A single freedom degree model of drilling bit-rock was established according to the vibration mechanism and its dynamic characteristics. Moreover, a novel identification method of rock and soil parameters for vibratio...A single freedom degree model of drilling bit-rock was established according to the vibration mechanism and its dynamic characteristics. Moreover, a novel identification method of rock and soil parameters for vibration drilling based on the fuzzy least squares(FLS)-support vector machine(SVM) was developed, in which the fuzzy membership function was set by using linear distance, and its parameters, such as penalty factor and kernel parameter, were optimized by using adaptive genetic algorithm. And FLS-SVM identification on rock and soil parameters for vibration drilling was made by changing the input/output data from single freedom degree model of drilling bit-rock. The results of identification simulation and resonance column experiment show that relative error of natural frequency for some hard sand from identification simulation and resonance column experiment is 1.1% and the identification precision based on the fuzzy least squares-support vector machine is high.展开更多
Rock–soil aggregate landslides(RSALs) are a common geological hazard in deeply incised valleys in southwestern China. Large-scale RSALs are widely distributed in the upper reaches of the Dadu River, Danba County, Sic...Rock–soil aggregate landslides(RSALs) are a common geological hazard in deeply incised valleys in southwestern China. Large-scale RSALs are widely distributed in the upper reaches of the Dadu River, Danba County, Sichuan Province, and are influenced by slope structure, which can be divided into open, lock, strip, and dumbbell types, as well as soil type and meso-structure, which can be classified as layered rock–soil aggregate, block-soil, and grainsoil. In this study, the evolution of four types of structures, such as layered-dumbbell, block-soil lock, banded block-soil, and block-soil open types, were analyzed by field surveys, surface and deep displacement monitoring, and Flac3 D. It was found that the Danba reach of the Dadu River showed incised valley through the evolution from wide to slow valley affected by internal and external geological processes since the Quaternary Glaciation. In the layered-dumbbell rock–soil aggregate, the main sliding pattern is multi-stage sliding at different depths. Circular sliding in the trailing edge and plane sliding along the bedrock in the front edge body occurin the block-soil-lock type aggregate. Large-scale multi-level and circular sliding over long distances occur in the banded block-soil aggregate. The blocksoil open type is stable, with only circular sliding occurring in local and shallow surfaces of the body. The monitoring and numerical simulation results further show that slope structure and regularity have diversified with RSALs. The results provide a basis for analyzing the stability mechanism of RSALs and preventing RSALs in deeply incised valleys.展开更多
Blasting has been widely used in mining and construction industries for rock breaking.This paper presents the results of a series of field tests conducted to investigate the ground wave propagation through mixed geolo...Blasting has been widely used in mining and construction industries for rock breaking.This paper presents the results of a series of field tests conducted to investigate the ground wave propagation through mixed geological media.The tests were conducted at a site in the northwestern part of Singapore composed of residual soil and granitic rock.The field test aims to provide measurement data to better understand the stress wave propagation in soil/rock and along their interface.Triaxial accelerometers were used for the free field vibration monitoring.The measured results are presented and discussed,and empirical formulae for predicting peak particle velocity (PPV) attenuation along the ground surface and in soil/rock were derived from the measured data.Also,the ground vibration attenuation across the soil-rock interface was carefully examined,and it was found that the PPV of ground vibration was decreased by 37.2% when it travels from rock to soil in the vertical direction.展开更多
Soil-rock mixtures containing macropore(SRMCM)is a kind of geological material with special mechanical properties.Located in the project area of Lenggu hydropower station on the Yalong River,Sichuan Province,China,the...Soil-rock mixtures containing macropore(SRMCM)is a kind of geological material with special mechanical properties.Located in the project area of Lenggu hydropower station on the Yalong River,Sichuan Province,China,there is an extremely unstable Mahe talus slide with a total volume of nearly160 million cubic meters,which is mainly composed of SRMCM.The study on the mechanical properties of SRMCM is of great significance for the engineering construction and safe operation.In this paper,laboratory tests and discrete element numerical tests based on three-dimensional scanning technology were conducted to study the influence of stone content,stone size,and the angle of the macropore structure on shear characteristics of SRMCM.The failure mechanism of SRMCM was discussed from a microscopic perspective.This work explains the internal mechanism of the influence of stone content,stone size,and the angle of the macropore structure on the strength of SRMCM through the microscopic level of stone rotation,force chain distribution,and crack propagation.As the macropore structure that intersects with the preset shear plane at a large angle could act as a skeleton-like support to resist the shear force,the fracture of the weak cemented surface of soil and stone in the macropore structure is an important cause of SRMCM destruction.展开更多
Physical mechanisms and influencing factors on the effective stress coefficient for rock/soil-like porous materials are investigated, based on which equivalent connectivity index is proposed. The equivalent connectivi...Physical mechanisms and influencing factors on the effective stress coefficient for rock/soil-like porous materials are investigated, based on which equivalent connectivity index is proposed. The equivalent connectivity index, relying on the meso-scale structure of porous material and the property of liquid, denotes the connectivity of pores in Representative Element Area （REA）. If the conductivity of the porous material is anisotropic, the equivalent connectivity index is a second order tensor. Based on the basic theories of continuous mechanics and tensor analysis, relationship between area porosity and volumetric porosity of porous materials is deduced. Then a generalized expression, describing the relation between effective stress coefficient tensor and equivalent connectivity tensor of pores, is proposed, and the expression can be applied to isotropic media and also to anisotropic materials. Furthermore, evolution of porosity and equivalent connectivity index of the pore are studied in the strain space, and the method to determine the corresponding functions in expressions above is proposed using genetic algorithm and genetic programming. Two applications show that the results obtained by the method in this paper perfectly agree with the test data. This paper provides an important theoretical support to the coupled hydro-mechanical research.展开更多
The objective of this work is to obtain the seismic safety coefficient and fracture surface and proceed with the seismic safety evaluation for the rock mass or soil mass surrounding a tunnel,and the limitation of eval...The objective of this work is to obtain the seismic safety coefficient and fracture surface and proceed with the seismic safety evaluation for the rock mass or soil mass surrounding a tunnel,and the limitation of evaluating seismic stability is considered using the pseudo-static strength reduction.By using the finite element software ANSYS and the strength reduction method,new methods of seismic safety evaluation for the rock mass or soil mass surrounding a tunnel are put forward,such as the dynamic finite element static shear strength reduction method and dynamic finite element shear strength reduction method.In order to prove the feasibility of the proposed methods,the results of numerical examples are compared with that of the pseudo-static strength reduction method.The results show that 1) the two methods are both feasible,and the plastic zone first appears near the bottom corners; 2) the safety factor of new method Ⅱ is smaller than that of new method I but generally,and the difference is very small.Therefore,in order to ensure the safety of the structure,two new methods are proposed to evaluate the seismic stability of the rock mass or soil mass surrounding a tunnel.A theoretical basis is provided for the seismic stability of the rock mass or soil mass and the lining surrounding a tunnel and also provided for the engineering application.展开更多
The stability of soil-rock mixtures(SRMs) that widely distributed in slopes is of significant concern for slope safety evaluation and disaster prevention. The failure behavior of SRM slopes under surface loading condi...The stability of soil-rock mixtures(SRMs) that widely distributed in slopes is of significant concern for slope safety evaluation and disaster prevention. The failure behavior of SRM slopes under surface loading conditions was investigated through a series of centrifuge model tests considering various volumetric gravel contents. The displacement field of the slope was determined with image-based displacement system to observe the deformation of the soil and the movement of the block during loading in the tests. The test results showed that the ultimate bearing capacity and the stiffness of SRM slopes increased evidently when the volumetric block content exceeded a threshold value. Moreover, there were more evident slips around the blocks in the SRM slope. The microscopic analysis of the block motion showed that the rotation of the blocks could aggravate the deformation localization to facilitate the development of the slip surface. The high correlation between the rotation of the key blocks and the slope failure indicated that the blocks became the dominant load-bearing medium that influenced the slope failure. The blocks in the sliding body formed a chain to bear the load and change the displacement distribution of the adjacent matrix sand through the block rotation.展开更多
The Yangtze Three Gorges Project (TGP) is the key backbone project to develop and harness the Yangtze river in China. As the largest water conservancy project in the world with the earth and rock excavation amounting ...The Yangtze Three Gorges Project (TGP) is the key backbone project to develop and harness the Yangtze river in China. As the largest water conservancy project in the world with the earth and rock excavation amounting up to 102.83×10 6 m 3, it is, therefore, the largest project on a scale of geomechanical engineering. The involvement of numerous domestic and foreign research institutes in the scientific research has promoted the development of geomechanics. Some rock and soil mechanical issues arising during construction of the Three Gorges Project are discussed in this article.展开更多
In this study, p o ly u reth an e foam ty p e th e rm o se t polym erizing, d u e to chem ical reaction b e tw e e n itsliquid ingredients, w as teste d as b in d e r afte r solidifying and th e n a rock-like m ateria...In this study, p o ly u reth an e foam ty p e th e rm o se t polym erizing, d u e to chem ical reaction b e tw e e n itsliquid ingredients, w as teste d as b in d e r afte r solidifying and th e n a rock-like m aterial m ixing w ith asandy silt ty p e soil w as prep ared . The uniaxial com pressive stren g th s （UCSs） o f p o ly u reth an e foamreinforced soil specim ens w ere d e term in ed for different p o ly u reth an e ratios in th e m ixture. A dditionally,a series o f te sts o n slake durability, im pact value, freezing-th aw in g resistance, and ab rasio n resistance ofp o ly u reth an e reinforced soil （PRS） m ix tu re w as co n d u cted . The UCS values over 3 M Pa w ere m easuredfrom th e PRS specim ens. The testin g results show ed th a t tre a te d soil can econom ically b ecom e adesirable rock-like m aterial in term s o f slake d u ra b ility a n d resistances ag ain st freezing-thaw ing, im pacteffect an d abrasion. As a n o th e r ch aracteristic o f th e rock-like m aterial m ade w ith p o ly u reth an e foam,u n it volum e w eig h t w as found to be q uite low er th a n th o se o f n atu ral rock m aterials.展开更多
To further understand the roles of carbonate and silicate rocks in regulating the atmosphere/soil CO_2level,the flux of CO_2 consumed by the chemical weathering of silicate and carbonate rocks was determined from the ...To further understand the roles of carbonate and silicate rocks in regulating the atmosphere/soil CO_2level,the flux of CO_2 consumed by the chemical weathering of silicate and carbonate rocks was determined from the elemental change in soil profiles.Results showed that the chemical weathering of carbonate rocks mainly occurred at the rock-regolith interface,and that the further weathering of the residua soil on the carbonate rocks was similar to that of the granite profile.Chemical weathering of the silicate rocks occurred through the whole profiles.Therefore,CO_2 consumed per volume by the silicate profiles[M_(sr)(CO_2)]and the residues on carbonate rocks[M_(cr)(CO2)]were calculated based on the elemental weathering gradients.CO_2 consumed by carbonate protolith[M_(cp)(CO_2)]was calculated from the elemental change at the rock-regolith interface.The M_(sr)(CO_2) were about tens to thousands orders of magnitude greater than M_(cr)(CO_2).Even so,this demonstrated that the residues on carbonate rocks could be a sink of CO2_ on long-term scales.The M_(cp)(CO_2) was about four times larger than M_(sr)(CO_2),which demonstrated that carbonate rocks played a more important role in regulating the CO_2 level than the silicate rocks did during the pedogenic process of the profiles.展开更多
In its cationic,trivalent form,Chromium(Cr)it is a micronutrient,and exhibits low environmental mobility.In hexavalent form,however,it is a human carcinogen and also highly mobile.Climate is a key environmental factor...In its cationic,trivalent form,Chromium(Cr)it is a micronutrient,and exhibits low environmental mobility.In hexavalent form,however,it is a human carcinogen and also highly mobile.Climate is a key environmental factor controlling weathering rates and stability of primary and secondary Cr-bearing minerals.Knowledge of Cr oxidation state and mineral residence is therefore essential to estimating the risk posed by Cr in serpentinites,chromite mine wastes,and soils developed on these parent materials.X-ray absorption spectroscopy(XAS)is currently the best available technique for determination of the relative abundance of Cr(III)and Cr(VI)in situ(that is,without digestion of solid phases).A brief review of relevant XAS studies of is presented below,focusing on studies in tropical climates1,as they will be most relevant to eastern Cuba’s extensively serpentinized ophiolite belt.Cr(III)-bearing spinels are usually the dominant and most refractory Cr host in ultramafic rocks.Previous XAS studies2 indicate that in tropical climates,Cr-spinels weather rapidly to form Cr(III)-bearing secondary Fe(III)(hydr)oxides(goethite,hematite).Manganese(Mn)is also enriched in ultramafic rocks2;as Mn(IV),it can also co-precipitate with Fe(III)(hydr)oxides,or form its own secondary(hydr)oxides.A previous study found up to 20%Cr(VI)in in a tropical,serpentine soil that contained substantial Mn,and a strong correlation between the*amounts of Cr(VI)and Mn(IV)in the soil profile2.Theresults of several XAS studies suggest that a close association of Mn(IV)and Cr(III)in secondary Fe(hydr)oxides is necessary for oxidation of Cr(III)to Cr(VI)via electron transfer reactions with Mn(IV);however,additional XAS studies have shown that organic matter3and Cr-bearing aluminosilicates4 may also be important sources of Cr(III)to the environment under specific conditions.The stability and fate of Cr has not been studied in detail for these two host phase types,to the best of our knowledge.Access to XAS facilities to perform Cr geochemical experiments is limited and will only become more so in the future.We are working to develop and apply(micro)Raman spectroscopy to evaluate Cr oxidation state and mineral residence(in crystalline and amorphous materials).In addition to standard Raman scattering,we are employing resonance Raman(785 nm laser)to enhance signal from Cr(VI)-bearing phases and laser-stimulated photoluminescence to identify Cr(III)associated with Al-rich alteration products展开更多
At least 15% of 0.1 million people residing in 117 villages of Tamnar block (Chhattisgarh, central India) are suffering from fluorosis diseases. In this work, the contamination of F- in the environment (i.e. water, so...At least 15% of 0.1 million people residing in 117 villages of Tamnar block (Chhattisgarh, central India) are suffering from fluorosis diseases. In this work, the contamination of F- in the environment (i.e. water, soil, rock and urine) of the Tamnar block is described. The concentration variations of F-, Cl-, NO3-, SO42-, Na+, K+, Mg2+, Ca2+, Al, Mn, Fe and Zn in the groundwater are reported. The F- content in the water was ranged from 1.7 - 17 mg/L with mean value of 9.0 ± 3.7 mg/L. Fluoride was enriched up to 3-, 54-, 69- and 244-folds in the urine, soil, dust and rock, respectively. The cluster and factor analysis models were used to apportion sources of F- and other elements in the water.展开更多
This study investigated the effect of rock fragments on tracer transport in broadleaved and coniferous forest soils from the 0 - 100 cm depth of Gongga Mountain in eastern margin of Qinghai Tibetan Plateau. Using repa...This study investigated the effect of rock fragments on tracer transport in broadleaved and coniferous forest soils from the 0 - 100 cm depth of Gongga Mountain in eastern margin of Qinghai Tibetan Plateau. Using repacked soil columns (20 cm in height and 10 cm in diameter) with different rock fragments contents (0%, 5%, and 15% in v/v), breakthrough curves of bromide (as non-reactive tracer) were obtained under saturated condition. A two-region model was applied and the parameters were estimated by inverse modeling. Results show that with increasing rock fragment content the dispersivity (<em>λ</em>) generally increased while the mobile-immobile partition coefficient (<em>β</em>) and the mass transfer coefficient (<em>ω</em>) decreased. The presence of rock fragments led to an increase in the fraction of immobile domain as well as soil tortuosity. A plausible explanation is that the soil beneath the rock fragments behaved as immobile domain and soil-rock interfaces could serve as preferential flow paths.展开更多
A methodology for calculating the thermal conductivity of soils and rocks is developed which takes into account their origin and mineralogical composition.This method utilizes three approaches.One is founded on the st...A methodology for calculating the thermal conductivity of soils and rocks is developed which takes into account their origin and mineralogical composition.This method utilizes three approaches.One is founded on the structural modeling of contact heat interaction between particles and fills and estimates the statistical probability distribution of the particles in the volume of the medium.The second approach analyses perturbation to the temperature field of the matrix medium by ellipsoidal inclusions.The third approach is to find the mean thermal conductivity of the solid skeleton in the universal model at different composition of rock-forming minerals.展开更多
This study investigated estuarine acidification, associated with drainage and excavation of acid sulfate soils, in areas used for commercial cultivation of Sydneyrock oysters (Saccostrea glomerata). Regular measuremen...This study investigated estuarine acidification, associated with drainage and excavation of acid sulfate soils, in areas used for commercial cultivation of Sydneyrock oysters (Saccostrea glomerata). Regular measurements of pH and electrical conductivity were collected in oyster cultivation areas and acidified reaches of the Hastings River estuary and Port Stephens estuary located on the mid north coast of New South Wales, Australia. Water quality information from acidified floodplain drains was also collected in theHastingsRiverfollowing heavy rainfall. Both estuaries experienced acidification of tributaries following periods of heavy rainfall. Drain outflow waters were acidic展开更多
A scheme is developed for analysing the interaction between afoundation and a nonlin- ear rock and soil medium, in which thefoundation is considered as a linear elastic body and a typicalboundary integral equation met...A scheme is developed for analysing the interaction between afoundation and a nonlin- ear rock and soil medium, in which thefoundation is considered as a linear elastic body and a typicalboundary integral equation method (BIEM) is employed. On the basis oftaking the nonlinear proper- ties of the medium into account, aperturbation BIEM is developed. The fundamental equations for thenonlinear coupling analysis are formulated, and typical problems aresolved and discussed by the pre- sent method.展开更多
基金Project(2012BAK09B02-05) supported by the National Key Technology R&D Program of China during the Twelfth Five-year PeriodProject(51274250) supported by the National Natural Science Foundation of China
文摘A single freedom degree model of drilling bit-rock was established according to the vibration mechanism and its dynamic characteristics. Moreover, a novel identification method of rock and soil parameters for vibration drilling based on the fuzzy least squares(FLS)-support vector machine(SVM) was developed, in which the fuzzy membership function was set by using linear distance, and its parameters, such as penalty factor and kernel parameter, were optimized by using adaptive genetic algorithm. And FLS-SVM identification on rock and soil parameters for vibration drilling was made by changing the input/output data from single freedom degree model of drilling bit-rock. The results of identification simulation and resonance column experiment show that relative error of natural frequency for some hard sand from identification simulation and resonance column experiment is 1.1% and the identification precision based on the fuzzy least squares-support vector machine is high.
基金funded by the National Science Foundation of China(Grant Nos.41702374,4177020938,2018YFC1505406)China Geological Survey projects(Grant Nos.DD20190640,20190505)
文摘Rock–soil aggregate landslides(RSALs) are a common geological hazard in deeply incised valleys in southwestern China. Large-scale RSALs are widely distributed in the upper reaches of the Dadu River, Danba County, Sichuan Province, and are influenced by slope structure, which can be divided into open, lock, strip, and dumbbell types, as well as soil type and meso-structure, which can be classified as layered rock–soil aggregate, block-soil, and grainsoil. In this study, the evolution of four types of structures, such as layered-dumbbell, block-soil lock, banded block-soil, and block-soil open types, were analyzed by field surveys, surface and deep displacement monitoring, and Flac3 D. It was found that the Danba reach of the Dadu River showed incised valley through the evolution from wide to slow valley affected by internal and external geological processes since the Quaternary Glaciation. In the layered-dumbbell rock–soil aggregate, the main sliding pattern is multi-stage sliding at different depths. Circular sliding in the trailing edge and plane sliding along the bedrock in the front edge body occurin the block-soil-lock type aggregate. Large-scale multi-level and circular sliding over long distances occur in the banded block-soil aggregate. The blocksoil open type is stable, with only circular sliding occurring in local and shallow surfaces of the body. The monitoring and numerical simulation results further show that slope structure and regularity have diversified with RSALs. The results provide a basis for analyzing the stability mechanism of RSALs and preventing RSALs in deeply incised valleys.
基金supported by the Land and Liveability National Innovation Challenge under L2 NIC Award No. L2NICCFP1-2013-1
文摘Blasting has been widely used in mining and construction industries for rock breaking.This paper presents the results of a series of field tests conducted to investigate the ground wave propagation through mixed geological media.The tests were conducted at a site in the northwestern part of Singapore composed of residual soil and granitic rock.The field test aims to provide measurement data to better understand the stress wave propagation in soil/rock and along their interface.Triaxial accelerometers were used for the free field vibration monitoring.The measured results are presented and discussed,and empirical formulae for predicting peak particle velocity (PPV) attenuation along the ground surface and in soil/rock were derived from the measured data.Also,the ground vibration attenuation across the soil-rock interface was carefully examined,and it was found that the PPV of ground vibration was decreased by 37.2% when it travels from rock to soil in the vertical direction.
基金funded by the National Natural Science Foundation of China(Grant No.41672258)the Land and Resources Science&Technology Project of Jiangsu Province(Grant No.2018045)。
文摘Soil-rock mixtures containing macropore(SRMCM)is a kind of geological material with special mechanical properties.Located in the project area of Lenggu hydropower station on the Yalong River,Sichuan Province,China,there is an extremely unstable Mahe talus slide with a total volume of nearly160 million cubic meters,which is mainly composed of SRMCM.The study on the mechanical properties of SRMCM is of great significance for the engineering construction and safe operation.In this paper,laboratory tests and discrete element numerical tests based on three-dimensional scanning technology were conducted to study the influence of stone content,stone size,and the angle of the macropore structure on shear characteristics of SRMCM.The failure mechanism of SRMCM was discussed from a microscopic perspective.This work explains the internal mechanism of the influence of stone content,stone size,and the angle of the macropore structure on the strength of SRMCM through the microscopic level of stone rotation,force chain distribution,and crack propagation.As the macropore structure that intersects with the preset shear plane at a large angle could act as a skeleton-like support to resist the shear force,the fracture of the weak cemented surface of soil and stone in the macropore structure is an important cause of SRMCM destruction.
基金supported by the Yalongjiang River Joint Fund by the National Natural Science Foundation of China(NSFC)Ertan Hydropower Development Company,LTD(Nos.50579091 and 50539090)+1 种基金NSFC(No.10772190)Major State Basic Research Project of China(No.2002CB412708)
文摘Physical mechanisms and influencing factors on the effective stress coefficient for rock/soil-like porous materials are investigated, based on which equivalent connectivity index is proposed. The equivalent connectivity index, relying on the meso-scale structure of porous material and the property of liquid, denotes the connectivity of pores in Representative Element Area （REA）. If the conductivity of the porous material is anisotropic, the equivalent connectivity index is a second order tensor. Based on the basic theories of continuous mechanics and tensor analysis, relationship between area porosity and volumetric porosity of porous materials is deduced. Then a generalized expression, describing the relation between effective stress coefficient tensor and equivalent connectivity tensor of pores, is proposed, and the expression can be applied to isotropic media and also to anisotropic materials. Furthermore, evolution of porosity and equivalent connectivity index of the pore are studied in the strain space, and the method to determine the corresponding functions in expressions above is proposed using genetic algorithm and genetic programming. Two applications show that the results obtained by the method in this paper perfectly agree with the test data. This paper provides an important theoretical support to the coupled hydro-mechanical research.
基金Project(2011CB013600) supported by State Key Program for Basic Research of ChinaProject(20136201110003) supported by the Education Ministry Doctoral Tutor Foundation of China+1 种基金Project(51368039) supported by the National Natural Science Foundation of ChinaProject(2013-4-94) supported by the Program of Science and Technology Research in Lanzhou City,China
文摘The objective of this work is to obtain the seismic safety coefficient and fracture surface and proceed with the seismic safety evaluation for the rock mass or soil mass surrounding a tunnel,and the limitation of evaluating seismic stability is considered using the pseudo-static strength reduction.By using the finite element software ANSYS and the strength reduction method,new methods of seismic safety evaluation for the rock mass or soil mass surrounding a tunnel are put forward,such as the dynamic finite element static shear strength reduction method and dynamic finite element shear strength reduction method.In order to prove the feasibility of the proposed methods,the results of numerical examples are compared with that of the pseudo-static strength reduction method.The results show that 1) the two methods are both feasible,and the plastic zone first appears near the bottom corners; 2) the safety factor of new method Ⅱ is smaller than that of new method I but generally,and the difference is very small.Therefore,in order to ensure the safety of the structure,two new methods are proposed to evaluate the seismic stability of the rock mass or soil mass surrounding a tunnel.A theoretical basis is provided for the seismic stability of the rock mass or soil mass and the lining surrounding a tunnel and also provided for the engineering application.
基金supported by National Key R&D Program of China(2018YFC1508503)
文摘The stability of soil-rock mixtures(SRMs) that widely distributed in slopes is of significant concern for slope safety evaluation and disaster prevention. The failure behavior of SRM slopes under surface loading conditions was investigated through a series of centrifuge model tests considering various volumetric gravel contents. The displacement field of the slope was determined with image-based displacement system to observe the deformation of the soil and the movement of the block during loading in the tests. The test results showed that the ultimate bearing capacity and the stiffness of SRM slopes increased evidently when the volumetric block content exceeded a threshold value. Moreover, there were more evident slips around the blocks in the SRM slope. The microscopic analysis of the block motion showed that the rotation of the blocks could aggravate the deformation localization to facilitate the development of the slip surface. The high correlation between the rotation of the key blocks and the slope failure indicated that the blocks became the dominant load-bearing medium that influenced the slope failure. The blocks in the sliding body formed a chain to bear the load and change the displacement distribution of the adjacent matrix sand through the block rotation.
文摘The Yangtze Three Gorges Project (TGP) is the key backbone project to develop and harness the Yangtze river in China. As the largest water conservancy project in the world with the earth and rock excavation amounting up to 102.83×10 6 m 3, it is, therefore, the largest project on a scale of geomechanical engineering. The involvement of numerous domestic and foreign research institutes in the scientific research has promoted the development of geomechanics. Some rock and soil mechanical issues arising during construction of the Three Gorges Project are discussed in this article.
文摘In this study, p o ly u reth an e foam ty p e th e rm o se t polym erizing, d u e to chem ical reaction b e tw e e n itsliquid ingredients, w as teste d as b in d e r afte r solidifying and th e n a rock-like m aterial m ixing w ith asandy silt ty p e soil w as prep ared . The uniaxial com pressive stren g th s （UCSs） o f p o ly u reth an e foamreinforced soil specim ens w ere d e term in ed for different p o ly u reth an e ratios in th e m ixture. A dditionally,a series o f te sts o n slake durability, im pact value, freezing-th aw in g resistance, and ab rasio n resistance ofp o ly u reth an e reinforced soil （PRS） m ix tu re w as co n d u cted . The UCS values over 3 M Pa w ere m easuredfrom th e PRS specim ens. The testin g results show ed th a t tre a te d soil can econom ically b ecom e adesirable rock-like m aterial in term s o f slake d u ra b ility a n d resistances ag ain st freezing-thaw ing, im pacteffect an d abrasion. As a n o th e r ch aracteristic o f th e rock-like m aterial m ade w ith p o ly u reth an e foam,u n it volum e w eig h t w as found to be q uite low er th a n th o se o f n atu ral rock m aterials.
基金supported by the National Natural Science Foundation of China(NSFC) grants(No.41073096 and 40473051)National Key Basic Research Program of China (2013CB956702)the Hundred Talents Program of the Chinese Academy of Sciences
文摘To further understand the roles of carbonate and silicate rocks in regulating the atmosphere/soil CO_2level,the flux of CO_2 consumed by the chemical weathering of silicate and carbonate rocks was determined from the elemental change in soil profiles.Results showed that the chemical weathering of carbonate rocks mainly occurred at the rock-regolith interface,and that the further weathering of the residua soil on the carbonate rocks was similar to that of the granite profile.Chemical weathering of the silicate rocks occurred through the whole profiles.Therefore,CO_2 consumed per volume by the silicate profiles[M_(sr)(CO_2)]and the residues on carbonate rocks[M_(cr)(CO2)]were calculated based on the elemental weathering gradients.CO_2 consumed by carbonate protolith[M_(cp)(CO_2)]was calculated from the elemental change at the rock-regolith interface.The M_(sr)(CO_2) were about tens to thousands orders of magnitude greater than M_(cr)(CO_2).Even so,this demonstrated that the residues on carbonate rocks could be a sink of CO2_ on long-term scales.The M_(cp)(CO_2) was about four times larger than M_(sr)(CO_2),which demonstrated that carbonate rocks played a more important role in regulating the CO_2 level than the silicate rocks did during the pedogenic process of the profiles.
文摘In its cationic,trivalent form,Chromium(Cr)it is a micronutrient,and exhibits low environmental mobility.In hexavalent form,however,it is a human carcinogen and also highly mobile.Climate is a key environmental factor controlling weathering rates and stability of primary and secondary Cr-bearing minerals.Knowledge of Cr oxidation state and mineral residence is therefore essential to estimating the risk posed by Cr in serpentinites,chromite mine wastes,and soils developed on these parent materials.X-ray absorption spectroscopy(XAS)is currently the best available technique for determination of the relative abundance of Cr(III)and Cr(VI)in situ(that is,without digestion of solid phases).A brief review of relevant XAS studies of is presented below,focusing on studies in tropical climates1,as they will be most relevant to eastern Cuba’s extensively serpentinized ophiolite belt.Cr(III)-bearing spinels are usually the dominant and most refractory Cr host in ultramafic rocks.Previous XAS studies2 indicate that in tropical climates,Cr-spinels weather rapidly to form Cr(III)-bearing secondary Fe(III)(hydr)oxides(goethite,hematite).Manganese(Mn)is also enriched in ultramafic rocks2;as Mn(IV),it can also co-precipitate with Fe(III)(hydr)oxides,or form its own secondary(hydr)oxides.A previous study found up to 20%Cr(VI)in in a tropical,serpentine soil that contained substantial Mn,and a strong correlation between the*amounts of Cr(VI)and Mn(IV)in the soil profile2.Theresults of several XAS studies suggest that a close association of Mn(IV)and Cr(III)in secondary Fe(hydr)oxides is necessary for oxidation of Cr(III)to Cr(VI)via electron transfer reactions with Mn(IV);however,additional XAS studies have shown that organic matter3and Cr-bearing aluminosilicates4 may also be important sources of Cr(III)to the environment under specific conditions.The stability and fate of Cr has not been studied in detail for these two host phase types,to the best of our knowledge.Access to XAS facilities to perform Cr geochemical experiments is limited and will only become more so in the future.We are working to develop and apply(micro)Raman spectroscopy to evaluate Cr oxidation state and mineral residence(in crystalline and amorphous materials).In addition to standard Raman scattering,we are employing resonance Raman(785 nm laser)to enhance signal from Cr(VI)-bearing phases and laser-stimulated photoluminescence to identify Cr(III)associated with Al-rich alteration products
文摘At least 15% of 0.1 million people residing in 117 villages of Tamnar block (Chhattisgarh, central India) are suffering from fluorosis diseases. In this work, the contamination of F- in the environment (i.e. water, soil, rock and urine) of the Tamnar block is described. The concentration variations of F-, Cl-, NO3-, SO42-, Na+, K+, Mg2+, Ca2+, Al, Mn, Fe and Zn in the groundwater are reported. The F- content in the water was ranged from 1.7 - 17 mg/L with mean value of 9.0 ± 3.7 mg/L. Fluoride was enriched up to 3-, 54-, 69- and 244-folds in the urine, soil, dust and rock, respectively. The cluster and factor analysis models were used to apportion sources of F- and other elements in the water.
文摘This study investigated the effect of rock fragments on tracer transport in broadleaved and coniferous forest soils from the 0 - 100 cm depth of Gongga Mountain in eastern margin of Qinghai Tibetan Plateau. Using repacked soil columns (20 cm in height and 10 cm in diameter) with different rock fragments contents (0%, 5%, and 15% in v/v), breakthrough curves of bromide (as non-reactive tracer) were obtained under saturated condition. A two-region model was applied and the parameters were estimated by inverse modeling. Results show that with increasing rock fragment content the dispersivity (<em>λ</em>) generally increased while the mobile-immobile partition coefficient (<em>β</em>) and the mass transfer coefficient (<em>ω</em>) decreased. The presence of rock fragments led to an increase in the fraction of immobile domain as well as soil tortuosity. A plausible explanation is that the soil beneath the rock fragments behaved as immobile domain and soil-rock interfaces could serve as preferential flow paths.
文摘A methodology for calculating the thermal conductivity of soils and rocks is developed which takes into account their origin and mineralogical composition.This method utilizes three approaches.One is founded on the structural modeling of contact heat interaction between particles and fills and estimates the statistical probability distribution of the particles in the volume of the medium.The second approach analyses perturbation to the temperature field of the matrix medium by ellipsoidal inclusions.The third approach is to find the mean thermal conductivity of the solid skeleton in the universal model at different composition of rock-forming minerals.
文摘This study investigated estuarine acidification, associated with drainage and excavation of acid sulfate soils, in areas used for commercial cultivation of Sydneyrock oysters (Saccostrea glomerata). Regular measurements of pH and electrical conductivity were collected in oyster cultivation areas and acidified reaches of the Hastings River estuary and Port Stephens estuary located on the mid north coast of New South Wales, Australia. Water quality information from acidified floodplain drains was also collected in theHastingsRiverfollowing heavy rainfall. Both estuaries experienced acidification of tributaries following periods of heavy rainfall. Drain outflow waters were acidic
文摘A scheme is developed for analysing the interaction between afoundation and a nonlin- ear rock and soil medium, in which thefoundation is considered as a linear elastic body and a typicalboundary integral equation method (BIEM) is employed. On the basis oftaking the nonlinear proper- ties of the medium into account, aperturbation BIEM is developed. The fundamental equations for thenonlinear coupling analysis are formulated, and typical problems aresolved and discussed by the pre- sent method.
