Study Of Construction Mechanical Behavior Of Super-large Cross-Section Shallow-Buried Bias Tunnel Excavating With CRD Method

At present, in all road tunnels in China, super-large cross-section flat tunnels that cross-sectional area is more than 150 square meters are still quite rare. Since the cross-section is super large, the flat rate is higher, the buried depth required for formating collapsing arch is deeper, and the sensitivity of tunnel on the issue of bias is increaseing, so the traditional construction mechanics theory has been required improving a higher level. This thesis will further study on construction mechanical behavior of surrounding rock ,tunnel lining, temporary support and system anchor of super-large cross-section shallow-buried bias tunnel excavating with CRD method, on the background of domestic rare large-span and super-large section tunnel---FuQuan Highway extension project QianOu Tunnel and base on the research methods of Combination of in-situ test and static finite element analysis. Some research fruits and conclusions are obtained as follows:1. Through generalizing the development history of large cross-section tunnel construction mechanics theory, this thesis systematically summed up the current status on the research of shallow-buried, bias and construction method, and put forward the current outstanding issue about construction mechanical behavior of super-large cross-section shallow-buried bias tunnel excavating with CRD method.2. Through the research on the theoretical solution of stress distribution around oval cavity under plane stress state, it raise a metric of deviation degree between actual heading shape and optimal shape under the original stress of surrounding rock when QianOu tunnel selected variable CRD method.3. A proper monitoring method was formulated to carry out the site-test at the field of QianOu tunnel and obtained preliminary data for experimental research. On data processing issue, it introduced Wavelet theory and speed-limit-truncate method. Through the research of the experiment result, it came to a conclusion of the general law of displacement and deformation of surrounding rock.4. According to the actual situation of QianOu tunnel it established the three-dimensional numerical model, verified the applicability of the numerical model, simulated the excavation process of the tunnel, and summarized the mechanical response and displacement and deformation law of surrounding rock, tunnel lining, temporary support and system anchor.5. Special research in shallow-buried issue of super-large cross-section tunnel leaded to establishment of the research method of shallow-buried issue, and put forward the concept of equivalent radius, as a indicator of shallow-buried properties.6. Special research in bias issue of super-large cross-section tunnel leaded to establishment of the research method of bias issue.7. Special research in deformation law of time-dependent of super-large cross-section tunnel leaded to establishment of the mathematical model of tunnel deformation law, and put forward the concept of equivalent stake number.