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Editor Work2004 Vol. 12, No. 2
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2004, 12(2): 113-117.
Abstract
From the concept of sustainable development, this paper explores the missions and approaches of engineering geology. The author points out that the environment which supports human survival and activity, the hazard which is undertaken by human, and the conditions of engineering development are mostly determined by the interaction in the geosphere system and dynamics processes. The geosphere dynamics may serve as foundation for assessment and prediction of engineering geological processes. The author suggests to deepen the study of dynamic processes in the engineering-geosphere system for further developmet of engineering geology as a whole.
From the concept of sustainable development, this paper explores the missions and approaches of engineering geology. The author points out that the environment which supports human survival and activity, the hazard which is undertaken by human, and the conditions of engineering development are mostly determined by the interaction in the geosphere system and dynamics processes. The geosphere dynamics may serve as foundation for assessment and prediction of engineering geological processes. The author suggests to deepen the study of dynamic processes in the engineering-geosphere system for further developmet of engineering geology as a whole.
2004, 12(2): 118-123.
As one of the top ten natural disasters, landslides have great impacts on the environment and on societies, and often cause vast economic losses and casualties. Many methods have been developed for the prediction or forecast of landslides; however, results are not very satisfactory. Two kinds of triggering factors are currently considered in prediction or forecast of landslides: natural and man-made. Under given geological and geomorphic conditions, rainfall becomes a key natural factor. Based on philosophical thoughts on the prediction or forecast of landslides, the authors suggest that the method of weather-slope forecast, in which probability of occurrence of landslides was calculated based on the forecast of rainfall, be enhanced,. As expected, by integrating the weather slope forecast with the monitoring of landslides, the resulting method could improve the accuracy of prediction or forecast of landslides.
As one of the top ten natural disasters, landslides have great impacts on the environment and on societies, and often cause vast economic losses and casualties. Many methods have been developed for the prediction or forecast of landslides; however, results are not very satisfactory. Two kinds of triggering factors are currently considered in prediction or forecast of landslides: natural and man-made. Under given geological and geomorphic conditions, rainfall becomes a key natural factor. Based on philosophical thoughts on the prediction or forecast of landslides, the authors suggest that the method of weather-slope forecast, in which probability of occurrence of landslides was calculated based on the forecast of rainfall, be enhanced,. As expected, by integrating the weather slope forecast with the monitoring of landslides, the resulting method could improve the accuracy of prediction or forecast of landslides.
2004, 12(2): 124-135.
The purplish-red mudstone of the Badong group of Middle Tertiary, which is widely distributed in the Badong, Wushan and Fengjie County of the Three Gorges reservoir, is often called as sliding-proned formation since most landslides occur in this formation. This paper assesses the expansive potential of the mudstone, weathering conditions, water-rock interaction and other behavior. The results show that the mineral content is approximately 17.9%, of which the montolian constitutes 1.27～6.01%, and the mix layer mineral is over 50%, and it is of a medium to strong gluing capacity and a weak expansive potential. The physical or mechanical weathering is dominant with limited changes in chemical components along the cross-section observed. The water is a dominant factor in controlling the mechnical weathering of mudstone. Therefore, the impacts of water level changes with the reservoir storage and discharge are assessed by field investigation and laboratory tests to assure the stability of the bank slope in the Three Gorges Reservoir.
The purplish-red mudstone of the Badong group of Middle Tertiary, which is widely distributed in the Badong, Wushan and Fengjie County of the Three Gorges reservoir, is often called as sliding-proned formation since most landslides occur in this formation. This paper assesses the expansive potential of the mudstone, weathering conditions, water-rock interaction and other behavior. The results show that the mineral content is approximately 17.9%, of which the montolian constitutes 1.27～6.01%, and the mix layer mineral is over 50%, and it is of a medium to strong gluing capacity and a weak expansive potential. The physical or mechanical weathering is dominant with limited changes in chemical components along the cross-section observed. The water is a dominant factor in controlling the mechnical weathering of mudstone. Therefore, the impacts of water level changes with the reservoir storage and discharge are assessed by field investigation and laboratory tests to assure the stability of the bank slope in the Three Gorges Reservoir.
2004, 12(2): 136-140.
The multi-cyclicity of Xigeda stratum and near-saturation of mudstone within it, which resulted from the sedimentary environment, lead to its engineering characteristics different from other soils. In this paper, authors first characterized moisture content of Xigeda stratum, and then evaluated its effect on engineering properties of soil. At last, it was concluded that uniform correlations exist between moisture content and the four engineering property indexes; maximal dry density ( d max ) ,compacting degree (K), and shear strength parameters (c、) in Xigeda stratum. It was also found that the optimal moisture content is close to natural moisture content of the randomly mixed Xigeda fill.
The multi-cyclicity of Xigeda stratum and near-saturation of mudstone within it, which resulted from the sedimentary environment, lead to its engineering characteristics different from other soils. In this paper, authors first characterized moisture content of Xigeda stratum, and then evaluated its effect on engineering properties of soil. At last, it was concluded that uniform correlations exist between moisture content and the four engineering property indexes; maximal dry density ( d max ) ,compacting degree (K), and shear strength parameters (c、) in Xigeda stratum. It was also found that the optimal moisture content is close to natural moisture content of the randomly mixed Xigeda fill.
2004, 12(2): 141-147.
The attenuation relationships are presented in terms of peak ground acceleration, vertical to horizontal ratio, specific ratio and the response spectra for given period based on site and focal mechanisms of the worldwide free-field near-fault records. A comparison of these relationships is made with the research result for Chi-Chi earthquake. It can be concluded that the influence of combined site and focal mechanism on near-fault ground motions is remarkable.
The attenuation relationships are presented in terms of peak ground acceleration, vertical to horizontal ratio, specific ratio and the response spectra for given period based on site and focal mechanisms of the worldwide free-field near-fault records. A comparison of these relationships is made with the research result for Chi-Chi earthquake. It can be concluded that the influence of combined site and focal mechanism on near-fault ground motions is remarkable.
2004, 12(2): 148-154.
Liquefaction of saturated sands remains an important topic in geotechnical earthquake engineering. Amongst various remedial measures available, the use of stone columns is one of the most popular choices. In this paper, a detailed review on effectiveness of densification, drainage and reinforcement of stone columns for the esistance of soil liquefaction during earthquakes is presented. Some problems worthy to be further studied are proposed.
Liquefaction of saturated sands remains an important topic in geotechnical earthquake engineering. Amongst various remedial measures available, the use of stone columns is one of the most popular choices. In this paper, a detailed review on effectiveness of densification, drainage and reinforcement of stone columns for the esistance of soil liquefaction during earthquakes is presented. Some problems worthy to be further studied are proposed.
2004, 12(2): 155-161.
Based on the rheological stress-strain relationship of soil, the characteristics of the s～t curve of an embankment are analyzed under instant loading, linear or approximately linear loading and multi-stage loading. A prediction model for settlement under the above-mentioned three loading sequences is then developed. The case studies verify the applicability of this model.
Based on the rheological stress-strain relationship of soil, the characteristics of the s～t curve of an embankment are analyzed under instant loading, linear or approximately linear loading and multi-stage loading. A prediction model for settlement under the above-mentioned three loading sequences is then developed. The case studies verify the applicability of this model.
2004, 12(2): 162-166.
Slope height is a controlling factor in stability of a slope. Based on the SMR system, the slope height coefficient is incorporated in CSMR, a system developed for hydroelectric slope rock mass rating. To apply the rating system in the classification of highway slopes, further modifications should be made. The slope height coefficient can be expressed as =a+b/H based on the mechanical analyses of some possible failure forms. This paper then presents two expressions of slope height coefficient for different combinations of strata and slope from statistic analyses of over 100 slopes. The modified CSMR has been validated and meets requirements for assessment of highway slope stability.
Slope height is a controlling factor in stability of a slope. Based on the SMR system, the slope height coefficient is incorporated in CSMR, a system developed for hydroelectric slope rock mass rating. To apply the rating system in the classification of highway slopes, further modifications should be made. The slope height coefficient can be expressed as =a+b/H based on the mechanical analyses of some possible failure forms. This paper then presents two expressions of slope height coefficient for different combinations of strata and slope from statistic analyses of over 100 slopes. The modified CSMR has been validated and meets requirements for assessment of highway slope stability.
2004, 12(2): 167-170.
The concrete face-plate dam of Heiquan Reservoir is 123.50 m high, the 4 th built high concrete face-plate dam in China. The landform at the dam site has been broken, the structures are developed, and the engineering-geological conditions are complex. The existence of Quaternary sand-gravel beds on the riverbed is unfavorable for the stability of the dam body. Thus, some specific structural measures were taken in design of the dam and well satisfied the specific geological conditions. This paper analyzes the engineering-geological conditions and the relevant engineering treatment measures.
The concrete face-plate dam of Heiquan Reservoir is 123.50 m high, the 4 th built high concrete face-plate dam in China. The landform at the dam site has been broken, the structures are developed, and the engineering-geological conditions are complex. The existence of Quaternary sand-gravel beds on the riverbed is unfavorable for the stability of the dam body. Thus, some specific structural measures were taken in design of the dam and well satisfied the specific geological conditions. This paper analyzes the engineering-geological conditions and the relevant engineering treatment measures.
2004, 12(2): 171-176.
A super-large pile group was adopted in the Li-Zigou large-span bridge, one of the major projects on the Nei-Kun railway. A physical model of the super-large pile group is constructed to gain a better understanding of its mechanical behavior by observing the distribution of internal forces and of its deformation behavior under horizontal load. The results show that the maximum bending moment shows up in the vicinage of the cross-connection of the pile and the bearing platform. The bending moment decreases linearly or nonlinearly with the load along the pile from top to bottom. The peak values of the bending moment and its variations differ depending on the combination of vertical and horizontal loads.
A super-large pile group was adopted in the Li-Zigou large-span bridge, one of the major projects on the Nei-Kun railway. A physical model of the super-large pile group is constructed to gain a better understanding of its mechanical behavior by observing the distribution of internal forces and of its deformation behavior under horizontal load. The results show that the maximum bending moment shows up in the vicinage of the cross-connection of the pile and the bearing platform. The bending moment decreases linearly or nonlinearly with the load along the pile from top to bottom. The peak values of the bending moment and its variations differ depending on the combination of vertical and horizontal loads.
2004, 12(2): 177-181.
In order to meet the need of the actual rock engineering, the methods are required to verify the result of the 3-D discontinuies network modeling. One method is to compare the figures between the section of the numerical model and the sampling window of in-situ model. The other method is to verify the data set of the numerical model using field data. When the modeling results are verified to have a good precision, They can be considered effective, and can be applied into the actual rock engineering.
In order to meet the need of the actual rock engineering, the methods are required to verify the result of the 3-D discontinuies network modeling. One method is to compare the figures between the section of the numerical model and the sampling window of in-situ model. The other method is to verify the data set of the numerical model using field data. When the modeling results are verified to have a good precision, They can be considered effective, and can be applied into the actual rock engineering.
2004, 12(2): 182-186.
The soil-water characteristic curve is very important for studying the physical and mechanical characteristics of unsaturated soils. Strength, volumetric strain and permeability coefficient, and even moisture-distribution above ground water surface can be determined by the soil-water characteristic curve. A mathematical model of soil-water characteristic curve is established, based on soil, structure and the shape of soil-water characteristic curve. Mathematical models of soil-water characteristic curve differ due to varying physical and mechanical properties of unsaturated soils. It is, thus, necessary to establish universal expression of soil-water characteristic curve. In this paper, mathematical models of soil-water characteristic curve are divided into four types based on the patterns of mathematical models. An universal mathematical model with unified functional pattern is derived. The soil-water characteristic curve of loessal soils in north Shaannxi loess plateau, is used to verify the universal mathematical model.
The soil-water characteristic curve is very important for studying the physical and mechanical characteristics of unsaturated soils. Strength, volumetric strain and permeability coefficient, and even moisture-distribution above ground water surface can be determined by the soil-water characteristic curve. A mathematical model of soil-water characteristic curve is established, based on soil, structure and the shape of soil-water characteristic curve. Mathematical models of soil-water characteristic curve differ due to varying physical and mechanical properties of unsaturated soils. It is, thus, necessary to establish universal expression of soil-water characteristic curve. In this paper, mathematical models of soil-water characteristic curve are divided into four types based on the patterns of mathematical models. An universal mathematical model with unified functional pattern is derived. The soil-water characteristic curve of loessal soils in north Shaannxi loess plateau, is used to verify the universal mathematical model.
2004, 12(2): 187-192.
Based on a sample, the most commonly used methods that can search the surface of unconfined flow were analyzed. The Elemental Conducting Matrix Adjustment Method was simplified and improved, and the Equivalent Penetration Coefficient Method was proposed. It is concluded that the Equivalent Penetration Coefficient Method is accurate, simple, and easy to be popularized.
Based on a sample, the most commonly used methods that can search the surface of unconfined flow were analyzed. The Elemental Conducting Matrix Adjustment Method was simplified and improved, and the Equivalent Penetration Coefficient Method was proposed. It is concluded that the Equivalent Penetration Coefficient Method is accurate, simple, and easy to be popularized.
2004, 12(2): 193-198.
A new method to evaluate leakage of karstic rock is introduced in this paper. The first step of the method is to establish a stochastic structure model of karstic rock using the data from the in situ measurement. The second step is to calculate the hydraulic conductivity tensor of karstic rock using the data from the stochastic structure model. The third step is to assess the leakage using the calculated hydraulic conductivity tensor based on the regional hydraulic condition. Then the distribution of leakage can be characterized by repeating the model runs. Among these three steps the first one is the most important and difficult step. At the end, the authors present a case study to demonstrate procedures and flow chart of the model development and its applications in engineering projects.
A new method to evaluate leakage of karstic rock is introduced in this paper. The first step of the method is to establish a stochastic structure model of karstic rock using the data from the in situ measurement. The second step is to calculate the hydraulic conductivity tensor of karstic rock using the data from the stochastic structure model. The third step is to assess the leakage using the calculated hydraulic conductivity tensor based on the regional hydraulic condition. Then the distribution of leakage can be characterized by repeating the model runs. Among these three steps the first one is the most important and difficult step. At the end, the authors present a case study to demonstrate procedures and flow chart of the model development and its applications in engineering projects.
2004, 12(2): 199-207.
The difference of shearing strength resulting from the direct shearing test and the tri-axial compression test and factors contributing to such a difference are seldom discussed. This paper addresses this issue by evaluating the effective shearing strengths of 11 sets of samples from 3 trial pits in 2 slopes of Hong Kong, which are obtained by the tri-axial test and direct shearing test. The results indicate that the group kt consisting of mid-fine particles and a smaller porosity has higher shear strength than the group skm consisting of mid-coarse particles and a larger porosity. For the same group of samples, the shearing strength obtained from the tri-axial test is larger than that from direct shearing test. The difference in effective cohesions c' ranges from 60 Pa to 60 kPa,while the difference in the effective friction angle ' ranges from 2 to 18. The effective cohesions (c') is linearly correlative to each other with a coefficient of correlation (R) of 0.849,while the effective friction angles (') is logarithmically correlative to each other with the R of 0.686. In addition, the differences of c' have a reciprocally linear correlation with the differences of ' and with the R of 0.377. The difference in shear strengths depends on material components and microstructure features, e.g. clay particles, quartz grains and clay minerals content. Among them, the clay content is logarithmically correlated with the difference of c and with the R of 0.776,while it has a reciprocally logarithmic correlation with the difference of ' and with the R of 0.733. Therefore, it is important to pay special attentions on variations in the clay content and the quartz content. This paper also discussed other factors that should also be considered, including the natural density and free iron oxides ratio.
The difference of shearing strength resulting from the direct shearing test and the tri-axial compression test and factors contributing to such a difference are seldom discussed. This paper addresses this issue by evaluating the effective shearing strengths of 11 sets of samples from 3 trial pits in 2 slopes of Hong Kong, which are obtained by the tri-axial test and direct shearing test. The results indicate that the group kt consisting of mid-fine particles and a smaller porosity has higher shear strength than the group skm consisting of mid-coarse particles and a larger porosity. For the same group of samples, the shearing strength obtained from the tri-axial test is larger than that from direct shearing test. The difference in effective cohesions c' ranges from 60 Pa to 60 kPa,while the difference in the effective friction angle ' ranges from 2 to 18. The effective cohesions (c') is linearly correlative to each other with a coefficient of correlation (R) of 0.849,while the effective friction angles (') is logarithmically correlative to each other with the R of 0.686. In addition, the differences of c' have a reciprocally linear correlation with the differences of ' and with the R of 0.377. The difference in shear strengths depends on material components and microstructure features, e.g. clay particles, quartz grains and clay minerals content. Among them, the clay content is logarithmically correlated with the difference of c and with the R of 0.776,while it has a reciprocally logarithmic correlation with the difference of ' and with the R of 0.733. Therefore, it is important to pay special attentions on variations in the clay content and the quartz content. This paper also discussed other factors that should also be considered, including the natural density and free iron oxides ratio.
2004, 12(2): 208-214.
Random blocks in underground tunnels are those uncertain blocks cut by random joints or fractures in bedrock, which have been observed in many existing underground factory buildings. Designers often reinforce these blocks by using systematic anchors, of which length and space are difficult to determine because of the randomness of the blocks position and the indeterminacy of the blocks geometry. This paper presents a case study in a hydropower station to demonstrate distribution patterns of the random joints based on geological conditions and rock structure of the underground caverns. Potential random blocks are then defined by combining different sets of joints, or by combining joints with the Type I and II structural planes. Stabilities of the random blocks are eventually evaluated using the block theory. Finally, the optimal anchor length can be determined as part of the design of the systematic anchors.
Random blocks in underground tunnels are those uncertain blocks cut by random joints or fractures in bedrock, which have been observed in many existing underground factory buildings. Designers often reinforce these blocks by using systematic anchors, of which length and space are difficult to determine because of the randomness of the blocks position and the indeterminacy of the blocks geometry. This paper presents a case study in a hydropower station to demonstrate distribution patterns of the random joints based on geological conditions and rock structure of the underground caverns. Potential random blocks are then defined by combining different sets of joints, or by combining joints with the Type I and II structural planes. Stabilities of the random blocks are eventually evaluated using the block theory. Finally, the optimal anchor length can be determined as part of the design of the systematic anchors.
2004, 12(2): 215-220.
This paper introduces the process of data mining using the MS Analysis Service and the essential principle of the algorithm of the Decision-Tree. The data mining method is used to analyze a set of the creep test data of argillite. As a result of data mining, several key factors are revealed. Their impacts on the deformation during the test are then assessed.
This paper introduces the process of data mining using the MS Analysis Service and the essential principle of the algorithm of the Decision-Tree. The data mining method is used to analyze a set of the creep test data of argillite. As a result of data mining, several key factors are revealed. Their impacts on the deformation during the test are then assessed.
2004, 12(2): 221-224.
The existing methods for testing the construction quality of road base are expensive, in terms of both labour and time, though they are direct and reliable. As a result, they can only be applied on limited measuring points, and can hardly reflect the quality of the whole road base continuously. In order to solve this problem, the relationship between the tamping degrees and the elastic velocities of road base materials is studied in laboratory. The study result can provide the physical foundation for the test of road base construction quality using wave propagation method. It is psooible to carry out the continuous and overall test of road base construction quality by wave propagation method.
The existing methods for testing the construction quality of road base are expensive, in terms of both labour and time, though they are direct and reliable. As a result, they can only be applied on limited measuring points, and can hardly reflect the quality of the whole road base continuously. In order to solve this problem, the relationship between the tamping degrees and the elastic velocities of road base materials is studied in laboratory. The study result can provide the physical foundation for the test of road base construction quality using wave propagation method. It is psooible to carry out the continuous and overall test of road base construction quality by wave propagation method.
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