTS I should like to thank the many people who have given so freely of their time in my behalf. I should like to thank especially Dr. W. C. Lacy, Dr. J. s. Sumner, and Dr. L. K. Lustig for their guidance and helpful criticisms in the form and content of this thesis. The base map was supplied by the University of Arizona Agricultural Engineering Department. In particular I would like to thank Mr. James Post for his help in the laboratory portion of this study. I also thank my brother Steven for swinging a 12 pound hammer in the hot sun, and my wife for all her invaluable aid in this project. ill TABLE OF CONTENTS Page ABSTRACT vili INTRODUCTION 1 Location Environment Methods of study -prtvro PREVIOUS WORK 7 Mode of Deposition 7 Physical Characteristics 10 Physiographies Relations 13 Cementation 16 Relation to Rainfall 18 Age Determinations 19 TERMINOLOGY 20 DESCRIPTION AND DISTRIBUTION 26 Alluvial Fans 26 Caliche on Sentinel Peak 32 SAMPLE TESTING PROCEDURES 35 GEOPHYSICAL INVESTIGATIONS 40 THE CALICHE PROFILE 48 Growth of the Caliche Profile 50 Source of Cementing Agents 54 CALICHE AND ENGINEERING 57 CONCLUSIONS AND RECOMMENDATIONS 61 Conclusions 61 Recommendations 64 USES OF CALICHE 66 iv V Page REFERENCES CITED 68 APPENDIX Typical Caliche Profile-Pinal Soil Series 74 Selected Seismic Velocities in the Caliche 75 Seismic Velocities and Rippability of Materials 77 Selected Bibliography 80 LIST OF ILLUSTRATIONS Figure Page I PHYSIOGRAPHIC UNITS OF THE TUCSON AREA 14 II CALICHE-GROUND SURFACE RELATIONSHIPS 25 III ISOPACHOUS MAP OF THE SUBSURFACE CALICHE IN THE TUCSON AREA 31 IV SEISMIC VELOCITY CURVE; 14TH STREET AT TULLER SCHOOL 45 V SEISMIC VELOCITY CURVE; CORNER OF SPEEDWAY AND CAMPBELL AVENUE 46 VI SEISMIC VELOCITY CURVE; SOUTHWEST CORNER OF SPEEDWAY AND QUEEN AVENUE 4? VII GENERALIZED CALICHE PROFILE 49 VIII ILLUSTRATION OF TYPICAL CALICHE PROFILE- FINAL SOIL SERIES 74 IX RELATION BETWEEN CARBONATE CONTENT AND UNCONFINED COMPRESSIVE STRENGTHS OF CALICHE 78 X RELATION BETWEEN CARBONATE CONTENT AND INFILTRATION RATE 79 XI MAP OF SURFACE AND NEAR SURFACE CALICHE DISTRIBUTION IN THE TUCSON AREA (in pocket) vi LIST OF TABLES Table I UNCONFINED COMPRESSIVE STRENGTHS OF SOME CALICHE SAMPLES IN THE TUCSON AREA II RIPPING, COST, PRODUCTION BY SHOCK WAVE VELOCITIES III RIPPABILITY VELOCITY CHART IV SELECTED SEISMIC VELOCITIES AND LOCATIONS V SEISMIC VELOCITIES AS RELATED TO RIPPABILITY OF MATERIALS ABSTRACT The caliche in the Tucson area is present at or near the surface in much of the area, and is more indurated at the toe of the fans than near the apex or in the interior. The caliche caps most of the ridges and is probably responsible for their preservation as ridges as the fans are dissected. Seismic velocities range from 1000 fps to 4500 fps for the caliche and unconfined com pressive strengths range from 200 to 300 psl to 2500 to 3000 psl depending on the orientation of the sample during testing and the type of caliche present. The seismic velocities are related to the thickness of the cap and to the continuity of the cap. The caliche profile is one of increasing carbonate cementation from the bottom to the top of the profile. Caliche development on the fans is due to the weathering of limestones in the drainage area and limestone fragments carried onto the fan. The carbonate material may be trans ported many times before it becomes fixed into the caliche profile. The significance of the caliche to engineering projects is primarily the increased cost of excavation. viii INTRODUCTION In the Tucson area, caliche is present in many places at or near the surface of the ground. The presence of caliche at a construction site usually in creases the cost of excavation. A knowledge of where caliche might be encountered and how difficult it may be to excavate would be of value to a contractor in estimating costs and assigning equipment. This report is a preliminary study of some engineering properties of the caliche and methods used to predict the excavation properties of the caliche. Some seismic velocities have been determined for the caliche, and an attempt to correlate them with equipment requirements for excavation of the caliche has been made. In addition, some unconflned compressive strengths have been determined for a few caliche samples. The map in the pocket shows distribution of the caliche at or near the surface. The degree of induration seems to be related to the physiography of the area. At least two environments of deposition are present in this area; one is on the alluvial fans in the basin, and the other is in the basic volcanic rocks to the west of Tucson. 1 2 Location The area under study is essentially within the Tucson Quadrangle (32° 001 to 32° 15* North latitude; 110° 45* to 111° 00* West longitude), in and around the city of Tucson, Pima County, Arizona. The area is bounded by the Santa Cruz River on the west, Rillito Creek on the north, Pantano Wash on the east, and the southern limit of the fan on which Tucson is located, on the south. Small areas just east of Pantano Wash and on Sentinel Peak were examined. The caliche distribution map is prepared for the entire area but the analysis of engineering properties pertains to the northern half of the area. This is primarily because most of the active and projected con struction is taking place in the northern part of the area. Environment The Tucson area is typical of most of the country in the desert portion of the southern part of the Basin and Range province. The central portion of the area is a structural and sedimentary basin with gentle slopes rising to the mountains that surround the area. Caliche is present at or very near the surface of these slopes. 3 The climate is semi-arid with an average of about ten inches of precipitation per year. Most of this occurs as thunder showers, and a great amount of sediment is carried in the washes after major rains. In this climate, the storm runoff is more devastating than would be the case if more vegetative cover was present and storm erosion is more pronounced. The vegetation of the area, which is adapted to a dry climate and has a minimum of leaves, offers little protection to the soil from the rains. Within the area, creosote bush, cacti, and rabbitbrush are dominant (Shreve and Mallory, 1933)• Because of the warm climate and the tendency for the water which is not carried away in the washes to be spread out over the surface in thin layers, much of the water is evaporated and recharge takes place primarily along the bottoms of the washes following the rains. The major drainage of the area is the Santa Cruz River which flows northward along the west side of the basin. Rillito Creek and its tributary, Pantano Wash, drain into the Santa Cruz River in the northwest comer of the area. The streams now run along the edges of the basin at approximately the contact between the alluvial fill and the rocks of the surrounding mountains. 4 The area has been one of aggradation Interspersed with short periods of erosion. Bryan (1925) has dated the present period of channel entrenchment in this area as beginning in the 1880's or about the time man intro duced large herds of grazing animals into the area. When the Army moved into Fort Lowell (1872), the area along Rillito Creek supported a heavy stand of willow and cottonwood, and grass hay was very abundant. At that time, the water table was within twenty feet of the sur face. The water table is now being depressed by withdrawal of groundwater for use in Tucson and surrounding areas. Methods of Study The field work for this study was undertaken during the summer of 1965 and a total of 73 days was spent in the field observing exposures and collecting samples.