The northern Adriatic coast, which forms part of the Dinaric karst system, is bordered by high mountains. Here, the occurrence
of rock-slides and rock-falls in road sections with high cuttings excavated in recent times and more than one century ago
has been documented. Some of these old slopes were stable for a long time before rock-slides started to occur. We propose
that these mass movements are favoured by karstification processes acting along joints in the exposed rock mass. The stress
changes induced by overburden removal (excavation) cause dilation in the mass joint systems reducing the rock mass strength
and facilitating the circulation of aggressive water. Changes in water pressure and temperature, wetting and drying cycles,
and corrosion processes along discontinuity planes entail a reduction through time of the shear strength of potential failure
surfaces. 相似文献
The potential of marble dust as a stabilizing additive to red tropical soils was evaluated. The evaluation involved the determination of the geotechnical properties of three different red tropical soils in their natural state as well as when mixed with varying proportions of marble dust. The parameters tested included the particle size distribution, specific gravity, Atterberg limits, the standard compaction characteristics, the compressive strength and the California bearing ratio (CBR). The strength tests were repeated after normal 28 day curing of the treated samples and also after accelerated 24 h curing at temperatures of 40°C, 60°C and 80°C.
Results showed that the geotechnical parameters of red tropical soils are improved substantially by the addition of marble dust; plasticity was reduced by 20 to 33% and strength and CBR increased by 30 to 46% and 27 to 55% respectively. The highest strength and CBR values were achieved at 8% marble dust. Results also showed that normal 28 day curing improved the strength of the marble dust-treated soil with over 80% strength gain achieved after 7 to 10 days of normal curing. Higher strength development was realised following accelerated 24 h curing at 60°C.
Although these results imply marked improvement in the geotechnical parameters of red tropical soils, the higher strength developed is not enough for the improved soil to be used as a base material in the construction of heavily trafficked flexible pavements. The improved material may, however, be successfully used as base material for lightly trafficked roads and as a sub-base material for heavily trafficked roads. 相似文献
Approximately 80% of the road network in Brazil is unpaved and shows evidences of a high erosion potential. In the semi-arid Caatinga Biome in the northeast of the country, a monitoring programme has been done for two years in order to analyze runoff and sediment production from unpaved rural road-ways and from embankments. Sediment production ranged from 0.30 to 0.92 Mg/ha yr, higher than in undisturbed areas, but generally lower than that reported for unpaved roads in other regions. However, this is a semi-arid area with low rainfall and runoff and, hence, with a limited hydrological connectivity and sediment production. Sediment production on an embankment with no vegetation was around ten times higher than on an embankment with vegetation. On the road surface, annual sediment production (normalized for gradient) in a section with traffic was three times higher than for a road surface without traffic. In addition, events that occurred after roadway maintenance activities generated peaks of sedi-ment concentration of over 5000 mg/L. These results suggest that sediment production from roads and embankments with bare surfaces is at least one order of magnitude higher than in undisturbed catch-ment areas. Maintenance activity and vehicle traffic contribute to an increase in sediment availability and impact on the sediment concentration, but less intensely on sediment loads, which depend on the runoff magnitude of the events occurring after roadway maintenance. It was also found that the natural vegetation of the semi-arid region potentially captures sediment on roadway embankments;thereby playing an important role in breaking connectivity between the sediment flow from unpaved roads and the natural drainage system of the catchment. 相似文献