| There are always some difficult engineering problems during construction, such as collapsible loess. Collapsible loess shows a structural model of high intensity, if meet water,it will speed collapsible and soften. Therefore, in order to guarantee the construction safety in loess area, we must solve the problem of collapsible loess. With the acceleration of the construction in recent years, people start to have a better understanding of the causes,physical characteristics, distribution patterns, strength index, chemical properties,impaction factors of collapsible loess, etc. Nowadays, the normal collapsible loess treatment measures during construction include: ① embanKment reinforcement method;② drainage consolidation method; ③ deep compaction method; ④ replacement cushion method; ⑤ chemical reinforcement method; ⑥ replacement method; ⑦ other methods.Various types of loess will come up during construction, and roadbed quality needs to be guaranteed by special treatment technology following analyzing the characteristics of loess and taKing appropriate measures.This research is based on Tao-Tong Highway, following analyzing the characteristics of loess in the region, it proposes the following two research objectives by combining current Tao-Tong Highway Diseases:(1) For the purpose of “Combining prevention and drainage,and Reduce the saturated yielding”, Surface water can be prevented from infiltrating to sub-grade base from both sides of sub-grade and roadbed slope, by setting rammed soil-cement piles and restoring overall drainage facilities;(2) For the purpose of“Compaction reinforcement, and Increase strength”, collapsibility of sub-grade loess can be weaKened and roadbase loading capacity can be improved by setting jet grouting piles in serious subsidence roadbase sections and fill-bacK areas of the bridge and culvert;(3)For the purpose of “ Restore function, and Ensure safety”, Highway roadbed disease treatment to improve the overall driving comfort and safety can be guaranteed, by improving the flatness of the roadbed and bridge differential settlement, and remediating the central belt and along the roadside fence.The main treatment measurements applied in this project include rammed soil-cementpile, soil impermeable concrete wall, and high-pressure jet grouting: 1) Highway Section with Grade II & IV Collapsible: High pressure jet grouting(rotary spray pile) Treatment for Roadbase, the piles are through the collapsible loess soil layer, and set φ80cm rammed soil-cement pile in toe; 2) Serious subsidence Highway Section with Grade II self-collapsibility, and before and after Grade III and IV collapsibility sections: set φ80cm rammed soil-cement pile in toe; 3) Highway section with less than Grade II self-collapsible loess, or stabilized foundation with both sides for dry lands with Grade II self-collapsibility:No Treatment; 4) Other Highway Sections: Set 2m-deep and 80cm-thicK Cement-soil wall to segregate water. Based on the previous treatment technologies, the construction worK in Tao-Tong Highway collapsible loess foundation treatment technology covers:construction technology, construction attentions, and Specific quality control plan in application of rammed soil-cement pile, soil impermeable concrete wall, and high-pressure jet grouting in specific construction.The author believes that the above mentioned several treatment methods are also applicable for the other highways in Ning Xia Province, however different methods are applicable for different situations and has its own specific characteristics. The constructor should apply the methods flexibly during construction, considering time schedule,environment, soil layer thicKness and other impaction factors, and combining the real project, and find out the most reasonable, economic, and quicK treatment measurements. |
PDF Full Text Request