GEOTECHNICAL INVESTIGATION

Transcription

1 GEOTECHNICAL INVESTIGATION 1 08 Railway Avenue South Milo, AB Prepared for: 108 Railway Avenue South Milo, Alberta TOL 1LO Date: File:

2 GEOTECHNICAL INVESTIGATION 108 Railway Avenue South, Milo, Alberta PAGE A. City of Calgary Report Requirements INTRODUCTION FIELD AND LABORATORY INVESTIGATIONS SITE DESCRIPTION SUBSURFACE FEATURES SUBSOIL CONDITIONS GROUND WATER CONDITIONS LABORATORY TESTING RECOMMENDATIONS GENERAL FOUNDATIONS Continuous and/or Spread Footings...& Cast in~piace Concrete Piles...& 5.3 GRADE SUPPORTED FLOOR SLABS...& 5.4 DRAINAGE LATERAL EARTH PRESSURES SUBGRADE PROTECTION TEMPORARY EXCAVATION SIDE SLOPES CEMENT TYPE PAVEMENTS INSPECTION EARTHQUAKE RESISTANT DESIGN CLOSURE APPENDIX I.. APPENDIX II.. SITE PLANS, DRAWINGS AND TEST HOLE LOGS ADDITIONAL RECOMMENDATIONS

3 A. City of Calgary Report Requirements The City of Calgary shall at all times be irrevocably and unconditionally entitled to fully use and rely on this report as addressee and party to the report, including all attachments, drawings and schedules, in each case notwithstanding any provision, disclaimer or waiver in the report to the contrary. The City of Calgary shall be entitled to provide copies of the report to City Council and City of Calgary employees, City of Calgary regulatory boards, affiliates, advisors, consultants, lenders and assignees, each of whom shall also be similarly entitled to fully use and rely on the report. The City of Calgary is at all times entitled to provide copies of the report to Alberta Environment and any other governmental authorities and regulatory bodies having jurisdiction. The City of Calgary may also contact the author or other parties to the report to obtain further information respecting the report or to discuss the report further. Pagel

4 1.0 INTRODUCTION The following report presents results of a geotechnical investigation at the site of the proposed fire hall located at 108 Railway Avenue, Milo, Alberta (see Drawing 1 1, Appendix 1). The purpose of the investigation was to determine the subsurface conditions at the site, and to provide geotechnical data for the design/construction of the proposed structures. Authorization to proceed with this investigation was received on July 25, 2016, from Byron Thompson of. Field work was carried out on August 5, A total of four (4) test holes (TH) were drilled at the site using a dry auger type drilling rig. Locations of the test holes are shown on the test hole location plan, Drawing 1 2, Appendix I. A test hole survey was performed by Curtis Engineering Associates Ltd. and referenced to a Temporary Bench Mark (TBM). The ground level of the existing fire hydrant located at the North East corner of the site was used as the TBM 2.0 FIELD AND LABORATORY INVESTIGATIONS Four (4) test holes were drilled at the site to delineate the stratigraphy and to provide samples for laboratory testing. The maximum depth of test hole penetration was 6.55 metres (21.50 feet) below existing grade. Disturbed soil samples were collected at regular intervals in the test holes. In addition, blow count for penetration of the pipe at 150 mm (6.0 inch) intervals in two test holes was observed to determine Standard Penetration Test N values (SPT N-Values) and insitu character of the site soils. Perforated standpipe was installed in two (2) test holes (TH-1 and TH-3) to permit ground water monitoring. Pagel

5 Standard laboratory tests were performed on representative soil samples acquired from the field, to determine their natural moisture contents, visual classifications, atterberg limits, and water-soluble sulphate contents. Results of these tests are summarized on the test hole logs, Drawing 1-3 to 1-6, Appendix I. 3.0 SITE DESCRIPTION The site of the proposed development is located in 108 Railway Avenue, Milo, Alberta. The topography of the site is relatively flat. Access to the site is readily obtained by truck-mounted equipment. At the time of investigation, the site was rough graded and occupied by an existing fire hall building 4.0 SUBSURFACE FEATURES 4.1 SUBSOIL CONDITIONS Based upon the test hole information, it is concluded that the stratigraphy of the site generally consists of a clay till layer from ground surface upto the maximum boring termination depth ranging from 3.50 metres (11.5 feet) to 6.55 metres (21.50 feet) below existing ground surface. The fine grained soils encountered are of firm to stiff in consistency as evidenced by Standard Penetration Tests on the soils encountered (The Standard Penetration is a record of the number of blows of 63.6 kg (140.0 lb) weight dropping 750mm (30.0 inches) required to drive a 50mm (2.0 inch) spoon 300mm (12.0) inches into the sub grade soil). Detailed soil information is summarized on the test hole logs Drawings 1-3 to 1-6, Appendix I. Page3

6 4.2 GROUND WATER CONDITIONS Perforated standpipe was installed in two (2) test holes to monitor the ground water level at the site. The ground water level readings, from the piezometer and as measured in test holes at completion of drilling, are summarized as follows. DEPTH TO WATER BELOW EXISTING GRADE 108 Railway Avenue, Milo, Alberta Test Hole No. August 5, 2016 August 8, 2016 TH m (4.49 feet}_ TH TH m (6.72 feet) TH Fluctuation of the ground water table can be expected, especially in response to snow melt or heavy rainfall. It is recommended that the client should continue to monitor the water table to provide up-to-date information, particularly immediately prior to the start of construction. Alternatively, arrangements can be made for Curtis Engineering Associates Ltd. to provide a water monitoring service. 4.3 LABORATORY TESTING Standard laboratory testing was performed on the selected samples acquired from the field were to determine their atterberg limits, natural moisture contents, and watersoluble sulphate contents. The natural moisture content of the samples varies between 17.96% and 28.49%. The water soluble sulphate content of the tested samples was 0.05%, and 2. 72%, which can Poge4

7 be considered as severe. The results of the Atterberg limit tests on the soil samples at the location of Test Hole No. 1 (TH-1 ), at a depth of 1.52 metres (5.0 feet), and TH-3, at a depth of 3.05 metres (10.0 feet) indicate that site soils are of medium plasticity with liquid limits of 44.7 and 47.6, and plastic limits of 17.8 and 19.1 respectively. The site soils have a medium to high degree of swelling potential and should experience medium to high volume change with the addition of water. The natural moisture content, atterberg limits, and water-soluble sulphate content results are presented on the test hole logs, Drawings 1-3 to 1-6, Appendix I. 5.0 RECOMMENDATIONS Based on interpretation of subsurface conditions found in the test holes, the following recommendations are believed to be pertinent for the design/construction of the proposed structure. 5.1 GENERAL It is understood that the proposed development will consist of expanding the existing fire hall building in Milo 5.2 FOUNDATIONS Based on the test holes information, continuous and spread footings and cast in place concrete piles are considered to be the suitable foundation systems for supporting 108 Railway Avenue South, Milo~ AB August~ 2016 PageS

8 CURTIS ENGINEERING ASSOCIATES L TO. structural loads of the proposed structures. The choice of the foundation type should be made on economic and structural considerations Continuous and/or Spread Footings Continuous and/or spread footings may be proportioned based on a maximum net allowable bearing pressure {Serviceability Limit State) of 96 kpa (2,000 psf) for footings founded in the clay till strata existent at the site. To obtain unfactored ultimate bearing resistance (ULS), the SLS pressure may be increased by a factor of three (3). A geotechnical resistance factor of 0.5 should be used in the ULS design scenario. The minimum soil cover above footings for frost protection is 1.37 and 2.13 metres {4.5 and 7.0 feet) below finished grade for heated and unheated structures, respectively. Footing surfaces should be hand-cleaned to remove all disturbed, loose or wet material. The minimum width of footing that can be used should conform to specifications in the appropriate building code. It is recommended that the footing subgrade should be inspected by Curtis Engineering Associates Ltd. to verify the bearing capacity of site soils at all building locations. Additional recommendations for continuous and spread footings are contained in Appendix II of this report Cast-in-Place Concrete Piles As an alternate to continuous and spread footings foundations, a cast-in-place concrete Page6

9 pile and grade beam foundation system may be utilized on the whole site. Straight shaft or belled cast-in-place concrete piles may be used as foundations for the proposed structures. Piles may be designed for end-bearing provided they have a minimum shaft diameter of 400 mm (16.0 inches) and a clean and dry base can be prepared. Piles should be founded at a minimum depth of 6.10 metres (20 feet) below existing ground surface in the clay till strata existing at the site. A net allowable end - bearing pressure (Serviceability Limit State) of 144 kpa (3,000 psf) may be used. To obtain unfactored ultimate bearing resistance (ULS), the SLS pressure may be increased by a factor of three (3). A geotechnical resistance factor of 0.4 should be used in the ULS design scenario. Piles may be belled at the bottom to a maximum of three (3) shaft diameters to increase the end bearing area. In addition to end-bearing, piles may be designed for skin friction. The allowable skin friction between pile and soil may be taken as 10 kpa (209 psf). It should be noted that allowable skin friction resistance in the upper 2.13 metres (7.0 feet) of pile embedment should be ignored to allow for seasonal moisture variation and frost penetration. In case of belled piles, the skin friction over height of bell and for a height equal to one (1) shaft diameter above top of bell should be ignored. In view of groundwater conditions existent at the site, Sleeving of the piles may be required during installation of piles. It is recommended that all piles be installed under full-time inspection by Curtis Engineering Associates Ltd. to verify the load-carrying capacities of the site soils at the specific building location. Other recommendations concerning cast-in-place concrete piles are contained in Appendix II of this report. Page7

10 5.2.3 Settlement Evaluation The recommended design parameters presented in this section are for preliminary design purposes. We believe that compliance with the recommendations would produce tolerable settlement under normal structures. It should be noted, however, that foundation settlements are a function of the foundation layout and the construction procedure. We recommend that Curtis Engineering Associates Ltd. should review the final design of the foundation system prior to construction. 5.3 GRADE SUPPORTED FLOOR SLABS Floor slabs supported on grade must be designed for the intended loads, including those resulting from materials storage and the operation of machinery. Any soft, organic and fill materials, as determined from inspection and proof-rolling, must be overexcavated and replaced by granular materials. Floor slabs should be supported on a well-compacted granular base to ensure uniform distribution of floor loadings over the subgrade. The required thickness of this base course is dependent upon the magnitude of the loadings, but should not be less than 100 mm {4.0 inches). The base course, and any other fill material used to replace soft subsoils, should be compacted to at least 98% of Standard Proctor dry density. Pertaining recommendations for concrete floor slabs supported on grade are contained in Appendix II. Page8

11 5.4 DRAINAGE Final site grading should direct surface run-off away from the proposed structure to prevent surface water infiltration. The backfill around the building should be compacted to a minimum 95% of Standard Proctor density and be graded with a positive slope away from the building to prevent surface ponding of water after settlement. In view of the site conditions, a weeping tile drainage system connected to a positive drainage should be installed for drainage of subsurface water. 5.5 LATERAL EARTH PRESSURES Lateral earth pressures on backfilled walls or during excavation can be estimated from the following equation. where; p = Lateral earth force per unit length of wall Ko = Coefficient of at rest earth pressure (Use 0.5) y = Unit weight of soil (Use 2,003 kg/m3) H = Wall Height The above expression does not include surcharge and/or hydrostatic loads and these should be added where applicable. 5.6 SUBGRADE PROTECTION Subgrade soils beneath foundation elements must be protected from frost penetration Milo Fire Deportment Page9

12 during and after construction. Detrimental heaving due to soil freezing and/or settlement resulting from subsequent thawing of frozen soils may result. It is essential to ensure that footings and floor slabs are not poured on frozen subsoils, and that the foundation soils are protected from frost actions at all times. Similarly, all foundation excavations must be protected from rain, snow and the ingress of free water. Surface ponding should not be allowed on any excavated surfaces. Unnecessary prolonged exposure of bearing surfaces should be avoided, to limit effects of weathering and deterioration of the integrity of the subgrade soils. 5.7 TEMPORARY EXCAVATION SIDE SLOPES Temporary excavations at the site should be sloped or shored for worker and foundation protection. Construction must conform to good practice and comply with regulations such as the Alberta Construction Safety Regulations. For temporary excavations in the natural soil existing at the site, a construction sideslope of 1.0 V: 1.5 H (1.0 Vertical to 1.5 Horizontal) may be used up to a depth of 3.05 metres (1 0.0 feet). Deeper excavations should be shored or sloped at a flatter angle. Any construction sideslope differing from the suggested one should be verified by Curtis Engineering Associates Ltd. Excavations must be protected from rain, snow and the ingress of free water. Prolonged exposure of excavated areas should be avoided to prevent deterioration of exposed soils with resultant slope instability. Similarly, excavated materials should be stockpiled away from the slope to avoid slope instability and to prevent materials falling into the excavation. The integrity of any adjacent structures should be protected by either underpinning or installing a retaining wall prior to the excavation of the subject site. 108 Railway Avenue South, Mila, AB Page10

13 5.8 CEMENT TYPE Severe concentrations (2.72%) of water soluble sulphates were found in the soil samples tested. Based on the test results, it is recommended that Type 50, sulphate resisting cement be used for concrete foundation elements. A minimum 28-day compressive strength of 35 MPa is recommended. Air entrainment (4 to 7 percent) should be used, especially for concrete exposed to freeze/thaw conditions. 5.9 PAVEMENTS In addition to the subsoil conditions, pavement requirements for truck or car parking areas are a function of vehicle load magnitude and frequency of load application. In the absence of any specific design data, the following recommendations are made for construction of pavements for parking areas. The subgrade should be scarified to a 150 mm (6.0 inch) depth and recompacted to 97% of Standard Proctor density at a moisture content at or near optimum moisture content. Sections as detailed below should then be applied. Heavy Trucks Asphalt Surface Crushed Gravel Base Pitrun Gravel Sub-base PARKING AREA PAVEMENTS Granular Base and Asphalt Pavement Thickness Compaction em Inch % of Standard Marshall density % of Standard Proctor density % of Standard Proctor density Cars & Light Trucks Asphalt Surface Crushed Gravel Base Pitrun Gravel Sub-base Granular Base and Asphalt Pavement Thickness Compaction em Inch % of Standard Marshall density % of Standard Proctor density % of Standard Proctor density Page11

14 The surficial soils at the site are considered lightly frost susceptible. Some heaving of the paved areas due to soil freezing in winter months can be expected. Any organic and soft fill encountered at the pavement subgrade should be over-excavated and replaced by granular material compacted to 98% of Standard Proctor density. Additional recommendations for pavements are presented in Appendix II, together with suggested gradation limits for crushed gravel base and pitrun sub-base materials INSPECTION It is recommended that Curtis Engineering Associates Ltd. be engaged to inspect all bearing surfaces beneath foundation elements prior to concreting, and to provide quality control and monitoring services during the construction stages of this project EARTHQUAKE RESISTANT DESIGN The proposed structure should be designed to resist the forces generated during an earthquake as outlined in Section of the Alberta Building Code, The soil conditions existent at a site exert a major influence on the amplitude and nature of earthquake motions transmitted to the ground surface during an earthquake. The subsoils at the site comprise of fine grained soils. It is recommended that a Site Class "D" may be used for earthquake resistant design of structure. Page12

15 CURTIS ENGINEERING ASSOC/A TES LTD. 6.0 CLOSURE The recommendations presented in this report were based on the interpreted subsurface conditions found in the four (4) test holes drilled at the site. Additional recommendations contained in Appendix II should be read in conjunction with the text of this report. It should be noted that natural conditions can be variable. Individual recommendations in this report should not be used out of context with the entire report and the interpretation of any part of this report should be made in consultation with our office to avoid any misinterpretation. Curtis Engineering Associates Ltd. does not accept responsibility to any third party for the use in whole or in part of the contents of this report. Should subsurface conditions other than those presented in this report be encountered during construction, the client should notify our office so that our recommendations presented herein can be reviewed and revised, if necessary. Respectfully Submitted, w Sarat Ponapalli, M.S., P.Eng. Geotechnical Engineer 1.08 Railway Avenue South, Milo, AB The As8ociallon of Profeeeional Engineers, Geologim and GeopfJysicist6 of Alberta Page13