Study On Expansion-tunneling Method With Advance Heading In Tunnel Construction

With the rapid development of Chinese transportation industry, the tunnel construction has entered into a climax in our country.More and more large cross-section tunnels have sprung up, what’s more, the projects of metro and light rail are built in some bigger cities. These large cross-section tunnels in the city center put forward higher requirements for blasting vibration and the surrounding rock stability in the process of tunnel construction. The expansion-tunneling method with advance heading can reduce the disturbance of the non-excavation surrounding rock and maintain the stability of surrounding rock. At the same time it is known and accepted by people with its unique advantage in reducing the blasting vibration. In addition, the expansion-tunneling method with advance heading can use the TBM machine to excavate the advance heading and then expand the tunnel to the design section by using the drilling and blasting method. Because the diameter of the TBM machine do not need to rely on the tunnel section, it is better to solve the problem of recycle of the TBM machine. Due to research about the expansion-tunneling method with advance heading is very few so far, so we make some researches about this kind of method, The main research contents and theoretical achievements are as follows:①In order to ascertain the research direction in this paper, the domestic and foreign research status about the expansion-tunneling method with advance heading and the existing problems at present are detailed.②The construction process of the expansion-tunneling method with advance heading, the advantages and disadvantages in this method as well as the matters should pay attention to in the construction process are briefly introduced, and then compare the expansion-tunneling method with advance heading with the other construction methods in suitable conditions, construction period, cost, etc. It further expounds the features of the expansion-tunneling method with advance heading.③For the problem about the expansion tunneling after the advance heading excavation, three expansion schemes are put forward in this article and then simulated by using ANSYS software under the condition of four and five class surrounding rock. The deformations and stresses at the important points in the tunnel are respectively analyzed. At last, the geological conditions of surrounding rock that the three expansion scheme is respectively applicable are put forward.④The effect of the advance heading from the perspective of theories and experiment data is argued: the advance heading provide free face for blasting operation, it can reduce the disturbance for non-excavation rock mass and decrease the vibration, as well as it can reduce the usage of explosive in the construction process of tunnel.⑤Comparing with the whole section of blasting excavation, the relationship between decreased value of explosive and vibration velocity is studied respectively by using ANSYS/LS-DYNA software under the condition of explosive quantity reduced by 10%, 20%, 30% in the expansion-tunneling method with advance heading, Those research results can provide theory guidance for engineering practice.⑥Numerical simulation for one tunnel engineering case adopting the expansion-tunneling method with advance heading is done.