5.23 Soil Compaction Testing Requirements Purpose This instruction has been developed to support projects where the reinstatement and compaction of soil is required following an excavation. The purpose of this instruction is to specify the minimum requirements and methodology for testing and recording soil compaction results using a Penetrometer. This instruction applies to Horizon Power employees and contractors involved in Horizon Power s underground projects. Safety Before commencement of work, a risk assessment must be carried out using the Risk Analysis Procedure (OSH-3.6-1-02), to identify and document the hazards and risks associated with the task and ensure appropriate control measures are implemented. It is important that, appropriate control measures must be identified, documented and implemented to lessen or control the identified hazards. The cable location must be identified and controls put in place to ensure that the electrical cable(s) are not damaged prior to commencing the soil compaction tests of the first layer of soil laid over a cable. All trenches left open shall be securely barricaded in accordance with Field Instruction FI 2.15 Temporary Safety Barriers and/or Warning Signs. Instruction The following penetrometers may be used as a means of testing the level of compaction of backfill: Perth Penetrometer: The Perth Penetrometer has a flat ended rod driven by a 9 kg mass, dropping 600 mm. (See Fig. 1 for picture of Perth Penetrometer). Note: The Perth Penetrometer method is limited to granular soils with a maximum particle size not exceeding 2 mm and requires the first layer of soil to be a minimum of 500 mm to complete the tests. Dynamic Cone Penetrometer: The Dynamic Cone Penetrometer has a steel cone ended rod driven by a 9 kg mass, dropping 510 mm. (See Fig. 2 for picture of Dynamic Cone Penetrometer) Number of Test Compaction testing of backfill materials shall be done along the length of the trench or excavation. Each backfill layer of 300 mm (excluding bedding sand) must be compaction tested at a minimum rate of one (1) test every 15 metres, at each driveway, road crossing and at each side of any structure. CS10 # 2225654 FI 5.23 Soil Compaction Testing Requirements Page 1 of 5
The evaluation criteria are a pre-determined number of blows which is required to drive the Penetrometer 300 mm above the Flat Ended or Cone Ended rod. The minimum number of blows for the various soil types is listed in Table 1 (below). Table 1 No. of Blows Sand Silty-clay Stone-based 6 22 11 Note: These figures are based on 90% relative compaction (or higher) of the surrounding soil. Test Procedure Material such as crushed rock, large gravel, root, organic matter or any other unfavourable material shall be removed as it will be difficult for the Penetrometer to penetrate and could also damage the electrical cable(s). The depth from ground level to the surface level of each layer to be tested must be measured to the nearest 10 mm and recorded on the Compaction Test Certificate (see Fig. 3). The Penetrometer must be held perpendicular with the tip on the surface of the layer to be tested. Note: When using the Perth Penetrometer gently tap the hammer on the anvil until a penetration of 150 mm is achieved. If using the Dynamic Cone Penetrometer gently tap the hammer until the cone has started to penetrate the surface. Raise the hammer to the stop and allow it to fall freely onto the anvil and count the number of blows required to drive the Penetrometer a distance of 300 mm. For a Perth Penetrometer, total penetration of 450 mm must include initial 150 mm. Note: The interpretation of results must be as specified in the relevant construction standard or contract applicable to the work undertaken. References Occupational Safety & Heath Act 1984 Occupational Safety & Health Regulations 1996 SHMS OSH-3.6-1-02 Job Risk Analysis (JRA) Procedure SHMS OSH-3.6-1-26 Personal Protective Equipment Field Instruction 2.6 Worksite Clothing / Personal Protective Equipment Requirements Field Instruction 2.23 Job Hazard and Risk Management (JRA) Field Instruction 2.15 Temporary Safety Barriers and / or Warning Signs CS10 # 2225654 FI 5.23 Soil Compaction Testing Requirements Page 2 of 5
Fig. 1 Perth Penetrometer CS10 # 2225654 FI 5.23 Soil Compaction Testing Requirements Page 3 of 5
Fig. 2 - Dynamic Cone Penetrometer CS10 # 2225654 FI 5.23 Soil Compaction Testing Requirements Page 4 of 5
Fig. 3 Compaction Test Certificate CS10 # 2225654 FI 5.23 Soil Compaction Testing Requirements Page 5 of 5