The distribution of light fraction carbon （LF-C） in the various size classes of aggregates and its relationship to water- stable aggregates as well as the influence of cultivation on the organic components in virgin...The distribution of light fraction carbon （LF-C） in the various size classes of aggregates and its relationship to water- stable aggregates as well as the influence of cultivation on the organic components in virgin and cultivated black soils were studied by wet sieving and density separation methods. The total organic carbon （TOC） and LF-C were significantly higher （P≤ 0.05） in the virgin soils than in the cultivated soils. The LF-C in aggregates of different size classes varied from 0.9 to 2.5 g kg^-1 in the cultivated soils and from 2.5 to 7.1 g kg^-1 in the virgin soils, whereas the ratio of LF-C to TOC varied from 1.9% to 7.3% and from 5.0% to 12.2%, respectively. After being incubated under constant temperature and controlled humidity for three months, the contribution of LF-C to TOC sharply decreased to an amount （1.7%4.5%） close to the level in soils that had been cultivated for 20 to 25 years （1.3%-8.8%）. As a result, the larger water-stable macro-aggregates （especially 〉 1 mm） decreased sharply, indicating that the LF-C pool in virgin soils declined quickly after cultivation, which reduced the water stability of soil aggregates.展开更多
Rainfall infiltration depth and mode can severely influence slope stability.With the sustained rainfall,the influenced region of slope gradually expands.By using the Green-Ampt model to the soil slope,infiltration reg...Rainfall infiltration depth and mode can severely influence slope stability.With the sustained rainfall,the influenced region of slope gradually expands.By using the Green-Ampt model to the soil slope,infiltration regulation was discussed under sustained and small intensity rainfall.And the infiltration rate of unsaturated soil was proposed according to the saturated infiltration theory.Because of the changing of initial moisture content in depth of slope,the saturated or unsaturated infiltration rate and depth could also be changeable with the sustained rainfall infiltration.Based on the principle of strength reduction,the calculation model of slope safety factor was established under different initial moisture contents and infiltration modes.Then,the slope stability was quantitatively analyzed through software FLAC3D.The calculation results of soil slope engineering show that there is a shorter period for slope stability under different initial moisture contents and unsaturated infiltration ways at the slope wetting front.The stability period of slope is 33.3%according to different initial moisture contents of wetting front less than that of the same initial moisture content of wetting front.And the slope is easier to fail under the unsaturated infiltration.The results agree well with the actual situation under sustained and small intensity rainfall.展开更多
To establish the movement relationship for the roof breaking under shallow mining conditions, the mechanical model of the roof rock beam was built, then the structure instability process of the roof rock beam was anal...To establish the movement relationship for the roof breaking under shallow mining conditions, the mechanical model of the roof rock beam was built, then the structure instability process of the roof rock beam was analyzed. The changing criterion of the vertical displacement was established and the relationship between the deflection and the rotary motion of roof block was determined. Regarding a mining face in Shangwan Mine, the responsing laws of the deflection and horizontal thrust of the roof rock beam were obtained through FLAC3D numerical analysis. The results show that the structure instability of the cracked roof rock beam depends on the interaction between the vertical load and the horizontal thrust.For the roof rock beam, when the vertical load keeps constant, the horizontal thrust fluctuating rises with increasing deflection. The horizontal thrust increases constantly with the deeper buried depth and the smaller span.展开更多
Retaining gob-side entryways and the stability of gas drainage boreholes are two essential techniques in the co-extraction of coal and gas without entry pillars （CECGWEP）. However, retained entryways located in deep...Retaining gob-side entryways and the stability of gas drainage boreholes are two essential techniques in the co-extraction of coal and gas without entry pillars （CECGWEP）. However, retained entryways located in deep coal mines are hard to maintain, especially for constructing boreholes in confined spaces, owing to major deformations. Consequently, it is difficult to drill boreholes and maintain their stability, which therefore cannot guarantee the effectiveness of gas drainage. This paper presents three measures for conducting CECGWEP in deep mines on the basis of effective space in retained entryways for gas drainage, They are combinations of retaining roadways and face-lagging inclined boreholes, retaining roadways and face-advancing inclined boreholes, and retaining roadways and high return airway inclined boreholes. Several essential techniques are suggested to improve the maintenance of retained entryways and the stabilization of boreholes. For the particular cases considered in this study, two field trials have verified the latter two measures from the results obtained from the faces 1111（1） and 11112（1） in the Zhuji Mine. The results indicate that these models can effectively solve the problems in deep mines. The maximum gas drainage flow for a single hole can reach 8.1 m^3/min and the effective drainage distance can be extended up to 150 m or more.展开更多
How to find more effective way to stabilize the borehole wall in the fault gouge section is the key technical challenge to control the stability of the borehole wall in the Wenchuan fault gouge section during the proc...How to find more effective way to stabilize the borehole wall in the fault gouge section is the key technical challenge to control the stability of the borehole wall in the Wenchuan fault gouge section during the process of core drilling. Here we try to describe the characters of deep fault gouge in fracture zones from the undisturbed fault gouge samples which are obtained during the core drilling. The X- Ray Diffraction （XRD）, X-Ray Fluorescence （XRF） and Scanning Electron Microscope （SEM） provided the detailed information of the fault gouge＇s microscopic characteristics on the density, moisture content, expansibility, dispersity, permeability, tensile strength and other main physical-mechanical properties. Based on these systematic experimental studies above and analysis of the fault gouge instability mechanism, a new technical procedure to stabilize the borehole wall is proposed -- a low water and a low loss low permeability drilling fluid system that consists of 4% day ＋ 0.5% CMC-HV ＋ 2% S-1 ＋ 3%sulfonated asphalt ＋ 1% SMC ＋ 0.5% X-1 ＋ 0-5% T type lubricant ＋ barite for core drilling in fault gouge sections.展开更多
The nonlinear Hoek-Brown failure criterion was introduced to limit analysis by applying the tangent method. Based on the failure mechanism of double-logarithmic spiral curves on the face of deep rock tunnels, the anal...The nonlinear Hoek-Brown failure criterion was introduced to limit analysis by applying the tangent method. Based on the failure mechanism of double-logarithmic spiral curves on the face of deep rock tunnels, the analytical solutions of collapse pressure were derived through utilizing the virtual power principle in the case of pore water, and the optimal solutions of collapse pressure were obtained by using the optimization programs of mathematical model with regard of a maximum problem. In comparison with existing research with the same parameters, the consistency of change rule shows the validity of the proposed method. Moreover, parametric study indicates that nonlinear Hoek-Brown failure criterion and pore water pressure have great influence on collapse pressure and failure shape of tunnel faces in deep rock masses, particularly when the surrounding rock is too weak or under the condition of great disturbance and abundant ground water, and in this case, supporting measures should be intensified so as to prevent the occurrence of collapse.展开更多
The reinforcement and stabilization of loess soil are duscussed by using fibers as the reinforcement and cement as the stabilization materials.To study the strength characteristics of loess soil reinforced by modified...The reinforcement and stabilization of loess soil are duscussed by using fibers as the reinforcement and cement as the stabilization materials.To study the strength characteristics of loess soil reinforced by modified polypropylene(MPP) fiber and cement,samples were prepared with six different fiber contents,three different cement contents,three different curing periods and three kinds of fiber length.The samples were tested under submergence and non-submergence conditions for the unconfined compressive strength(UCS),the splitting tensile strength and the compressive resilient modulus.The results indicated that combined reinforcement by PP fiber and cement could significantly improve the early strength of loess to 3.65–5.99 MPa in three days.With an increase in cement content,the specimens exhibited brittle fracture.However,the addition of fibers gradually modified the mode of fracture from brittle to ductile to plastic.The optimal dosage of fiber to reinforce loess was in the range of 0.3%–0.45% and the optimum fiber length was 12 mm,for which the unconfined compressive strength and tensile strength reached their maxima.Based on the analysis of failure properties,cement-reinforced loess specimens were susceptible to brittle damage under pressure,and the effect of modified polypropylene fiber as the connecting "bridge" could help the specimens achieve a satisfactory level of ductility when under pressure.展开更多
基金Project supported by the State Key Basic Research Development Program (No. G1999011804) the Knowledge Innovation Program of the Chinese Academy of Sciences (No. KZCXZ-SW-416).
文摘The distribution of light fraction carbon （LF-C） in the various size classes of aggregates and its relationship to water- stable aggregates as well as the influence of cultivation on the organic components in virgin and cultivated black soils were studied by wet sieving and density separation methods. The total organic carbon （TOC） and LF-C were significantly higher （P≤ 0.05） in the virgin soils than in the cultivated soils. The LF-C in aggregates of different size classes varied from 0.9 to 2.5 g kg^-1 in the cultivated soils and from 2.5 to 7.1 g kg^-1 in the virgin soils, whereas the ratio of LF-C to TOC varied from 1.9% to 7.3% and from 5.0% to 12.2%, respectively. After being incubated under constant temperature and controlled humidity for three months, the contribution of LF-C to TOC sharply decreased to an amount （1.7%4.5%） close to the level in soils that had been cultivated for 20 to 25 years （1.3%-8.8%）. As a result, the larger water-stable macro-aggregates （especially 〉 1 mm） decreased sharply, indicating that the LF-C pool in virgin soils declined quickly after cultivation, which reduced the water stability of soil aggregates.
基金Project(2010(A)06-b)supported by the Scientific Research Fund of Yunnan Provincial Transport Department of ChinaProject(51108293)supported by the National Natural Science Foundation of China+1 种基金Project(2013PY37)supported by the Cultivated Foundation of Taizhou University of ChinaProject(LY13E080008)supported by the Zhejiang Provincial Natural Science Foundation of China
文摘Rainfall infiltration depth and mode can severely influence slope stability.With the sustained rainfall,the influenced region of slope gradually expands.By using the Green-Ampt model to the soil slope,infiltration regulation was discussed under sustained and small intensity rainfall.And the infiltration rate of unsaturated soil was proposed according to the saturated infiltration theory.Because of the changing of initial moisture content in depth of slope,the saturated or unsaturated infiltration rate and depth could also be changeable with the sustained rainfall infiltration.Based on the principle of strength reduction,the calculation model of slope safety factor was established under different initial moisture contents and infiltration modes.Then,the slope stability was quantitatively analyzed through software FLAC3D.The calculation results of soil slope engineering show that there is a shorter period for slope stability under different initial moisture contents and unsaturated infiltration ways at the slope wetting front.The stability period of slope is 33.3%according to different initial moisture contents of wetting front less than that of the same initial moisture content of wetting front.And the slope is easier to fail under the unsaturated infiltration.The results agree well with the actual situation under sustained and small intensity rainfall.
基金supported by the National Natural Science Foundation of China (Nos. 51474188, 51074140, and 51774112)the Natural Science Foundation of Hebei Province of China (No. E2014203012)+4 种基金the International Cooperation Project of Henan Science and Technology Department (No. 182102410060)International Cooperative Talent Project of Henan Province (No. 2016GH22)the Doctoral Fund of Henan Polytechnic University of China (No. B2015-67)the Research Fund of State and Local Joint Engineering Laboratory for Gas Drainage & Ground Control of Deep Mines (Henan Polytechnic niversity)of China (No. G201614)Taihang Scholars Program
文摘To establish the movement relationship for the roof breaking under shallow mining conditions, the mechanical model of the roof rock beam was built, then the structure instability process of the roof rock beam was analyzed. The changing criterion of the vertical displacement was established and the relationship between the deflection and the rotary motion of roof block was determined. Regarding a mining face in Shangwan Mine, the responsing laws of the deflection and horizontal thrust of the roof rock beam were obtained through FLAC3D numerical analysis. The results show that the structure instability of the cracked roof rock beam depends on the interaction between the vertical load and the horizontal thrust.For the roof rock beam, when the vertical load keeps constant, the horizontal thrust fluctuating rises with increasing deflection. The horizontal thrust increases constantly with the deeper buried depth and the smaller span.
基金Acknowledgments The research was supported by Program for Changjiang Scholars and Innovative Research Team in University （IRT_I4R55）, and the National Natural Science Foundation of China under Grant No. NSFC-51274193.
文摘Retaining gob-side entryways and the stability of gas drainage boreholes are two essential techniques in the co-extraction of coal and gas without entry pillars （CECGWEP）. However, retained entryways located in deep coal mines are hard to maintain, especially for constructing boreholes in confined spaces, owing to major deformations. Consequently, it is difficult to drill boreholes and maintain their stability, which therefore cannot guarantee the effectiveness of gas drainage. This paper presents three measures for conducting CECGWEP in deep mines on the basis of effective space in retained entryways for gas drainage, They are combinations of retaining roadways and face-lagging inclined boreholes, retaining roadways and face-advancing inclined boreholes, and retaining roadways and high return airway inclined boreholes. Several essential techniques are suggested to improve the maintenance of retained entryways and the stabilization of boreholes. For the particular cases considered in this study, two field trials have verified the latter two measures from the results obtained from the faces 1111（1） and 11112（1） in the Zhuji Mine. The results indicate that these models can effectively solve the problems in deep mines. The maximum gas drainage flow for a single hole can reach 8.1 m^3/min and the effective drainage distance can be extended up to 150 m or more.
基金supported by the Land&Resources Ministry of China,the China Geological Survey and the research institute of prospecting technology in the Chinese Academy of Geological Sciences,sincere thanks heresupported by National Natural Science Foundation of China(Grant Nos.41272331,51204027)the State Key Laboratory of Geohazard Prevention&Geoenvironment Protection(Grant Nos.SKLGP2012Z007,SKLGP2014Z001,SKLGP2015Z010)
文摘How to find more effective way to stabilize the borehole wall in the fault gouge section is the key technical challenge to control the stability of the borehole wall in the Wenchuan fault gouge section during the process of core drilling. Here we try to describe the characters of deep fault gouge in fracture zones from the undisturbed fault gouge samples which are obtained during the core drilling. The X- Ray Diffraction （XRD）, X-Ray Fluorescence （XRF） and Scanning Electron Microscope （SEM） provided the detailed information of the fault gouge＇s microscopic characteristics on the density, moisture content, expansibility, dispersity, permeability, tensile strength and other main physical-mechanical properties. Based on these systematic experimental studies above and analysis of the fault gouge instability mechanism, a new technical procedure to stabilize the borehole wall is proposed -- a low water and a low loss low permeability drilling fluid system that consists of 4% day ＋ 0.5% CMC-HV ＋ 2% S-1 ＋ 3%sulfonated asphalt ＋ 1% SMC ＋ 0.5% X-1 ＋ 0-5% T type lubricant ＋ barite for core drilling in fault gouge sections.
基金Project(2013CB036004)supported by National Basic Research Program of ChinaProjects(51178468,51378510)supported by National Natural Science Foundation of ChinaProject(CX2013B077)supported by Hunan Provincial Innovation Foundation for Postgraduate,China
文摘The nonlinear Hoek-Brown failure criterion was introduced to limit analysis by applying the tangent method. Based on the failure mechanism of double-logarithmic spiral curves on the face of deep rock tunnels, the analytical solutions of collapse pressure were derived through utilizing the virtual power principle in the case of pore water, and the optimal solutions of collapse pressure were obtained by using the optimization programs of mathematical model with regard of a maximum problem. In comparison with existing research with the same parameters, the consistency of change rule shows the validity of the proposed method. Moreover, parametric study indicates that nonlinear Hoek-Brown failure criterion and pore water pressure have great influence on collapse pressure and failure shape of tunnel faces in deep rock masses, particularly when the surrounding rock is too weak or under the condition of great disturbance and abundant ground water, and in this case, supporting measures should be intensified so as to prevent the occurrence of collapse.
基金Project(050101)supported by Horizontal Research Foundation of PLA Air Force Engineering University,ChinaProject(51478462)supported by the National Natural Science Foundation of China
文摘The reinforcement and stabilization of loess soil are duscussed by using fibers as the reinforcement and cement as the stabilization materials.To study the strength characteristics of loess soil reinforced by modified polypropylene(MPP) fiber and cement,samples were prepared with six different fiber contents,three different cement contents,three different curing periods and three kinds of fiber length.The samples were tested under submergence and non-submergence conditions for the unconfined compressive strength(UCS),the splitting tensile strength and the compressive resilient modulus.The results indicated that combined reinforcement by PP fiber and cement could significantly improve the early strength of loess to 3.65–5.99 MPa in three days.With an increase in cement content,the specimens exhibited brittle fracture.However,the addition of fibers gradually modified the mode of fracture from brittle to ductile to plastic.The optimal dosage of fiber to reinforce loess was in the range of 0.3%–0.45% and the optimum fiber length was 12 mm,for which the unconfined compressive strength and tensile strength reached their maxima.Based on the analysis of failure properties,cement-reinforced loess specimens were susceptible to brittle damage under pressure,and the effect of modified polypropylene fiber as the connecting "bridge" could help the specimens achieve a satisfactory level of ductility when under pressure.
