紫色土丘陵区田间道基础及工程处理

紫色土丘陵山区地形起伏不平,不同的地形部位形成不同的土地利用类型,具有不同路基基础.本文针对紫色土丘陵山区冲田(冬水田)、塝田(水旱轮作田)和旱地路基基础,进行田间道路基分析及路基处理研究.冲田粘粒含量最大,达到41.35%;塝田次之,含量为22.25%;旱地最小,含量只有11.23%.冲田的塑性指数最大,达到21.47;塝田次之,为16.98;旱地最小,只有8.11.田间道过冲田段主要为填方路段,淤泥较多,力学性质差,路基处理时先挖除1m厚的淤泥,然后换填取自旱地的路基土,并分层碾压,压实度大于90%,道路两侧设计条石挡土墙;塝田段先换填0.5m厚的淤泥,同时增高路基以保证道路连续,然后碾压;旱地段只需清除表层腐殖土后铺设路面材料,不做特殊处理.

The Subgrade of Field Roads and Their Engineering Treatment in Hilly Areas of Purple Soil

In the hilly areas of purple soil ,where the terrain is uneven ,there are different cultivated land types and diverse subgrade foundations in different geographical locations .In a study reported in this pa-per ,the subgrade foundations of field roads in valley paddy fields (winter paddy fields) ,slope paddy fields (paddy rice-upland crop rotation fields) and dry land in the hilly areas of purple soil were investigated ,and their engineering treatments were studied .The valley paddy fields contained the greatest amount of clay (41.35% ) and plasticity index (21.47) ,followed by the slope paddy fields (22.25% and 16.98) and dry land (11.23% and 8.11) .The section of a field road through the valley paddy field is normally character-ized by much silt and poor mechanical property .It is recommended ,therefore ,that in the treatment of its subgrade ,excavation of the silt be made with a depth of 1 m at first ,followed by its replacement with the subgrade soil from dry land and roller compaction layer by layer to achieve a compactness of >90% ,with retaining walls on both sides of the road .For the section a field road through the slope field ,it is advisable to replace the silt 0.5 in depth with the soil from dry land and raise the subgrade so as to ensure a continu-ous road before roller compaction .For the section a field road through dry land ,no special treatment is needed .However ,the surface humus soil should be cleared before the pavement materials are laid .