Comprehensive treatment project of the geological disasters in Yanjiagou small watershed of Shanyang County
1. Introduction
At about 0:30 on August 12, 2015, an oversize landslide occurred in Yanjiagou, Zhongcun Town, Shanyang County, Shaanxi Province (the landslide volume was 1.68 million cubic meters), and 65 people died in this accident. The landslide blocked Yanjiagou for more than 280m, forming a barrier dam with a height of about 60m, threatening the safety of tens of thousands of people in Zhongcun Town.
Figure 1 Accumulation area of the barrier dam formed by the landslide masses
2. Treatment solution
In order to eliminate the hidden danger of geological disasters in the barrier dam, a comprehensive treatment and restoration scheme with zoning and grading was adopted. (1) For the core area of the landslide, the control measures of "blasting of dangerous rock mass, grading and sloping of accumulation area and drainage outside accumulation area" were adopted to improve the stability of dam body. (2) The measures of "reinforced concrete retaining wall, rubble concrete retaining wall, masonry retaining wall, etc." were adopted in Yanjiagou debris flow area to reduce the source of loose debris flow in the river basin. (3) Two huge concrete retaining dams were designed in the main flood discharge ditch, which reduces the impact damage of debris flow to the downstream side. (4) For dangerous areas, the treatment scheme of resettlement and ecological restoration was adopted.
3. Construction situation
This project lasted for 2 years, and measures such as blasting, desilting, blocking, dredging, relocation and ecological restoration were completed.
Figure 2 Sloping, excavation and construction of the open channel in core landslide area
Figure 3 Construction of the flood discharge canal and reinforced concrete retaining wall
4. Achieved accomplishment
This project has been constructed since 2016 and finished in 2017. At present, it is found out after 2 hydrologic years of inspection on engineering effect that the disaster prevention and mitigation effect is good.
Figure 4 Completion of the platform slope protection and drainage ditch works in the core landslide area
Figure 5 Completion of Construction works in the flood discharge ditch D1 and the retaining dam D2
5. FAQ
Q1: What are the potential safety hazards of geological disasters in large landslide deposits in mountainous areas?
A: The terrain in mountainous area is narrow, and the landslide deposits are easy to block the flood discharge channel. It is very likely to become a huge dammed lake under the action of heavy rainfall. Once the landslide occurs, the potential debris flow is large in volume, wide in spread and extremely harmful.
Q2: What is the train of thought for the dam body treatment against landslide in mountainous areas?
A: Actively adopt the comprehensive trains of ideas of "cutting slope to reduce the height of dam body", "blocking, protecting fixing loose parts", "moving, avoiding and reducing the vulnerability of disasters" and "recovering and rebuilding the ecological system".
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