Laserfiche WebLink
Timm Comer <br />Mill Platform Machine Vibration Effects <br />Project 74201125G <br />September, 20, 2012 <br />AS <br />"W"i <br />The machine foundation vibrations were applied to a beam modeled in QUAKE/W. The beam was given <br />material properties to simulate a 3 foot thick concrete mat foundation. Initial stress conditions were <br />calculated with a static stress boundary condition applied to the foundation equal to one half of the <br />maximum allowable bearing capacity given in the geotechnical report, i.e. 3,500 pounds per square foot <br />(psf). The material was modeled as a dry fill without pore water pressures. Generation of pore water <br />pressure is not expected to occur due to the granular nature of the fill and because water infiltration is <br />limited by the geomembrane liner. To simulate the machine vibrations a boundary condition was defined <br />along the foundation as a stress function with time. A sinusoidal function was used to model the vertical <br />oscillation of the stresses. The assumption was made that stresses induced from dynamic loads would <br />not exceed the maximum allowable bearing capacity given in the geotechnical report, i.e. 7,000 psf. The <br />sine waves representing the vibrations had a maximum stress of 7,000 psf, a minimum stress equal to the <br />initial foundation load of 3,500 psf. The wave lengths of the sine functions were equal to the operating <br />angular velocity (rotations per minute, rpm) of the ball and rod mills which were 15.58 rpm and 14.12 rpm, <br />respectively. The sine waves representing the machine vibrations are shown in Figure 4. The vibrations <br />were applied to the foundation independent from one another. <br />Time (sec) <br />Figure 4: Machine Vibrations <br />The model was subjected to the foundation vibrations for 1 year and the soil response was recorded. The <br />vertical displacements immediately beneath the mill foundation are plotted in Figure 5 for a period of 60 <br />seconds. The results show that under the stress levels imparted by the foundation vibrations, the <br />structural fill deflects linearly according to the relationships defined by the shear modulus used in the <br />linear - equivalent elastic model. After an initial peak strain, a deflection pattern is established and is <br />consistent with time. This indicates no significant degradation of shear strength in the structural fill which <br />could lead to larger displacements over time. <br />S1projects \1125g squaw gulch valley leach facililty design\h2 - design \mill platform machine vibration letters sept 2012 \mill platform machine vibrations (3).doc 4 <br />