Study on graded gravel basement in Tibet

Abstract

The highway construction in Tibet should take local building materials as the main material because of the poor transportation and bad climate. The resources of natural gravel stone used in highway construction are plentiful in Tibet. If asphalt pavement adopts graded gravel stone flexible base course, it can increase the performance of road and decrease construction cost compared with traditional semi-rigid basement. Through theoretical analysis, lab experiment, road test and study on graded gravel stone flexible basement under the special natural conditions in Tibet, this paper puts forward some pavement performance and design and construction technology of graded gravel stone flexible basement in Tibet. It can protect fragile ecological environment and make the pavement structure economical, durable, safe and reliable in Tibet which is alpine with strong radiation, complex geology and a lack of road material. The traffic of Tibet is inconvenient. The average of highway grade is less than grade 4 because of special geological and geographic conditions. The highway density is only 1.86 km/100 km2. Only Qingzang highway can be used perennial in G109, G317, G318, G214, and G219 (national highway). Tibet is high in altitude, low in atmospheric pressure with coldness and strong radiation, so freeze damage of road is severe. Tibet is sensitive to external interference, thus its ecological environment is very fragile. Maintenance of traditional semi-rigid basement is difficult, so structural durability of pavement is important in the abominable condition. On the other hand, highway construction in Tibet should take local materials as the main ones because of the poor transportation. The resources of natural gravel used in road construction are plentiful in Tibet. This paper researches pavement performance of flexible basement in Tibet with special geological and climate conditions. The flexible basement can avoid reflection cracks which often appear in semi-rigid basement. It can avoid basement frost boiling because of good water permeability too. Tibet is sensitive to external interference , so its ecological environment is very fragile, so adopting local materials can protect the environment. The test road is west section of national highway 318 in Xigaze city.