Foot frame bottom plate type fixed parts, sealed inner lining structure, underground chamber and construction method

A tripod base plate, characterized in that the tripod base plate (2) is annular, and comprises a fixed base plate (7) and an umbrella shaped tripod (8),

• wherein the fixed base plate (7) has a length direction and a width direction,
• wherein the umbrella shaped tripod (8) has a length direction and a width direction,
• the umbrella shaped tripod (8) including a connecting part and an umbrella shaped part,
• wherein the umbrella shaped part is set at the top of the connecting part such that the umbrella shaped part faces the connecting part and has protrusions on both sides in the length direction of the umbrella shaped tripod (8),
• wherein the umbrella shaped tripod (8) is fixedly connected to the fixed base plate (7) along the length direction of the fixed base plate (7) at the connecting part, thereby forming a clamp having a semi open containment space between the umbrella shaped part of the umbrella shaped tripod (8) and the fixed base plate (7),
• wherein a height of the semi open containment space near the connecting part is h1, a height of the semi open containment space near an open side of the clamp is h2, and h1>h2.