Study On Global Stability Evaluation And Failure Mechanism Of Dense Storage Cavern Group In Salt Rock

Dense storage cavern group in salt rock is involved with global stability evaluation,failure surge mechanism, interaction and temporal and spatial evolution of cavern group,which are the key isues need to be solved urgently in the design and construction ofcavern group. The deformation reinforcement theory (DRT) under the framework of3Dnonlinear finite element method provides a new and unified theory and method to studythe above problems. In this dissertation, the influence of all kinds of instability factors isstudied based on an unified and quantitative global stability criterion of salt rock densestorage cavern group. The geomtchanical model test of salt rock cavern group is carriedout, and the computational results are compared with model tests results. The DRT isextended to the visco-plastic theory and time-dependent deformation and damageevolution are considered.The main research work and findings are as follows:(1) The relation curve between plastic complementary energy and strengthreduction factor (K～△E relation curve) is used as the quantitative key criterion ofglobal stability in cavern group, and the unbalanced force is used as the effectiveindicator of cavern failure. Based on the unified and quantitative criterion of all kinds ofinstability factors (K～△E relation curve), the influence of factors such as cavernshape, cavern diameter, cavern space, cavern depth, mudstone intercalation, caverngroup internal pressure, cavern group pressure loss, cavern group layout to the globalstability of salt rock dense cavern group is studied. The global stability and failureananlysis of oil and gas storage cavern group in Jintan salt mine is carried out.(2) Based on that unbalanced force is the internal effective driving force of failure,the interaction and failure surge mechanism of storage cavern group is revealed. Thecritical space of storage cavern is determined and it is found that there are two differentfailure patterns when the cavern space is less or greater than critical space.(3) The geomtchanical model test of salt rock four-cavern group is carried out, andthe computational results are compared with model tests results. The unbalanced forcedistribution law of numerical simulation and falure position and pattern of model testindicate that there is a good correlation beween unbalanced force and failure, and therefore the effectiveness and accuracy of DRT in the global stability and faureanalysis are verified.(4) The DRT is extended to the visco-plastic theory and time-dependentdeformation and damage evolution are considered. The DRT consideringspatio-temporal evolution is developed. Based on the relation curve between plasticcomplementary energy and time (T～△E relation curve), the method of globalstability evaluation and failure spatio-temporal evolution analysis during the processof non-equilibrium evolution of salt rock cavern group is realized. The spatio-temporalevolution ananlysis of double-cavern of salt rock and oil and gas storage cavern groupin Jintan salt mine under pressure loss is carried out, and the results indicate theavailability and effectiveness of DRT in rheological long-term stability and failurespatio-temporal evolution analysis.