Technique Of Collapsible Loess Foundation Treatment And The Application In Longcheng Highway

The loess was piled up by Quaternary Period, and took the silt particles as itsbases. It is rich in pore and poor in natural moisture.It also has yellow or brownyellow unconsolidated sediment. Collapsible loess is one kind of loess which emergeadditional distortion because of the structure failure of the loess which is moistenedby water. The structure failure is caused by overlying soil gravity stress or`thecombined action of gravity stress and additional stress. Recent statistics show that40﹪already built highways are collapsible loess roadbed. Collapsible characteristicsare the main cause of the sub grade damage. The loess holds the special position inthe engineering field because of its special ingredient and nature.With the development of science and technology, people have a betterunderstanding about the Collapsible loess since the1920’s. By far, people have donemany researches on its cause of formation, distribution, physical property, chemicalproperty, intensity indictor and influencing factors. The often used managementmethods of collapsible loess is: Cushion method, deep-compacting method,substitution method, consolidation method, chemical stabilization method andothers.When meeting the collapsible loess in construction, attentions are usuallypaid on issues about: which treatment technique is more economical and effectivethan others and treatment more efficiency and detecting technical.Depending on Longcheng super highway, the author makes systematicalexperimental comparison and theory research on physical mechanics properties of thecollapsible loess in Shanxi province. The main contents are the technical treatmentprogram of sub grade, the construction technique and the appraisal of the processingeffect and so on. And through the field test, we systematically studied the constructiontechnology and the treatment effect of Dynamic Consolidation, Spodosol cushionlayer, Cement Fly-ash Grave, and Downhole Dynamic Compaction. Through the testsof many methods, we think a lot of methods that are mentioned above are also suitedin collapsible loess areas of Shanxi province. meanwhile every way has its owncharacteristic in construction, engineers must use the right methods to gain the most reasonable and economic effect. Finally the author made a conclusion of themethod of Collapsible loess foundation and put forward some suggestions.