What is "excavation of tunnel markou road slot"?

First of all, let's find out what is called "tunnel mouth", that is, the rock layer on the side wall of the tunnel. \ r \ Secondly, what about "jumping off the side wall of the tunnel"? \ r \ nActually, this is a construction method. Markou excavation refers to an excavation construction method of lining after removing earthwork. \ r \ nIn the soft rock stratum with poor stability, for the sake of construction safety, the arch section is excavated first, that is, the top arch is constructed to support the surrounding rock at the top, and then the lower section and side wall are excavated under the protection of the top arch. The top arch must be well supported before excavating the side wall rock stratum. "Job-hopping", as its name implies, is an interval slot, that is, \ r \ when excavating the rock strata on both sides of the side wall (commonly known as digging the horse mouth), it must be staggered from left to right in sections to avoid the top arch hanging and sinking. \ r \ During construction, the upper pilot tunnel and the lower pilot tunnel must be excavated. When excavating the upper section, a large amount of ballast can be loaded through a series of leakage holes between the upper pilot tunnel and the lower pilot tunnel, which not only improves the discharge efficiency of ballast, but also reduces the construction interference. When the tunnel length is short and the rock stratum is dry, only the upper pilot tunnel can be set. In this case, in order to avoid the interference of transportation and construction, the upper section of construction can be completed first, and then the lower section can be constructed. This method is suitable for soft rock, but its compressive strength should be able to withstand the higher support stress in arch support; It is also suitable for cavern construction with large span or height in hard rock stratum, so as to simplify the arch frame and concrete pouring operation during top arch construction. This method is also called comparison method in foreign literature, and it is also called arch first and then wall method or supporting arch method. \ r \ Finally, job-hopping is very common in engineering, not only in tunnels, but also in retaining wall construction that we often see. For example, when building a retaining wall, it is necessary to dig out all the earth and stone at the design position of the retaining wall to facilitate the construction of the retaining wall. However, where retaining walls need to be built, the geological conditions are mostly not very good. If all the retaining walls are dug before being built, landslides will occur and the engineering quantity will increase greatly. In order to reduce the engineering quantity as much as possible, the retaining wall can be built in sections, that is, a section of masonry can be dug. In order to speed up the progress, it is possible to excavate in several sections at the same time without landslide, and then excavate earth and stone in the sections to build retaining walls. Finally, the retaining walls built in sections are connected into a whole. This method of interval excavation is called markou excavation. Every excavation is called makou. The width of the horse's mouth is generally about two meters. For example, a 20-meter retaining wall is to be built now, and the soil quality of the site is not good, so it is decided to excavate in Makou. If it is divided into two meters, it can be divided into ten sections. First, excavate 1.4.7. 10 to complete the masonry, then excavate 2.5.8, and finally excavate 3.6.9. This is the most typical excavation method in Makou. Makou excavation is the excavation method before lining the tunnel side wall.