Abstract:
In this study an attempt was made to investigate the causes of failure due to sub base
and subgrade soil properties and remedial measures of damaged pavement. The study
focused on performing laboratory tests, taking representative pavement material
samples (i.e sub-base and selected fill) from different portions of the road and making
the necessary laboratory tests on the collected samples. Additional natural subgrade
samples from left and right hand side of the road were also taken for laboratory
testing.
The case study road pavement was damaged in different stations were seen during
field observation. From field investigation in the study area was observed several type
of pavement damaged such as; Raveled, transverse cracked, patched, differential
settlement/depression, rutting, shoved/corrugation, and potholes/debonding layers of
damaged.
To find out the real cause of pavement damaged related to soil pavement layer
properties was conduct different laboratory test. Such as; sieve analysis (Wet method)
to check the soil layer grain size distribution, Atterberg limit (LL and PL test) to find
out the plasticity index of their soil, Compaction test (Modified) to get Maximum Dry
Density and Optimum Moisture Content of the soil and finally California Bearing
Ratio test to check the soil strength and stability.
The laboratory results showed that the soil materials used along the road have high
percentage clayey material for half of the natural subgrade soil sample (rated as fair
to poor materials for road use) and low percentages of clayey and silt/gravel/sand
materials of sub-base and selected fill soil samples. The OMC are almost high for all
the soil samples the exception of few samples. The MDD values were ranged from
1.33 kg/m³ to 2.25 kg/m³ for the soil materials. The Plasticity Indices and Liquid
limits are very high for all Sub-base, selected fill and natural subgrade soil samples
with the exception of few samples. Most of CBR values for the selected fill soil
materials almost meet specification requirements while that of Sub-base and natural
Subgrade soil - materials almost did not meet the specification requirements with the
exception of few samples. Conclusively, the pavement failure may necessarily be due
to weak/ poor soil pavement layer performance in the different failed location.
Finally, a different remedial measure (i.e Patching, Sealing, Digging out and replace
good soil and structural or non-structural overlay) was made with respect to their
different type of pavement damaged in the study road.
