Design method of expansive surrounding rock tunnel bottom plate

The invention discloses a design method of an expansive surrounding rock tunnel bottom plate. The design method of the expansive surrounding rock tunnel bottom plate comprises the following steps: 1) acquiring the total deformation of the surrounding rock without the anchor rod reinforcing action; 2) selecting the expansive surrounding rock tunnel bottom plate and adopting anchor rod support; 3) when the anchor rod support cannot be accepted, selecting open type bottom plate support; 4) when the open type bottom plate support cannot be accepted, selecting flexible composite type bottom plate support; and 5) when the flexible composite type bottom plate support cannot be accepted, selecting rigid inverted arch support. The load of the bottom plate is obtained by obtaining surrounding rock deformation without the anchor rod reinforcing action, surrounding rock deformation under the anchor rod reinforcing action and surrounding rock deformation under the expansion action, and the form and the parameters of the bottom plate support are determined by comparing the load of the bottom plate with the unstability critical load of the bottom plate, so that the design parameters of the bottom plate support is more reliable and reasonable, the quality of the tunnel bottom plate can be improved and the construction expenditure of the bottom plate support can be saved.