Laserfiche WebLink
<br /> <br />The two most important strength characteristics of the slope matenals are: P) the internal angle of <br />• friction (~) in degrees and 21 existing cohesion of the material in place (cn) in tons per sq. ft. Pore <br />pressure ratios, material density, phreatic surfaces and shrink/s~oell potential are other factors which <br />can also be important. <br />In lay terms, cohesion is a measure of resistance to shearing forces due to bonding between particles <br />in afine-grained soil. The internal angle of friction is a measure of resistance to shearing forces due <br />to friction among large soil particles. Clays generally have a very high cohesion and very little <br />internal friction. Sands and gravels, on the other hand, usually have high internal friction angles and <br />little or no cohesion. <br />Since the slope that is being considered is primarily a poorly sorted sand and gravel deposit with very <br />little clay, almost all of its resistive strength will be due to internal friction. Cohesion is minimal in <br />this soil. See Table 1 below taken from Huang- Stability Analysis of Earth Slopes. <br />. <br /> <br /> <br />L'N'IFl ED <br />CLnSSIF!Cn TION <br /> <br /> <br /> <br />OIL TYPE PROCTOR <br />MA%IMOM <br />DRY <br />DENSITY <br />pc( COMPx CrtON <br />OPrIMVM <br />MOISTURE <br />CONTENT <br />'k <br />si COMPM1CTED <br />COHESION <br />Co <br />ts( <br />SeTV RATEO <br />COHESION <br />C,•, <br />K( <br />FRIC[lON <br />eNOLE <br /> <br />deg <br />G`~.' well graded clean gravels, graveLsand niizture >119 <1J.3 >38 <br />GP poorly graded clean gravels, gravel sand mixture >I10 <12.4 >}7 <br />G11 silly gravels, poorly graded gravel-sand-silt >111 <11.5 >14 <br />GC clayey gravels. poorly graded gravel-sand-clay >I15 <14.7 >31 <br />SW well graded clean sands, gravelly sands 119.5 17.7 x2.5 0.11-0.04 7821 <br />SP poorly graded clean saris, sand-gravel rtsizture IIOs'_ I: 4x 1.0 0.:1-0.06 7721 <br />SM silty sands, poorly graded sand silt misture Ili:l 11.5x0.1 0.5320.06 021x0.07 34x1 <br />SA7-SC sand-self-clay with slightly plastic fines 11921 I' 820 S 0.'_f 2007 0 IS-0.06 33x3 <br />SC clayey sands. poorly graded sand-clay misture I15_I 11 7_0.4 0.78_0 I6 0 I?20.06 7123 <br />.ML inorganic silts and clayui silts 107_1 19?x0.7 0.7020 10 0.09_• 32x2 <br />ML~CL mixtures of inorgani: sills and clays 109_2 16.8x0.7 0.66x018 0_'3x• 32x2 <br />CL inorganc clays of low to medium plasticty 108x1 I7.J x3 0.91x011 O.la x0.0'_ '_8 _? <br />OL organic silts and silty clays or low plazticily <br />MH inorganic clayey silts. elastic silo 82x1 36.7x3 ? 0.76x0.71 0.21x0.09 2523 <br />CH inorganic clays of high plasticity 9ax2 25.Sx L: 1.07x0.35 0.12'0.06 19x5 <br />OH organic clays and silly clays <br />•dcnacs imurficiem mta. > it grater WRri. < u leu dw <br />I~tt Bureau M fkclamarian. 1971. 1 PH=157 1 Nltn', 1 u1=95.8 kPal <br />• Table ] -Slope Stability Characteristics of Various Materials <br />Carol .4nn Permit CDMG Application ~ ~ <br />