Mechanical analysis of instability of overburden structure in goaf under surface load

In order to evaluate the stability of the overburden in the long-wall goaf under the load of the surface structures, the “voussoir beam” structural mechanics model is used for reference, combined with the additional stress obtained by the analytical solution of the Boussinesq formula to be transferred in the foundation The stress circle of, and the stress form of the overburden structure in the goaf under the action of the surface load is put forward.Based on the voussoir beam theory in the mine rock strata control theory, using the key block analysis method of the “voussoir beam” structure, the force model of the key rock block for the stability of the overburden in the long-wall goaf under the action of the surface load is derived, and the calculation formula for the force of the key rock block of the overburden structure in the long-wall goaf under the action of the surface load is also got.Based on the S-R stability theory of the key rock of the “voussoir beam” structure, the S-R stability criterion model of the “voussoir beam” structure in the overburden of the long-wall goaf under the influence of surface loads is established, and the slip and rotation loss are also derived.It shows that the overburden structure of the goaf formed by longwall mining under surface load is still a “voussoir beam” structure.Under surface load, the stability of the overburden structure of the goaf and the position and size of the surface load, the key rock Factors such as block depth, lumpiness, rotation angle, bearing load value, and friction coefficient between rock blocks are related.Using the newly established S-R stability criterion model for the overburden structure of the goaf under the action of the surface load, the foundation stability of a new 8-storey building affected by coal mining was evaluated, and it was compared with the traditional additional stress method(using the depth of influence of surface load and the height of overburden failure are overlapped to determine the stability of the overburden in the goaf).The results show that the S-R stability determination method of the overburden in the goaf under the action of surface load is sufficient in basic data.It is more accurate under the conditions.This evaluation method judges the stability of the goaf by analyzing whether the additional stress in the foundation of the ground engineering construction acts on the overburden structure of the long-wall goaf to determine the stability of the goaf, and can quantitatively analyze the effect of surface loads on the stability of the overburden structure of the goaf.Therefore, a traditional semi-quantitative evaluation method has been developed to determine the stability of the goaf by using whether the depth of the impact of the surface load and the height of the overburden damage overlap.