Phaj tshuab

Phaj cow tshuab yog ib hom neeg ua haujlwm dej khov uas tsim cov dej khov nab kuab uas tsis yooj yim ntawm cov ntawv khov kho no yog qhuav, tsis muaj hmoov, thiab muaj lub sijhawm txias txias dua, nqaij ua nqaij, tshuab cua txias, dej txias, thiab lwm yam}

Lub cbfi phaj kas cees ua ke ntau yam thev naus laus zis ua yeeb yam, thiab muaj cov dej khov rau hauv cov tshuab hluav taws xob, thiab muaj cov dej khov rau sab nrauv cov khoom siv muaj zoo corrosion tsis kam, seismic tiv taus, thiab siab tsis kam {}}