As a protective device installed on vertical shafts or deep pits,covers have long provided sufficient protection for the general public.After recent years of development,manhole covers have evolved into various materials and types,and more and more fields are using cast iron materials.Walking on the street,we can see more and more manhole covers sinking.So what are the reasons for these manhole covers sinking,and how will we solve the problem of manhole covers sinking?

　　1.The design scale of the well cover and its surrounding structure is low,and there is no special reinforcement design for the backfill around the well and the structural layers of the road surface around the well.

　　2.The planning and layout of pipeline engineering within the range of motor vehicle lanes is unreasonable.

　　3.A large number of heavy overloaded vehicles in urban transportation have caused damage to inspection wells and their surroundings.

　　4.The structural stiffness difference between the well and the surrounding path is significant,and due to their own weight and vehicle loads,they will inevitably settle differently.

　　5.The reinforcement construction of the well circle is not standardized.

　　6.The installation of manhole covers is not standardized.

　　Due to the fact that the settlement speed of the structure slows down over time until it stops settling,the damage to the asphalt around the well after the road is put into use for a long time is not caused by the sinking of the inspection well.It should be due to the continuous elastic deformation of the well cover under long-term load,causing the asphalt around the well to deform to its limit under the repeated action of the well cover frame,resulting in fatigue damage and fracture damage.There are many occurrences in winter,with cracks often appearing within the range of 20CM,and the wellbore does not sink significantly.The main reason for exacerbating this situation is the inaccurate control of the upper level of the well cover,which leads to an excessive gap between the well cover and the concrete in the well circle.The concrete in the well circle is not constructed according to the designed thickness and width,and the concrete is not compacted properly.