Qhov zoo ua haujlwm raws li lub neej ntawm cov khoom. Thaum ua tiav ntawm kev ua tiav, cov khoom lag luam pob zeb muag tau raug soj ntsuam nruj thiab ntau yam zoo ua ntej tawm hauv lub hoobkas. Qhov kev tshuaj ntsuam no suav nrog qhov ntsuas ntawm qhov ntev ntawm geometric - suav nrog qhov loj me, qhov tiaj tus, thiab qhov sib txawv ntawm lub kaum sab xis - nrog rau, qhov tseem ceeb tshaj, kev ntsuas qhov pom zoo. Cov tom kawg suav nrog kev tshuaj xyuas zoo ntawm qhov chaw txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhawm rau txhuam cov pob txha, nws yuav tsum tau muab tshem tawm cov khoom tsis zoo.
Rau cov khoom uas yuav tsum tau tshwj xeeb waterproofing muaj peev xwm, random sampling kuj yog ua los ntawm lub cev kev ntsuam xyuas cov cuab yeej, xws li cov rau cov dej nqus tus nqi thiab flexural zog. Cov kev tshuaj xyuas no feem ntau ua raws li cov qauv kev lag luam sab hauv lossis cov kev qhia tshwj xeeb tau pom zoo los ntawm tus neeg muag khoom thiab cov neeg siv khoom, yog li ua kom ntseeg tau tias txhua pawg ntawm cov khoom xa los ntawm lub Hoobkas ua tau raws li cov qauv kev xav tau.
Cov pob zeb mos yog ib hom pob zeb uas muaj kev ntxhib los mos thiab yooj yim ntawm kev ua. Nws tsis yog hais txog ib qho tshwj xeeb ntau yam ntawm pob zeb, tab sis kuj yog ib lub sij hawm sib sau ua ke rau ib pawg ntawm cov pob zeb sib koom ua ke ntawm lub cev. Kev faib tawm thoob plaws hauv qhov xwm txheej, chav kawm ntawm pob zeb no tau ntev ua lub luag haujlwm tseem ceeb hauv thaj chaw xws li kev tsim vaj tsev, kho kom zoo nkauj sab hauv, thiab kho kom zoo nkauj, vim nws qhov yooj yim ntawm extraction thiab malleability. Kev tsim thiab ua cov pob zeb mos ua cov txheej txheem uas sib xyaw ua ke cov khoom siv tes ua haujlwm nrog cov thev naus laus zis niaj hnub, nrog lub hom phiaj tseem ceeb ntawm kev hloov cov khoom siv pob zeb rau hauv cov khoom tiav uas ua tau raws li ntau hom kev ua haujlwm.