# Application of a Geotextile in the Treatment of Post-Subsidence in Karst Areas
## 5 Conclusions  
In this paper, a geotextile has been proposed to lay above a sinkhole in the process of soil-filling after subgrade subsidence has occurred, and the stability of the newly reinforced soil structure has been determined to increase as a result. The optimization of the anchorage length and buried depth of the geotextile was explored through numerical modeling with eleven different conditions and was conducted by finite element analysis with the PLAXIS 2D software package. By comparing the numerical test results with the model test results, the soil pressure, displacement of the soil, tensile force, and the deformation of geotextile were analyzed to explore the effects of the anchorage length and buried depth on the treatment of subsidence.  
The variations of the soil pressure, tensile force, and the relative settlement for the numerical modeling were consistent with those of the model test, which proves the feasibility of the numerical modeling. A sufficient anchorage length that is at least greater than 0.25\(B\) is required to ensure the safety and stability of the treated structure. With the increase of the anchorage length of the geotextile, greater soil pressure is transferred from the subsidence area to the stable area and the soil displacement is better controlled, which improves the treatment of subsidence. When the anchorage length of the geotextile is inadequate, the geotextile could be damaged as the more length is pulled out and a smaller tensile force exists during the process of subsidence. As the anchorage length of geotextile increased from 375 mm to 1500 mm, the surface settlement was effectively reduced from 1.05% to 34.18% when comparing to the situation without a geotextile. Furthermore, the buried depth of the geotextile is one of the key factors controlling the development of subsidence, while it has less influence on the tensile force and the deformation of the geotextile. The application of a geotextile has a great effect on the treatment of subsidence and differential surface deformation is mitigated with the use of a deeper buried depth for the geotextile. As the buried depth of the geotextile increased from 2 m to 6 m, the surface settlement was effectively reduced from 29.14% to 65.91% when the settlement corresponding to a buried depth of 2 m was used as the reference value.  
Considering the safety and cost of treatment of subgrade subsidence using geotextiles, the treatment method considered here is suggested with an appropriate geotextile anchorage length that is the length of subsidence width and an appropriate buried depth in the range from 3 m to 4 m. The method, although focused on the treatment of subgrade subsidence due to sinkholes in karst areas, could be adapted to subsidence in other areas (e.g., former mining exploitation areas) and structures (e.g., railways). This work provides a new vision for the treatment of sinkholes using geosynthetic materials.  
Figure 19: Minimum anchorage ratio of the geotextile for different buried depths of the geotextile (\(H\)).  
**Author Contributions:** Conceptualization and methodology, D.W. and J.W.; software and validation, Y.L. ([PERSON]), J.W. and Y.L. ([PERSON]); writing--original draft preparation, C.L.; writing--review and editing, Y.Y., D.W. and C.L.; supervision, D.W., Y.Y. and Y.L. ([PERSON]). All authors have read and agreed to the published version of the manuscript.  
**Funding:** This research was supported by Natural Science Foundation of China Grant (No. 42067044), Natural Science Foundation of Guangxi Grant (No. 2018 GXNSFAA294130) and Innovation Project of GUET Graduate Education (No. 2020 YCXS123).  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** Not applicable.  
**Conflicts of Interest:** The authors declare no conflict of interest.