GEOTECHNICAL INVESTIGATION

Transcription

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2 GEOTECHNICAL INVESTIGATION Proposed Student Union Building Killeen, Texas Kleinfelder Project No August 18, 2008

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4 TABLE OF CONTENTS IMPORTANT INFORMATION ABOUT YOUR GEOTECHNICAL ENGINEERING REPORT... iii PAGE 1.0 INTRODUCTION 1.1 General Subsurface Exploration Field Tests Laboratory Tests Sample Logging SUBSURFACE MATERIALS AND CONDITIONS 2.1 Stratigraphy and Geology Subsurface Water FOUNDATION DESIGN CRITERIA 3.1 General Expansive Soil Considerations Structural Support Using Drilled Piers Interior Floor Slab Seismic Design Criteria Utility/Service Lines FOUNDATION CONSTRUCTION RECOMMENDATIONS 4.1 Site Preparation, Grading, and Drainage Considerations Select Fill Material Compaction and Testing Foundation Construction Criteria SUBGRADE RECOMMENDATIONS 5.1 Design Considerations Subgrade Support Characteristics Subgrades On Or Consisting of Expansive Soils Specifications DESIGN REVIEW LIMITATIONS OF THIS INVESTIGATION REFERENCES APPENDIX

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7 GEOTECHNICAL INVESTIGATION PROPOSED STUDENT UNION BUILDING KILLEEN, TEXAS 1.0 INTRODUCTION 1.1 GENERAL This investigation of subsurface materials and conditions was performed for the proposed Student Union Building for Central Texas College in Killeen, Texas (refer to Plates I and II in the Appendix). The purpose of this investigation has been to: Explore the subsurface materials and conditions present at selected, truck accessible site locations by core drilling and sampling; Perform laboratory tests to classify the soils and evaluate the strength characteristics of the subsurface materials; and Analyze the results of field and laboratory tests to provide limited and specific geotechnical design and construction criteria for the proposed building and Plaza area subgrade. The report is divided into two major sections; i.e., a TEXT section followed by an APPENDIX. The TEXT section contains descriptive information regarding the field operations and laboratory testing as well as results and recommendations based on interpretations of field and laboratory results. The APPENDIX immediately follows the TEXT and contains site and boring location maps, laboratory test results, and the boring logs. Therefore, this report contains both factual data and interpretation of the data, which must not be separated. 1.2 SUBSURFACE EXPLORATION The drilling operations were conducted on July 9, 2008 using a CME 75 drill rig. The borings were located in the field by Kleinfelder personnel based on a site plan provided by CTC. GPS coordinates of each boring location were recorded using a portable handheld GPS receiver, and are shown in Table 1.1 below. The approximate locations are shown on Plate II in the Appendix. If more precise location and elevation data are desired, then a registered professional land surveyor should be retained to locate the borings and determine the ground surface elevations. The drilling procedures for the core borings are summarized in Table /WAC8R076 1 August 18, 2008

8 TABLE 1.1 : BORING DETAILS Boring Depth Latitude Longitude B-1 25 ft N W B-2 25 ft N W B-3 25 ft N W B-4 25 ft N W B-5 10 ft N W B-6 10 ft N W Note: These readings are approximate. TABLE 1.2: DRILLING PROCEDURES Material Type Clay and Severely Weathered Limestone Shaly Limestone Drilling Procedure Auger drilling and intermittent sampling with a split-spoon sampler in conjunction with standard penetration tests Continuous sampling with an NX-size core barrel equipped with a carbide drill bit using water as a drilling fluid, or auger drilling and intermittent sampling with a split-spoon sampler in conjunction with standard penetration testing. Core Recovery (R) and Rock Quality Designation (RQD) were recorded during the drilling process. Samples of the subsurface materials were extruded from the samplers in the field, classified visually, and labeled as to location and depth. Disturbed samples were placed in plastic bags. Selected rock cores deemed suitable for strength testing in the laboratory were wrapped in plastic or placed in plastic bags. Samples were arranged in core boxes and transported to the laboratory for further analysis. During the field operations, the borings were observed for subsurface water during dry drilling. These observations are noted on the boring logs and are also discussed in subsequent sections of this report. The core borings were filled and plugged after completion. 1.3 FIELD TESTS Standard Penetration Tests (SPT s) were performed in the borings to provide in-situ strength estimates, obtain samples of granular soils, and to verify weathered limestone hardness. The SPT tests were conducted in general compliance with applicable ASTM requirements. Results of the SPT tests are shown on the individual Log of Boring sheets /WAC8R076 2 August 18, 2008

9 1.4 LABORATORY TESTS Samples of subsurface materials from the borings were visually examined and classified in the laboratory. Liquid and plastic limit tests and No. 200-mesh sieve tests were performed on selected samples to establish index properties and grain size characteristics, and to properly classify the soils according to the Unified Soil Classification System. The results of these tests expressed as Liquid Limit, Plasticity Index, and percent passing the 200-mesh sieve are summarized on Plate III and are also shown on the boring logs. Strength properties of the rock materials were evaluated through the use of unconfined compression tests on selected rock core samples. The results of these tests are summarized on Plate III and on the boring logs, which are reported in tons per square feet. Soil samples were not available for laboratory strength testing. 1.5 SAMPLE LOGGING Soil samples were not available for hand penetrometer testing. The rock materials were qualitatively evaluated using the Rock Quality Designation (RQD) system (1), which is a standard method for rating drill core quality. The RQD values are shown on the boring logs in the column containing the symbol (RQD). RQD is defined as the sum of the lengths of pieces of rock core greater than or equal to four inches in a core run, divided by the total length of that core run. RQD is expressed as a percentage and categorized according to the following Table 1.3. TABLE 1.3: CLASSIFICATION OF ROCK BY RQD VALUE RQD Rock Quality Less than 25 Very poor Poor Fair Good Excellent The percent recovery (REC) is simply the total length of material recovered in a specific core run interval divided by the total length of the core run. The term fracture used on the boring logs is a discontinuity in the retrieved core, but does not necessarily represent a continuous failure plane in the rock caused by previous movement or stresses /WAC8R076 3 August 18, 2008

10 2.0 SUBSURFACE MATERIALS AND CONDITIONS 2.1 STRATIGRAPHY AND GEOLOGY Specific types and depths of subsurface strata observed in the borings drilled for this investigation are shown on the boring log sheets contained in the Appendix. For discussion purposes, the subsurface materials observed in the borings have been divided into major strata types as described below in Table 2.1. The thickness range and general descriptions are based solely on the materials observed in the borings drilled for this investigation. TABLE 2.1: MAJOR STRATA TYPES WITHIN BUILDING BORINGS Strata Depth to Top of Strata (ft) Depth to Base of Strata (ft) General Description I /2 to 2 ASPHALT over about 10 CRUSHED LIMESTONE BASE (15-inches base in Boring B-6) II 1 1 to 9 LEAN TO FAT CLAY; tan and light gray, with various amounts of fossils, broken limestone, and limestone seams. (Not observed in Boring B-5) III 1 to 9 12 to 15 SEVERELY WEATHERED LIMESTONE; yellow-tan and light gray, clayey, calcareous, with various amounts of sand, broken limestone fragments, and interbedded layers of fat clay and broken limestone IV 8.5 to SHALY LIMESTONE; gray and dark gray, highly fractured, fossiliferous, with interbedded layers of harder limestone and softer shale/marl The above descriptions are general and range of depths approximate because boundaries between different strata are seldom clear and abrupt in the field. In addition, the lines separating major strata types on the Log of Boring sheets do not necessarily represent distinct lines of demarcation for the various strata. Based on the available geologic maps of the area (2), and the contents of the borings, it is our opinion that the natural materials are part of the Walnut Formation. The Walnut Formation is composed of interbedded clay, limestone, fossil beds, and shale. The clays and shales exhibit moderate to high 95751/WAC8R076 4 August 18, 2008

11 plasticity. The fossil beds consist primarily of oyster shells and fragments that often occur as massive beds cemented by both clay and calcium carbonates. The severely weathered limestone noted in Table 2.1 is an intermediate soil-rock product that has weathered in place over a period of millions of years. In general, severely weathered limestone is more soil-like than rock-like, but there are layers of broken rock that are harder and more resistant to weathering. 2.2 SUBSURFACE WATER The borings were drilled to depths of 10 to 25 feet without or prior to using water as a drilling fluid for core drilling. Water is used in the rock core drilling process to lubricate the drill bit and discharge cuttings. At the time of our field exploration, groundwater was not observed in the borings that were drilled dry nor prior to using drilling fluid in the other borings. It is not unusual, however, to encounter shallow groundwater within the Walnut Formation, especially during and after periods of rainfall. The water tends to percolate down through the surficial soils until encountering a relatively impervious layer, and then either flow down gradient or become trapped. Water also tends to fill fractures and joints within the rock mass, particularly within the weathered zone. The water observations conducted for this investigation are short-term and should not be interpreted as a groundwater study. However, the presence of groundwater may affect construction and long-term performance of the proposed foundations and pavements /WAC8R076 5 August 18, 2008

12 3.0 FOUNDATION DESIGN CRITERIA 3.1 GENERAL The project consists of a new Student Union Building with a foundation area of about 25,000 square feet. The building will have a partial second story, with a brick facade. Further details regarding structural loads were not provided during the preparation of this report. Based on the above information, and the results of the borings, specific design and construction recommendations for the foundations are provided in the following sections of this chapter. Primary foundation design considerations for this site include soil movement potential and foundation support characteristics. These and other design considerations are discussed in the following sections. Please contact Kleinfelder for additional recommendations for a structurally suspended foundation if desired as an alternative foundation to account for the anticipated soil movement potential. 3.2 EXPANSIVE SOIL CONSIDERATIONS Clay soils in the Central Texas area are subject to expansive soil movements, which include swelling under moist conditions and shrinking under dry conditions. The moisture fluctuations occur due to seasonal wet and dry cycles, but are also be influenced after construction by grading and drainage, landscaping, groundwater conditions, and the presence of paving. Therefore, the soil movement is difficult to determine due to the many unpredictable variables involved. To estimate the potential expansive soil movement for this site, Texas Department of Transportation (TxDOT s) Potential Vertical Rise (PVR) procedure has been used. The results of the laboratory tests, engineering judgment, and experience have also been considered. Potentially expansive soils extended to depths of 9-feet. Based on TxDOT s method for estimating shrink/swell movements, the calculated potential vertical rise (PVR) for a typical ground supported slab will be about 1-1/2 to 2 inches in magnitude. It must be recognized that these are not exact numbers, but only an indication of the approximate range of potential movements. However, this degree of potential movement is considered low to moderate as compared to other sites in the Central Texas area. Removing and replacing 4-feet of existing soil with select fill will reduce the estimated soil movement potential to less than 1-inch in magnitude. Select fill requirements are provided in Section 4.2. Actual soil movements will depend on the subsurface moisture fluctuations over the life of the structure. Soil movements may be less than those calculated if moisture variations are minimized after construction /WAC8R076 6 August 18, 2008

13 Significantly larger soil movements than estimated could occur due to inadequate site grading, poor drainage, ponding of rainfall, and/or leaking utilities. 3.3 STRUCTURAL SUPPORT USING DRILLED PIERS Straight-shaft drilled piers are recommended for structural support. Piers should extend at least 4-feet into the Stratum IV SHALY LIMESTONE. The pier depth is advised in part to provide anchoring against side shear uplift induced by the clay soils above about the 9-foot depth. Since the borings extended a maximum of 25 feet, the piers should not exceed 25 feet in depth without further analysis by Kleinfelder. Piers may be sized so as not to exceed an allowable end-bearing pressure of 20,000 pounds per square foot (psf) when bearing on a hard layer. An allowable side friction capacity of 1,000 psf (either tensile or compressive) may be used in the SEVERELY WEATHERED LIMESTONE beginning 10 feet below the existing ground surface or final ground surface, whichever is deeper. Side friction may be increased to 2000 psf in the Stratum IV SHALY LIMESTONE. Settlements of properly designed and constructed piers should be less than ½ inch. Uplift forces will act on the piers as the clayey soils surrounding the pier shaft swell. These forces will be resisted by penetration of the pier below the clay soils. The uplift will create tensile stresses in the concrete that must be resisted by vertical steel reinforcement. One method of estimating the potential uplift force on each of the piers uses the following equation (3). where U p = (πd)(α)(z a )(S p ) U p = uplift load, lbs. d = shaft diameter, ft. α = factor applied to vertical absorption pressure to account for shaft/soil friction angle. S p = absorption pressure determined under zero volume change constraint, psf. Z a = length of shaft over which active clay soils are expected to create uplift, ft. Based on correlations of PI and our experience with similar soils, the recommended soil design values are as follows: α = 0.3 S p = 3,500 psf for the clay zone Z a = 9 feet or to the top of severely weathered limestone The preceding equation represents an upper limit for uplift forces on drilled piers installed in relatively dry soil conditions. In accordance with reference 3, "Compressive loads to be considered in reinforcement calculations should be restricted to perhaps one half of the dead load because substantial swell can often 95751/WAC8R076 7 August 18, 2008

14 occur before the structure is completed." The uplift equation is based on the assumption that the clayey soils within only the upper 9 feet of the final ground surface contribute to uplift forces acting on the drilled piers. The above equation assumes that at least 4 feet of removal and replacement has been achieved beneath the structure so that foundation elements connected to the piers are not also exerting uplift forces on the piers. The vertical steel reinforcement to resist tensile loads should extend over the full shaft length to within six inches of the bottom. This reinforcement should not preclude the use of additional reinforcement for axial compression, axial tension from external loads, lateral load considerations, or minimal reinforcement required by codes. Additional pier design criteria are provided in Section 4.4 of this report. Groundwater was not encountered during dry drilling. However, it is not known whether groundwater will be present during installation of the drilled shafts. Groundwater in the Killeen area is often intermittent, and the water travels through fractures or other more permeable zones in the soil/rock. It is not unusual to encounter groundwater in drilled shafts on a random basis, i.e. water may not occur in adjacent shafts. We recommend that 2 test shafts be drilled just outside of the building area to assess the groundwater and caving conditions. The Contractor should be prepared to case the excavations if required to control groundwater. 3.4 INTERIOR FLOOR SLAB To reduce the estimated soil movement potential to less than 1 inch in magnitude, the interior floor slab must be supported on a pad of select fill material achieved by removing at least 4 feet of existing clayey soils and replacing with non-expansive imported material. The removal must extend a horizontal distance of 2 feet or more beyond the building perimeter. Select fill must then be placed and compacted as recommended in Section 4.2 of this report. Supporting the floor slab in this manner results in an estimated PVR value of about 1 inch or less. With the removal and replacement method, we recommend that an impervious seal consisting of at least 12 inches of clay soil be constructed on top of the backfill material around the building perimeter. The intent of this impervious seal is to reduce surface runoff water from infiltrating the backfill. The seal must be sloped away from the foundation. In addition, a plug of clay soil must be placed at the exit points of the utilities from the foundation to reduce water intrusion into the utility trenches. The need for vapor barriers, and where to place them, must be determined by the architect/structural engineer based on the proposed floor treatment, building function, concrete properties, placement 95751/WAC8R076 8 August 18, 2008

15 techniques, and the construction schedule. When moisture barriers are used, precautions should be taken during the initial floor slab concrete curing period to reduce differential curing and possible curling of the slabs. 3.5 SEISMIC CONSIDERATIONS For structural designs based upon the 2006 IBC (4), the following Criteria will apply. The Site Class is C. The Mapped Spectral Response Acceleration at short periods (S S ) is about 0.10g, and the Mapped Spectral Response Acceleration at a 1 second period (S 1 ) is about 0.04g. Site Coefficients F a and F V are 1.2 and 1.7 respectively. Hazards associated with slope stability, soil liquefaction, surface rupture, and lateral spreading are not considered an issue with this site due to the study area being in a seismically inactive area and the site being underlain at a shallow depth by bedrock. 3.6 UTILITY/SERVICE LINES Based on our previous experience, clay soils are corrosive to buried metals. Corrosion protection should be provided for such metals. If granular backfill materials are used for the utility lines, then a clay plug must be placed at the exterior foundation penetrations to avoid water intrusion and collection within the utility trenches. Note that soil movement potential beneath the building has been reduced by the removal and replacement of existing materials with select fill beneath the building, but not outside of the building. The estimated movement differential is about 1 inch. Thus, sidewalks, curbs, utility lines, and other structures may experience differential movements when transitioning from natural soil support onto or into the fill pad. This movement potential is believed to be low to moderate, but the designer should decide whether to use flexible joints which account for such movement /WAC8R076 9 August 18, 2008

16 4.0 FOUNDATION CONSTRUCTION RECOMMENDATIONS 4.1 SITE PREPARATION, GRADING, AND DRAINAGE CONSIDERATIONS Surficial vegetation, root systems, utilities, and any other underground structures must be removed beneath planned building areas prior to construction. The stripping depth must be based on field observations with particular attention given to old drainage areas, uneven topography, and wet soils. The stripped subgrade must be firm and able to support the construction equipment without displacement. Soft or yielding subgrade must be corrected and made stable before construction proceeds. Proof-rolling should be used to detect soft spots or pumping subgrade areas. Proof-rolling should be performed using a heavy pneumatic tired roller, loaded dump truck, or similar piece of equipment weighing at least 25 tons. Note that 4 feet of removal of existing soils and replacement with select fill is advised for the foundation area. Proof-rolling is intended to achieve additional compaction and to locate unstable areas, and must be observed by Kleinfelder. Soft spots or areas of pumping subgrade observed must be undercut and reworked. Where fill placement is planned, the proof-rolling must occur once the existing soils have been excavated and before the fill is placed and compacted. Proof-rolling is intended not only for the foundation area, but also within all areas of pavement, sidewalks, walls and other locations that will support surface loads. Prior to fill placement, the exposed subgrade must be scarified to a depth of approximately 6 inches; moisture conditioned, and recompacted to the density specified for fill. Decorative vegetation and irrigation systems must not be located near foundations. It is important to provide proper grading and drainage around the foundation to not only prevent ponding of water but also to quickly remove the water to limit infiltration. As a general guideline, we suggest the following criteria be used for perimeter drainage: 1. The building pad or the finished floor elevation must be elevated from the exterior finished grade to assist in draining the surface water away from the structure. 2. Where possible extend paved surfaces up to the building line to serve as a barrier to soil moisture evaporation and infiltration. These surfaces must slope away from the building. 3. Outlets for gutter systems must discharge water either into storm drains or onto paved surfaces, which quickly remove the water from the area. 4. In those areas where grassed ditches should be used to direct surface water away from the building area, the ditch must be designed hydraulically to accommodate the volume of water. In addition, the ditch centerline must be located well away from the foundation, preferably at least 10 feet, and must be provided with a slope of 3 to 5 percent. The slope from the building to the ditch must be at least 10 percent /WAC8R August 18, 2008

17 5. Area drains connected to storm drains and/or concrete lined ditches may also be considered to facilitate drainage where other measures are insufficient to handle and quickly remove surface water. 4.2 SELECT FILL MATERIAL Select fill material must be a non-expansive, well-graded soil with sufficient binder material for compaction purposes. Select Fill should meet the requirements of 2004 TxDOT Item 247, Type A, Grade 3 or better. If another local source of select fill is desired, the following specification may be used as a guide: Maximum Aggregate... 3 inches Percent Retained on #4 Sieve Percent Retained on #40 Sieve Plasticity Index Non-Organic Please note that locally available crusher fines are generally acceptable for use as select fill below the building, provided that these materials are confined by grade beams. However, crusher fines are highly variable and will require evaluation by Kleinfelder on a case-by-case basis. The select fill material and near surface onsite soils must be compacted to at least 95 percent of ASTM D1557 maximum dry density near optimum moisture content. A maximum compacted lift thickness of six inches must be specified, with each lift tested for compliance prior to the addition of subsequent lifts. The placement and compaction of fill material must be observed, monitored, and tested by Kleinfelder on a full-time basis. 4.3 COMPACTION AND TESTING Fill must be placed in horizontal lifts. Field density tests must be taken as each lift of fill material is placed. Generally, one field density test per lift for each 5,000 square feet of compacted area is recommended. For small areas or critical areas, the frequency of testing may need to be increased to one test per 2,500 square feet. At a minimum, three tests per lift must be required. Each lift must be compacted, tested, and approved before another lift is added. The purpose of field density tests is to provide some indication that uniform and adequate compaction is being obtained. The actual quality of the fill, as compacted, must be the responsibility of the contractor and satisfactory results from the tests must not be considered as a guarantee of the quality of the contractor's filling operations. Backfill placed within utility trenches that cross under pavement or building areas must be properly compacted. Numerous parking, drive, sidewalk, and landscape areas have undergone settlement due to soft backfill within utility trenches. Backfill placed in utility trenches or other excavated areas within the building or paved area must be placed in lifts, compacted, and tested in accordance with these earthwork 95751/WAC8R August 18, 2008

18 recommendations. Trenches should be opened a sufficient width to safely allow compaction equipment access to the backfill and to safely allow for confirmation testing to occur. Backfill must be placed in horizontal lifts, and if the trench is over 4 to 5 feet deep, the side slopes must be benched before placing the backfill. 4.4 FOUNDATION CONSTRUCTION CRITERIA The following construction criteria and general guidance must be observed during foundation construction: 1. A minimum pier shaft diameter of 24 inches is normally specified to allow for cleaning, minimum construction tolerances, and conventional concrete mix designs. Smaller diameters may be used at the discretion of the structural engineer. 2. The foundation construction must be observed by Kleinfelder to determine that the proper bearing material has been reached in accordance with the recommendations given herein. 3. The foundation excavations must be checked for size and cleaned of loose material prior to the placement of concrete. Precautions must be taken during the placement of reinforcement and concrete to prevent the loose excavated material from falling into the excavation. 4. Prior to the placement of concrete, water must be removed from the foundation excavations. 5. Concrete must be placed promptly after the excavations are completed, cleaned, and observed. Under no circumstances must a pier shaft be drilled that cannot be filled with concrete before the end of the work day. 6. The reinforcement steel cage placed in the shaft must be designed from the standpoint of meeting two requirements: (1) the structural requirements for the imposed loads; and (2) stability requirements during the placement of concrete. 7. Groundwater was not encountered during our field exploration while dry drilling. However, temporary steel casing may be required to seal out groundwater or prevent the pier holes from caving. Special concrete design and construction procedures as described in ACI and ACI 336.3R should be specified in order to properly extract the casing during concrete placement. In particular, the pier concrete should be placed at a minimum slump of 6 inches when temporary steel casing is used. Temporary casing may not be required in all the pier holes, so it is advisable that the bid schedule include installation of temporary casing as a separate unit-price bid item /WAC8R August 18, 2008

19 5.0 SUBGRADE RECOMMENDATIONS 5.1 DESIGN CONSIDERATIONS Only recommendations concerning the subgrade were requested by The Client for the plaza area. The borings encountered asphaltic pavement over crushed limestone base material, underlain by lean to fat clay in 5 of the 6 borings, and by severely weathered limestone in Boring B-5. The crushed limestone base portion of the existing pavement section may provide a desirable subgrade, providing that this or any exposed subgrade is prepared in accordance with the recommendations contained herein. Subgrade support characteristics based on the available information and assuming the subgrade is prepared in accordance with recommendations provided herein are presented in Section 5.2. Subgrade should be prepared to provide a suitable platform for supporting the intended pavement or other surface cover and to support the anticipated traffic. In the absence of other design requirements (such as for a proprietary pavement system or product), the subgrade should be prepared to meet the specifications typically provided for general pavement support. These specifications are provided in Section SUBGRADE SUPPORT CHARACTERISTICS Based on the LEAN TO FAT CLAY that was encountered below the pavement structure, a Resilient Modulus of 4.2 is advised for design. A greater value is expected when the subgrade consists of severely weathered limestone or crushed limestone base, but this lower value is advised to account for the unknown depth at which the clay may exist below other exposed subgrades. 5.3 SUBGRADES ON OR CONSISTING OF EXPANSIVE SOILS Subgrade with expansive soil or underlain by expansive soil can experience cracking and deformation due to shrink/swell movements. It is therefore important to minimize moisture changes in the subgrade to reduce shrink/swell movements. Note that a soil movement potential of up to about 2 inches in magnitude has been estimated for this project. The surface of the plaza area supported by the prepared subgrade and the adjacent areas must be well drained to prevent water from ponding within the area during the life of the project. Proper maintenance must be performed on cracks in the finished surface to prevent water passing through to the base or subbase material. Extending the base material out about 3 feet from the edge of the pavement curb will also aid in reducing edge related cracking. Even with these precautions, some movements and related cracking may still occur, requiring periodic maintenance /WAC8R August 18, 2008

20 Pavement islands often provide a means of water infiltration into the base material below the pavement. If islands are used, then we recommend that a synthetic lining or clay soils be used to limit infiltration of water into the base. Water entry into the base will cause softening of the base, which will cause potholes and/or ruts to form if the traffic loads are sufficient. The presence of trees and vegetation adjacent to paved areas on expansive soils may exacerbate the formation of cracks in these pavements due to moisture loss in the underlying subgrade from transpiration to the root systems of the vegetation. Soil moisture loss from vegetation can extend a distance from the vegetation about equal to its height. The problem is more severe during dry conditions in non-irrigated locations. 5.4 SPECIFICATIONS Surficial vegetation, root systems, utilities, and any other underground structures must be removed beneath planned subgrade areas prior to construction. The existing asphaltic concrete layer must be removed as well. The stripping depth must be based on field observations with particular attention given to old drainage areas, uneven topography, and wet soils. The stripped subgrade must be firm and able to support the construction equipment without displacement. Soft or yielding subgrade must be corrected and made stable before construction proceeds. Proof-rolling should be used to detect soft spots or pumping subgrade areas. Proof-rolling should be performed using a heavy pneumatic tired roller, loaded dump truck, or similar piece of equipment weighing at least 25 tons. Proof-rolling is intended to achieve additional compaction and to locate unstable areas, and must be observed by Kleinfelder. Soft spots or areas of pumping subgrade observed must be undercut and reworked. Where fill placement is planned, the proof-rolling must occur once the existing soils have been excavated and before the fill is placed and compacted. Proof-rolling is intended not only for the foundation area, but also within all areas of pavement, sidewalks, walls and other locations that will support surface loads. Prior to fill placement, the exposed subgrade must be scarified to a depth of approximately 6 inches; moisture conditioned, and recompacted to the density specified for fill. The subgrade should be compacted to at least 95% of TEX-113-E maximum dry density (or ASTM D 698) at a moisture content range of -1.0% to +3.0% of optimum moisture content. Fill material should be placed in 6-inch compacted lifts, with each lift tested to confirm compaction and moisture compliance /WAC8R August 18, 2008

21 6.0 DESIGN REVIEW Kleinfelder was provided with preliminary site plans and design information. The recommendations contained in this report are based on this information. We must be consulted of any changes so that we may re-evaluate our recommendations. We also must be given the opportunity to review construction documents to affirm that our recommendations have been interpreted correctly. We cannot be responsible for misinterpretations if not given the opportunity to review aspects of the project that are based on the contents of this report. Such a review is considered an additional service /WAC8R August 18, 2008

22 7.0 LIMITATIONS OF THIS INVESTIGATION Recommendations contained in this report are based on our field observations and subsurface explorations, limited laboratory tests, and our present knowledge of the proposed construction. It is possible that soil conditions could vary between or beyond the points explored. If soil conditions are encountered during construction that differ from those described herein, we should be notified immediately in order that a review may be made and any supplemental recommendations provided. If the scope of the proposed construction, including the proposed loads or structural locations, changes from that described in this report, our recommendations should also be reviewed. We have prepared this report in substantial accordance with the generally accepted geotechnical engineering practices as it exists in the site area at the time of our study. No warranty, either express or implied, is made. The recommendations provided in this report are based on the assumption that an adequate program of tests and observations will be conducted by Kleinfelder during the construction phase in order to evaluate compliance with out recommendations. Other standards or documents referenced in any given standard cited in this report, or otherwise relied upon by the author of this report, are only mentioned in the given standard; they are not incorporated into it or included by reference, as that latter term is used relative to contracts or other matters of law. This report may be used only by Central Texas College and their designated agents and only for the purposes stated within a reasonable time from its issuance, but in no event later than one (1) year from the date of the report. Land or facility use, on and off-site conditions, regulations, or other factors may change over time, and additional work may be required with the passage of time. Based on the intended use of the report, Kleinfelder may recommend that additional work be performed and that an updated report be issued. Noncompliance with any of these requirements by Central Texas College and their designated agents or anyone else will release Kleinfelder from any liability resulting from the use of this report by any unauthorized party and Central Texas College and their designated agents agree to defend, indemnify, and hold harmless Kleinfelder from any claim or liability associated with such unauthorized use or noncompliance. The scope of work for this subsurface exploration and geotechnical report did not include environmental assessments or evaluations regarding the presence or absence of wetlands or hazardous substances in the soil, surface water, or groundwater at this site /WAC8R August 18, 2008

23 Kleinfelder has conducted subsurface exploration and provided recommendations for this project. We recommend that Kleinfelder be given the opportunity to provide final design for this project, if required. In the event Kleinfelder is not, at a minimum, retained to review the final project plans and specifications to evaluate if our recommendations have been properly interpreted, we will assume no responsibility for misinterpretation of our recommendations. We recommend that all earth work during construction be monitored by a representative from Kleinfelder, including site preparation, installation of piers, and placement of structural fill and trench backfill. The purpose of these services would be to provide Kleinfelder the opportunity to observe the actual soil conditions encountered during construction, evaluate the applicability of the recommendations presented in this report to the soil conditions encountered, and recommend appropriate changes in design or construction procedures if conditions differ from those described herein /WAC8R August 18, 2008

24 8.0 REFERENCES (1) Deere, D.U. & D.W. Deere, "The Rock Quality Designation (RQD) Index in Practice," In Rock Classification Systems for Engineering Purposes, ASTM STP 984, ASTM, Philadelphia, 1988, pages (2) Geologic Atlas of Texas, Waco Sheet, Bureau of Economic Geology, The University of Texas at Austin, Austin, Texas, (3) O'Neill, Michael W. & Poormoayed, Nader, "Methodology for Foundations on Expansive Clays," Journal of the Geotechnical Engineering Division, ASCE, Volume 106, No. GT 12, December, (4) International Code Council, International Building Code, Copyright 2006, Publications West Flossmoor Road, County Club Hills, Illinois, First printing, January /WAC8R August 18, 2008

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26 PROJECT NO.: DRAWN : August 18, 2008 DRAWN BY : ARH CHECKED BY : OF FILENAME : PLATE I SITE LOCATION MAP STUDENT UNION BUILDING KILLEEN, TEXAS PLATE I

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28 Boring No. Sample Depth (ft.) Liquid Limit Plastic Limit Plasticity Index Percent Passing No. 200 Sieve Moisture Content (%) Unit Dry Weight (pcf) Unconfined Compressive Strength (tsf) Strain at Failure (%) B B B B B B B B B B B B B B B B B B B Summary of Laboratory Results Project: CTC Student Union Project Number: Plate III

29 KEY TO LOGS OF BORINGS DRILLING AND SAMPLING SYMBOLS AND TERMS: Thin-Walled Tube Sample Auger Sample/Drilling Split Spoon Sample & Standard Penetration Test Continuous Core Sample TxDOT Cone Penetrometer Test Bag Sample Water Level Initial Measurement Water Level Subsequent Measurement Hand Penetrometer : An indicator of fine-grained soils consistency. Reported as tons per square foot (tsf). Core Recovered : Length of rock core recovered as a percent of the total continuous core sample length. RQD : Rock Quality Designation (RQD) is a measure of the integrity of recovered core samples. Reported in percentage as the sum of core pieces greater than 4 inches in length. Blow Count : Indicator of soil or rock density/consistency, and correlates to the soil strength. Blow count columns used to report values for both the SPT and the TxDOT Cone Penetrometer. Each column refers to the number of hammer blows required to advance the split spoon sampler or cone 6 inches. Note that the seating blows (first 6 inch drive) are not reported. For the SPT the N value is the sum of the values for the second and third drive. In cases where resistance was high during the first, second or third drive, the number of inches of penetration for 50 blows of the hammer is reported. RELATIVE DENSITY OF COARSE-GRAINED SOILS CONSISTENCY OF FINE-GRAINED SOILS Penetration Resistance Blows/foot Relative Density Hand Penetrometer Readings, tsf Consistency (see Note) 0-4 Very Loose <1 Soft 4-10 Loose 1-2 Firm Medium Dense 2-3 Stiff Dense 3-4 Very Stiff over 50 Very Dense >4.0 Hard Note: Some clays may have lower unconfined compressive strengths because of planes of weakness or cracks within the soil. The consistency rating of such soils are based on penetrometer readings. TERMS CHARACTERIZING SOIL STRUCTURE: Fissured : Containing cracks, usually more or less vertical Laminated : Composed of thin layers of varying color and texture, typically horizontal Interbedded : Composed of alternate layers of different soil types Calcareous : Containing appreciable quantities of calcium carbonate Well graded : Having wide range in grain sizes and substantial intermediate particle sizes Poorly graded : Predominantly one grain size, or having some intermediate size missing Slickensided : Having inclined planes of weakness that are slick and glossy in appearance GENERAL DEGREE OF WEATHERING: Unweathered : Rock in its natural state before being exposed to weathering agents Slightly weathered : Noted predominantly by color change with no disintegrated zones Weathered : Complete color change with zones of slightly decomposed rock Severely weathered : Complete color change with consistency, texture, and appearance approaching soil SUBSURFACE CONDITIONS: Soil and rock descriptions on the boring logs are a compilation from field data as well as from laboratory test results. The stratification lines represent the approximate boundary between materials and the actual transition can be gradual. Water level observations have been made in the borings at the times indicated. Note that fluctuations in groundwater level(s) may occur due to variations in rainfall, hydraulic conductivity of soil strata, construction activity, and other factors.

30 LOG OF BORING NO. B - 1 Project Description: Location: Approx. Surface Elevation: CTC Student Union Killeen, Texas Not Provided Depth Symbol/USCS Samples Hand Penetrometer, tsf Penetration, blows/ft Core Recovered, % RQD, % MATERIAL DESCRIPTION 1.5" ASPHALT over 8.5" CRUSHED LIMESTONE BASE LEAN to FAT CLAY; tan and light gray, with fossils, broken limestone, and weathered to severely weathered limestone seams 0.8' Liquid Limit Plastic Limit Plasticity Index % Passing No. 200 Sieve Moisture Content, % 13 Unit Dry Weight, pcf Unc. Compressive Strength, tsf Strain at Failure, % " 2" SEVERELY WEATHERED LIMESTONE; yellow-tan and light gray, clayey, calcareous, with various amounts of sand, broken limestone fragments, and interbedded layers of fat clay and broken limestone ---- fossiliferous below 8.5 feet 7.0' " SHALY LIMESTONE; gray and dark gray, highly fractured, fossiliferous, with interbedded layers of harder limestone and softer shale/marl 12.0' Completion Depth: Date Boring Started: Date Boring Completed: Logged by: Project No.: 25 ft. 7/9/08 7/9/08 H. Radtke Remarks: 25.0' Boring was advanced to a depth of 15.0 feet prior to using water as a drilling fluid. Groundwater was not encountered above that depth. Stratification lines represent approximate strata boundaries, as in-situ the transitions may be gradual. This Log of Boring is not intended for bidding or estimating purposes. Boring log(s) should not be reproduced separately from the engineering report unless said report is specifically included by reference.

31 LOG OF BORING NO. B - 2 Project Description: Location: Approx. Surface Elevation: CTC Student Union Killeen, Texas Not Provided Depth Symbol/USCS Samples Hand Penetrometer, tsf Penetration, blows/ft 8 21 Core Recovered, % RQD, % MATERIAL DESCRIPTION 1.5" ASPHALT over 10.5" CRUSHED LIMESTONE BASE LEAN to FAT CLAY; tan and light gray, with fossils, broken limestone, and weathered to severely weathered limestone seams 1.0' Liquid Limit Plastic Limit Plasticity Index % Passing No. 200 Sieve 83 Moisture Content, % 23 Unit Dry Weight, pcf Unc. Compressive Strength, tsf Strain at Failure, % " 5" SEVERELY WEATHERED LIMESTONE; tan and gray, clayey, calcareous, with various amounts of sand, broken limestone fragments, and interbedded layers of fat clay and broken limestone 6.5' 10 2" SHALY LIMESTONE; gray and dark gray, highly fractured, fossiliferous, with interbedded layers of harder limestone and softer shale/marl 13.0' " 20 1" ' Completion Depth: Date Boring Started: Date Boring Completed: Logged by: Project No.: 25 ft. 7/9/08 7/9/08 H. Radtke Remarks: Boring was advanced to a depth of 25.0 feet using dry drilling techniques. Groundwater was not encountered above that depth. Stratification lines represent approximate strata boundaries, as in-situ the transitions may be gradual. This Log of Boring is not intended for bidding or estimating purposes. Boring log(s) should not be reproduced separately from the engineering report unless said report is specifically included by reference.

32 LOG OF BORING NO. B - 3 Project Description: Location: Approx. Surface Elevation: CTC Student Union Killeen, Texas Not Provided Depth Symbol/USCS Samples Hand Penetrometer, tsf Penetration, blows/ft Core Recovered, % RQD, % MATERIAL DESCRIPTION 2" ASPHALT over 8" CRUSHED LIMESTONE BASE FAT to LEAN CLAY; tan and light gray, some orange from 1 to 3 feet, with fossils, broken limestone, and weathered to severely weathered limestone seams 0.8' Liquid Limit 55 Plastic Limit 20 Plasticity Index 35 % Passing No. 200 Sieve 92 Moisture Content, % 23 Unit Dry Weight, pcf Unc. Compressive Strength, tsf Strain at Failure, % " SEVERELY WEATHERED LIMESTONE; tan, yellow-tan, and light gray, clayey, calcareous, with various amounts of sand, broken limestone fragments, and interbedded layers of fat clay and broken limestone 9.0' 4" SHALY LIMESTONE; gray and dark gray, highly fractured, fossiliferous, with interbedded layers of harder limestone and softer shale/marl 12.5' Completion Depth: Date Boring Started: Date Boring Completed: Logged by: Project No.: 25 ft. 7/9/08 7/9/08 H. Radtke Remarks: 25.0' Boring was advanced to a depth of 15.0 feet prior to using water as a drilling fluid. Groundwater was not encountered above that depth. Stratification lines represent approximate strata boundaries, as in-situ the transitions may be gradual. This Log of Boring is not intended for bidding or estimating purposes. Boring log(s) should not be reproduced separately from the engineering report unless said report is specifically included by reference.

33 LOG OF BORING NO. B - 4 Project Description: Location: Approx. Surface Elevation: CTC Student Union Killeen, Texas Not Provided Depth Symbol/USCS Samples Hand Penetrometer, tsf Penetration, blows/ft Core Recovered, % RQD, % MATERIAL DESCRIPTION 2.5" ASPHALT over 9.5" CRUSHED LIMESTONE BASE LEAN to FAT CLAY; tan and light gray, with fossils, broken limestone, and weathered to severely weathered limestone seams 1.0' Liquid Limit 53 Plastic Limit 19 Plasticity Index 34 % Passing No. 200 Sieve 85 Moisture Content, % 18 Unit Dry Weight, pcf Unc. Compressive Strength, tsf Strain at Failure, % " SEVERELY WEATHERED LIMESTONE; yellow-tan and light gray, clayey, calcareous, with various amounts of sand, broken limestone fragments, and interbedded layers of fat clay and broken limestone 9.0' " SHALY LIMESTONE; gray and dark gray, highly fractured, fossiliferous, with interbedded layers of harder limestone and softer shale/marl 15.0' Completion Depth: Date Boring Started: Date Boring Completed: Logged by: Project No.: 25 ft. 7/9/08 7/9/08 H. Radtke Remarks: 25.0' Boring was advanced to a depth of 15.0 feet prior to using water as a drilling fluid. Groundwater was not encountered above that depth. Stratification lines represent approximate strata boundaries, as in-situ the transitions may be gradual. This Log of Boring is not intended for bidding or estimating purposes. Boring log(s) should not be reproduced separately from the engineering report unless said report is specifically included by reference.

34 LOG OF BORING NO. B - 5 Project Description: Location: Approx. Surface Elevation: CTC Student Union Killeen, Texas Not Provided Depth Symbol/USCS Samples Hand Penetrometer, tsf Penetration, blows/ft 2" 4.5" Core Recovered, % RQD, % MATERIAL DESCRIPTION 1.5" ASPHALT over 10.5" CRUSHED LIMESTONE BASE SEVERELY WEATHERED LIMESTONE; tan, clayey, calcareous, with various amounts of sand, broken limestone fragments, and interbedded layers of fat clay and broken limestone 1.0' Liquid Limit Plastic Limit Plasticity Index % Passing No. 200 Sieve Moisture Content, % 9 Unit Dry Weight, pcf Unc. Compressive Strength, tsf Strain at Failure, % 5 4" 4.5" ---- tan and gray below 6.5 feet " ' Completion Depth: Date Boring Started: Date Boring Completed: Logged by: Project No.: 10 ft. 7/9/08 7/9/08 H. Radtke Remarks: Boring was advanced to a depth of 10.0 feet using dry drilling techniques. Groundwater was not encountered above that depth. Stratification lines represent approximate strata boundaries, as in-situ the transitions may be gradual. This Log of Boring is not intended for bidding or estimating purposes. Boring log(s) should not be reproduced separately from the engineering report unless said report is specifically included by reference.