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Editor Work2001 Vol. 9, No. 3
Previous Issue
2001, 9(3): 227-232.
Abstract
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The unloading fracture zone of high rock slope is very significant in rock slope engineering. In this paper, firstly, the basic regularities of secondary stress distribution resulted from slope excavation and river during cutting are studied, and then a general model for formation mechanism of unloading fracture zone is suggested. It reveals that the unloading fracture can be discriminated into two basic types, i. e. tensile fracturing and shear relaxing. Moreover, the engineering behaviors of the unloading fracture zone and its mechanical significance are discussed. On this basis, we propose a numerical simulation approach to the unloading fracture zone in slope excavation. Finally, as a typical example, the distribution of unloading fracture zone of high slope at Three-Gorges shiplock is figured out and its progressive development process is simulated numerically.
The unloading fracture zone of high rock slope is very significant in rock slope engineering. In this paper, firstly, the basic regularities of secondary stress distribution resulted from slope excavation and river during cutting are studied, and then a general model for formation mechanism of unloading fracture zone is suggested. It reveals that the unloading fracture can be discriminated into two basic types, i. e. tensile fracturing and shear relaxing. Moreover, the engineering behaviors of the unloading fracture zone and its mechanical significance are discussed. On this basis, we propose a numerical simulation approach to the unloading fracture zone in slope excavation. Finally, as a typical example, the distribution of unloading fracture zone of high slope at Three-Gorges shiplock is figured out and its progressive development process is simulated numerically.
2001, 9(3): 233-240.
The hazard of loess slumping is a special type of slope failure in the northern part of China loess plateau. The paroxysm and high frequency of the slumping always lead to cave-houses and general houses to collapse, people casualties, and seriously damage of railways, highways and long pipelines. The loess slumping is of two mechanisms, landslide and collapse, and a deformation process of sliding followed by collapse. So it was usually treated as landslide or collapse. Based on field investigation and microscopic analysis of the geologic hazard of loess in an area 300km between Jingbian county of Shaanxi Province and Pucian County of Shanxi Province, the authors found that the hazards of loess slumping are controlled by the content of clay, which has obvious regional character: the area with content of clay (0.005m) less than 10%, is called sand-loess area, in which of slumping is most heavy. The area with content of clay between 10% and 20% is called typical loess area in which slumping is weak. The area with content of clay more than 20% is called clay-loess area in which no slumping is developed. On the basis of researching the formation mechanism and conditions for the hazards of loess slumping, the authors suggest corresponding engineering countermeasures.
The hazard of loess slumping is a special type of slope failure in the northern part of China loess plateau. The paroxysm and high frequency of the slumping always lead to cave-houses and general houses to collapse, people casualties, and seriously damage of railways, highways and long pipelines. The loess slumping is of two mechanisms, landslide and collapse, and a deformation process of sliding followed by collapse. So it was usually treated as landslide or collapse. Based on field investigation and microscopic analysis of the geologic hazard of loess in an area 300km between Jingbian county of Shaanxi Province and Pucian County of Shanxi Province, the authors found that the hazards of loess slumping are controlled by the content of clay, which has obvious regional character: the area with content of clay (0.005m) less than 10%, is called sand-loess area, in which of slumping is most heavy. The area with content of clay between 10% and 20% is called typical loess area in which slumping is weak. The area with content of clay more than 20% is called clay-loess area in which no slumping is developed. On the basis of researching the formation mechanism and conditions for the hazards of loess slumping, the authors suggest corresponding engineering countermeasures.
2001, 9(3): 241-246.
A series of new views and approches to solving the practical problems of landslide is reviewed in the paper and the recent investigation prediction and prevention of the loess landslides were conducted in the Loess Plateau of China.Based on the existing evidences of irrigation-induced high-speep loess landslide the movement models of this kind of landslide are constructed. The formulae of sliding path, velocity,and distance of the landslide and speed of loess mud flow are deduced on the principle of variation. The whole process of Heifangtai loess landslide located in areas of Liujiaxia,Yanguoxia and Bapanxia reservoirs,Gansu Province are simulated and calculated from these formulae. The obtained results are consistent with the practical cases.
A series of new views and approches to solving the practical problems of landslide is reviewed in the paper and the recent investigation prediction and prevention of the loess landslides were conducted in the Loess Plateau of China.Based on the existing evidences of irrigation-induced high-speep loess landslide the movement models of this kind of landslide are constructed. The formulae of sliding path, velocity,and distance of the landslide and speed of loess mud flow are deduced on the principle of variation. The whole process of Heifangtai loess landslide located in areas of Liujiaxia,Yanguoxia and Bapanxia reservoirs,Gansu Province are simulated and calculated from these formulae. The obtained results are consistent with the practical cases.
2001, 9(3): 247-252.
The Eastern China coastal belt is a marginal zone connecting sea and continent, and is a multifunctional natural complex with abundant natural resources and high development potential. But natural environment is complicated and changable in the coastal belt, and ecoenvironment is also very weak. Many departments and subjects are involved in resources exploitation in the castal belt. While environmental engineering geological problems(EEGP) have arisen in the course of resources exploitation, so it is very important to strengthen the study of environmental engineering geology(EEG) in the castal belt. Main EEGP in the course of resource exploitation in the coastal belt are analysed, BP model of Neural net is used in evaluation and zoning of engineering geological environmental quality in the coastal belt and adjacent areas. Based on this research, a sustainable development strategy for the coastal belt of eastern China are discussed in this paper.
The Eastern China coastal belt is a marginal zone connecting sea and continent, and is a multifunctional natural complex with abundant natural resources and high development potential. But natural environment is complicated and changable in the coastal belt, and ecoenvironment is also very weak. Many departments and subjects are involved in resources exploitation in the castal belt. While environmental engineering geological problems(EEGP) have arisen in the course of resources exploitation, so it is very important to strengthen the study of environmental engineering geology(EEG) in the castal belt. Main EEGP in the course of resource exploitation in the coastal belt are analysed, BP model of Neural net is used in evaluation and zoning of engineering geological environmental quality in the coastal belt and adjacent areas. Based on this research, a sustainable development strategy for the coastal belt of eastern China are discussed in this paper.
2001, 9(3): 253-257.
Xiashu loess deposits are widely distributed on various geomorphic elements at different height, such as hilltop, terrace, foothill and basin etc. It is composed of both loess and red loam, with significantly different composition and structure, especially their stable water content. So we can consider the Xiashu loess deposits to be inhomogeneous. When they are located above the ground water table or in opening state these soils are unsaturated and a negative pore water pressure may appear. Then matrix suction could also be developed. But any downward net flux must be controlled in order to constrain the increasing tendency of saturation when soil behavior is used in construction practice.
Xiashu loess deposits are widely distributed on various geomorphic elements at different height, such as hilltop, terrace, foothill and basin etc. It is composed of both loess and red loam, with significantly different composition and structure, especially their stable water content. So we can consider the Xiashu loess deposits to be inhomogeneous. When they are located above the ground water table or in opening state these soils are unsaturated and a negative pore water pressure may appear. Then matrix suction could also be developed. But any downward net flux must be controlled in order to constrain the increasing tendency of saturation when soil behavior is used in construction practice.
2001, 9(3): 258-262.
Through analyzing dynamic deformation testing results of no-clay weak interbed belong to different granulometric composition, we show that damping ration(d) increase along with dynamic strain(d added. Granulometric composition and moisture content will control the damping ration.Testing results show that dynamic effect by earthquake is no evident for no-clay (coarse clastic soil) weak interbed. The dynamic mechanical property of no-clay weak interbed is better than saturated sand soil of raveling and middle density.
Through analyzing dynamic deformation testing results of no-clay weak interbed belong to different granulometric composition, we show that damping ration(d) increase along with dynamic strain(d added. Granulometric composition and moisture content will control the damping ration.Testing results show that dynamic effect by earthquake is no evident for no-clay (coarse clastic soil) weak interbed. The dynamic mechanical property of no-clay weak interbed is better than saturated sand soil of raveling and middle density.
2001, 9(3): 263-266.
Taking the rock mass in coal mines as example, this paper analyses the relation between major and minor discontinuities, proposes a statistical method of discontinuities in rock mass in coal mines, suggests the statistical and calculation methods of the trace spacings in the coexistence of multiple sets of discontinuities in the same rock mass, and show a way to to determine the maximum movable domains of the critical blocks in the roadway and to select the optimum axial direction using these statistical parameters. The result provides a scientific basis for support design of roadways.
Taking the rock mass in coal mines as example, this paper analyses the relation between major and minor discontinuities, proposes a statistical method of discontinuities in rock mass in coal mines, suggests the statistical and calculation methods of the trace spacings in the coexistence of multiple sets of discontinuities in the same rock mass, and show a way to to determine the maximum movable domains of the critical blocks in the roadway and to select the optimum axial direction using these statistical parameters. The result provides a scientific basis for support design of roadways.
2001, 9(3): 267-271.
The jointed and whole structure types of lock bay wall for the permanent ship lock of Three-Gorges project are computed and analyzed by using a method for simulation and computation of 3-D contact nonlinear structure temperature creep in the paper. The study shows that the vertical tensile stress value of strcture concrete can efficiently reduced by horizontal joints of lock bay wall, the maximum tensile stress value of anchored bars and average tensile stress value of anchored bars are increased, the stress distribution of anchored bars is more discrete, and tension stress concentration of anchored bars appears on the conjunction of horizontal and vertical joints.
The jointed and whole structure types of lock bay wall for the permanent ship lock of Three-Gorges project are computed and analyzed by using a method for simulation and computation of 3-D contact nonlinear structure temperature creep in the paper. The study shows that the vertical tensile stress value of strcture concrete can efficiently reduced by horizontal joints of lock bay wall, the maximum tensile stress value of anchored bars and average tensile stress value of anchored bars are increased, the stress distribution of anchored bars is more discrete, and tension stress concentration of anchored bars appears on the conjunction of horizontal and vertical joints.
2001, 9(3): 272-276.
According to the indoor disintegration test results of disturbed and undisturbed soil samples,this paper deals with the relationship of solum disintegration with mineral composition, chemical composiuion, texture, grain size, physical properties and moisture of the solum, and composition of groundwater and its table fluctuation.
According to the indoor disintegration test results of disturbed and undisturbed soil samples,this paper deals with the relationship of solum disintegration with mineral composition, chemical composiuion, texture, grain size, physical properties and moisture of the solum, and composition of groundwater and its table fluctuation.
2001, 9(3): 277-281.
The test and study of the foundation bearing capacity are of realistic sigenifcance in full use and tapping of the potential of the foundation bearing capacity,reasonabe selection of the foundation bearing stratum, improvement of the quality of exploration work,and development of the techniques of geotechnical exploration. The systematic discription of the test and study process of the foundation bearing capacity at the site of blast furnace No.2 of Tangshan Iron Steel Co.LTD. And a test technique for the study has been applyed. It is the lab simulation Loading test.
The test and study of the foundation bearing capacity are of realistic sigenifcance in full use and tapping of the potential of the foundation bearing capacity,reasonabe selection of the foundation bearing stratum, improvement of the quality of exploration work,and development of the techniques of geotechnical exploration. The systematic discription of the test and study process of the foundation bearing capacity at the site of blast furnace No.2 of Tangshan Iron Steel Co.LTD. And a test technique for the study has been applyed. It is the lab simulation Loading test.
2001, 9(3): 282-285.
Applying comprehensive analysis method of field geological investigation, shallow high-resolution seismic reflection sounding and geological structure analysis, we studies engineering-geological conditions in Shimeiwan area of Hainan, and found three types of unfavorable sites, i.e., water-saturated sand layer, silt layer, and active fault. In the paper a recommendation of site selection and foundation treatment is made. The result shows that the intergrated method has more advantage over the traditional method in engineering-geological survey in larger area.
Applying comprehensive analysis method of field geological investigation, shallow high-resolution seismic reflection sounding and geological structure analysis, we studies engineering-geological conditions in Shimeiwan area of Hainan, and found three types of unfavorable sites, i.e., water-saturated sand layer, silt layer, and active fault. In the paper a recommendation of site selection and foundation treatment is made. The result shows that the intergrated method has more advantage over the traditional method in engineering-geological survey in larger area.
2001, 9(3): 286-290.
The muddy-clayey soils was mixed with powdered fly ash in different proportion and was tested for its permeability, consolidation, direct shear, and triaxial shear strengths, respectively. The mechanism of the consolidation of soft-soil foundations powdered fly ash are studied in detail, and the change of engineering mechanical properties of the clayey soil mixed with the fly ash is elucidated in detail. The test result shows that using powdered fly ash to consolidate soft-soil foundations is inexpensive and effective.
The muddy-clayey soils was mixed with powdered fly ash in different proportion and was tested for its permeability, consolidation, direct shear, and triaxial shear strengths, respectively. The mechanism of the consolidation of soft-soil foundations powdered fly ash are studied in detail, and the change of engineering mechanical properties of the clayey soil mixed with the fly ash is elucidated in detail. The test result shows that using powdered fly ash to consolidate soft-soil foundations is inexpensive and effective.
2001, 9(3): 291-296.
So far as staiblity analysis of slope, both searching and determing the potential sliding surface and creating model of reliability analysis are two important aspects in theoretical research and application from limit equilibrium theory. In this paper, according to the conventional calculation formula for slope stability analysis, the constrained condition determined by random variable is proposed for the stability and reliability analysis of soil slope by using chance constrained programming. Finnaly, a real case as an example is taken to calcualte the minimum safety coefficient and reliability index.
So far as staiblity analysis of slope, both searching and determing the potential sliding surface and creating model of reliability analysis are two important aspects in theoretical research and application from limit equilibrium theory. In this paper, according to the conventional calculation formula for slope stability analysis, the constrained condition determined by random variable is proposed for the stability and reliability analysis of soil slope by using chance constrained programming. Finnaly, a real case as an example is taken to calcualte the minimum safety coefficient and reliability index.
2001, 9(3): 297-301.
Considering the uncertainty of the measurement data, the complexity of determining calculation parameters, the fuzzy character of describing the stability states in the analysis of slope stability, this paper introduces a new method called vertex method that can be used in the stability analysis of slopes. By using this method we can get a fuzzy set of FS (factor of safety) of a slope from some uncertain soil parameters, and then determine the stability states of this slope by a kind of classification method. Finally, a case study is demonstrated to describe the procedure of this method.
Considering the uncertainty of the measurement data, the complexity of determining calculation parameters, the fuzzy character of describing the stability states in the analysis of slope stability, this paper introduces a new method called vertex method that can be used in the stability analysis of slopes. By using this method we can get a fuzzy set of FS (factor of safety) of a slope from some uncertain soil parameters, and then determine the stability states of this slope by a kind of classification method. Finally, a case study is demonstrated to describe the procedure of this method.
2001, 9(3): 302-307.
There existed deviation in determination of the discontinuity trace length in rock mass by using sampling window method, during the field sampling relatively to infinite two-dimensional rock mass. Therefore, the field sampling deviation of trace length has to be corrected in real rock engineering to get the corrected mean trace length. the sampling window method proposed by Prof. Kulatilake in 1984 is briefly reviewed and some modification of it is proposed in this paper. the improved method is more reliable and perfect in calculation. It is convenient to obtain correct discontinuity trace length in infinite two-dimensional rockmass by means of computer program.
There existed deviation in determination of the discontinuity trace length in rock mass by using sampling window method, during the field sampling relatively to infinite two-dimensional rock mass. Therefore, the field sampling deviation of trace length has to be corrected in real rock engineering to get the corrected mean trace length. the sampling window method proposed by Prof. Kulatilake in 1984 is briefly reviewed and some modification of it is proposed in this paper. the improved method is more reliable and perfect in calculation. It is convenient to obtain correct discontinuity trace length in infinite two-dimensional rockmass by means of computer program.
2001, 9(3): 308-311.
Based upon the time series ARMA model, a basic principle of the time series analysis is analysized and a model of the rock-mass deformation monitoring data is constructed. The method was used in monitoring data analysis of critical rock mass on Banyan Mountain, and some results were obtained.
Based upon the time series ARMA model, a basic principle of the time series analysis is analysized and a model of the rock-mass deformation monitoring data is constructed. The method was used in monitoring data analysis of critical rock mass on Banyan Mountain, and some results were obtained.
2001, 9(3): 312-316.
There are many methods for calculating the consolidation coefficient of soils, which they have both advantages and disadvantages, but can not used for calculating the consolidation coefficient at anytime. In this paper, summarizing all their advantages, the authors find a new method for calculating the coefficient at anytime after large amount of consolidation tests of soils, by this way, it very effective to the result of the site observations with it.
There are many methods for calculating the consolidation coefficient of soils, which they have both advantages and disadvantages, but can not used for calculating the consolidation coefficient at anytime. In this paper, summarizing all their advantages, the authors find a new method for calculating the coefficient at anytime after large amount of consolidation tests of soils, by this way, it very effective to the result of the site observations with it.
2001, 9(3): 317-320.
Shear failure is a most common failure in rock foundation, which often takes place in intact, jointed and weak rock foundations. On the basis of Hoek-Brown strength criterion and limit equilibrium method, the authors introduce two methods for determining ultimate bearing capacity. Finally, an engineering example from chongqing is offered in order to prove the methods to be reliable.
Shear failure is a most common failure in rock foundation, which often takes place in intact, jointed and weak rock foundations. On the basis of Hoek-Brown strength criterion and limit equilibrium method, the authors introduce two methods for determining ultimate bearing capacity. Finally, an engineering example from chongqing is offered in order to prove the methods to be reliable.
2001, 9(3): 321-325.
Element free Galerkin method (EFGM), a newly developed means of numerical method in geotechnical engineering is introduced in this paper. The method has more advantage in numerical analyses as it only needs the information of nodes rather than elements. Some patterns of different parameters are calculated and analyzed in combination with EFGM matrix formulata of comsolidation. And the condition of interface in the discontinuous derivative is studied with jump function. The caalculation result indicates that the EFGM tratment is more accurate.
Element free Galerkin method (EFGM), a newly developed means of numerical method in geotechnical engineering is introduced in this paper. The method has more advantage in numerical analyses as it only needs the information of nodes rather than elements. Some patterns of different parameters are calculated and analyzed in combination with EFGM matrix formulata of comsolidation. And the condition of interface in the discontinuous derivative is studied with jump function. The caalculation result indicates that the EFGM tratment is more accurate.
2001, 9(3): 326-330.
Bey monitoring on vibration caused by tamped pile constructions in two cases, this paper discusses the effect of various construction states on vibration parameters and concludes the effect is confined to a limit area around the pound point.
Bey monitoring on vibration caused by tamped pile constructions in two cases, this paper discusses the effect of various construction states on vibration parameters and concludes the effect is confined to a limit area around the pound point.
2001, 9(3): 331-335.
On the basis of displacement-time series of the slope, a nonlinear dynamic model is set up according to Backus generalized linear inversion theory in this paper. Due to the equivalence between autonomous gradient system and catastrophe model, a standard cusp catastrophe model can be obtained through variable substitution. The method is used in analysis of displacement data of Huangci landslide and Wolongsi landslide and in understanding how slopes evolve before sliding. The result shows that the nonlinear dynamic model can make satisfactory prediction results. Is it most important that there is a sudden fall of D, which indicates the occurrence of catastrophe (when D=0).
On the basis of displacement-time series of the slope, a nonlinear dynamic model is set up according to Backus generalized linear inversion theory in this paper. Due to the equivalence between autonomous gradient system and catastrophe model, a standard cusp catastrophe model can be obtained through variable substitution. The method is used in analysis of displacement data of Huangci landslide and Wolongsi landslide and in understanding how slopes evolve before sliding. The result shows that the nonlinear dynamic model can make satisfactory prediction results. Is it most important that there is a sudden fall of D, which indicates the occurrence of catastrophe (when D=0).
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