A F Howland Associates

A F Howland Associates

7 services found

A F Howland Associates Services

  • Site Investigation

  • Cable Percussion Boring

    Cable Percussion Boring

    Light-cable percussion is the most common drilling method used for geotechnical site or ground investigations. Depending upon access limitations and favourable ground conditions deep boreholes up to 50m depth can be formed. Light-cable percussion drilling uses a mobile rig with a winch of between one to two tonne capacity driven by a diesel engine and a tripod derrick of about 7m height. The derrick folds down so that the rig can be towed by a...

  • Dynamic Cone Penetrometer (DCP) Test

    Dynamic Cone Penetrometer (DCP) Test

    The California Bearing Ratio (CBR) test is a penetration test developed by the California State Highway Department and is used to determine the mechanical strength of a soil. The test can be carried out on site or in the laboratory. The VBR test is carried out using a cylindrical plunger which penetrates the soil at a given rate. The relationship between the force and penetration can then be used to calculate the CBR value of the soil being tested.

  • Dynamic Probing

    Dynamic Probing

    Dynamic probing involves driving a cylindrical sacrificial or fixed cone into the ground using a high frequency percussive hammer. The diameter and angle of the cone will depend upon the chosen method. For example the heavy or super heavy dynamic probe has an angle of 90 degrees. The cone is attached to a 1m section steel rod with a nominal diameter of approximately 35mm and graduation markings set at 100mm intervals. Depending upon the chosen method,...

  • Rotary Core Drilling

    Rotary Core Drilling

    The rotary drilling technique is normally used for forming a deep observation borehole or for obtaining representative samples of rock which could not be recovered using conventional light cable percussion drilling methods. Powered rotary cutting tools use a cutter head on the end of a shaft, which is driven into the ground as it rotates. The system requires lubrication (air, water or drilling mud) to keep the cutting head cool and remove the soil or...

  • Trial Pit Excavations

    Trial Pit Excavations

    This technique is normally used for recovering near surface large bulk samples of granular soil or if close visual examination of the strata is required. The main advantage of this method when compared to percussion drilling is the relative speed with which the work can be carried out. The disadvantage is the level of surface disturbance suffered and the difficulty in carrying out the effective reinstatement of the excavations. Trial pits can be...

  • Plate Loading Test

    Plate Loading Test

    Plate load tests are used to make a determination of the vertical deformation and strength characteristics of soil and can allow an estimate of ultimate bearing capacity, shear strength and modulus of sub-grade reaction to be made. The method involves applying a load through a rigid plate and assessing the amount of penetration with time. The test may be carried out at ground surface or in shallow pits and trenches. Common uses are to assess the...

  • Window and Windowless Sampling

    Window and Windowless Sampling

    Percussive window or windowless sampling involves driving cylindrical steel tubes into the ground using a high frequency percussive hammer. Usually the hammer is driven by a hydraulic power pack, but electric and pneumatic hammers are also available to suit particular site conditions. The drilling rig is normally track or crawler mounted and some of the rigs are small enough to be driven through a conventional sized door way. However, in areas where...