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HomeMy WebLinkAboutGeotechnical Report 520 S. Main Street, Suite 2531 ● Akron, OH 44311 ● Tel: 330.572.2100 ● Fax: 330.572.2101 www.gpdgroup.com GPD Group, Inc. GEOTECHNICAL REPORT BU Number: 873711 Site Name: Carmel-Springmill Site Data: 635 West 131st Street Carmel (Hamilton County), Indiana 46032 Latitude 39° 58' 37.20'' N, Longitude 86° 10' 10.50'' W Proposed 150-ft Monopole GPD Group is pleased to submit this Geotechnical Report for the aforementioned tower. It is our understanding that the existing monopole will be replaced with a new monopole. The purpose of the following report is to summarize the soil/rock conditions encountered during the subsurface exploration at this site and provide geotechnical engineering parameters for the design of the proposed foundation system. We at GPD Group appreciate the opportunity to provide continuing professional services to you. Please feel free to contact us with any questions or if you need additional assistance. Respectfully Submitted, Delbert J. Channels, P.E. GPD Group, Inc. Attachments: Boring Location Plan Boring Log Atterberg Limits’ Results Photographs Unified Soil Classification System General Notes Previous Boring Log – (Doc ID 1348387) GPD# 2022777.873711.04 February 25, 2022 02/25/2022 Proposed 150-ft Monopole BU Number: 873711 2/25/2022 Page 2 REGIONAL AND SITE GEOLOGY The United States Department of Agriculture (“USDA”) Soil Survey of Hamilton County, Indiana, and the United States Geological Survey (“USGS”) maps were reviewed to assess the subsurface geology and sedimentary makeup of the site location, as well as the topography of the region. The site is located in a cleared area of woods and the ground surface is relatively flat. The surrounding area is comprised of gently rolling hills with trees, and the existing tower site is adjacent to an existing electrical substation. The site elevation ranges from about 860 to 861 feet above sea level. The frost depth in this region is 40 inches per NAVFAC DM 7.01. According to the USDA, the surficial soils in this area consist primarily of silt loam from the Shoals and Crosby soil groups. The silt loam indicates a high concentration of silt and sand with clay deposits in the topsoil. Recent deposits of sand and gravel are also present throughout the area depending on the proximity to rivers and streams. USGS maps show that the underlying bedrock in the Muscatatuck Group consists of Devonian-aged dolostone and limestone. SEISMIC SITE CLASSIFICATION The International Building Code (IBC) requires a site soil profile determination extending to a depth of 100 feet for seismic site classification. The scope of services for this project required that borings be drilled to a maximum depth of about 50 feet. The noted site classification considers that bedrock exists below the maximum depth of subsurface exploration. Based on the available field and laboratory test results and our knowledge and experience with the local site geology, a Seismic Site Classification “D” should be used for design of the structures according to the “International Building Code and Related Codes, Section 1613.5.2 Site Class Definitions. Based on the soils encountered during this geotechnical investigation, the liquefaction potential of the site is considered low. GEOTECHNICAL EXPLORATION Drilling and soil sampling was performed by Geotill Engineering, Inc. using a Diedrich D-50 drill rig with hollow-stem augers and an automatic SPT hammer. One (1) sample boring was drilled near the proposed tower location to a depth of about fifty (50) feet. The boring location was laid out by the driller using a measuring tape and pacing methods. The location of the boring should be considered accurate only to the degree implied by the means and methods used to define them. Refer to the attached Boring Location Plan for more information. Representative samples were obtained by the split-barrel sampling procedure in general accordance with appropriate ASTM standards. In the split-barrel sampling procedure, the number of blows required to advance a standard 2-inch O.D. split-barrel sampler the last 12 inches of the typical total 18-inch penetration by means of a 140-pound hammer with a free fall of 30 inches, is the standard penetration resistance value (N). Sampling depths and penetration distance, plus the standard penetration resistance values, are shown on the attached boring log. The samples were sealed and mailed to our laboratory for soil classification in general accordance with ASTM D-4220. At the completion of drilling the borehole was backfilled with bentonite. The subsurface conditions encountered at the boring location are indicated on the attached boring log. The stratification boundaries on the boring log represent the approximate location of changes in soil/rock types; in-situ, the transition between materials may be gradual. The boring log includes visual classifications of the materials encountered during drilling as well as the driller’s interpretation of the subsurface conditions between samples. LABORATORY TESTING The samples were classified in the laboratory based on visual observation, texture and plasticity. The descriptions of the soils indicated on the boring log are in accordance with the enclosed General Notes and the Unified Soil Classification System. Estimated group symbols according to the Unified Soil Classification System are given on the boring log. A brief description of this classification system is attached to this report. Proposed 150-ft Monopole BU Number: 873711 2/25/2022 Page 3 The laboratory testing program consisted of performing the following tests: ❖ Natural water content tests (ASTM D-2216) ❖ Washing soils through #200 Sieve (ASTM D-1140) ❖ Atterberg limits tests (ASTM D-4318) ❖ Soil Resistivity Test (Laboratory, ASTM G187-12A) ❖ Soil Resistivity Test (Field, ASTM G-57-06) ❖ Soil pH Test (ASTM D-4972) ❖ Sulfate Test (AASHTO T290) ❖ Chloride Test (AASHTO T291) Information from these tests was used in conjunction with field penetration test data to evaluate soil strength in- situ and soil classification. Results of these tests are attached and provided on the boring log. SOIL RESISTIVITY AND REACTIVITY Soil resistivity and pH testing was performed as a part of the geotechnical investigation at this site. A composite sample was obtained within the upper 10-ft for laboratory testing. Laboratory resistivity measurements were obtained using a Miller-400A Analog Resistance Meter implementing the 2-electrode method in conjunction with an electrolyte box in accordance with ASTM G-187-12A. It should be noted that the soil samples were saturated for this testing procedure. Based on the laboratory test results, the tested soil is rated “Corrosive” with resistivity measurements on average of about 3,100 ohm-cm (refer to Table 2 below). Soil pH tests were conducted in accordance with ASTM D-4972. An average soil pH of 7.5 was measured at 22°C for the surficial soils at the project location. Additionally, ground resistivity testing was performed at this site. Field resistivity measurements were obtained using a MILLER-400A Analog Resistance Meter implementing the Wenner 4-electrode method in accordance with ASTM G-57-06 with an electrode spacing of 2, 4, 8, and 16 feet. Based on the field test results, most of the soil is rated “Moderately Corrosive” (refer to the tables below). Table 1: Field Soil Resistivity Data Center-to-Center Pin Spacing (ft) Average Resistivity (Ohm-cm) Corrosion Rating 2 6,090 Moderately Corrosive 4 6,971 Moderately Corrosive 8 8,350 Moderately Corrosive 16 7,507 Moderately Corrosive 25 5,985 Moderately Corrosive Table 2: Soil Resistivity Classification System Resistivity (Ohm-cm) Soil Type Corrosion Rating 0 to 1,000 Moist Clay Extremely Corrosive 1,000 to 3,000 Moist Clay Highly Corrosive 3,000 to 5,000 Clay Corrosive 5,000 to 10,000 Silty Clay/Clayey Silt Moderately Corrosive 10,000 to 20,000 Sandy Silt Mildly Corrosive >20,000 Sand/Gravel/Rock Non-Corrosive Sulfate and Chloride testing was also performed as a part of the geotechnical investigation at this site in accordance with AASHTO T290 and T291. Based on the sulfate and chloride laboratory test results, the corrosion potential for the soil is “Negligible” with test results of less than 5 ppm, each. See Sulfate and Chloride tables below for acceptable testing ranges. Proposed 150-ft Monopole BU Number: 873711 2/25/2022 Page 4 Table 3: Sulfate Corrosion Rating Sulfate (ppm) Corrosion Rating <150 Negligible 150 to 1,500 Moderate 1,500 to 10,000 Severe >10,000 Very Severe Table 4: Chloride Corrosion Rating Chloride (ppm) Corrosion Rating <500 Negligible >500 Corrosive GROUNDWATER Groundwater was encountered during drilling operations at a depth of about 13 feet below grade and at the completion of drilling operations at a depth of about 4 feet below grade as noted on the attached boring log. However, it is important to note that the boring caved in at a depth of 10-ft below grade subsequent to removing tools. It is also important to note that the previous geotechnical report (Doc ID 1348387) encountered groundwater at a depth of 4 feet below grade. Therefore, buoyant unit weights should be utilized below a depth of 4 feet. It should be noted that fluctuations in the groundwater level can occur and perched water can develop over low permeability soil or rock strata following periods of heavy or prolonged precipitation. Long term monitoring in cased holes or piezometers would be necessary to accurately evaluate the potential range of groundwater conditions on the site. PREVIOUS GEOTECHNICAL STUDY A geotechnical report was previously completed by Devine Engineering, Inc. (DEI Project No. 00-115-E dated August 16, 2000). The boring log from this study has been included as an appendix. GEOTECHNICAL RECOMMENDATIONS Based on the results of this study, it is our opinion that either a cast-in-place concrete pier or a shallow foundation system would be appropriate for support of a monopole at this site. However, a cast-in-place concrete pier foundation is preferred due to the observed shallow groundwater. The following net design parameters may be used to design the proposed foundation system. A factor of safety of 3 should be applied to the ultimate bearing pressure values provided below. The cohesion, internal angle of friction and unit weight parameters along with the vertical modulus of subgrade reaction, horizontal modulus of subgrade reaction, sliding friction coefficient, and strain values given in the following tables are based on the results of the sample boring, lab testing, published values and our past experience with similar soil/rock types. These values should, therefore, be considered approximate. Proposed 150-ft Monopole BU Number: 873711 2/25/2022 Page 5 Table 5: Monopole – Drilled Pier – Ultimate Design Parameters Depth (feet) USCS Unit Weight (pcf) Horizontal Modulus of Subgrade Reaction (pci) ε50 Ultimate Bearing Pressure (psf) Internal Angle of Friction (Degrees) Cohesion (psf) 0 – 3.51 SP, CL 115 Ignore1 Ignore1 Ignore1 - - 3.5 – 6 CL 120/582 80 0.007 6,000 0 1,000 6 – 12 CL-ML 63 240 0.005 15,000 0 3,000 12 – 17 SC 58 60 - 12,000 32 0 17 – 22 CL 58 160 0.005 12,000 0 2,000 22 – 30 SM 68 250 - 21,000 40 0 30 – 50 CL 68 300 0.004 24,000 0 4,000 2The upper 3.5-ft or one-half pier diameter length (D/2), whichever is greater, should be ignored due to potential frost effects and construction disturbance considerations. 2Bouyant unit weights should be used below a depth of 4 feet. Table 6: Monopole – Shallow Foundation – Ultimate Design Parameters Depth (feet) USCS Unit Weight (pcf) Ultimate Bearing Pressure (psf) Sliding Friction Coefficient @ Base Vertical Modulus of Subgrade Reaction (pci) Internal Angle of Friction (Degrees) Cohesion (psf) 0 – 3.51 SP, CL 115 Ignore1 Ignore1 Ignore1 - - 3.5 – 6 CL 120/582 6,000 0.35 100 0 1,000 6 – 12 CL-ML 63 15,000 0.35 300 0 3,000 1The upper 3.5-ft should be ignored due to potential frost effects and construction disturbance considerations. 2Bouyant unit weights should be used below a depth of 4 feet. The above parameters are provided for the design of either a cast-in-place concrete pier or a shallow foundation system. In the event that a different foundation or tower type is chosen, these parameters are not considered valid and GPD Group should be notified immediately to provide appropriate design parameters, as warranted. EARTHWORK Where required, all surfaces cut to subgrade elevation or subgrades to receive fill should be proof-rolled under the direction of an on-site geotechnical engineer or their representative. Proof-rolling should be performed with a minimum 20 ton dump truck. Two (2) passes, (1 forward and 1 backward) should be made at normal walking speed. Any soft, loose, yielding, or obviously contaminated zones should be undercut as directed by the engineer. All backfill placed adjacent to foundations should be select material, as approved by a qualified geotechnical engineer. For all filling operations, the following should be observed: 1. Prior to use, the approved fill material should be tested as outlined in ASTM D-698 to determine the maximum dry density and optimum moisture content for silty or cohesive soils, or ASTM D-4253 and D-4254 for clean granular soils. For each change in borrow material, additional tests will be required. 2. For all fill or backfill used, the fill material should be placed on the approved subgrade in controlled lifts, with each lift compacted to a stable condition, and to a minimum of 98% maximum dry density per ASTM D-698 at a moisture content within 1.5% of optimum for cohesive or silty borrow. Controlled lifts of granular material should be compacted to 80% relative density per ASTM D-4254. Proposed 150-ft Monopole BU Number: 873711 2/25/2022 Page 6 3. All filling operations should be observed by a qualified soils technician with field density tests made, to assure compaction to specification. Backfill may consist of mixes of natural soil or crushed aggregate meeting one of the following USCS Classifications: GW, GP, GM, GC, SW, SP, SM, SC, CL, ML, or any dual symbol combinations of the preceding. Backfill material should contain a maximum organic content of 1 percent, and a maximum particle size of 3- inches. Excavated site soils are considered acceptable for reuse as structural fill at this project location. The contractor should expect to encounter groundwater near a depth of about 4 feet below grade, and should maintain the necessary equipment to properly dewater the excavation. CONSTRUCTION CONSIDERATIONS Drilled pier foundations should be designed with a minimum shaft diameter of 36 inches to facilitate clean out of the pier excavation. Temporary casing may be required during the pier excavation in order to control possible groundwater seepage and to support the sides of the excavation in weak soil zones. Casing should not extend below the rock surface. Care should be taken so that the sides and bottom of the excavations are not disturbed during construction. The bottom of the shaft should be free of loose soil or debris prior to reinforcing steel and concrete placement. It is essential that piers designed using the provided properties are cast against native soil/rock. Overexcavation and forming of piers is not permitted. A concrete slump of at least 6 inches is recommended to facilitate temporary casing removal. It should be possible to remove the casing from a pier excavation during concrete placement provided that the concrete inside the casing is maintained at a sufficient level to resist any earth and hydrostatic pressures outside the casing during the entire casing removal procedure. QUALIFICATIONS The analysis and recommendations presented in this report are based upon the data obtained from the boring performed at this site and from other information discussed in this report. This report does not reflect variations that may occur across the site or due to the modifying effects of weather. This report has been prepared for the exclusive use of Crown Castle for specific application to the project discussed herein and has been prepared in accordance with generally accepted geotechnical engineering practices. No warranties, either expressed or implied, are intended or made. In the event that changes in the nature or design as outlined in this report are planned, the conclusions and recommendations contained in this report shall not be considered valid unless GPD Group reviews the changes and either verifies or modifies the conclusions of this report in writing. The scope of services for this project does not include either specifically or by implication any environmental assessment of the site or identification of contaminated or hazardous materials or conditions. If the owner is concerned about the potential for such contamination, other studies should be undertaken. BORING LOCATION PLANSite Name: Carmel-SpringmillBU Number: 873711GPD Job Number: 2022777.873711.04Date: February 2022© 2022 Google HTML Link: https://www.google.com/maps/@39.97714,-86.16948,1142m/data=!3m1!1e3h B-1 N Resistivity Testing 5 16 2.5 4.5+ 4.5+ 3.0 28 56 67 89 100 100 100 100 73 100 100 100 Gravel, 18 inches Medium Dense dark tan fine to medium coarse SAND (SP) with gravel and little clay Stiff brown GRAVELLY CLAY (CL) with some sand Glacial Till sampled as: Very Stiff dark grayish brown SANDY SILTY CLAY (CL-ML) with little silt Hard dark grayish brown and tan with gravel below 8.5 feet Glacial Till sampled as: Medium Dense dark tan and grayish brown CLAYEY SAND (SC) with little gravel Glacial Till sampled as: Stiff to Very Stiff brown with blueish gray SANDY CLAY (CL) with little gravel Very Dense brown SILTY SAND (SM) with interbedded clay Hard brown SANDY CLAY (CL) with little gravel Dark grayish brown below 38.5 feet Boring terminated at 50.0 feet SS 1 SS 2 SS 3 SS 4 SS 5 SS 6 SS 7 SS 8 SS 9 SS 10 SS 11 SS 12 12 23 11 9 17 18 12 12 9 12 12 17 32 12 16 66 56 3-5-6 (11) 2-3-6 (9) 10-17-20 (37) 16-19-21 (40) 8-12-13 (25) 3-7-8 (15) 17-37-50/3" 50/1" 27-50/5" 50/5" 50/3" 50/1" AT TIME OF DRILLING 13.00 ft LOGGED BY Connor Groves DRILLING METHOD Hollow Stem Auger - 3 1/4" ID CHECKED BY Dustin Vincent GROUND ELEVATION GROUND WATER LEVELS: DATE STARTED February 7, 2022 COMPLETED February 7, 2022 DRILLING CONTRACTOR Geotill Engineering, Inc. HOLE SIZE AT END OF DRILLING 4.00 ft (caved in below 10 feet) NOTES D-50 Drill Rig with Automatic Hammer GRAPHICLOGDEPTH(ft)0 10 20 30 40 50 PLASTICITYINDEXPOCKET PEN.(tsf)RECOVERY %(RQD)MATERIAL DESCRIPTION SAMPLE TYPENUMBERMOISTURECONTENT (%)LIQUIDLIMITPLASTICLIMITFINES CONTENT(%)ATTERBERG LIMITS ESTIMATEDN VALUEBoring Number: B-1 CLIENT Crown Castle PROJECT NUMBER 2022777.873711.04 PROJECT NAME Carmel-Springmill PROJECT LOCATION Carmel, IN ATV - GINT STD US LAB.GDT - 2/25/22 10:13 - F:\GEOTECH\JOBS\GINT PROJECTS (STARTED AFTER 032414)\GINT PROJECTS 2018\CROWN - 873711 - CARMEL.GPJ 0 10 20 30 40 50 60 0 20 40 60 80 100 B-1 B-1 ML CL MH CH 66 56 CL-ML P L A S T I C I T Y I N D E X LIQUID LIMIT Fines Classification 17 32 12 16 SANDY SILTY CLAY(CL-ML) SANDY LEAN CLAY(CL) LL PL PI 5 16 ATTERBERG LIMITS' RESULTS 6.0 18.5 BOREHOLE DEPTH CLIENT Crown Castle PROJECT NUMBER 2022777.873711.04 PROJECT NAME Carmel-Springmill PROJECT LOCATION Carmel, IN ATTERBERG LIMITS - GINT STD US LAB.GDT - 2/16/22 10:50 - F:\GEOTECH\JOBS\GINT PROJECTS (STARTED AFTER 032414)\GINT PROJECTS 2018\CROWN - 873711 - CARMEL.GPJ 1) 2) VIEW OF DRILLING BENTONITE BACKFILL 873711 - Carmel-Springmill - Photographs 3) SOIL SAMPLES 873711 - Carmel-Springmill - Photographs Letter Symbol GW GP GM GC SW SP SM SC ML CL OL MH CH OH PT Organic clays of medium to high plasticity. Peat, muck, and other highly organic soils. Well-graded sands and gravelly sands, little or no fines. Poorly-graded sands and gravelly sands, little or no fines. Silty sands, sand-silt mixtures Inorganic clays of low to medium plasticity, gravelly clays, sandy clays, silty clays, lean clays. Unified Soil Classification System Clayey sands, sandy-clay mixtures. Organic clays of medium to high plasticity. Inorganic silts, micaceous or diatomaceous fines sands or silts, elastic silts. Description Silts and Clays Liquid Limit greater than 50% Gravels With Fines Clean Sands Major Divisions Clean Gravels SandsMore than ½ passing through the No. 200 sieveInorganic silts, very fine sands, rock flour, silty or clayey fine sands.GravelsMore than ½ coarse fraction retained on the No. 4 sieveInorganic clays of high plasticity, fat clays. Consistency Classification Highly Organic SoilsCoarse-grained SoilsMore than ½ retained on the No. 200 SieveFine-grained SoilsMore than ½ passing through theNo. 200 SieveSands With Fines Silts and Clays Liquid Limit less than 50% Well-graded gravels and gravel-sand mixtures, little or no fines. Poorly-graded gravels and gravel-sand mixtures, little or no fines. Silty gravels, gravel-sand-silt mixtures. Clayey gravels, gravel-sand-clay mixtures. Cohesive SoilsGranular Soils Description - Blows Per Foot (Corrected)Description - Blows Per Foot (Corrected) MCS <5 5 ¯ 15 16 ¯ 40 41 ¯ 65 >65 SPT <4 4 ¯ 10 11 ¯ 30 31 ¯ 50 >50 Very loose Loose Medium dense Dense Very dense Very soft Soft Firm Stiff Very Stiff Hard MCS <3 3 ¯ 5 6 ¯ 10 11 ¯ 20 21 ¯ 40 >40 SPT <2 2 ¯ 4 5 ¯ 8 9 ¯ 15 16 ¯ 30 >30 MCS = Modified California Sampler SPT = Standard Penetration Test Sampler