Geology 229 Engineering Geology. Lecture 12. Elementary Soil Mechanics (cont. 2) (West, Ch. 7)

Transcription

1 Geology 229 Engineering Geology Lecure 12 Elemenary Soil echanic (con. 2) (We, Ch. 7)

2 Ouline of hi Lecure 1. Compacion/Conolidaion

3 Soil denificaion include compacion and conolidaion. Denificaion compacion + conolidaion Compacion i one kind of denificaion ha i realized by rearrangemen of oil paricle ihou ouflo of aer. I i realized by applicaion of mechanic energy. I doe no involve fluid flo, bu ih moiure changing. Conolidaion i anoher kind of denificaion ih fluid flo aay. Conolidaion i primarily for clayey oil. Waer i queezed ou from i pore under load.

4 The engineering purpoe of compacion i o increae he maerial deniy. 1. Compacion effor, 2. oil ype and gradaion, 3. moiure conen, and 4. dry deniy are he 4 conrol facor o he exen of compacion.

5 Increae permeabiliy and decreae compreibiliy Loer compreibiliy Higher compreibiliy We, Figure 7.11 Plaiciy Char

6 Sandard Procor Te Compacion Effor i calculaed ih he folloing parameer hammer old volume 1/30 cubic foo Compac in 3 layer 25 blo/layer 5.5 lb hammer 12" drop cylindrical conainer

7 Dry of opimum e of opimum

8 Toal or e deniy : + Solid deniy dry deniy d d d < > Q, Alo e have and ha o d d d d d + + 1

9 The purpoe of conducing he Procor e i for finding ou he opimal aer conen and guide he compacion projec in he field. Pracically, you kno he aer conen, you meaure he e deniy, and hen calculae he dry deniy. Sure you can alo bake he ample and direcly meaure he dry deniy d.

10 Zero-air-void deniy: A cerain aer conen, ha i he deniy called if here i no air in he void G G a v z 1+ ).. ( (zav) G G or by G hen G hen / /, 1,, /, / 1 dry G G G G ) )(1 (1 ) (1 ) (1 1

11 Zero-air-void deniy: A cerain aer conen, ha i he deniy called if here i no air in he void ( z. a. v) G 1+ G (zav) I i clear ha in he above equaion, pecific graviy of he olid and he aer deniy are conan, he zero-air-void deniy i inverely proporional o aer conen. For a given oil and aer conen he be poible compacion i repreened by he zero-air-void curve. The acual compacion curve ill alay be belo. For dry oil he uni eigh increae a aer i added o he oil becaue he aer lubricae he paricle making compacion eaier. A more aer i added and he aer conen i larger han he opimum value, he void pace become filled ih aer o furher compacion i no poible becaue aer i a kind like incompreible fluid. Thi i illuraed by he hape of he zero-air-void curve hich decreae a aer conen increae.

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13 No e can make anoher decripion of compacion in he engineering ene: Compacion i for making he opimum deniy a cloe a he zero-air-void a poible Alo e can conclude ha more compacion effor make he opimum deniy cloed o (zav) by he fac of he 2 linear line have differen lope.

14 Compacion curve for differen oil ih he ame compac effor (We, Figure 7.19); fine grain oil need more aer o reach opimum and coare grain oil need le aer o reach opimum.

15 In conra o compacion, conolidaion i he reducion in volume of clayey oil under exernal loading a aer drained ou from pore. aer olid ve 0 1 aer olid e H H e e, hen H H 1 + e e0 1 Apparenly, conolidaion i he reaon for urface ubidence in area of groundaer or oher crual fluid over-dra. 0

16 Compacion Equipmen A. Type of Acion * Ramming * ibraion * Saic Roller

17 B. Ramming Rammer have a lo frequency (800 blo/minue), and a higher roke (1.5" o 3.5 heigh). A he machine operae he ramming acion break don he oil, puhe he paricle cloer ogeher, and force air ou of he void.

18 C. ibraion ibraory machine are diinguihed by heir high frequency (2,000 o 6,000 blo/minue) and a lo ampliude. The vibraory acion e he oil paricle in moion, hich rearrange hem ino a dener packing.

19 Type of Roller 1. Smooh Wheel Roller or Smooh Drum Roller are uiable for hin layer, and for finihing operaion. 2. Pneumaic Rubber-Tired Roller have a erie of rubber ire ide-by-ide inead of a mooh drum. Compacion i achieved by a combinaion of eigh and kneading acion. 3. Sheepfoo Roller are drum ih a large number of "heepfoo" projecion. They are mo effecive in compacing clayey oil. The iniial pa in he field compac he loer porion of he lif, ih ubequen pae compacing he middle and upper porion. The roller i aid o "alk ou" a he oil i compaced and he fee do no penerae a deeply a he iniial pa. 4. ibraory Roller ork ell in compacing granular oil. ibraory acion can be ued ih mooh drum, rubber ired, or heepfoo roller.

20 Field Compacion A. Relaive Compacion Relaive compacion i a ay of comparing compacion on he conrucion ie ih he laboraory compacion reul. I i defined a:

21 Field Compacion (con.) B. Waer Conen In he field i ha been found ha oil compac beer a aer conen on he dry ide of he opimum aer conen. C. Deerminaion of Dry Uni Weigh in he Field To mehod in common ue oday o deermine uni eigh and aer conen in he field are: he Sand Cone ehod, AST D-1556 he nuclear and non-nuclear deniy meer.