# Reinforcement Effect of a Concrete Mat to Prevent Ground Collapses Due to Buried Pipe Damage
## 2 Ground Reinforcement Method  
### Literature Review  
Protecting buried pipes requires technology for minimizing the deformation of the ground near the buried pipes. Several studies have been conducted on ground reinforcement methods to prevent ground subsidence and protect buried pipes. [PERSON], et al. [18] analyzed the relationship between the longitudinal deformation of buried pipes and the static load by forming a geosynthetic layer on top of the buried pipes. In order to achieve this, they [18] conducted an experimental study on the sagging and deformation characteristics of the buried pipes against a static load. [PERSON] and [PERSON] [19] assessed the earth pressure that acts on buried pipes according to the distribution of the bearing pressure and the ground conditions. This was done while considering that the underground movement of buried pipes is significantly affected by the characteristics of the backfilling materials. [PERSON] and [PERSON] [20] conducted an experiment on the deformation of a high-density polyethylene (HDPE) pipe in reinforced sand under a repeated load. They [20] also analyzed the behavioral relationship according to the relative density of the soil and the pipe burial depth. [PERSON], et al. [21] simulated geosynthetic reinforced ground in the upper part of the cavity. They carried out a numerical analysis according to the tensile strength of the geosynthetic, the length of the reinforcement layer, and the cavity size, for examining the correlation between the size of the cavity and the ground reinforcement conditions. According to a study by [PERSON] and [PERSON] [22], the stress and deformation generated near the buried pipes were reduced when a geosynthetic layer was installed near the buried pipes. [PERSON], et al. [23] and [PERSON] and [PERSON] [24] conducted experiments and numerical analyses for reinforcing the sand with geocells. They discovered that the geocells distribute the underground stress in the lateral direction, thereby reducing the load that is acting on the buried pipes. [PERSON], et al. [25] conducted a plate bearing test by reinforcing a foundation structure and the lower part of the road pavement with several layers of geocells. They [25] discovered that the underground stress was reduced as the number of geocell layers and the elastic modulus of the ground increased. [PERSON] and [PERSON] [26] studied the ground reinforcement effect using a variety of geosynthetic materials to improve the bearing capacity of the ground under the pavements. Additionally, [PERSON], et al. [27] confirmed, through experimental and numerical analysis, that a geogrid bridging platform can decrease the excessive stress and the deformation generated in buried pipes. [PERSON], et al. [28] also conducted a numerical analysis on an experimental model for protecting buried pipes, while considering the sand-rubber mixed soil and the geocell-reinforced foundation. Accordingly, when the geocell and sand-rubber mixed soil are used simultaneously, the ground surface settlement and the sagging of the buried pipes are reduced, even when a repeated load is applied to the ground surface. [PERSON] and [PERSON] [29] examined the risk index while considering a variety of factors that influence the occurrence of ground subsidence, such as damage in the water supply system in cities. Other experimental and numerical analyses on ground reinforcement technology for protecting buried pipes and on technology for reducing underground stress using reinforcement materials have been performed.  
Most previous studies used geosynthetic materials for ground reinforcement to protect buried pipes; however, the flexibility of geosynthetic materials causes the sagging of materials under a continuous load. As a result, this limits the prevention of underground cavity expansion and the relaxation zone. Therefore, this study examined the effect of underground stress reduction by using a concrete mat with a high strength as a reinforcement material.