Laserfiche WebLink
<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />,I <br />I <br />I <br />II <br />I <br />I <br /> <br />the transition width, provided the sidefill is compacted. Defining <br />the narrow trench width as a trench having a width at the top of the <br />pipe equal to or less than the outside horizontal span plus one foot <br />(300 mm), and assuming a conservative linear variation, the variable <br />trench bedding factor can be determined by: <br /> <br />s,. = (8[. - lJr.) [~ - (& + 1.0)] + s" <br />Bw-(&+ 1.0) <br /> <br />Where: Be . outside horizontal span of pipe, feet (metres) <br />Bd = trench width at top of pipe, feet (metres) <br />Bdt = transition width at top of pipe, feet (metres) <br />Bfe = bedding factor, embankment <br />Bft = fixed bedding factor, trench <br />Bfv . variable bedding factor, trench <br /> <br />The SAlIM program prompts the !.;"c.. for all the necessary data to <br />calculate the variable trench DeaQ~~g factors, This information <br />incorporates the majority of the data ~sed for determining an <br />embankment bedding factor. <br /> <br />2.2 "hank.eDt Installations <br /> <br />Embankment installations are subdivided into two groups: <br /> <br />o Positive projection pipe is installed with the top of the <br />pipe prOjecting above the surface of the natural ground, or <br />compacted fill, and then covered with earth fill, This type <br />also includes pipe installed in extremely wide trenches. <br /> <br />o Negative projection pipe is installed in relatively shallow <br />trenches of such depth that the top of the pipe is below the <br />level of the natural gt' ',d surface or compacted fillt and <br />then covered with earth ~.ll to a height appreciably greater <br />than the distance from the natural ground surface or original <br />compacted fill surface to tbe top of the pipe. <br /> <br />In determining the loading on embankment installations, SAlIM <br />requires the inputing of the projection ratio, settlement ratio, <br />lateral pressure ratio and lateral pressure fraction, <br /> <br />The projection ratio, PI is the vertical distance between the <br />outside top of the pipe and the r~tural ground surface, divided by <br />the outside horizontal diameter : the pipe. <br /> <br />The settlement ratio, r a' is the factor which determines the <br />direction of action of !ne frictional forces and is dependent upon <br />the settlement and deflection of the pipe and the compression of the <br />soil adjacent to the pipe. These values range from 0.0 to 1,0 for <br />positive projection conditions and -1.0 to 0.0 for negative <br />projection conditions. <br /> <br />3 <br />