A Geologic Investigation of Foundation Failures in Small Buildings in Tucson, Arizona
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A geologic investigation of foundation failures in small buildings in Tucson, Arizona Item Type text; Thesis-Reproduction (electronic) Authors Crossley, Robert William, 1946- 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 03/10/2021 18:41:45 Link to Item http://hdl.handle.net/10150/554059 A GEOLOGIC INVESTIGATION OF FOUNDATION FAILURES IN SMALL BUILDINGS IN TUCSON, ARIZONA by Robert W. Cross!ey A Thesis Submitted to the Faculty of the DEPARTMENT OF MINING AND GEOLOGICAL ENGINEERING In Partial Fulfillment of the Requirements For the Degree of MASTER OF SCIENCE WITH A MAJOR IN GEOLOGICAL ENGINEERING In the Graduate College THE UNIVERSITY OF ARIZONA 1 9 6 9 STATEMENT DY AUTHOR This thesis has been submitted in partial fulfillm ent of require ments 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 permission for extended quotation from or reproduction of th is m anuscript in whole or in p a rt may be granted by the head o f 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 a ll other instances, however, permission must be obtained from the author. SIGNED: Lu~ APPROVAL BY THESIS DIRECTOR This thesis has/been approved on the date shown below: D ateDR. W ./JZ LACY DateDR. W Professorfessc of Mining and Geological Engineering ACKNOWLEDGMENTS The writer is grateful to Doctor W. C. Lacy who suggested this topic and served as thesis advisor, and to Doctor W. C. Peters and Doctor 0. F. Abel who served on the committee. Data on subsurface geology by Mr. R. W. D avis, Mr. R. S t r e it z , and Mr. E. F. Pashley was essential to the analysis of results, as were the hydrologic maps provided by The University of Arizona Department of Agricultural Engineer ing. The w riter also wishes to acknowledge information and suggestions by members of the City's Inspections Department and by several local engineers and c o n tracto rs. i i i TABLE OF CONTENTS Page LIST OF ILLUSTRATIONS............................................................................................ v i ABSTRACT......................................................................................................................... v i i i 1. INTRODUCTION....................................................................................................... 1 1.1 Purpose................................................................................................ 1 CM CM CM CO VO ID LO CO 1.2 Procedure......................................... 1.3 Previous Work................................ 2. GEOGRAPHY OF THE TUCSON BASIN................ 2.1 The Basin and Range Province 2.2 The Tucson Basin......................... 2.3 Geology of the Ranges.............. 2 .4 The Basin F i l l .............................. 3. INVESTIGATION OF FOUNDATION PROBLEMS IN TUCSON........................... 9 3.1 Explanation of Terms................................................................. 9 3.2 Results of Investigation ........................................................ 10 3.3 Possible Explanations............................................................... 11 4. GEOLOGIC HISTORY OF THE TUCSON BASIN................................................ 14 4.1 The Paleozoic Era ........................................................................ 14 4 .2 The Mesozoic E ra ................................................................. 14 4.3 The Early Tertiary Period ...................................................... 15 4 .4 The Basin and Range Orogeny.................................................. 16 4.5 Post-Orogenic Activities in the Tucson Basin............ 19 4.6 The Pleistocene Epoch............................................................... 21 4 .7 Recent Geologic H is to ry ........................................................... 22 5. INFLUENCE OF GEOLOGY AND HYDROLOGY ON FRACTURE PATTERNS.... 24 5.1 Role o f Terrace D eposits......................................................... 24 5 .2 Role o f C ollapsing S o il........................................................... 28 5 .3 Role o f C a lic h e ............................................................................. 30 iv V TABLE OF COHTENTS-Continued Page 5 .4 Role o f Ground Water D e p le tio n ........................................... 31 5.5 Role of Basement Geology and Tectonic Activity.... .43 5.6 Results of the Geologic Investigation ........................... 44 6. ENGINEERING ASPECTS OF FOUNDATION FAILURE...................................... 47 6.1 Ground In s t a b ilit y and the P u b lic .................................... 47 6.2 Recommendations for Zoning and Planning....................... 49 6.3 Recommendations for Building Codes.................................. 50 6.4 Recommendations for U tilitie s ............................................. 52 6 .5 Future Foundation Problems in Tucson.............................. 53 7. SUMMARY AND CONCLUSIONS............................................................................... 56 REFERENCES 57 LIST OF ILLUSTRATIONS Figure Page la . Cross Section Showing T ra d itio n a l Basin and Range C o n fig u ra tio n ............................................................................................ 4 lb . Map Showing Geologic Provinces o f the Southwest................ 4 2. Basement Depth Contour Map of the Tucson Basin (from R. W. D a v is ).............................................................................................. 8 3. Map Showing Areas o f Foundation F a ilu re s in Tucson............ 12 4. Map Showing Fracture Pattern Superimposed on Terraces in Tucson (Terraces by G. Smith, 1938).................................... 2G 5. Isopacheous Map Showing C aliche D is trib u tio n in Tucson ( a f t e r R. S t r e i t z ) ................................................................................. 32 6. Ground Water Table Contour Map (Based on Data from Department o f A g ric u ltu ra l Engineering, 1 96 7)..................... 35 7. Isopacheous Map of Sediments Dewatered in Tucson from 1947 to 1967 (from Department of Agricultural Engineer in g ) ................................................................................................................ 37 8. Cross Section Through Severely Fractured Area in Tucson (subsurface data by Robert S treitz) ........................................... 39 9. Cross Section Through Severely Fractured Area (subsur face data by Robert S t r e i t z ) ........................................................... 40 10. Cross Section Through Trouble-Free Area in Tucson (subsurface data by Robert S treitz) ........................................... 41 11. Lithofacies Map of Dewatered Sediments (1947-1967)......... 42 12. S tru c tu ra l Contour Map Showing Contact Between R illito Beds and Quaternary Basin Fill (from Pashley).. 45 LIST OF ILLUSTRATIONS-Continued Figure Page 13. Map Showing Zones L ik e ly to Experience Land Subsi dence in .th e F u tu re............................................................................... 54 14. Intensity Pattern of Building Foundation Failures in In Tucson, A rizo n a ........................................................................................ Pocket ABSTRACT Buildings in certain areas in Tucson are subject to damage in the form of cracked foundations, walls, and floors, The cause is presumed to be d if f e r e n t ia l movement re s u ltin g from ground in s t a b ilit y . During the summer of 1968 the w riter inspected small buildings throughout Tucson, noting the location and severity of cracks in walls and foundations. Zones of greatest intensity of foundation failures are located on the Cemetery Terrace and can be correlated with layers of subsurface sand from which ground water has been withdrawn within the last decade. Ground in s t a b ilit y is re la te d to regional and lo cal geology. The two major causes of foundation problems in Tucson are believed to be (1) pockets of low density unstable soils which were deposited in a water deficient environment and which experience a great loss of volume under conditions of saturation and loading, and (2) land subsi dence caused by increased effective stress on subsurface strata which have been dewatered. v i i i 1. INTRODUCTION Late one summer a family returned from vacation to their fashion able east Tucson home to find that their backyard patio had been reduced to a mass of concrete rubble, a side wall had completely collapsed, and a portion of the footings had settled more than a foot. The expensive home lay on a terrace above Pantano Hash. It was a one story structure, only a few years old, and built by a reputable contractor. Many people have the mistaken impression that foundation failures must be associated w ith v is ib ly unstable te r r a in , such as swamps, peat bogs, land-shore interfaces, and regions subject to earthquakes and land slides. The soils of the semi-arid Southwest appear firm