Subgrade construction is frequently interrupted due to precipitation,soil shortage,and environmental protection.Therefore,increasing the thickness layer is required to reduce construction costs and to allow highways t...Subgrade construction is frequently interrupted due to precipitation,soil shortage,and environmental protection.Therefore,increasing the thickness layer is required to reduce construction costs and to allow highways to be placed into service earlier.This paper presents a series of full-scale field experiments evaluating the compaction quality of gravel subgrade with large-thickness layers of 65 cm and 80 cm using heavy vibratory rollers.An improved sand cone method was first proposed and calibrated to investigate the distribution of soil compaction degree across the full subgrade depth.Results showed that dynamic soil stresses caused by the heavy vibratory rollers were 2.4–5.9 times larger than those of traditional rollers,especially at deeper depths,which were large enough to densify the soils to the full depth.A unified empirical formula was proposed to determine the vertical distribution of dynamic soil stresses caused by roller excitation.It was demonstrated that soils were effectively compacted in a uniform fashion with respect to the full depth to 96.0%–97.2%and 94.1%–95.4%for the large-thickness layers of 65 cm and 80 cm within 6 or 7 passes,respectively.Empirically,linear formulae were finally established between soil compaction degree and the subgrade reaction modulus,dynamic modulus of deformation,dynamic deflection,and relative difference of settlement to conveniently evaluate the compaction qualities.It is demonstrated that increasing the thickness layer by means of heavy rollers can significantly reduce the cost and time burdens involved in construction while ensuring overall subgrade quality.展开更多
Geosynthetic-reinforced soil retaining walls(GSRWs)have been widely used in civil engineering projects.However,as the climate changes,extreme weather conditions and natural hazards are likely to become more frequent o...Geosynthetic-reinforced soil retaining walls(GSRWs)have been widely used in civil engineering projects.However,as the climate changes,extreme weather conditions and natural hazards are likely to become more frequent or intense,posing a huge threat to the stability of GSRWs.In this paper,the effect of groundwater level fluctuations on the seismic response of GSRWs is investigated.First,a dynamic numerical model was established and validated through centrifugal shaking-table test results.Using the established numerical model,the seismic response of GSRWs under four different groundwater level conditions was then investigated,i.e.,an earthquake occurring at a low groundwater level(Case LW),an earthquake occurring when the groundwater level rises(Case RW),an earthquake occurring at a high groundwater level(Case HW),and an earthquake occurring when the groundwater level drops(Case DW).The results show that the GSRW in Case DW has the worst seismic stability because of the drag forces generated by the water flowing to the outside of the GSRW.For Case RW,deformation of the GSRW under earthquake forces was prevented by the drag forces generated by the water flowing to the inside of the GSRW and the water pressure acting on the outside of the facing,giving the GSRW the best seismic stability in this case.Compared with Case LW,the seismic stability of a GSRW in Case HW is worse,because the high groundwater level will generate excess pore-water pressure during an earthquake.On this basis,we provide engineering design suggestions to be considered by practitioners.展开更多
1Introduction Several characteristics of natural soils complicate the relationship between their mechanical behaviour and geotechnical construction and maintenance in the field.These characteristics include the presen...1Introduction Several characteristics of natural soils complicate the relationship between their mechanical behaviour and geotechnical construction and maintenance in the field.These characteristics include the presence of three phases(solid particle,water,and air),particle constitutions of various minerals(such as quartz,kaolinite,and montmorillonite),and an exceptionally wide range of particle size fromμm-scale(clay particles smallerthan2μm)to100-mm scale(suchas somegravelsandpebbles)。展开更多
基金the National Natural Science Foundation for Young Scientists of China(No.51608306)the Shandong Provincial Natural Science Foundation of China(Nos.ZR2021ME103 and ZR2021QE254)+1 种基金the Shandong Transportation Science and Technology Foundation(Nos.2020-MS1-044,2021B63,and 202060804178)the Young Scholar Future Plan Funds of Shandong University,China。
文摘Subgrade construction is frequently interrupted due to precipitation,soil shortage,and environmental protection.Therefore,increasing the thickness layer is required to reduce construction costs and to allow highways to be placed into service earlier.This paper presents a series of full-scale field experiments evaluating the compaction quality of gravel subgrade with large-thickness layers of 65 cm and 80 cm using heavy vibratory rollers.An improved sand cone method was first proposed and calibrated to investigate the distribution of soil compaction degree across the full subgrade depth.Results showed that dynamic soil stresses caused by the heavy vibratory rollers were 2.4–5.9 times larger than those of traditional rollers,especially at deeper depths,which were large enough to densify the soils to the full depth.A unified empirical formula was proposed to determine the vertical distribution of dynamic soil stresses caused by roller excitation.It was demonstrated that soils were effectively compacted in a uniform fashion with respect to the full depth to 96.0%–97.2%and 94.1%–95.4%for the large-thickness layers of 65 cm and 80 cm within 6 or 7 passes,respectively.Empirically,linear formulae were finally established between soil compaction degree and the subgrade reaction modulus,dynamic modulus of deformation,dynamic deflection,and relative difference of settlement to conveniently evaluate the compaction qualities.It is demonstrated that increasing the thickness layer by means of heavy rollers can significantly reduce the cost and time burdens involved in construction while ensuring overall subgrade quality.
基金the National Natural Science Foundation of China(No.41877224)the China Scholarship Council(No.202006265003)the National Key Research and Development Program of China(No.2019YFC1509900)。
文摘Geosynthetic-reinforced soil retaining walls(GSRWs)have been widely used in civil engineering projects.However,as the climate changes,extreme weather conditions and natural hazards are likely to become more frequent or intense,posing a huge threat to the stability of GSRWs.In this paper,the effect of groundwater level fluctuations on the seismic response of GSRWs is investigated.First,a dynamic numerical model was established and validated through centrifugal shaking-table test results.Using the established numerical model,the seismic response of GSRWs under four different groundwater level conditions was then investigated,i.e.,an earthquake occurring at a low groundwater level(Case LW),an earthquake occurring when the groundwater level rises(Case RW),an earthquake occurring at a high groundwater level(Case HW),and an earthquake occurring when the groundwater level drops(Case DW).The results show that the GSRW in Case DW has the worst seismic stability because of the drag forces generated by the water flowing to the outside of the GSRW.For Case RW,deformation of the GSRW under earthquake forces was prevented by the drag forces generated by the water flowing to the inside of the GSRW and the water pressure acting on the outside of the facing,giving the GSRW the best seismic stability in this case.Compared with Case LW,the seismic stability of a GSRW in Case HW is worse,because the high groundwater level will generate excess pore-water pressure during an earthquake.On this basis,we provide engineering design suggestions to be considered by practitioners.
基金the Research Grants Council(RGC)of Hong Kong Special Administrative Region Government(HKSARG)of China(Nos.15217220,15220221,15226822,and N_Poly U534/20)。
文摘1Introduction Several characteristics of natural soils complicate the relationship between their mechanical behaviour and geotechnical construction and maintenance in the field.These characteristics include the presence of three phases(solid particle,water,and air),particle constitutions of various minerals(such as quartz,kaolinite,and montmorillonite),and an exceptionally wide range of particle size fromμm-scale(clay particles smallerthan2μm)to100-mm scale(suchas somegravelsandpebbles)。
