2007 Vol. 15, No. 1

论文
From the field investigation,the authors discovered the massive rock mass with cleavages in northwestern Yunnan.The spatial distribution and occurrence of cleaved rock mass are controlled by the regional activity faults.From Yanjing in Tibet to Lijiang in Yunnan,there are three densely cleaved rock mass zones which are arrayed in right en-echelon formation and are consistent with the orientation of the Yunnan-Tibet railway in-northwestern Yunnan.In northwestern Yunana,the endogenetic force is closely coupled with the exogenetic force.The massive cleaved rock mass has special and complex property.Based on the fieldwork and analysis,this paper discusses the distribution and property of the massive cleaved rock mass in detail.The effect of the cleaved rock mass to the railway projects is analyzed to prevent geologic hazard,gushing water in tunnelling,distortion burst in the surrounding rocks.The discovery and analysis are useful to the railway projects in northwestern Yunnan. From the field investigation,the authors discovered the massive rock mass with cleavages in northwestern Yunnan.The spatial distribution and occurrence of cleaved rock mass are controlled by the regional activity faults.From Yanjing in Tibet to Lijiang in Yunnan,there are three densely cleaved rock mass zones which are arrayed in right en-echelon formation and are consistent with the orientation of the Yunnan-Tibet railway in-northwestern Yunnan.In northwestern Yunana,the endogenetic force is closely coupled with the exogenetic force.The massive cleaved rock mass has special and complex property.Based on the fieldwork and analysis,this paper discusses the distribution and property of the massive cleaved rock mass in detail.The effect of the cleaved rock mass to the railway projects is analyzed to prevent geologic hazard,gushing water in tunnelling,distortion burst in the surrounding rocks.The discovery and analysis are useful to the railway projects in northwestern Yunnan.
Highly Incised Slope(HIS) is a new type of geological hazard in the mountainous region of Three Gorges Reservoir.Investigation and experimental analyses are carried out at 47 HISs in Wanzhou area.The findings show that there are four failure modes in HIS.They are collapse,surface weathering,diversity of weathering,and soil sliding or collapse.Factors of influencing on failure modes in HIS are(1) the HIS materials,HIS characteristics,the hydrologic and weather condition,the HIS shape,and the engineering treatment time.According to the different failure modes in HISs,stabilization methods are recommended to be the guideline of design and construction. Highly Incised Slope(HIS) is a new type of geological hazard in the mountainous region of Three Gorges Reservoir.Investigation and experimental analyses are carried out at 47 HISs in Wanzhou area.The findings show that there are four failure modes in HIS.They are collapse,surface weathering,diversity of weathering,and soil sliding or collapse.Factors of influencing on failure modes in HIS are(1) the HIS materials,HIS characteristics,the hydrologic and weather condition,the HIS shape,and the engineering treatment time.According to the different failure modes in HISs,stabilization methods are recommended to be the guideline of design and construction.
In the course of the tunnel construction at the karst mountain area,the karst conduit connectivity has a great importance to determine the quantity of welling water and water pressure,and to protect the tunnel construction.This paper presents a case study during Baziling tunnel construction of Yiwan railway.It systematically analyzes the characteristics of grain size,the rock and minerals component,roundness of karst conduit deposits.It applies the theory of sedimentation to study hydraulic characteristic of fragmental deposits.Finally it examines the source of the deposits.According to this result,it analyzes karst conduit connectivity of thee area,and provides the references for the design of the tunnel construction. In the course of the tunnel construction at the karst mountain area,the karst conduit connectivity has a great importance to determine the quantity of welling water and water pressure,and to protect the tunnel construction.This paper presents a case study during Baziling tunnel construction of Yiwan railway.It systematically analyzes the characteristics of grain size,the rock and minerals component,roundness of karst conduit deposits.It applies the theory of sedimentation to study hydraulic characteristic of fragmental deposits.Finally it examines the source of the deposits.According to this result,it analyzes karst conduit connectivity of thee area,and provides the references for the design of the tunnel construction.
This paper presents a stability analysis of the fractured rock mass slope used as the foundation of a tunnel-type anchorage of a suspension bridge across Baling river.he western anchorage of the bridge is buried in the slope.The study takes into account the slope geological conditions and the loading from the bridge in the analysis.The slope stability analysis model is developed on the basis of the virtual work principle,where the rock stratification planes and the adverse discontinuities are incorporated. This paper presents a stability analysis of the fractured rock mass slope used as the foundation of a tunnel-type anchorage of a suspension bridge across Baling river.he western anchorage of the bridge is buried in the slope.The study takes into account the slope geological conditions and the loading from the bridge in the analysis.The slope stability analysis model is developed on the basis of the virtual work principle,where the rock stratification planes and the adverse discontinuities are incorporated.
This paper presents the investigation of the fault activities and the radon contents in faults in Tianhui area,Shanxi Province.The fault activities are evaluated and classified.The characteristics of geological hazards in Tianshui area are examined.The relationship between the fault activity and the degree of geological hazard is investigated in detail.The results show that the fault activity and the geological hazard degree are closely related,and the fault activity is one of the main factors that controls geological hazards in Tianshui area. This paper presents the investigation of the fault activities and the radon contents in faults in Tianhui area,Shanxi Province.The fault activities are evaluated and classified.The characteristics of geological hazards in Tianshui area are examined.The relationship between the fault activity and the degree of geological hazard is investigated in detail.The results show that the fault activity and the geological hazard degree are closely related,and the fault activity is one of the main factors that controls geological hazards in Tianshui area.
Jinchuan mining site is the only site for large-scale production of the nonferrous ores in China.It is a site with adverse conditions such as deep depth,high in-situ stress and highly crushed rocks.The mining is there extremely difficult.As the mining depth increases and the mining area expands,the in-situ stresses of the stope has become more and more severe.Therefore,it is urging to disclose and examine the conditions of the in-situ insitu stresses and the corresponding techniques for the large stopes.The mining started 30 years ago.Since then,a large amount of engineering experience have been accumulated for solving the problems.As a result,the first-stage construction of the mines has been implemented without much problem.However,with the development of second-stage construction,especially when level pillars of multi section mining are becoming thinner,the activity of the ground pressure of stopes are much severe,the deformation of tunnels is too large to be controlled,and the potential risk of stop failures isevident.This paper presenta a review of the behavior of the ground pressure and its control techniques in China nd abroad.Next,the problems in the No.1 ore-body of the mining site are described.Finally,the paper presents a dynamic feedback engineering approach to address the problems for safe mining.This approach is based on the integration of numeric analysis,in-situ monitoring and engineering experience. Jinchuan mining site is the only site for large-scale production of the nonferrous ores in China.It is a site with adverse conditions such as deep depth,high in-situ stress and highly crushed rocks.The mining is there extremely difficult.As the mining depth increases and the mining area expands,the in-situ stresses of the stope has become more and more severe.Therefore,it is urging to disclose and examine the conditions of the in-situ insitu stresses and the corresponding techniques for the large stopes.The mining started 30 years ago.Since then,a large amount of engineering experience have been accumulated for solving the problems.As a result,the first-stage construction of the mines has been implemented without much problem.However,with the development of second-stage construction,especially when level pillars of multi section mining are becoming thinner,the activity of the ground pressure of stopes are much severe,the deformation of tunnels is too large to be controlled,and the potential risk of stop failures isevident.This paper presenta a review of the behavior of the ground pressure and its control techniques in China nd abroad.Next,the problems in the No.1 ore-body of the mining site are described.Finally,the paper presents a dynamic feedback engineering approach to address the problems for safe mining.This approach is based on the integration of numeric analysis,in-situ monitoring and engineering experience.
Based on the CU triaxial tests on compacted silt from the Beijing to Kowloon railway subgrade,the stress-strain relationship analysis is made on the silt under different cell pressures,water contents and degrees of compaction.It is found that the compacted silt exhibits a work hardening character under high cell pressure,exhibits a work softening character under low cell pressure,and exists a yield stress.The effects of water content and compaction on soil strength and stress-strain curves are distinct.The common softening formulation of soils is adopted to describe the softening curves under low cell pressure which is less than the yield stress.For the hardening curves,the Duncan-Chang model is used.Combining the stimulation methods mentioned above,the stress-strain relationship of the compacted silt is depicted well. Based on the CU triaxial tests on compacted silt from the Beijing to Kowloon railway subgrade,the stress-strain relationship analysis is made on the silt under different cell pressures,water contents and degrees of compaction.It is found that the compacted silt exhibits a work hardening character under high cell pressure,exhibits a work softening character under low cell pressure,and exists a yield stress.The effects of water content and compaction on soil strength and stress-strain curves are distinct.The common softening formulation of soils is adopted to describe the softening curves under low cell pressure which is less than the yield stress.For the hardening curves,the Duncan-Chang model is used.Combining the stimulation methods mentioned above,the stress-strain relationship of the compacted silt is depicted well.
To analyze the expansion of the cylindrical cavity in loess,a reasonable numerical model was presented based on field investigation.The potential function theory and Laplace transform technique wwere used to solve the problem.The analytical solution of stresses,pore pressure and displacement induced by inner water pressure were derived in Laplace transform domain.Numerical results were obtained by inverse Laplace transformation.The effects of rainfall duration and saturation on dynamic response of the cavity were discussed.It shows that the hydrodynamic force is the key factor of the cavity expansion in loess.The rainfall duration has great effects on the stress and displacement. The influence of saturation on displacements is remarkable. To analyze the expansion of the cylindrical cavity in loess,a reasonable numerical model was presented based on field investigation.The potential function theory and Laplace transform technique wwere used to solve the problem.The analytical solution of stresses,pore pressure and displacement induced by inner water pressure were derived in Laplace transform domain.Numerical results were obtained by inverse Laplace transformation.The effects of rainfall duration and saturation on dynamic response of the cavity were discussed.It shows that the hydrodynamic force is the key factor of the cavity expansion in loess.The rainfall duration has great effects on the stress and displacement. The influence of saturation on displacements is remarkable.
The evaluation of fkarst collapse risks is a complex and important issue.After normal school function is accepted as a subjection function,and the real numbers addition and multiplication is occupied as composite role.Aiming at the evaluation of karst collapse risk,the model for the karst collapse risk is established with two stage fuzzy synthetic judgment theory and the analytic hierarchy process,.There are four evaluation results,stability,relative stability,relative instability,instability.From application to some engineering practice in Guangzhou,the results show that the method is reliable and has significant engineering and academic values. The evaluation of fkarst collapse risks is a complex and important issue.After normal school function is accepted as a subjection function,and the real numbers addition and multiplication is occupied as composite role.Aiming at the evaluation of karst collapse risk,the model for the karst collapse risk is established with two stage fuzzy synthetic judgment theory and the analytic hierarchy process,.There are four evaluation results,stability,relative stability,relative instability,instability.From application to some engineering practice in Guangzhou,the results show that the method is reliable and has significant engineering and academic values.
In this paper,we have discussed the method for analysis of stress-strain ratio associated with rock creep.Creep is one of the most important characteristics of rock.Under different stress states,rock creep curves show the behavior of geometry-comparability.We can gain the isochronous-modulus curves from the curves of stress-strain ratios.The constitutive equation of rock is so complex that well accepted method is still not available in the open literuary erure.At present,the analysis ofstress-strain ratio can be a good approach to further the examination of rock creep behavior. In this paper,we have discussed the method for analysis of stress-strain ratio associated with rock creep.Creep is one of the most important characteristics of rock.Under different stress states,rock creep curves show the behavior of geometry-comparability.We can gain the isochronous-modulus curves from the curves of stress-strain ratios.The constitutive equation of rock is so complex that well accepted method is still not available in the open literuary erure.At present,the analysis ofstress-strain ratio can be a good approach to further the examination of rock creep behavior.
Based on the CU test results of Malan Loess samples,the stress-strain relationship equation is derived for the constitutional equation of Malan Loess in the framework of the conventional theory of soil mechanics.The theoretical model is used to well simulated the test results for axial strain 115% under different confining pressures furthermore,the model has only two parameters(a and b) and the two parameters can be obtained easily from the conventional triaxial compression test. Based on the CU test results of Malan Loess samples,the stress-strain relationship equation is derived for the constitutional equation of Malan Loess in the framework of the conventional theory of soil mechanics.The theoretical model is used to well simulated the test results for axial strain 115% under different confining pressures furthermore,the model has only two parameters(a and b) and the two parameters can be obtained easily from the conventional triaxial compression test.
Accordingto the fuzzy characteristics of slope stability,a fuzzy neural network model is presented to predict slope stability.In this model,theintention of acquiringthe initialfuzzy rule sets can be achieved only by using the desired input-output data pairs.Then,employing neural networks learning techniques,the fuzzy logic rules,input-output fuzzy membership functions and weights in network can be easily tuned.So the rule matching is reduced.The velocity of inference is accelerated.Adaptabilityof the system is greatly improved.At last,the collected data of slope stability are adapted to train and test the model.The forecasted results show that the proposed method is feasible and effective in predicting slope stability. Accordingto the fuzzy characteristics of slope stability,a fuzzy neural network model is presented to predict slope stability.In this model,theintention of acquiringthe initialfuzzy rule sets can be achieved only by using the desired input-output data pairs.Then,employing neural networks learning techniques,the fuzzy logic rules,input-output fuzzy membership functions and weights in network can be easily tuned.So the rule matching is reduced.The velocity of inference is accelerated.Adaptabilityof the system is greatly improved.At last,the collected data of slope stability are adapted to train and test the model.The forecasted results show that the proposed method is feasible and effective in predicting slope stability.
This paper presents a brief review about the existing methods for interpreting pre-consolidation pressure in clays from piezocone penetration tests.The empirical methods are compared and evaluated on the basis of the piezocone tests data on marine clay sites in Lianyun Port,while the pre-consolidation pressure determined from oedometer tests were used as the reference values.The simplest method is the method directly relating the pre-consolidation pressure to the net cone tip resistance.The study finds that this method is the most effective method. This paper presents a brief review about the existing methods for interpreting pre-consolidation pressure in clays from piezocone penetration tests.The empirical methods are compared and evaluated on the basis of the piezocone tests data on marine clay sites in Lianyun Port,while the pre-consolidation pressure determined from oedometer tests were used as the reference values.The simplest method is the method directly relating the pre-consolidation pressure to the net cone tip resistance.The study finds that this method is the most effective method.
Dynamic compaction is one of the common methods for site improvement.But the influence zone of dynamic compaction often can not be estimated well,which has become a problem restricting the wide application of the method.This paper examines thefield measured data during the site improvement with the dynamic compaction at a harbor.,The influence zone in the ground in terms of the depth and horizontal distance is presented from the field monitored data.The monitored data include the ground vibration displacements,velocity and acceleration at different depths and distances during the impacting of the hammer.The vibration displacement,velocity,and acceleration against the depth and distance are plotted as the attenuation curves for the assessment.of the tamping. Dynamic compaction is one of the common methods for site improvement.But the influence zone of dynamic compaction often can not be estimated well,which has become a problem restricting the wide application of the method.This paper examines thefield measured data during the site improvement with the dynamic compaction at a harbor.,The influence zone in the ground in terms of the depth and horizontal distance is presented from the field monitored data.The monitored data include the ground vibration displacements,velocity and acceleration at different depths and distances during the impacting of the hammer.The vibration displacement,velocity,and acceleration against the depth and distance are plotted as the attenuation curves for the assessment.of the tamping.
In soft clay,because of its consolidation and creep,time effect is detectable in deep excavation.In this paper,finite element method coupled with Biot consolidation theory is used to research the behavior of deep excavation.The first linear spring is used to stimulate the consolidation.The elastic module is considered about the influence of the excavating stress-path and stress-history.The other part of the model(KELVE model) is used to stimulates the creep of clay.Its two parameters are gained approximately through partly analyzing the real deformation in the engineering.Then the deformation associated with whole excavation is analyzed step by step during the process of excavation.Normally-consolidated and saturated clay is assumed,and plane strain problem is considered.When analyzing a real example of deep excavation in saturated soft clay,the curve of the wall horizontal displacement computed is quite inosculated to the field measured ones,so it indicates that this finite element code is good for stimulating time-dependent behaviors of excavation.The reason why there are some curves not-well-inosculated is also explained.The sedimentation rule of post-wall ground surface is provided in addition. In soft clay,because of its consolidation and creep,time effect is detectable in deep excavation.In this paper,finite element method coupled with Biot consolidation theory is used to research the behavior of deep excavation.The first linear spring is used to stimulate the consolidation.The elastic module is considered about the influence of the excavating stress-path and stress-history.The other part of the model(KELVE model) is used to stimulates the creep of clay.Its two parameters are gained approximately through partly analyzing the real deformation in the engineering.Then the deformation associated with whole excavation is analyzed step by step during the process of excavation.Normally-consolidated and saturated clay is assumed,and plane strain problem is considered.When analyzing a real example of deep excavation in saturated soft clay,the curve of the wall horizontal displacement computed is quite inosculated to the field measured ones,so it indicates that this finite element code is good for stimulating time-dependent behaviors of excavation.The reason why there are some curves not-well-inosculated is also explained.The sedimentation rule of post-wall ground surface is provided in addition.
The passive pile has received high attentions in recent years.This paper presents a systemic three-dimensional numerical analysis for the complicated interaction between pile and soil under preloading.The paper establishes 3D model using FLAC(3D) for the working property study of single row piles.The effect of some key parameters on the interaction is mainly researched.They include preloading condition,stiffness of pile and soil distributing.Based on the results of numerical analysis,the interaction mechanism between passive pile and soil in soft clay is further expatiated,and a linear distributing pattern of soil pressure along pile is obtained with a linear curving method. The passive pile has received high attentions in recent years.This paper presents a systemic three-dimensional numerical analysis for the complicated interaction between pile and soil under preloading.The paper establishes 3D model using FLAC(3D) for the working property study of single row piles.The effect of some key parameters on the interaction is mainly researched.They include preloading condition,stiffness of pile and soil distributing.Based on the results of numerical analysis,the interaction mechanism between passive pile and soil in soft clay is further expatiated,and a linear distributing pattern of soil pressure along pile is obtained with a linear curving method.
According to the difference of growing scales of fractures in rocks,fractured domains can be divided into continuous and discrete domains.Different mathematical models of groundwater movement are used in the continuous and discrete domain.The problem can be solved by domain decomposition algorithm.An equivalent continuum medium model is applied to the continuous domain and a stochastic fractured network model to the discrete domain.Hence,according to the continuous conditions of groundwater table and flux in the common boundary of the two domains,the coupled models can be solved.Furthermore,the coupled model based on the domain decomposition algorithm is applied to simulation of three-dimensional seepage field in the dam site of Jinping hydroelectric power station.Compared the observed results with the calculated groundwater table,the result shows that the coupled model based on the domain decomposition algorithm is effective and can be applied to practical engineering. According to the difference of growing scales of fractures in rocks,fractured domains can be divided into continuous and discrete domains.Different mathematical models of groundwater movement are used in the continuous and discrete domain.The problem can be solved by domain decomposition algorithm.An equivalent continuum medium model is applied to the continuous domain and a stochastic fractured network model to the discrete domain.Hence,according to the continuous conditions of groundwater table and flux in the common boundary of the two domains,the coupled models can be solved.Furthermore,the coupled model based on the domain decomposition algorithm is applied to simulation of three-dimensional seepage field in the dam site of Jinping hydroelectric power station.Compared the observed results with the calculated groundwater table,the result shows that the coupled model based on the domain decomposition algorithm is effective and can be applied to practical engineering.
Fiber as a good reinforcement material was mainly applied to cement and concrete,however,very limited information has been reported on the use of randomly distributed discrete fibers for soil reinforcement.In this paper,an experimental program was reported to study the individual and combined effects of randomly oriented fiber and cement additives on the geotechnical characteristics of clay soil.Three percentages of fiber contents,i.e.(0.05)%,0.15% and 0.25% by weight of raw soil and two percentages pf cement contents,i.e.,5% and 8% were randomly included in to the soil.Twelve samples were prepared and subjected to unconfined compression tests.The results of this study clearly show that both the polypropylene fiber and cement can improve the strength and stability of raw soil.Fiber inclusion can change the brittle behavior of cement soil to the ductile behavior.The increase in the strength caused by the combined action of cement and fiber is more than the sum of the increase caused by each of them individually.Polypropylene fibers are characterized in terms of their mechanical properties and microstructures.The microstructures were obtained from scanning electron microscopy(SEM) analysis.It is found that there are interfacial interactions between fibers and other substance(such as the hydrations of cement,minerals of clay soil),which can produce significant effects on the bonding strength and friction between the reinforcement and the soil matrix. Fiber as a good reinforcement material was mainly applied to cement and concrete,however,very limited information has been reported on the use of randomly distributed discrete fibers for soil reinforcement.In this paper,an experimental program was reported to study the individual and combined effects of randomly oriented fiber and cement additives on the geotechnical characteristics of clay soil.Three percentages of fiber contents,i.e.(0.05)%,0.15% and 0.25% by weight of raw soil and two percentages pf cement contents,i.e.,5% and 8% were randomly included in to the soil.Twelve samples were prepared and subjected to unconfined compression tests.The results of this study clearly show that both the polypropylene fiber and cement can improve the strength and stability of raw soil.Fiber inclusion can change the brittle behavior of cement soil to the ductile behavior.The increase in the strength caused by the combined action of cement and fiber is more than the sum of the increase caused by each of them individually.Polypropylene fibers are characterized in terms of their mechanical properties and microstructures.The microstructures were obtained from scanning electron microscopy(SEM) analysis.It is found that there are interfacial interactions between fibers and other substance(such as the hydrations of cement,minerals of clay soil),which can produce significant effects on the bonding strength and friction between the reinforcement and the soil matrix.
Hazard potential evaluation of regions underlain mined caverns is one of difficult technical problems in highway engineering.Two-dimensional and three-dimensional FEM are applied to evaluate the hazard potential of underground mined caverns to the highway on their above ground.The underground caverns are multi-layered and inclined.The numerical results show that the mined caverns have potential hazards to highway.The affected zone along the highway must be improved. Hazard potential evaluation of regions underlain mined caverns is one of difficult technical problems in highway engineering.Two-dimensional and three-dimensional FEM are applied to evaluate the hazard potential of underground mined caverns to the highway on their above ground.The underground caverns are multi-layered and inclined.The numerical results show that the mined caverns have potential hazards to highway.The affected zone along the highway must be improved.
Based on a series of experiments,the mechanical properties of rock-salt,including compaction characteristic,compressive strength,and deformation behaviors under cyclic loading were studied.The following contents were discussed in detail:(1)Effects of small particle content of the samples on the compaction characteristic of rock-salt;(2) the value distributions of compressive strength of nature rock-salt;(3) the effects of grain size,dry density and water content on compressive strength;and(4) the development regularity of dynamic strain of rock-salt under traffic cyclic loading.The findings in this paper can be useful to the road construction in salt-lake areasin western China. Based on a series of experiments,the mechanical properties of rock-salt,including compaction characteristic,compressive strength,and deformation behaviors under cyclic loading were studied.The following contents were discussed in detail:(1)Effects of small particle content of the samples on the compaction characteristic of rock-salt;(2) the value distributions of compressive strength of nature rock-salt;(3) the effects of grain size,dry density and water content on compressive strength;and(4) the development regularity of dynamic strain of rock-salt under traffic cyclic loading.The findings in this paper can be useful to the road construction in salt-lake areasin western China.
This paper is to establish a relationship between wave velocities of concrete pile shaft measured with the ultrasonic wave method and the low-strain reflected wave method.It proposes a simplified formula for the ratio of wave velocity in infinite medium to that in one dimensional bar The viscoelastic theory based on standard linear solid model is adopted in the formulation of the formula.Experimental results show that the ratio of the ultrasonic wave velocity to the 1.054 timed low-strain reflected wave velocity ranges from 1.03 to 1.12.The ratio decreases with increasing in the age,the Youngs modulus and the strength of concrete. This paper is to establish a relationship between wave velocities of concrete pile shaft measured with the ultrasonic wave method and the low-strain reflected wave method.It proposes a simplified formula for the ratio of wave velocity in infinite medium to that in one dimensional bar The viscoelastic theory based on standard linear solid model is adopted in the formulation of the formula.Experimental results show that the ratio of the ultrasonic wave velocity to the 1.054 timed low-strain reflected wave velocity ranges from 1.03 to 1.12.The ratio decreases with increasing in the age,the Youngs modulus and the strength of concrete.
Using red sandstone plates for curtain walls of buildings is not common in China and abroad.There are almost neither standards for testing evaluation nor regulations for quality control and acceptance.On the basis of the national standard entitled Technical code for metal and stone curtain walls engineering(JGJ133-2001) and the property of red sandstones,this paper puts forward the indexes for testing evaluation of red sandstone plates as the curtain walls.The indexes include the physical and strength indexes. The red sandstone plates which are initially selected have to be tested to meet the design indexes.Especially the red sandstone should be tested for its stability under the conditions of the artificial rainstorm,strong wind and high temperatures.In the meantime,the relevant indexes must be evaluated and estimated.The red sandstone satisfying the indexes can then be used as curtain walls. Using red sandstone plates for curtain walls of buildings is not common in China and abroad.There are almost neither standards for testing evaluation nor regulations for quality control and acceptance.On the basis of the national standard entitled Technical code for metal and stone curtain walls engineering(JGJ133-2001) and the property of red sandstones,this paper puts forward the indexes for testing evaluation of red sandstone plates as the curtain walls.The indexes include the physical and strength indexes. The red sandstone plates which are initially selected have to be tested to meet the design indexes.Especially the red sandstone should be tested for its stability under the conditions of the artificial rainstorm,strong wind and high temperatures.In the meantime,the relevant indexes must be evaluated and estimated.The red sandstone satisfying the indexes can then be used as curtain walls.
In mountainous terrains of European and American countries,conventional stone-gabion retaining walls are usually applied to the reinforcement of middle-or small-scale slopes,preventions from erosion or rush-out of bank slopes or roadbeds.Such applications are also found in southwest areas of China.The technique is easy in construction,use local materials and is flexible in adaptability.On the basis of keeping the merits of this conventional technique as much as possible,the authors have improved it and presented a revised technique.It is the stratified net-mesh reinforced stone-gabion retaining wall. The new technique can be characterized with multiple functions.They include stronger reinforcement strength,anti-rust function,efficient drainage,easy realization of virescence and monitoring.It is expected to have considerable economic benefits in slope reinforcement projects. In mountainous terrains of European and American countries,conventional stone-gabion retaining walls are usually applied to the reinforcement of middle-or small-scale slopes,preventions from erosion or rush-out of bank slopes or roadbeds.Such applications are also found in southwest areas of China.The technique is easy in construction,use local materials and is flexible in adaptability.On the basis of keeping the merits of this conventional technique as much as possible,the authors have improved it and presented a revised technique.It is the stratified net-mesh reinforced stone-gabion retaining wall. The new technique can be characterized with multiple functions.They include stronger reinforcement strength,anti-rust function,efficient drainage,easy realization of virescence and monitoring.It is expected to have considerable economic benefits in slope reinforcement projects.
Through the laboratory test of the effect of salt contents on the strength of cement-mixed non-organic clays,The threshold of 3.5% was obtained.When the salt content of the clay is lower than this value,the strength of cement-soil will be increased due to solute salts dcrystallization and expansion.Conversely,when the soil have a higher salt content than the threshold,the strength of cemented clays will be greatly reduced due to structural destruction of cemented clays by the excessive crystallization and expansion of the salt.In addition,the corrosion mechanism of sulfate,chloride and magnesium salt to cemented clays is also discussed.And finally,based on the mechanism of the effect of salt on the strength of the cement-mixed clays,the prevention measures are suggested in case of the destruction to the cemented-mixed clays under high salt content conditions. Through the laboratory test of the effect of salt contents on the strength of cement-mixed non-organic clays,The threshold of 3.5% was obtained.When the salt content of the clay is lower than this value,the strength of cement-soil will be increased due to solute salts dcrystallization and expansion.Conversely,when the soil have a higher salt content than the threshold,the strength of cemented clays will be greatly reduced due to structural destruction of cemented clays by the excessive crystallization and expansion of the salt.In addition,the corrosion mechanism of sulfate,chloride and magnesium salt to cemented clays is also discussed.And finally,based on the mechanism of the effect of salt on the strength of the cement-mixed clays,the prevention measures are suggested in case of the destruction to the cemented-mixed clays under high salt content conditions.