Device for detecting compactness of back of molded concrete lining

The invention discloses a device for detecting the compactness of the back of a molded concrete lining. The device comprises a compressed structure and a resistance display instrument; the compressedstructure comprises a cylinder, a first plate body and a second plate body; the first plate body is arranged at the upper end of the cylinder; the second plate body is movably arranged in the cylinder, so that a closed space with an adjustable volume can be formed in the cylinder; a plurality of springs are arranged between the first plate body and the second plate body; and resistance wires are wound on the springs; and the resistance display instrument is electrically connected with the resistance wires through conductors so as to display the resistance change of the resistance wires when the resistance wires are extruded. The device is easy to manufacture and low in cost; a user only needs to install the device on the back of the lining and lay lines when using the device, so that complex and tedious constructi