The Investigation Analysis And Research Of The Typical Section Piping In Dongting Lake Area Used For Risk Removal And Prevention

Dongting Lake,the most important and dangerous emergency area in the middle reaches of the Yangtze River,boasts various weaknesses on flood control,embodying in long coastline,long-term disrepair,low standard secondary dyke,and frequent piping situation in the lake’s dike.Since the foundation of People’s Republic of China,the Dongting Lake has been suffered from varying degrees of floods and droughts for more than 40 years,one flood and drought in 1.5 years on average.If we are able to realize and cope with such emergent situation that can easily collapse the dike,and study the preventing and governing methods of dike piping,it will be of great practical significance and social benefits to improve the level of flood prevention and emergency decision-making as well as operation management in the Lake area.This research,taking the Dongting Lake as the studying region,through sorting its current situation of existing natural water systems,important embankments,as well as flood control projects,summarizes the existing types of dangerous conditions and cases,and analyzes the regulation measures when the dangers occur and their follow-up improvement methods with combining with the cases.Setting the emergency rescue and treatment measures of the serious piping in the Yangjiao section of Zijiang,in the Heshan District of Yiyang City in 2018 as an example,the software of Lizheng geotechnical seepage,was utilized to calculate and analyze the seepage situation before and after remediation of this section.The conclusions made by this research are as follows:The Dongting Lake involves 251 dangerous sections in all important embankments,with a length of 353.4 km totally.As classified the problems in each embankment section,its major driving factors are:First,the embankment and its body part have strong permeability;Second,the pressure of high water level is continuously infiltrated during flood season;Third,although the surface of the permeable foundation is covered by cohesive soil,there are weak points in some parts.(2)Through analyzing and summarizing nearly 100 cases of piping-related dangers occurring in the area,this paper elaborates rescue measures of dangerous situations,such as leakage(piping),de-sloping,infiltration,piping and quicksand,so as to propose improvement measures in later period.(3)Based on the dangerous condition of the Yangjiao part of the Zijiang embankment in Heshan District,Yiyang City,the causes of the dangers were the prolonged high water level,rainwater immersion,and the impacts by human activities with combined with scene’s data and seepage analysis.Moreover,the principal restoration measures were:supporting the foot of the slope within the embankment;soil-filling and later treatment of the collapse part of its top mainly by filling grout,sand and cobble to pressure and immerse platform in the inner slope.Through seepage analysis before and after the treatment,the treatment achieved remarkable effects.