Method for calculating three-dimensional support pressure of shield excavation face of composite stratum with soft upper part and hard lower part

The invention discloses a three-dimensional support pressure calculation method for a shield excavation face of a composite stratum with a soft upper portion and a hard lower portion, and belongs to the technical field of shield tunnel construction. The method comprises the steps of establishing a three-dimensional mechanical model according to the characteristics of the shield excavation face of the composite stratum with the soft upper portion and the hard lower portion, calculating basic assumption of the model, establishing a moment balance equation, solving the balance equation and obtaining the final support pressure. The calculation method is clear, the three-dimensional support pressure of the shield excavation face of the composite stratum with the soft upper portion and the hard lower portion can be obtained only by substituting the actual engineering parameters into the calculation formula, and compared with a traditional calculation method, the three-dimensional LEM model considers the curved surf