( ( The sand ) ( ( ( is commonly ) ( added ( to ( ( fracking fluids ) ( for ( ( the purpose ) ( of ( keeping ( ( unduced ( hydraulic fractures ) ) open ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT The) (NN sand)) (VP (VBZ is) (ADVP (RB commonly)) (VP (VBN added) (PP (TO to) (NP (NP (VBG fracking) (NNS fluids)) (PP (IN for) (NP (NP (DT the) (NN purpose)) (PP (IN of) (S (VP (VBG keeping) (S (NP (JJ unduced) (JJ hydraulic) (NNS fractures)) (ADJP (JJ open)))))))))))) (. .)))
The sand is commonly added to fracking fluids for the purpose of keeping unduced hydraulic fractures open.
(ROOT (S (NP (NNP Fracking)) (VP (VBZ is) (NP (NP (DT another) (NN term)) (PP (IN for) (NP (JJ hydraulic) (NN fracturing))))) (. .)))