Combined with the real example of monitoring pressure on the supporting system in the long span underground space of DK7+692 section at Jiao-Xin line of Chongqing light railway

it is set forth the methods about choosing the support system and its parameter

digging methods of underground space

measuring and testing methods for the stress of the support system;the testing results and variation pattern were analyzed for the stress of the initial supporting I-steel

axial stress of bolt

stress of shot-concrete

supporting pressure of temporary I-steel and stress of steel of the second lining

then

the reason for deformation of the support system induced by sharp increase of I-steel was determined.Based on this

considering the real problem

the construction plan and the support system is changed

the deformation of support system was under control and the danger was avoided

the informative construction and construction safety were realized.