Research purposes: The research w as done on the driv ing and damp ing b last techno log ies for construction o f shallow small c lear - d istance tunne l of light ra il transit in X inzheng, Chongqing under the favorab le geo log ica l conditions of so ft and hard m ixed strata and the w eak rock pillar to guarantee the stabilities of the w a ll rock and supporting structure and the safety of underground pipe lines and ach ieve the good smoo th b lasting e ffect.
Research conclusions: ( 1) The large pipe roof construction was adopted to the sha llow area w ith filling so ft so il around the tunnel porta.l The positive tri- bench method, the positive b i- bench method w ith rem aining the core so i,l the positive b i- benchmethod and fu llw a ll excavationm ethod w ere used alongw ith smooth blast ing respect ively to the w all rocks of G radeⅢ, Ⅳ, Ⅴ and Ⅵ . These construction techno log ies w ere available for construction of the sha llow tunne l w ith clear- d istance of less than 5. 8 m betw een tw o tunne ls under favorab le geo log ica l condit ions. ( 2) The vibration caused by the blast ing in the cu thole was big w hen blasting for sma ll clear- distence tunne.l When the exp losion w as conducted to the areas o f the different geological condit ions w ith tw o smooth b lasting me thods ( presplitting smooth blasting and rema in ing the smooth surface layer in advance) , and the stra ight and inc lined ho ling m ethods w ere used,the v ibrat ion ve locity of the groundm easured spo tw as 1. 8 cm / s and the v ibration ve loc ity o f the sidew a ll lin ing of the ad jacent tunne lw as 11. 02 cm / s. These v ibration velocities met the code requ irements, obtaning good b lasting effec.t It show ed the damp ing blast w as feasible.
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