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<br />. <br /> <br />. <br /> <br />. <br /> <br />EM 1110.2.2504 <br />31 Mar 94 <br /> <br />0.5 <br /> <br />LEGEND <br /> <br />0.4 <br /> <br />o CK 0 DIRECT SIMPLE SHEAR (DSS) <br />o <br />o C'b UNDRAINED CONSOLIDATED TRIAXIAL COMPRESSION (TCI <br /> <br />/_~c.- "---:-/-------- 0 <br />~O 0 CXJ/DSS 0 <br /> <br />0.3 <br /> <br />CI)"I Q. <br /> <br /> <br />o <br /> <br />0.2 <br /> <br />00 <br /> <br />I <br /> <br />00 <br /> <br />VARVED CLAY <br />0.1 (SILTLAYERI <br /> <br />MAINE ORGANIC <br />VARVED CLAY <br />(CLAY LAYER) <br /> <br />TRIESTE <br /> <br />ATCHAFALAYA <br /> <br />o <br />o <br /> <br />80 <br /> <br />100 <br /> <br />20 <br /> <br /><<l 60 <br />PLASTICITY INDEX, PI, % <br /> <br />Figure 3-2. Relatlonahip between the ratio SJp and plutlclty Index lor normally conaolldated claya (aller Gardner <br />1977) <br /> <br />slrenglh due 10 Ihe generation of negative pore pressures <br />which can dissipale wilh lime. Such negative pore <br />pressures allow sleep Iemporary culs 10 be made in clay <br />soils. Active earth pressures calculaled using undrained <br />paramelelS are minimum (somelimes negative) values <br />Ihal may be unconservative for design, They should be <br />used, however, 10 calculate crack deplhs when checldng <br />Ihe case of a water-filled crack. <br /> <br />3-4. In snu Testing of Foundation Materials <br /> <br />a. ,Advantages. FOr designs involving coarse-grain <br />foundation materials, undiSlurbed sampling is usually <br />impractical and in situ testing is Ihe only way 10 oblain <br />an, esIimaIe of malerial properties oIher than pure <br />assumption. Even' where undistUlbed samples can be <br />obtained, !he use of in situ methods 10 supplemenl con- <br />ventiooal IestS may provide several advanlages: lower <br />COSIS, testing of Ii greater volume of material, and Iest- <br />ing at !he in situ SIresS state. A1!hough numerous IypeS <br />of in situ Iests have been devised, those masl currently <br />applicable 10 wall design are Ihe SPI', the cone penetta- <br />tion tesI (CPT). and !he pressuremeter tesl (PMr). <br /> <br />(10) AI high stress levels. such as below !he base of <br />a high wall, !he undrained slrenglh is lower than !he <br />drained slrenglh due 10 generation of positive pore pres- <br />sures during shear. Consequently, Ihe mass stability of <br />walls on fm~grain foundations should be checked using <br />both drained and undrained slrengths. <br /> <br />b. ,Standard penetration test. The SPI' (ASlM <br />0-1586 (1984)) is routinely used 10 estimate !he relative <br />density and friction angle of sands using empirical cor- <br />relations. To minimize effects of overburden SIresS, !he <br />penettation resistance, or N value (blows per foot), is <br />usually correcled 10 an effective vertical overburden <br /> <br />(11) CeI1ain materials such as clay shales exhibit <br />sreaI1Y reduced shear S1renglh once shearing has initi- <br />ated. For walls founded on such malerials, sliding analy- <br />ses should include a check using residual shear <br />slrenglhs. <br /> <br />3-5 <br />