| Karst is a big issue which has great influence to foundation stability and troubles project construct all along. Therefore, it has great significance to know the karst development law and to find efficient processing method to deal with it. This paper presents the status of the karst base of Kunming Xiaosao Airport Platform in the condition of construction foundation load above, and has its own suggestions and measures to the karst cave which is below the foundation. The presentation states with the research object of karst cave under Kunming Xiaosao Airport Platform, through strict site investigation and according to the reconnaissance information as long as the key issue about the karst growth characteristics of karst cave and the analysis of foundation stability. Analysis method of qualitative and semi-quantitive as well as virtual numeral analysis method were used. Follows are the major content and suggestions.1. The karst status on surface are as follows in research district: clint, grike, dissolved groove, karst depression, doline, sink hole, and dissolved valley, while the karst growth under earth are like these status: concealed district, grike, dissolution pore, dissolved fissure, and karst cave etc. The growth characteristics of karst billabong and karst filler have their own characters, which grows stronger in earth layer boundary and layer structure line. Furthermore, D3z white cloud rock layer grows stronger than those in lixivial layer. The karst cave under research areas mainly has two styles: channel-like style and cave style, while channel-like style grows more concentrate than cave style. In a nut shell, the most advantaged areas of karst growth located in 2070-2075m. The under earth karst cave grows stronger in broken layer and drape center which as kind of long diameter caves, and the RQD value of roof rock is low and the roof is very thin.2. Most elements and constraints are the major influence effects of karst growth in research areas. The quality of rock and growth status can influence the karst growth. As the boundary of F10 broken lay, karst growth in white cloud rock in northeast areas are distinctive, while less growth in southwest lixivial layer; the geographical structure has effects in karst growth. in one direction, under earth karst growing along the structure line, the growth axes of dissolved billabong, dissolved filler are consistant with the structure line, and the under earth karst cave growth also has this characters; under earth water can influence karst growth, karst growth on and under surface water conflux district is stronger; topography and physiognomy can affects the karst growth. in cliff areas, karst growth only on earth surface, while in respectively plain areas, karst growth on or under earth grows stronger, while in lower village, karst grows are among best of all. And in karst billabong, it grows in a large scale.3. Collapse problems in research district are caused by earth dissolving and karst roof broking. And many other reasons caused inhomogeneity in research areas, as the boundary of F10 karst Collapse serious in karst billabong, and filler areas of northeast, and few in southwest areas, while it has, is in a large scale.4. Elements which influence stability of karst base are many aspects and has its own characteristics: rock texture gap, rock stronger, layer structure, cave style, and embedding condition, outsource load style, underearth water, and filler in cave. I as well as the author, selected four elements which can give most influence to karst cave as a evaluation system: rock stronger, roof thickness, cave style, cave diameter, and then with these influence elements as an evaluation standard to appraisal research district karst stability. The results turns out be consistant with the later semi-quantitative evaluation method, and all of this can confirm that, this qualitative evalutation system is practical and credible.5. On the basis of karst cave distortion conceptualism, evaluate kast cave with some mechanical semi-quantitative broken methods in boring research areas such as: anti-cut, anti-beat, anti-bend, and partly stability etc, we can know, the stability status of karst cave under stake pressure in research areas. The analysis expressed that, the karst cave roof stability in research district are good, 79 drill points are stable in 118 of karst roof which are pressed under stake, account 67% of the total.6. it simulates the model karst cave stability with numeral modeling method, all the results approaches to the conclusion while using qualitative and semi-quantitive method, and we get that the semi-quantitive method is a good guardians. More, this paper also simulates the processing circumstances of typical karst cave with numeral method which has a great effect, it also has best reference value for karst cave of all the region.7. This paper also has treatment method for karst cave collapse problems and exiting stability in research district, to sink problems, on the basis of good drainage, it can combined with refill, grouting etc such measure to deal with, For karst cave, to fill with concrete is being suggested and while for karst canal, the best way to deal with it is to span it with reinforced concrete cover plate.
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