Geotechnical Exploration and Evaluation Report

Transcription

1 Geotechnical Exploration and Evaluation Report Pavement Coring and Evaluation UNF Parking Lot 3 Jacksonville, Florida CSI Geo Project No.: Prepared by CSI Geo, Inc St. Johns Bluff Road S., Suite 200 Jacksonville, FL Tel: (904) Fax: (904) Prepared for Arcadis U.S., Inc. August 03, 2018

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3 TABLE OF CONTENTS SECTION PAGE NO. 1.0 Project Information General Project Information 1.2 Existing Conditions and Project Description 2.0 Geotechnical Exploration Field Exploration 3.0 Subsurface Conditions General 3.2 Soil Conditions 3.3 Asphalt Pavement System Thickness 3.4 Groundwater Condition 4.0 Geotechnical Engineering Evaluation and Recommendations Basis for Evaluation & Recommendations 4.2 Evaluation of Existing Parking Lot Asphalt and Limerock Subgrade Soils 4.3 Unsuitable Soils Excavation Backfill and Compaction 4.4 Existing Asphalt Pavement Repair Recommendations 5.0 Report Limitations APPENDICES Site Location Map Field Exploration Plan General Subsurface Profiles Photographs Field Test Procedures i

4 1.0 PROJECT INFORMATION 1.1 General Project Information The site is located at the University of North Florida (UNF) parking Lot 3 in Jacksonville, Florida (Exhibit No. 01). The intent of this geotechnical exploration was to explore the existing subsurface conditions within the entire parking and drives in order to (1) evaluate the condition of the existing pavement, determine the pavement system thickness and the type of soils present; and (2) provide pertinent recommendations for the repaving of the entire pavement system Parking Lot 3 Exhibit No Parking Lot Existing Conditions and Project Description The existing Parking Lot 3 is located south of the College of Education and Human Services Building No. 57 at the University of North Florida. The existing parking lot accommodates an asphalt pavement, which appears to be in poor condition. Our visual observation of the existing asphalt pavement indicated the presence of alligator cracks, block cracks, potholes, raveling, joint failure and pavement lifting (Photo No. 01). Based on the information provided to us, we understand that the University proposes to repave the entire parking Lot 3. Additional photographs of the existing parking pavement are included in the Appendix. UNF Parking Lot 3 Pavement Coring and Evaluation Page 1 of 16

5 Photo No. 01- Northern portion of the existing parking Lot 3 UNF Parking Lot 3 Pavement Coring and Evaluation Page 2 of 16

6 2.0 GEOTECHNICAL EXPLORATION 2.1 Field Exploration The entire parking pavement was cored at eight selected locations (C-1 through C-8). The pavement cores were placed generally at locations where pavement was observed to have experienced raveling, potholes, cracking or lifting. General core locations are presented on the Field Exploration Plan sheet included in the Appendix. At each pavement core location, the subgrade soils were explored by advancing a hand auger to depths of 3 to 5 feet beneath the existing grades in order to determine the type of soils present. Soil samples obtained during the field exploration program were visually classified in the field and then reviewed and reclassified as needed. The General Subsurface Profiles sheet in the Appendix, present the soil classification based on the AASHTO Soil Classification System for each soil type encountered. The stratification lines and depth designations on the General Subsurface Profiles represent the approximate boundaries between soil types. UNF Parking Lot 3 Pavement Coring and Evaluation Page 3 of 16

7 3.0 SUBSURFACE CONDITIONS 3.1 General An illustrated representation of the subsurface conditions encountered in the explored areas is shown on the General Subsurface Profiles sheet included in the Appendix. The soil conditions outlined below highlight the major subsurface stratification. A discussion of field sampling procedures is included in the Appendix. When reviewing the boring profiles and the subsurface conditions outlined below, it should be understood that the soil conditions may vary between boring locations and that the transition between soil strata may be gradual. 3.2 Soil Conditions Review of the General Subsurface Profiles indicates that the existing pavement system within the explored areas consists of 0.5 to 2 inches of asphalt over 6 to 15 inches of limerock base, followed by fine sands (A-3) until the boring termination depth of 3 to 5 feet below the existing grades. The subsurface conditions encountered at core locations C-1 and C-6 consist of unsuitable organic soils (A-8 based on the AASHTO Soil Classification System) mixed with large roots and many wood pieces (Photos Nos. 02 and 03). Location C-1 encountered a 2.5 feet thick layer of unsuitable soils at a depth of 1.5 feet below the existing grade. Location C-6 encountered a 6- inch layer of unsuitable soils directly beneath the limerock base material and another 2 feet thick layer at a depth of 2.5 feet below the existing grade. Generally, the unsuitable organic soils (A- 8) mixed with large roots and wood pieces appear to be highly erratic in nature. It is emphasized that due to the erratic nature of these soils, the thickness and depth of the unsuitable material may vary from those noted herein, and that in some locations the unsuitable material may be deeper. It is also noted that pavement core C-7, performed within the area which was previously explored in 2017 (UNF Lot 3 Pavement Distress Investigation Report, CSI Geo Project No , dated June 05, 2017) and appeared to have been recently patched, encountered construction debris (as before) consisting of trash directly beneath the asphalt pavement (Photo Nos. 04 and 05). It appears that during the recent repairs of the pavement section, the limerock base surface in this portion of the parking area was not properly cleaned and made free of construction debris prior to placement of the new asphalt layer. UNF Parking Lot 3 Pavement Coring and Evaluation Page 4 of 16

8 Photo No. 02 C-1 location showing unsuitable organic soils mixed with large roots and wood pieces. Photo No C-6 location showing unsuitable organic soils mixed with wood pieces. UNF Parking Lot 3 Pavement Coring and Evaluation Page 5 of 16

9 Construction Debris directly underneath the asphalt pavement layer Photo No. 04 Previously explored and patched area showing debris beneath the asphalt pavement Construction Debris directly underneath the asphalt pavement layer Photo No. 05 Previously explored and patched area showing debris beneath the asphalt pavement UNF Parking Lot 3 Pavement Coring and Evaluation Page 6 of 16

10 3.3 Asphalt Pavement System Thickness The table below summarizes the existing pavement system thickness and crack depths. Existing Pavement System Thickness and Crack Depth Core Material Layer Thickness Pavement Crack Depth (ft), Description & AASHTO No. Asphalt Limerock Depth Classification of Soil Beneath Limerock Base (in) (in) (in) Fine Sand (A-3) C Organic Fine Sand (A-8)* Fine Sand (A-3) C Fine Sand (A-3) C Fine Sand (A-3) C Fine Sand (A-3) C Fine Sand (A Organic Fine Sand (A-8)* C Fine Sand (A-3) Organic Fine Sand (A-8)* Fine Sand (A-3) C Fine Sand (A-3) C Fine Sand (A-3) Note * Should be regarded as unsuitable due to the organic contents mixed with large roots and wood pieces 3.4 Groundwater Conditions The groundwater level was measured and recorded as encountered at the time of drilling. The depth of groundwater level was measured to be about 2.8 to 3.3 feet below the existing grades. The depths of the groundwater levels at the boring locations are marked on the General Subsurface Profiles sheets in the Appendix. UNF Parking Lot 3 Pavement Coring and Evaluation Page 7 of 16

11 Fluctuations of the groundwater levels should be anticipated as a result of topographic changes, seasonal climatic variations, surface water runoff patterns, fluctuations of adjacent water bodies, and other factors. During seasonal high precipitation, groundwater levels can be expected to rise above the levels recorded during this exploration. Therefore, design should account for the possibility of groundwater level variations and based on the assumption and such variations will occur. UNF Parking Lot 3 Pavement Coring and Evaluation Page 8 of 16

12 4.0 GEOTECHNICAL ENGINEERING EVALUATION AND RECOMMENDATIONS 4.1 Basis for Evaluation & Recommendations The geotechnical evaluation as presented in this report is based on our site observations, field data obtained, and our understanding of the project information as previously described in this report. The discovery of site and/or subsurface conditions during construction that deviate from the data obtained in this exploration should be reported to CSI Geo, Inc. (CSI Geo) for evaluation and review. 4.2 Evaluation of Existing Parking Lot Asphalt and Limerock The thickness of the existing asphalt layer ranged from 0.5 and 2 inches with an average of 1.1 inches. Generally, the asphalt pavement was found to be in poor condition. Our visual observation of the asphalt pavement indicated the presence of alligator cracks, block cracks, potholes, raveling, and lifting as shown on additional photos included in the Appendix. Based on the results of our exploration, the critical distress cracks mostly included full depth cracks and some partial depth cracks, which were found to range from 0.3 to 1.5 inches deep with an average of 0.9 inches (Photos Nos. 06 through 10). A summary table of the existing asphalt thickness and crack depths is presented in Section 3.3 of this report. Pavement cracks and potholes were noticed along certain portions of the parking area, especially along the pavement joints (Photo No. 11), most notably along the drives. It appears that the surface water run off patterns of the existing parking lot are towards the pavement joints, which, if not properly sealed result in seepage of surface water and formation of flow channels directly beneath the asphalt layer, which eventually undermines the structural integrity of the pavement system, leading to pavement cracks, failure and potholes. UNF Parking Lot 3 Pavement Coring and Evaluation Page 9 of 16

13 Photo No. 06 Pavement Core C-1 Photo No. 07 Pavement Core C-2 UNF Parking Lot 3 Pavement Coring and Evaluation Page 10 of 16

14 Photo No. 08 Pavement Core C-4 Photo No. 09 Pavement Core C-5 UNF Parking Lot 3 Pavement Coring and Evaluation Page 11 of 16

15 Photo No. 10 Pavement Core C-8 Photo No. 11 Surface water run off along the existing failed asphalt joints and cracks UNF Parking Lot 3 Pavement Coring and Evaluation Page 12 of 16

16 Furthermore, based on the results of our findings in the area of pavement core C-7 (Photo Nos. 04 and 05), it is our opinion that the cause of the pavement surface lifting and cracking within the previously explored and recently patched area can be attributed to the presence of construction debris or trash still left directly beneath the asphalt layer. It appears that the existing limerock base surface was not properly cleaned and made free of construction debris prior to placement of the most recent asphalt layer Subgrade Soils Based on the findings of our geotechnical exploration, and evaluation of the subsurface conditions, it was discovered that certain areas of the existing parking lot are underlain by organic material mixed with large roots and wood pieces. Generally, the unsuitable organic soils mixed with large roots and wood pieces appear to be highly erratic in nature and extend to depths of 4 and 4.5 feet at C-1 and C-6 respectively. It is emphasized that due to the erratic nature of these soils, the thickness and depth of the unsuitable material may vary between boring locations and from those noted herein, and that in some locations the unsuitable material may be deeper. Due to the presence of unsuitable organic material mixed with large roots and wood pieces, it is our opinion that the areas of C-1 and C-6 may experience pavement surface subsidence in the near future. The unsuitable organic material mixed with large roots and wood pieces often undergo slow long term settlements mainly under its own weight unless it is removed and replaced with clean compacted sands. The presence of organic material mixed with large roots and wood pieces would typically cause small cavities or voids bridged by large objects. Surface loading and water seepage combined with decay of the roots and wood pieces generally result in gradual undermining of the large objects which tend to result in sudden or long term surface depressions or unevenness. Furthermore, C-7 encountered construction debris directly beneath the asphalt pavement. Construction debris left directly beneath the asphalt layer will often prevent the bonding of asphalt to the limerock base surface and create voids beneath the asphalt layer. The presence of construction debris and voids directly beneath the asphalt, subsequently, create channels for UNF Parking Lot 3 Pavement Coring and Evaluation Page 13 of 16

17 water to accumulate. At high temperatures, steam from the accumulated water creates bubbles and air pockets causing lifting and cracking of the pavement surface. 4.3 Unsuitable Soils Excavation Backfill and Compaction We recommend that the encountered organic material mixed with large roots and wood pieces should be removed in their entirety and replaced with clean compacted sands. Depending on the groundwater level during construction, groundwater control may be required during the removal of the unsuitable material so that the process may be performed in the dry condition. Undercutting below the groundwater level could result in inadequate removal of the unsuitable material and could make backfill placement and compaction very difficult. Upon satisfactory completion of the removal of unsuitable soils, backfill should then be placed in lifts not exceeding 12 inches. Each lift of fill should be compacted until densities equivalent to at least 95 percent of the Modified Proctor maximum dry density are uniformly obtained. Fill material should consist of an inorganic, non-plastic, granular soil containing less than 10 percent material passing through the No. 200 mesh sieve (relatively clean sand with an AASHTO Classification of A-3). 4.4 Existing Asphalt Pavement Repair Recommendations Based on the results of our exploration, the existing asphalt thickness ranges from 0.5-inch to 2 inches with an average of about 1.1 inches. The depth of pavement cracks was found to range from 0.3 to 1.5 inches deep with an average of 0.9 inches. The majority of the observed cracks extend to full depth. It is therefore our opinion that partial depth milling of the existing pavement will not remove all the cracks. If left in place, these cracks will eventually reflect through the new asphalt layer to the surface. The average thickness of the existing pavement is just about 1 inch with some areas of just 0.5- inch thick asphalt. This leaves no room for sufficient milling without getting into and disturbing the limerock base. Also, milling the existing pavement by less than 1 inch will not provide enough room for resurfacing with adequate thickness without having to modify the existing surrounding curb profiles. UNF Parking Lot 3 Pavement Coring and Evaluation Page 14 of 16

18 Based on the results of our investigation, we strongly recommend that the pavement replacement steps include the following: 1. Remove the entire existing asphalt pavement layer. 2. Rework and recompact the existing limerock base. Without modifying the existing curb profiles, plane the limerock layer to just enough to provide room for at least 1.5 inches thick of new asphalt pavement. 3. Prior to placement of the new asphalt layer, the exposed limerock base should be proofrolled and any yielding areas should be removed and replaced with compacted limerock material. The limerock base should be compacted to at least 98 percent of its Modified Proctor maximum dry density. 4. A 1-1/2 (minimum) inch layer of Type III (or FDOT Type S-1) asphalt concrete having a minimum marshall stability of 1,000 pounds is recommended for a wearing surface in automobile access road and parking areas. For heavy traffic areas, truck parking and drive areas, 2 inches of Type III or Type S-1 asphalt concrete is recommended. The asphalt concrete layer shall be compacted to at least 96 percent of laboratory density. UNF Parking Lot 3 Pavement Coring and Evaluation Page 15 of 16

19 5.0 REPORT LIMITATIONS The subsurface exploration program including our evaluation and recommendations was performed in general accordance of accepted geotechnical engineering principles and standard practices. CSI Geo is not responsible for any independent conclusions, opinions, or interpretations made by others based on the data presented in this report. This report does not reflect any variations that may occur adjacent or between soil borings. The discovery during construction of any site or subsurface condition that deviate from the findings and data as presented in this report should be reported to CSI Geo for evaluation. We recommend that CSI Geo be given the opportunity to review the final design drawings and specifications to ensure that our recommendations are properly included and implemented. UNF Parking Lot 3 Pavement Coring and Evaluation Page 16 of 16

20 APPENDIX

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24 Existing pavement showing joint failure and pavement raveling

25 Existing pavement showing pavement raveling

26 Existing pavement showing joint failure, pavement raveling and potholes

27 Existing pavement showing pavement raveling and cracks

28 Existing pavement showing severe potholes

29 Existing pavement showing pavement raveling, cracks and potholes

30 Existing pavement showing cracks

31 Existing pavement showing raveling and severe cracks

32 Existing pavement showing raveling, cracks and potholes

33 Existing pavement showing raveling and severe cracks

34 Previously explored and patched area showing pavement lifting and cracking

35 Core location C-7 within previously explored and patched area

36 FIELD TEST PROCEDURES Auger Borings The auger borings were advanced by the use of a hand auger. The soils encountered were identified in the field from the cuttings brought to the surface by the augering process. Representative soil samples were placed in glass jars and transported to our laboratory where they were examined by a geotechnical engineer to confirm field classifications.

37 SERVICES OFFERED Geotechnical & Foundations Engineering Construction Materials Testing (CMT) Construction Engineering & Inspection (CEI) 2394 St. Johns Bluff Road, Suite 200. Jacksonville, FL (904) Phone (904) Fax