The Port Harcourt Enugu expressway is part of a national road grid that links parts of southern and northern Nigeria. The severe pavement failure between Umuahia and Okigwe section of the expressway covering a distanc...The Port Harcourt Enugu expressway is part of a national road grid that links parts of southern and northern Nigeria. The severe pavement failure between Umuahia and Okigwe section of the expressway covering a distance of about 30 km was investigated by geotechnical and mineralogical assessment of disturbed and undisturbed samples of the underlying soils. Also vertical electrical sounding was performed at the failed sections. Results indicate that the section is underlain by shales of the Imo Formation, and soils are composed of 27% and 74% sand and fines respectively. The Atterberg limit values are moderate to high, with liquid limit in the range of 49-54%, plasticity index 11.1-24.4% and linear shrinkage 17.86-23.57% respectively. Abrasion test results of 0.58 to 16% indicate shales of low durability. The 24 hour free swell tests results range from 33-70% implying soils of moderate to high hydro-affinity and volume change. These data corroborate the X-ray diffraction analyses results which show montmorillonite and kaolinite as the main clay minerals present in the soils. Undrained cohesion range from 9 to 54 kPa and frictional angle from 13° to 29°. High settlement amounts and field observation of intense failure correlated well with the engineering properties and the clay minerals. The soils indicate mainly MI-MH and A-7-5 soils on the USC and AASHTO classification system respectively, implying poor quality soils as subgrade materials. stabilisation. Result of the study will be useful in remedial works areas underlain by the shales. The engineering properties may be modified and upgraded by on the failed sections of the road and future pavement design in展开更多
The paper presents examples of technological designs for concrete placement in road bridges constructed during the S5/S 10 expressway extension in Poland. The project included eight concrete or composite bridge struct...The paper presents examples of technological designs for concrete placement in road bridges constructed during the S5/S 10 expressway extension in Poland. The project included eight concrete or composite bridge structures with different numbers of decks. The concrete placement technology is presented for the following bridge decks： slabs cast-in-situ, composite with precast or VFT （prefabricated composite beam） beams and mixed with cast in situ slabs and VFT-WIB （filler beam） beams. Continuous concrete placement was adopted for almost all the bridge superstructures except the mixed-type decks where construction joints were necessary. To control shrinkage, formwork deformations and existing restraints, the concrete was poured in layers and in stages. The design pace of concrete placement was moderate to be regulated at site without compromising safety and quality. The placement methods enabled both efficient and safe concrete pours.展开更多
文摘The Port Harcourt Enugu expressway is part of a national road grid that links parts of southern and northern Nigeria. The severe pavement failure between Umuahia and Okigwe section of the expressway covering a distance of about 30 km was investigated by geotechnical and mineralogical assessment of disturbed and undisturbed samples of the underlying soils. Also vertical electrical sounding was performed at the failed sections. Results indicate that the section is underlain by shales of the Imo Formation, and soils are composed of 27% and 74% sand and fines respectively. The Atterberg limit values are moderate to high, with liquid limit in the range of 49-54%, plasticity index 11.1-24.4% and linear shrinkage 17.86-23.57% respectively. Abrasion test results of 0.58 to 16% indicate shales of low durability. The 24 hour free swell tests results range from 33-70% implying soils of moderate to high hydro-affinity and volume change. These data corroborate the X-ray diffraction analyses results which show montmorillonite and kaolinite as the main clay minerals present in the soils. Undrained cohesion range from 9 to 54 kPa and frictional angle from 13° to 29°. High settlement amounts and field observation of intense failure correlated well with the engineering properties and the clay minerals. The soils indicate mainly MI-MH and A-7-5 soils on the USC and AASHTO classification system respectively, implying poor quality soils as subgrade materials. stabilisation. Result of the study will be useful in remedial works areas underlain by the shales. The engineering properties may be modified and upgraded by on the failed sections of the road and future pavement design in
文摘The paper presents examples of technological designs for concrete placement in road bridges constructed during the S5/S 10 expressway extension in Poland. The project included eight concrete or composite bridge structures with different numbers of decks. The concrete placement technology is presented for the following bridge decks： slabs cast-in-situ, composite with precast or VFT （prefabricated composite beam） beams and mixed with cast in situ slabs and VFT-WIB （filler beam） beams. Continuous concrete placement was adopted for almost all the bridge superstructures except the mixed-type decks where construction joints were necessary. To control shrinkage, formwork deformations and existing restraints, the concrete was poured in layers and in stages. The design pace of concrete placement was moderate to be regulated at site without compromising safety and quality. The placement methods enabled both efficient and safe concrete pours.
