Geophysical Investigation Into the Remote Causes of Road Failure Along Farin Gada- Zabolo Road, Jos, North Central

Detailed geophysical investigation for road failure using Schlumberger and the Werner Arraygeophysical investigation was carried out. These investigations were done with the aim ofrevealing the horizontal and the vertical geological discontinuities using their electrical resistivity,intrinsic property of the materials, probable zones of untimely failure along the road. The VESreadings of the Schlumberger array method showed that the failed sections of the road had lowresistivity values that ranges from 19.3Ωm (ohm-meter) to 80.5Ωm (ohm-meter) while the unfailedsections of the road had resistivity values that ranged from 210.5Ωm (ohm-meter) to 491.2 Ωm(ohm-meter). The failed sections of the road from interpretation had high content of clay in themwhich is responsible for the failure while the unfailed section is made up of sand mainly. For theWerner array survey, investigation revealed that only the soils around Horizontal Electrical profile2 (HEP2) were competent because of their high resistivity ranges from 343.06Ωm (ohm-meter) to2092.30Ωm(ohm-meter) while soils in profiles HEP1 and HEP3 were made up of soils that areincompetent because of their relative low resistivity values ranging from 40.80Ωm(ohm-meter) to543.80Ωm(ohm-meter). VES readings obtained at locations 9,11,13,14 and 15 had soils that werecompetent because of their high resistivity values that ranged from19.3Ωm (ohm-meter) to197.4Ωm (ohm-meter) and were collected from the undamaged sections of the road while locations1,2,3,4,5,6,7,8,10,12,16,17,18,19,20,21,22,23,24 and 25 had low resistivity values that rangedfrom 205.3Ωm(ohm-meter) to 1049.8Ωm(ohm-meter) and were collected from the damagedsections of the road. The causes of the road failure in the study area were found mainly to be as aresult of clayey top soil/ sub grade soils due to the nature of the geology of the area which is mainlygranitic in nature that contain a lot of feldspars which upon weathering gives rise to clay (kaolin).The continuous decomposition into clay (kaolin), poses a great threat to the road due to expansion and contraction of the clay. The coarse grained type of the Biotite Granites are more resistant toweathering and have lesser amount of feldspars in them and upon weathering gives birth tolaterites, gravels and sand which have high resistivity values as seen in the undamaged sections ofthe road while the medium to fined grain type of Biotite Granites have a very high amount offeldspar content in them and upon weathering gives rise to clay which have low resistivity valuesas seen in the damaged sections of the road. The presence of thin pavements which are unable towithstand pressure exerted on the road was also another cause of the road failure. Hence, the resultof this research will form the tools for which the causes of the road failure can be identified andhow they can be remedied within the study area using appropriate measures.