The scale of fluctuation is one of the vital parameters for the application of random field theory to the reliability analysis of geotechnical engineering. In the present study, the fluctuation function method and wei...The scale of fluctuation is one of the vital parameters for the application of random field theory to the reliability analysis of geotechnical engineering. In the present study, the fluctuation function method and weighted curve fitting method were presented to make the calculation more simple and accurate. The vertical scales of fluctuation of typical layers of Tianjin Port were calculated based on a number of engineering geotechnical investigation data, which can be guidance to other projects in this area. Meanwhile, the influences of sample interval and type of soil index on the scale of fluctuation were analyzed, according to which, the principle of determining the scale of fluctuation when the sample interval changes was defined. It can be obtained that the scale of fluctuation is the basic attribute reflecting spatial variability of soil, therefore, the scales of fluctuation calculated according to different soil indexes should be basically the same. The non-correlation distance method was improved, and the principle of determining the variance reduction function was also discussed.展开更多
Mass movements are very common problems in the eastern Black Sea region of Turkey due to its climate conditions, geological, and geomorphological characteristics. High slope angle, weathering, dense rainfalls, and ant...Mass movements are very common problems in the eastern Black Sea region of Turkey due to its climate conditions, geological, and geomorphological characteristics. High slope angle, weathering, dense rainfalls, and anthropogenic impacts are generally reported as the most important triggering factors in the region. Following the portal slope excavations in the entrance section of Cankurtaran tunnel, located in the region, where the highly weathered andesitic tuff crops out, a circular toe failure occurred. The main target of the present study is to investigate the causes and occurrence mechanism of this failure and to determine the feasible remedial measures against it using finite element method(FEM) in four stages. These stages are slope stability analyses for pre-and postexcavation cases, and remediation design assessments for slope and tunnel. The results of the FEM-SSR analyses indicated that the insufficient initial support design and weathering of the andesitic tuffs are the main factors that caused the portal failure. After installing a rock retaining wall with jet grout columns and reinforced slope benching applications, the factor of safety increased from 0.83 to 2.80. In addition toslope stability evaluation, the Rock Mass Rating(RMR), Rock Mass Quality(Q) and New Austrian Tunneling Method(NATM) systems were also utilized as empirical methods to characterize the tunnel ground and to determine the tunnel support design. The performance of the suggested empirical support design, induced stress distributions and deformations were analyzed by means of numerical modelling. Finally, it was concluded that the recommended stabilization technique was essential for the dynamic long-term stability and prevents the effects of failure. Additionally, the FEM method gives useful and reasonably reliable results in evaluating the stability of cut slopes and tunnels excavated both in continuous and discontinuous rock masses.展开更多
A total of 60 VES （geo-electrical resistivity soundings） and ten exploratory core holes （boreholes） were carried out along the axis of a proposed earth dam site as part of an overall geotechnical investigation for...A total of 60 VES （geo-electrical resistivity soundings） and ten exploratory core holes （boreholes） were carried out along the axis of a proposed earth dam site as part of an overall geotechnical investigation for the design and construction of an earth dam along Dansak River, Shemankar River Basin, Jos Plateau, Nigeria. The geophysical interpretation revealed four to five geo-electric layers corresponding to lithologic units （1） topsoil from 0-2 m with a resistivity value of 〈 100-320 ohm-m, （2） weathered/slightly weathered basalt fi＇om 0.6 m to 20 m characterized by resistivity value of 27-130 ohm-m, followed by （3） basalt/fractured basalts with resistivity value of 130-400 ohm-m and （4） the basement rocks with resistivity value 〉 320 ohm-m to 3,021 ohm-m. Exploratory borehole drilling encountered a series of lithologic units viz： overburden （clay, silt and sand） weathered basalt, slightly weathered basalt, fresh/fractured basalts, weathered migmatite and migmatites/migmatite gneiss. Exploratory core analysis in terms of CR （core recovery） and RQD （rock quality designation） revealed an average of 70%-90% and 75%-90%, respectively. Lugeon test gave Lugeon values of 1-5 for the ten core holes. However, fractures with Lugeon value from 〉 5-15 lugeon were encountered on borehole numbers BH 1, 7, 8, 9 and 10. Grouting is recommended to seal this shallow to medium depth （0-15 m） fractures to reduce or eliminate possible seepage when the dam is constructed. The rock mass index grading for the dam axis ranges from good to excellent.展开更多
The coastal region around Sri Lanka have been subjected to considerable changes since Pleistocene and one remarkable observation is the occurrence of submarine canyons in eight places of the Island. The literature say...The coastal region around Sri Lanka have been subjected to considerable changes since Pleistocene and one remarkable observation is the occurrence of submarine canyons in eight places of the Island. The literature says that the head of the largest canyon at Trincomalee is situated 200 m from the shore. The objective of this paper is to highlight the extension of the canyon structure by studying the recent geotechnical investigations around the Mahaweli delta. A number of boreholes were constructed for groundwater investigations around the Mahaweli river floodplains and the other boreholes were constructed to determine the depth to the bedrock for a bridge foundation at the river outfall. The depth to the bedrock at the river outfall is more than 75 m and decreases towards upstream. The shape of the bedrock below the thick fluvial sediments in the studied area indicates the head of canyon should be marked more than 35 km from the shore towards inland. It is obvious that the submarine canyon at Trincomalee is only a part of a very large canyon. The thick fluvial sedimentary deposit over this canyon within the land is a result of erosion of bedrock along a shear zone or fault and then the rise of sea level in recent times.展开更多
The use of GPR （ground penetrating radar） as an auxiliary tool in geotechnical and environmental site investigations has increased in Brazil during the past few years. GPR has been used to delineate contamination pl...The use of GPR （ground penetrating radar） as an auxiliary tool in geotechnical and environmental site investigations has increased in Brazil during the past few years. GPR has been used to delineate contamination plumes, to aid in geological modelling, to detect buried structures and in archaeological surveys. This paper describes and discusses the results ofa GPR site investigation carried out at Gramacho Municipal Solid Waste Landfill in the State of Rio de Janeiro, Brazil. A field study was conducted to detect failure surfaces in its slopes and within the waste mass. The results have shown that： （l） Slip surfaces could be indicated by small continuous voids within the waste mass since there is a good contrast between the dielectric constant of air and municipal waste; （2） Greenhouse gases pools could also be indicated by large voids within the waste mass since there is a good contrast between the dielectric constant of carbon dioxide, methane and municipal waste; （3） Leachate pools present a high electric conductivity that could be easily detected by GPR.展开更多
基金Supported by the National Natural Science Foundation of China(No.41272323)Tianjin Natural Science Foundation(No.13JCZDJC 35300)
文摘The scale of fluctuation is one of the vital parameters for the application of random field theory to the reliability analysis of geotechnical engineering. In the present study, the fluctuation function method and weighted curve fitting method were presented to make the calculation more simple and accurate. The vertical scales of fluctuation of typical layers of Tianjin Port were calculated based on a number of engineering geotechnical investigation data, which can be guidance to other projects in this area. Meanwhile, the influences of sample interval and type of soil index on the scale of fluctuation were analyzed, according to which, the principle of determining the scale of fluctuation when the sample interval changes was defined. It can be obtained that the scale of fluctuation is the basic attribute reflecting spatial variability of soil, therefore, the scales of fluctuation calculated according to different soil indexes should be basically the same. The non-correlation distance method was improved, and the principle of determining the variance reduction function was also discussed.
文摘Mass movements are very common problems in the eastern Black Sea region of Turkey due to its climate conditions, geological, and geomorphological characteristics. High slope angle, weathering, dense rainfalls, and anthropogenic impacts are generally reported as the most important triggering factors in the region. Following the portal slope excavations in the entrance section of Cankurtaran tunnel, located in the region, where the highly weathered andesitic tuff crops out, a circular toe failure occurred. The main target of the present study is to investigate the causes and occurrence mechanism of this failure and to determine the feasible remedial measures against it using finite element method(FEM) in four stages. These stages are slope stability analyses for pre-and postexcavation cases, and remediation design assessments for slope and tunnel. The results of the FEM-SSR analyses indicated that the insufficient initial support design and weathering of the andesitic tuffs are the main factors that caused the portal failure. After installing a rock retaining wall with jet grout columns and reinforced slope benching applications, the factor of safety increased from 0.83 to 2.80. In addition toslope stability evaluation, the Rock Mass Rating(RMR), Rock Mass Quality(Q) and New Austrian Tunneling Method(NATM) systems were also utilized as empirical methods to characterize the tunnel ground and to determine the tunnel support design. The performance of the suggested empirical support design, induced stress distributions and deformations were analyzed by means of numerical modelling. Finally, it was concluded that the recommended stabilization technique was essential for the dynamic long-term stability and prevents the effects of failure. Additionally, the FEM method gives useful and reasonably reliable results in evaluating the stability of cut slopes and tunnels excavated both in continuous and discontinuous rock masses.
文摘A total of 60 VES （geo-electrical resistivity soundings） and ten exploratory core holes （boreholes） were carried out along the axis of a proposed earth dam site as part of an overall geotechnical investigation for the design and construction of an earth dam along Dansak River, Shemankar River Basin, Jos Plateau, Nigeria. The geophysical interpretation revealed four to five geo-electric layers corresponding to lithologic units （1） topsoil from 0-2 m with a resistivity value of 〈 100-320 ohm-m, （2） weathered/slightly weathered basalt fi＇om 0.6 m to 20 m characterized by resistivity value of 27-130 ohm-m, followed by （3） basalt/fractured basalts with resistivity value of 130-400 ohm-m and （4） the basement rocks with resistivity value 〉 320 ohm-m to 3,021 ohm-m. Exploratory borehole drilling encountered a series of lithologic units viz： overburden （clay, silt and sand） weathered basalt, slightly weathered basalt, fresh/fractured basalts, weathered migmatite and migmatites/migmatite gneiss. Exploratory core analysis in terms of CR （core recovery） and RQD （rock quality designation） revealed an average of 70%-90% and 75%-90%, respectively. Lugeon test gave Lugeon values of 1-5 for the ten core holes. However, fractures with Lugeon value from 〉 5-15 lugeon were encountered on borehole numbers BH 1, 7, 8, 9 and 10. Grouting is recommended to seal this shallow to medium depth （0-15 m） fractures to reduce or eliminate possible seepage when the dam is constructed. The rock mass index grading for the dam axis ranges from good to excellent.
文摘The coastal region around Sri Lanka have been subjected to considerable changes since Pleistocene and one remarkable observation is the occurrence of submarine canyons in eight places of the Island. The literature says that the head of the largest canyon at Trincomalee is situated 200 m from the shore. The objective of this paper is to highlight the extension of the canyon structure by studying the recent geotechnical investigations around the Mahaweli delta. A number of boreholes were constructed for groundwater investigations around the Mahaweli river floodplains and the other boreholes were constructed to determine the depth to the bedrock for a bridge foundation at the river outfall. The depth to the bedrock at the river outfall is more than 75 m and decreases towards upstream. The shape of the bedrock below the thick fluvial sediments in the studied area indicates the head of canyon should be marked more than 35 km from the shore towards inland. It is obvious that the submarine canyon at Trincomalee is only a part of a very large canyon. The thick fluvial sedimentary deposit over this canyon within the land is a result of erosion of bedrock along a shear zone or fault and then the rise of sea level in recent times.
文摘The use of GPR （ground penetrating radar） as an auxiliary tool in geotechnical and environmental site investigations has increased in Brazil during the past few years. GPR has been used to delineate contamination plumes, to aid in geological modelling, to detect buried structures and in archaeological surveys. This paper describes and discusses the results ofa GPR site investigation carried out at Gramacho Municipal Solid Waste Landfill in the State of Rio de Janeiro, Brazil. A field study was conducted to detect failure surfaces in its slopes and within the waste mass. The results have shown that： （l） Slip surfaces could be indicated by small continuous voids within the waste mass since there is a good contrast between the dielectric constant of air and municipal waste; （2） Greenhouse gases pools could also be indicated by large voids within the waste mass since there is a good contrast between the dielectric constant of carbon dioxide, methane and municipal waste; （3） Leachate pools present a high electric conductivity that could be easily detected by GPR.
