Nonlinear rheologieal property and numerical analysis of complicated cavern-surrounding-rock underground

WANG Zhirong; GUO Zhiwei; WANG Quangeng; CHEN Lingxia; ZHANG Limin

doi:10.16186/j.cnki.1673-9787.2017.06.008

Abstract：Based on the characteristics of Pingdingshan salt field, an equivalent composite unit mathematical model was built to replace the interbedded salt rock. The triaxial creep simulation curve of the model was con-sistent with experimental result of the interbedded salt rock. Meanwhile,three-dimensional numerical simulation of underground cavern was conducted by ABAQUS and the law of creep zone extension and volume reduction under different pressure was discussed. The results show that:(1)The equivalent composite unit has good nu-merical stability at steady-state creep stage. The mudstone interlayer can effectively limit the visco plastic areas and movement of surrounding rock. (2)The composite unit basically presents as small linear deformation under the confining pressure (8 MPa) . The cavern volume shrinkage rate and creep duration showed the lowest val-ues of 3% and 2. 5 respectively. With the increase of internal pressure(8~12 MPa),the equivalent composite unit began to show nonlinear creep deformation. The the volume shrinkage rate reached to a small value (3. 5%) after a short time (2. 5 a). With the rapid decrease of internal pressure(≤4 MPa),the surrounding rock showed nonlinear large deformation with the duration of steady creep and creep rate were increasing. The creep of surrounding rock will occur in next five years. (3) The viscosity coefficient of the plastic zone in the test area is increasing with time,which shows the deformation trend is more and more stable in the process of gas storage. Therefore,store pressure should be controlled in an appropriate range(4~12 MPa) when wheel-ing,particularly the duration of small internal pressure should be reduced.