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Editor Work2008 Vol. 16, No. 5
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2008, 16(5): 577-583.
Abstract
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Mo re than fifty ground co llapse pits w ere formed in succession about 20 days after the 5. 12 Wen chuan Great E arthquake. They w ere in Lijiayuanzh i v illage at the southeastern o fAnchang town, Anx ian county in front o f Longmen Shan. This paper ana lyzes the possib le reasons o f the p it fo rmation using the propert ies o f strata, rock, g roundw ater, erosion and topso i.l Primarily, it w as the pre- cond ition that the ca lcareous cemented sandy cong lom erate of Jurassic period presented below the g round surface. The rock co llapse and excess porew ater pres sure caused by serious seism ic groundmo tion w ere the start- up factors. A ftershocks resu lted in the emergence and deve lopment of so il holes. Furthermore, groundw ater change acce lerated th is process. Las,t the soil eng ineering properties determ ined the shape o f the pits. A t the same t ime, this paper a lso pays attent ion to other possible rea sons inc lud ing buried fault activ ity and soil particle loss due to groundw ater flow. The paper presents the relavant background evidences. It is desirab le that th is paperwould bring some innovative ideas to find out the real reasons of the p it format ion.
Mo re than fifty ground co llapse pits w ere formed in succession about 20 days after the 5. 12 Wen chuan Great E arthquake. They w ere in Lijiayuanzh i v illage at the southeastern o fAnchang town, Anx ian county in front o f Longmen Shan. This paper ana lyzes the possib le reasons o f the p it fo rmation using the propert ies o f strata, rock, g roundw ater, erosion and topso i.l Primarily, it w as the pre- cond ition that the ca lcareous cemented sandy cong lom erate of Jurassic period presented below the g round surface. The rock co llapse and excess porew ater pres sure caused by serious seism ic groundmo tion w ere the start- up factors. A ftershocks resu lted in the emergence and deve lopment of so il holes. Furthermore, groundw ater change acce lerated th is process. Las,t the soil eng ineering properties determ ined the shape o f the pits. A t the same t ime, this paper a lso pays attent ion to other possible rea sons inc lud ing buried fault activ ity and soil particle loss due to groundw ater flow. The paper presents the relavant background evidences. It is desirab le that th is paperwould bring some innovative ideas to find out the real reasons of the p it format ion.
2008, 16(5): 584-591.
Double- arch tunnel is a k ind o f new tunnel form. It has a large span, complica ted structure and cock amam iew orking procedure. Therefore, it is difficult to be constructed under unsymmetrical pressure and comp lex geo log ical cond itions. E specially, a series of eng ineering problems, such as lin ing crack ing and tunne l slope de fo rmation, o ften occur in the entrance po rtal reg ion. Th is paper is based on the pro ject of Fux i tunnel and uses both geo log ical analysis and numerical simulation method. The stress- stra in processes of lining and rock mass are ex am ined systemat ically during the construction of the double- arch tunnel under unsymme trical pressure and com plex geological cond it ions. The comprehensive ana lysis show s that ow ing to the in fluence of theF5 fau l,t fragmenta l structure rockmass w as encountered in the portal reg ion. Due to poor rockmass and unsymmetrical pressure, lining and surrounding rock occurred settlem ent and lateral deform ation after tunne l excavat ion. The slope deformation mode w as creep sliding- fracturing wh ich w as is a result from surround ing rock deformat ion. Based on the above analysis, a conclusion w as drawn that control of the tunnel vau lt deformat ion is a key step to contro l the who le de fo rmation o f the entrance reg ion.
Double- arch tunnel is a k ind o f new tunnel form. It has a large span, complica ted structure and cock amam iew orking procedure. Therefore, it is difficult to be constructed under unsymmetrical pressure and comp lex geo log ical cond itions. E specially, a series of eng ineering problems, such as lin ing crack ing and tunne l slope de fo rmation, o ften occur in the entrance po rtal reg ion. Th is paper is based on the pro ject of Fux i tunnel and uses both geo log ical analysis and numerical simulation method. The stress- stra in processes of lining and rock mass are ex am ined systemat ically during the construction of the double- arch tunnel under unsymme trical pressure and com plex geological cond it ions. The comprehensive ana lysis show s that ow ing to the in fluence of theF5 fau l,t fragmenta l structure rockmass w as encountered in the portal reg ion. Due to poor rockmass and unsymmetrical pressure, lining and surrounding rock occurred settlem ent and lateral deform ation after tunne l excavat ion. The slope deformation mode w as creep sliding- fracturing wh ich w as is a result from surround ing rock deformat ion. Based on the above analysis, a conclusion w as drawn that control of the tunnel vau lt deformat ion is a key step to contro l the who le de fo rmation o f the entrance reg ion.
2008, 16(5): 592-597.
The geological condition of a high and steep slope is comp lex. Itsweak structural p laneswell develop. The excavated height and ratio are high. The excavated faces are many for the sake of the space of the deformation. There are many failure evidences at the slope. On the basis of geological condition investigation, the rock mass structure and the affected factors of the slope are studied. It indicates that the deformation of the slope is controlled by weak structural p lanes in weathered and off - loaded rock mass. The deformation and failure mode is block failure by combination relations of structural p lanes. The future deformation characters are simulated with 3DEC. The monitored data shows that the stability of the superficial and the manipulative block is low. The whole slope could fail.
The geological condition of a high and steep slope is comp lex. Itsweak structural p laneswell develop. The excavated height and ratio are high. The excavated faces are many for the sake of the space of the deformation. There are many failure evidences at the slope. On the basis of geological condition investigation, the rock mass structure and the affected factors of the slope are studied. It indicates that the deformation of the slope is controlled by weak structural p lanes in weathered and off - loaded rock mass. The deformation and failure mode is block failure by combination relations of structural p lanes. The future deformation characters are simulated with 3DEC. The monitored data shows that the stability of the superficial and the manipulative block is low. The whole slope could fail.
2008, 16(5): 598-604.
There aremany outw ash deposits distributed in the m iddle- e levation area of them idd le reaches of the Dadu river. Ow ing to the dense structure o f the outw ash deposits, and the detritus is cemented in some deg rees sometimes. So the deform ation and fa iluremechan ism o f the outw ash deposits under scour ing o f riverw ater flow are different from those of other deposits. This paper invest igates the outw ash deposits on a reservo ir bank and tests them. A conclusion is obtained that the outw ash deposits should be classified as m ixture so il w ith coarse granule and g iant granule. The granules w ere tabled densely, and the ou tw ash deposit intensity is higher than o ther depos its. B ased on the findings, a detailed study is g iven on the deform ation and fa ilure mechan ism of the outw ash de posits under act ion o f riverw ater flow by them eans of geo log ica l process analysis and numerical simulat ion analysis. It is figured out that the outw ash deposits shou ld be fa iled like eroding- co llapsing under riverw ater action.
There aremany outw ash deposits distributed in the m iddle- e levation area of them idd le reaches of the Dadu river. Ow ing to the dense structure o f the outw ash deposits, and the detritus is cemented in some deg rees sometimes. So the deform ation and fa iluremechan ism o f the outw ash deposits under scour ing o f riverw ater flow are different from those of other deposits. This paper invest igates the outw ash deposits on a reservo ir bank and tests them. A conclusion is obtained that the outw ash deposits should be classified as m ixture so il w ith coarse granule and g iant granule. The granules w ere tabled densely, and the ou tw ash deposit intensity is higher than o ther depos its. B ased on the findings, a detailed study is g iven on the deform ation and fa ilure mechan ism of the outw ash de posits under act ion o f riverw ater flow by them eans of geo log ica l process analysis and numerical simulat ion analysis. It is figured out that the outw ash deposits shou ld be fa iled like eroding- co llapsing under riverw ater action.
2008, 16(5): 605-610.
Soilmodel parameters are critical in assuring reliability of numerical results of commonly used finite elementmethod for simulating deformation of supporting structure for deep foundation p it. The Duncan - Chang E- model, a nonlinear elastic modelwidely used in the geotechnical engineering, is chosen in this paper. A retaining structure with double - row p iles is used as an examp le for the sensibility analyses. The results show that the main parameters influencing the deformation of supporting structure are k、G、Rf and . The increase of G、Rf or n can result in an increase in the disp lacement and the increase of k can result in the decrease of the disp lacement. On the whole, the sensibility of the Duncan - ChangModel Parameters to the disp lacement is greater than the sensibility to the moment in the structure.
Soilmodel parameters are critical in assuring reliability of numerical results of commonly used finite elementmethod for simulating deformation of supporting structure for deep foundation p it. The Duncan - Chang E- model, a nonlinear elastic modelwidely used in the geotechnical engineering, is chosen in this paper. A retaining structure with double - row p iles is used as an examp le for the sensibility analyses. The results show that the main parameters influencing the deformation of supporting structure are k、G、Rf and . The increase of G、Rf or n can result in an increase in the disp lacement and the increase of k can result in the decrease of the disp lacement. On the whole, the sensibility of the Duncan - ChangModel Parameters to the disp lacement is greater than the sensibility to the moment in the structure.
2008, 16(5): 611-615.
Th is paper is to study the selection of rat iona l slope rat io and slope deformat ionmechanism in loose de posits, w hich is the basis o f slope stability evaluat ion and supporting design. A m an- made slope comprising loose deposits in Southw estCh ina is taken as an example. B ased on study on the characteristics o f loose deposits, rationa l slope ratio is def ined according to the terrain. Tw o- dimensional fin ite e lementmethod is used to study deformation mechanism of the cut slope and to determ ine potent ial slide surface. A t las,t the suppo rt ing m easures are put for w ard according to the slope stability ana lysis. The slope has loose deposits of 70m in th ickness comprising a lluvia,l pro luv ia,l and debris f low deposits. The slope ratio is designed as 1: 0. 75 because the eng ineering flat is located at the low er part o f the slow slope, whose upper part is steeper. The resu lt of numerica l simu lation indicates that the cut slope area and the slope crest area generate tension stresses. The max imum shear stress concentrates at the low er part o f the slope, w h ich result in tension cracks at the slope top and shearing deformation at low er part o f the slope. W hen the shear ing deformation develops upw ards to the tension cracks, the slopew ou ld show an overa ll in stability. A ccording to the mechan ism analysis and result of slope stab ility evaluat ion, a synthetical supporting measure is pu t forw ard to con form the stab ility of the slope during ex cavation and operation periods. Them easure includes anchoring p ile, anchor cable fram e, anchor bo lt fram e, and dra inage.
Th is paper is to study the selection of rat iona l slope rat io and slope deformat ionmechanism in loose de posits, w hich is the basis o f slope stability evaluat ion and supporting design. A m an- made slope comprising loose deposits in Southw estCh ina is taken as an example. B ased on study on the characteristics o f loose deposits, rationa l slope ratio is def ined according to the terrain. Tw o- dimensional fin ite e lementmethod is used to study deformation mechanism of the cut slope and to determ ine potent ial slide surface. A t las,t the suppo rt ing m easures are put for w ard according to the slope stability ana lysis. The slope has loose deposits of 70m in th ickness comprising a lluvia,l pro luv ia,l and debris f low deposits. The slope ratio is designed as 1: 0. 75 because the eng ineering flat is located at the low er part o f the slow slope, whose upper part is steeper. The resu lt of numerica l simu lation indicates that the cut slope area and the slope crest area generate tension stresses. The max imum shear stress concentrates at the low er part o f the slope, w h ich result in tension cracks at the slope top and shearing deformation at low er part o f the slope. W hen the shear ing deformation develops upw ards to the tension cracks, the slopew ou ld show an overa ll in stability. A ccording to the mechan ism analysis and result of slope stab ility evaluat ion, a synthetical supporting measure is pu t forw ard to con form the stab ility of the slope during ex cavation and operation periods. Them easure includes anchoring p ile, anchor cable fram e, anchor bo lt fram e, and dra inage.
2008, 16(5): 616-619.
The exploration adits w all stress f ie ld o f one eng ineer ing slope w as system ically tested, adopting the stress restoringmethod w ith simplicity, exped it iousness and economy. Accord ing to test resu l,t the slope stress fie ld w as back- analyzed by FLAC2D. The resu lt ind icated that the slope stress field had dist inct zonation in depth. The curve of stress magn itude in depth had typical hump character istic, w hich corresponds to the theoretical analysis. The outcome is of sign ificance to exam ine the deformation, crack ing and re lie f o f the slope.
The exploration adits w all stress f ie ld o f one eng ineer ing slope w as system ically tested, adopting the stress restoringmethod w ith simplicity, exped it iousness and economy. Accord ing to test resu l,t the slope stress fie ld w as back- analyzed by FLAC2D. The resu lt ind icated that the slope stress field had dist inct zonation in depth. The curve of stress magn itude in depth had typical hump character istic, w hich corresponds to the theoretical analysis. The outcome is of sign ificance to exam ine the deformation, crack ing and re lie f o f the slope.
2008, 16(5): 620-624.
This paper relies on geotechn ical engineering investigat ion of high loess embankment slope in the oilfield site northw estern of China. It is based on the analysis o f eng ineering geo log ical cond itions and deformation character istics. It stud ies the slope deform ation and failuremechan ism. A three- dimension geo log icalmodel is es tablished to analyze the distribution of stress and stra in of the loess f ill slope. The FLAC3D so ftw are is used to simu late the deform ationm echan ism o f the slope. The numerica l resu lt ind icates that them ain transform and fa il zone beg in from abrupt hole surroundings and follow s face o f slope to get dow n a 20- 25 meter. The bottom interface is the surface o f contact betw een theHo loceneE poch f ill earth storey Q4 and the orig ina l loessQ3. The numerica l re su lt further ind icates that the slope has adequate stab ility aga inst landslide. Any large deformation and fa ilure o f the slope is found to be impossib le.
This paper relies on geotechn ical engineering investigat ion of high loess embankment slope in the oilfield site northw estern of China. It is based on the analysis o f eng ineering geo log ical cond itions and deformation character istics. It stud ies the slope deform ation and failuremechan ism. A three- dimension geo log icalmodel is es tablished to analyze the distribution of stress and stra in of the loess f ill slope. The FLAC3D so ftw are is used to simu late the deform ationm echan ism o f the slope. The numerica l resu lt ind icates that them ain transform and fa il zone beg in from abrupt hole surroundings and follow s face o f slope to get dow n a 20- 25 meter. The bottom interface is the surface o f contact betw een theHo loceneE poch f ill earth storey Q4 and the orig ina l loessQ3. The numerica l re su lt further ind icates that the slope has adequate stab ility aga inst landslide. Any large deformation and fa ilure o f the slope is found to be impossib le.
2008, 16(5): 625-629.
Researchers in eng ineer ing geo logy and geomorpho logy alw ays pay close attention to the rock w eathering rate. Howver, it is diff icult to f ind the quantitat ive results o f rock w eathering rates because they are ex treme ly low under the natural env ironmen.t Th is paper stud ies the relativew ea thering rate o f tu ff b locks form ing the ancient c ity w a ll of Quzhou. The w eather ing th ickness contrasts betw een the tuff b locks and the adjacent quartz sand b lock are used to ca lculate the tuffw eather ing rate on the basis o f the quartz sand block. It is found tha t from the construction time inM ing Dynasty to presen,t the tuff b lock has an averaged w eathering rate of 0. 086mm per year.
Researchers in eng ineer ing geo logy and geomorpho logy alw ays pay close attention to the rock w eathering rate. Howver, it is diff icult to f ind the quantitat ive results o f rock w eathering rates because they are ex treme ly low under the natural env ironmen.t Th is paper stud ies the relativew ea thering rate o f tu ff b locks form ing the ancient c ity w a ll of Quzhou. The w eather ing th ickness contrasts betw een the tuff b locks and the adjacent quartz sand b lock are used to ca lculate the tuffw eather ing rate on the basis o f the quartz sand block. It is found tha t from the construction time inM ing Dynasty to presen,t the tuff b lock has an averaged w eathering rate of 0. 086mm per year.
2008, 16(5): 630-633.
The layer subsidence of hard c lay at deep depth in Shangh iai lags beh ind the w ater level change. It is necessary to study the permeability of the hard c lay. A series of tests on the clay permeability w as carried out in or der to settle some quest ions. These quest ions include initial hydraulic grad ien,t inf luence of hard agg lutinate to the permeab ility and re lation o f permeability to pressure and pore. The result show s that the seepage velocity keeps a linear relation to the hydrau lic grad ientw el,l abiding the Darcy law. The compact agglutinate has little influence on permeab ility. The permeability reduces w hile the stress increases and changes w ith pores fo llow ing the exponent ia l law. Base on the test resu lts, the permeab ility change o f the natura l hard clay during 1989- 2007 is estima ted. The boundary w ater level dropped almost 30 meters. The hard layer subsidence caused the perm eab ility reduction but the average permeability change w as not so much.
The layer subsidence of hard c lay at deep depth in Shangh iai lags beh ind the w ater level change. It is necessary to study the permeability of the hard c lay. A series of tests on the clay permeability w as carried out in or der to settle some quest ions. These quest ions include initial hydraulic grad ien,t inf luence of hard agg lutinate to the permeab ility and re lation o f permeability to pressure and pore. The result show s that the seepage velocity keeps a linear relation to the hydrau lic grad ientw el,l abiding the Darcy law. The compact agglutinate has little influence on permeab ility. The permeability reduces w hile the stress increases and changes w ith pores fo llow ing the exponent ia l law. Base on the test resu lts, the permeab ility change o f the natura l hard clay during 1989- 2007 is estima ted. The boundary w ater level dropped almost 30 meters. The hard layer subsidence caused the perm eab ility reduction but the average permeability change w as not so much.
2008, 16(5): 634-638.
Th is paper stud ies the expansive behav iour o f a new k ind o f expansive rock - brecc iatedm arl and fac to rs that influences the behaviour. A fter th is kind of rock is disturbed, the rock can absorb w ater and occur expan sion. It can br ing its' structure de fo rmation and damage even. The expensive force index is studied in the ba lancepressure method and the fu ll inflat ionmethod w ith GDG h igh pressure instrumen.t The rock samp le is laterally con fined. The paper po ints out the reason that the index of the full inf la tionm ethod is bigger than that o f the balance method. It stud ies the expansion law s and factors that influences expensive deformation w hen ample fu lw ater is sup plied to the brecciatedmarl in lateral restra int free expansion tes.t The rock samp le comes from Ta ihangshan tunne l of ShiTai Railw ay. The test result tells us that brecc iated marl is d ifferent from the o ther norm al expansive rocks. The ax ia l de fo rmation ratio increases as the rock w ater content ratio increases and reduces as the rock density in creases.
Th is paper stud ies the expansive behav iour o f a new k ind o f expansive rock - brecc iatedm arl and fac to rs that influences the behaviour. A fter th is kind of rock is disturbed, the rock can absorb w ater and occur expan sion. It can br ing its' structure de fo rmation and damage even. The expensive force index is studied in the ba lancepressure method and the fu ll inflat ionmethod w ith GDG h igh pressure instrumen.t The rock samp le is laterally con fined. The paper po ints out the reason that the index of the full inf la tionm ethod is bigger than that o f the balance method. It stud ies the expansion law s and factors that influences expensive deformation w hen ample fu lw ater is sup plied to the brecciatedmarl in lateral restra int free expansion tes.t The rock samp le comes from Ta ihangshan tunne l of ShiTai Railw ay. The test result tells us that brecc iated marl is d ifferent from the o ther norm al expansive rocks. The ax ia l de fo rmation ratio increases as the rock w ater content ratio increases and reduces as the rock density in creases.
2008, 16(5): 639-644.
The 4# mine goaf in GuangxiBeishan mining Co. L td. is large and irregular in the form. The geological structure of surrounding rocks at the goaf is the anticline structure of Shangfu - Kenyue and the fracture of Indo - Chinese epoch and stage of Yanshan. Besides above structure character of the surrounding rocks, The paper further p resents the rock strata boundary and alteration of the marl and reef limestone in the goaf, aswell as the rock physi2 cal and mechanical indexes. Therefore, the paper classifies three engineering geology group s of rock mass. They are marlite, dolomite and reef limestone. The detailed field investigation of surrounding rockswas carried out by the methods of scan line and bulk density to show the comp rehensive condition of rock engineering geology. Based on the field investigation result, the geometrical parameters for the distribution ofmine goaf structural p laneswere ob2 tained using the cluster analysis. Characteristics of geometrical parameters p robabilitywas obtained about the struc2 tures p lanes. The normal distribution function model wasworked out. The 52and 300dip directions of the two p rimary dominant structure p lanes and the 75dip angle of the p rimary dominant structure p lanes. The results show that thismathematicalmodel can effectively stimulate the joint and fissure distribution in the 4# mine goaf.
The 4# mine goaf in GuangxiBeishan mining Co. L td. is large and irregular in the form. The geological structure of surrounding rocks at the goaf is the anticline structure of Shangfu - Kenyue and the fracture of Indo - Chinese epoch and stage of Yanshan. Besides above structure character of the surrounding rocks, The paper further p resents the rock strata boundary and alteration of the marl and reef limestone in the goaf, aswell as the rock physi2 cal and mechanical indexes. Therefore, the paper classifies three engineering geology group s of rock mass. They are marlite, dolomite and reef limestone. The detailed field investigation of surrounding rockswas carried out by the methods of scan line and bulk density to show the comp rehensive condition of rock engineering geology. Based on the field investigation result, the geometrical parameters for the distribution ofmine goaf structural p laneswere ob2 tained using the cluster analysis. Characteristics of geometrical parameters p robabilitywas obtained about the struc2 tures p lanes. The normal distribution function model wasworked out. The 52and 300dip directions of the two p rimary dominant structure p lanes and the 75dip angle of the p rimary dominant structure p lanes. The results show that thismathematicalmodel can effectively stimulate the joint and fissure distribution in the 4# mine goaf.
2008, 16(5): 645-650.
Th is paper is based on the characters o f soft clayey soils and observed sett lem ent data of one highw ay in L ianyungang area. It ana lyses the affecting factors of the in- data accumu lated sett lement through sing le factor a nalysism ethod andmu ltifactor ana lysis method. It takes in to considerat ion of the fine settlement and conso lidation effec.t Pseu- orthogonal design me thod is put forw ard, and is used in the actual pro jec.t The resu lts conc lude: preloading method and the height of filled so ilhave reasonab le affects to composite foundat ion settlement in th is pro ject on th is seaside clay area. A s a resu l,t it is suggested that ad just pre load ing method and control the he ight o f filled so il at f irst in the area where the range of thickness of soft c layey is sma l.l
Th is paper is based on the characters o f soft clayey soils and observed sett lem ent data of one highw ay in L ianyungang area. It ana lyses the affecting factors of the in- data accumu lated sett lement through sing le factor a nalysism ethod andmu ltifactor ana lysis method. It takes in to considerat ion of the fine settlement and conso lidation effec.t Pseu- orthogonal design me thod is put forw ard, and is used in the actual pro jec.t The resu lts conc lude: preloading method and the height of filled so ilhave reasonab le affects to composite foundat ion settlement in th is pro ject on th is seaside clay area. A s a resu l,t it is suggested that ad just pre load ing method and control the he ight o f filled so il at f irst in the area where the range of thickness of soft c layey is sma l.l
2008, 16(5): 651-656.
The especia lly big w ater invasion event occurred on September 11, 2006 in N anjing gypsum m ine. It changed the g roundw ater flow field of them in ing area and surround ing influenced area, and resulted in ground set t lement and ground fissures over the m in ing space and periphery zone, and led to surface structure destroyed such as road, houses, and w orkshops, and caused tremendous econom ic losing inc lud ing m ine c losed up. The N anjing gypsum m ine is a typical underground deep m ine w ith geo log ica l eng ineering issues. The main factors influencing the underg round m ining stab ility, m ine hazard, and geo- env ironm ental problems are rock mass properties and the ir structures, wh ich are especia lly as faults, jo ints or fissures etc. , the ir sa le, mechanics and spatia,l and wa ter abundance and conductiv ity. The intensive karst w ater abundance zones ex ist in the rock layer above the ore bed and in its south, wh ich are the d irect w ater invasion source. The soft rock ( ore ) properties, together w ith deep m ining, m ining d isturbance to the orig ina l stress fie ld surround ing the m in ing space, the de format ion activa tion o f the ex isting fau lts or jo ints or fissures, provides thew ater invasion hazard conditions.
The especia lly big w ater invasion event occurred on September 11, 2006 in N anjing gypsum m ine. It changed the g roundw ater flow field of them in ing area and surround ing influenced area, and resulted in ground set t lement and ground fissures over the m in ing space and periphery zone, and led to surface structure destroyed such as road, houses, and w orkshops, and caused tremendous econom ic losing inc lud ing m ine c losed up. The N anjing gypsum m ine is a typical underground deep m ine w ith geo log ica l eng ineering issues. The main factors influencing the underg round m ining stab ility, m ine hazard, and geo- env ironm ental problems are rock mass properties and the ir structures, wh ich are especia lly as faults, jo ints or fissures etc. , the ir sa le, mechanics and spatia,l and wa ter abundance and conductiv ity. The intensive karst w ater abundance zones ex ist in the rock layer above the ore bed and in its south, wh ich are the d irect w ater invasion source. The soft rock ( ore ) properties, together w ith deep m ining, m ining d isturbance to the orig ina l stress fie ld surround ing the m in ing space, the de format ion activa tion o f the ex isting fau lts or jo ints or fissures, provides thew ater invasion hazard conditions.
2008, 16(5): 657-662.
Soil has very high compressive strength and elast ic eng ineering geo log ical character in freeze state. But w ith the e levation of the ground temperature, the tw o characters can w eaken quick ly and performance slow ly change. The change can lead to the intensity reduc ing and destroying o f the bu ild ing base. Perm afrost in D aX ing ganM ountains possess c ircumpo lar lat itude and low a lt itude characterist ics. Th is paper bu ilds on that base founda t ion analyses permafrost distribution characteristic and eng ineering geo log ical characteristics evaluat ion o f permafrost in D a h ingganmountains. It exam ines the cases of destroy ing building base because of frost heav ing and thaw sett le ment. The paper puts forw ard the idea andmake use o f therm al pipe to reduce so il temperature for ensuring stab ili zation in perm afrost and reduc ing destabilizing due to w ater destroy ing bu ilding base.
Soil has very high compressive strength and elast ic eng ineering geo log ical character in freeze state. But w ith the e levation of the ground temperature, the tw o characters can w eaken quick ly and performance slow ly change. The change can lead to the intensity reduc ing and destroying o f the bu ild ing base. Perm afrost in D aX ing ganM ountains possess c ircumpo lar lat itude and low a lt itude characterist ics. Th is paper bu ilds on that base founda t ion analyses permafrost distribution characteristic and eng ineering geo log ical characteristics evaluat ion o f permafrost in D a h ingganmountains. It exam ines the cases of destroy ing building base because of frost heav ing and thaw sett le ment. The paper puts forw ard the idea andmake use o f therm al pipe to reduce so il temperature for ensuring stab ili zation in perm afrost and reduc ing destabilizing due to w ater destroy ing bu ilding base.
2008, 16(5): 663-666.
Rock mass volumetric joint count is one of the most important indexes to evaluate the integrity of rock mass. In - situ measurementmethodsmainly include directmeasurementmethod, spacingmethod, and joint num2 bermethod. All of these measurement methods, p rincip les and their respective disadvantages are analyzed in the paper. Combined with p ractical examp les, it is believed that directmeasurementmethod is relatively accurate, but it requires adequate measurement area that is as large as possible. Data coming from spacing method are slightly low, so it has to be multip lied by correction factor of 1. 05～1. 1; Joint numbermethod is strongly influenced by the azimuth of the surveyed surface. In app lication, it requires enough samp les. Their average value is used as the car2 dinal number. It has to be multip lied by experience correction factor of 1. 4～1. 7.
Rock mass volumetric joint count is one of the most important indexes to evaluate the integrity of rock mass. In - situ measurementmethodsmainly include directmeasurementmethod, spacingmethod, and joint num2 bermethod. All of these measurement methods, p rincip les and their respective disadvantages are analyzed in the paper. Combined with p ractical examp les, it is believed that directmeasurementmethod is relatively accurate, but it requires adequate measurement area that is as large as possible. Data coming from spacing method are slightly low, so it has to be multip lied by correction factor of 1. 05～1. 1; Joint numbermethod is strongly influenced by the azimuth of the surveyed surface. In app lication, it requires enough samp les. Their average value is used as the car2 dinal number. It has to be multip lied by experience correction factor of 1. 4～1. 7.
2008, 16(5): 667-671.
Thew eathered co lumnar strom atolites are w ide ly d istributed in the study area and have a strong rock streng th and the reg ional variability. The rock strength is the important factor for slope stability. E va luation of slope stability needs to analyze the field test data as stochastic variab le to obtain the reliable ind icators of rock strength. Th is paper bases on the statistica l analysis of the po int load test data of medium w eathered co lumnar stromato lites limestone in study area and uses the fitt ing of probab ility density function w ith the x 2 check m ethod. It draw s the conc lusion that probab ility d istribut ion fo rm of the rock streng th. The compressive strength and tensile strength are subject to the lognormal d istribution. This result is further combined w ith the fitt ing results o f the streng th o f sim ilar rock lithology. A a resu l,t th is paper estab lishes the probab ility d istribution function for po int load test strength o f medium w eathered co lumnar strom ato lites limestone in the study area. The limestone po int load strength w as de duced w ith Bayes estimat ion. The predict ive value of rock strength is obtained. The re lative error is less and sam pling confidence is over 70%. The tensile streng th w as 2. 29MPa, the compressive strength w as 72. 42MPa. The method for the rock streng th w as est imated to be effective, the va lues obtained w ith the method had the important practical significance to eva luate slope stab ility andmanage the slope.
Thew eathered co lumnar strom atolites are w ide ly d istributed in the study area and have a strong rock streng th and the reg ional variability. The rock strength is the important factor for slope stability. E va luation of slope stability needs to analyze the field test data as stochastic variab le to obtain the reliable ind icators of rock strength. Th is paper bases on the statistica l analysis of the po int load test data of medium w eathered co lumnar stromato lites limestone in study area and uses the fitt ing of probab ility density function w ith the x 2 check m ethod. It draw s the conc lusion that probab ility d istribut ion fo rm of the rock streng th. The compressive strength and tensile strength are subject to the lognormal d istribution. This result is further combined w ith the fitt ing results o f the streng th o f sim ilar rock lithology. A a resu l,t th is paper estab lishes the probab ility d istribution function for po int load test strength o f medium w eathered co lumnar strom ato lites limestone in the study area. The limestone po int load strength w as de duced w ith Bayes estimat ion. The predict ive value of rock strength is obtained. The re lative error is less and sam pling confidence is over 70%. The tensile streng th w as 2. 29MPa, the compressive strength w as 72. 42MPa. The method for the rock streng th w as est imated to be effective, the va lues obtained w ith the method had the important practical significance to eva luate slope stab ility andmanage the slope.
2008, 16(5): 677-682.
M any cut slopes w ere formed on w estern section of the Changde- Jishou Expressw ay inH unan prov ince, where the topograph ica l and geo log ica l conditions are complex. Stab ility issues of the cut slopes are outstand ing. Based on a deta iled geo log ical survey, this paper presents the structure classificat ion o f the cut slopes accord ing to the relat ionship betw een rock mass occurrence and slope dip direction. The relationsh ip betw een deformation and failure mechan ism and its composit ion, rock structure and w ea thering extent is studied in detai.l The paper fur ther identif ies the deformation and fa iluremodes o f the cut slopes. It suggests the safe tymeasures corresponding to different slope types and failuremodes. The suggestionsw ere ut ilized and achieved exce llent resu lts.
M any cut slopes w ere formed on w estern section of the Changde- Jishou Expressw ay inH unan prov ince, where the topograph ica l and geo log ica l conditions are complex. Stab ility issues of the cut slopes are outstand ing. Based on a deta iled geo log ical survey, this paper presents the structure classificat ion o f the cut slopes accord ing to the relat ionship betw een rock mass occurrence and slope dip direction. The relationsh ip betw een deformation and failure mechan ism and its composit ion, rock structure and w ea thering extent is studied in detai.l The paper fur ther identif ies the deformation and fa iluremodes o f the cut slopes. It suggests the safe tymeasures corresponding to different slope types and failuremodes. The suggestionsw ere ut ilized and achieved exce llent resu lts.
2008, 16(5): 683-687.
Ankang C ity and the surrounding areas adjacent to Xunyang Hydropow er S tation reservo ir ta il zone lo ca te on the terrace and the h igh- and low floodpla in of the left bank of the H anjiang R iver. The ground has the typ ical dua listic- structure characteristics. The surface layer of the h igh floodp la in genera lly d istributes relatively th ick artif icial fil.l The bond w ater dynam ic theory and the infiltration flow characteristics of the clay so il are ap plied to de term ine the re lations among the pressurew ater level and the aqu ifer belt of clay layerw ater leve.l In th is research, different submergence cr itical depths are defined by foundation types, depths of bur ia,l fill layer th ick ness of different buildings and the type o f crops of suburbs, etc. the paper calcu lates the g roundw ater Backwa ter V alue and the burial depth o f clay layerw ater- bearing zone in seven d ifferent normal impounded level cond itions to investigate the submergence area and degree. A s a resul,t a reasonable norma l impounded level is determ ined ul t imate ly. Th is result can prov ide a re liab le geological basis for them igration resettlementw ork of th is pro ject reser vo ir area.
Ankang C ity and the surrounding areas adjacent to Xunyang Hydropow er S tation reservo ir ta il zone lo ca te on the terrace and the h igh- and low floodpla in of the left bank of the H anjiang R iver. The ground has the typ ical dua listic- structure characteristics. The surface layer of the h igh floodp la in genera lly d istributes relatively th ick artif icial fil.l The bond w ater dynam ic theory and the infiltration flow characteristics of the clay so il are ap plied to de term ine the re lations among the pressurew ater level and the aqu ifer belt of clay layerw ater leve.l In th is research, different submergence cr itical depths are defined by foundation types, depths of bur ia,l fill layer th ick ness of different buildings and the type o f crops of suburbs, etc. the paper calcu lates the g roundw ater Backwa ter V alue and the burial depth o f clay layerw ater- bearing zone in seven d ifferent normal impounded level cond itions to investigate the submergence area and degree. A s a resul,t a reasonable norma l impounded level is determ ined ul t imate ly. Th is result can prov ide a re liab le geological basis for them igration resettlementw ork of th is pro ject reser vo ir area.
2008, 16(5): 688-693.
D rastically in fluenced by hum an activ ities, the w ater qua lity of theM iddle Lake of X iamen Island has been seriously polluted. In order to allev iate w ater pollution of the lake, a projectw as planned. It is the sea wa ter diversion pro ject from w est to eas.t The pro ject w ill change groundw ater environm en.t The most important the im pact in on the g round w ater environm ent o f the who le island. W ill the pro ject improvew ater qua lityw ithout causing ex tra prob lem s? W ill it decrease sea w ater invasion, groundw ater- seaw ater interaction, and nutriment reciproca t ion betw een freshw ater bodies and seaw ater as w el?l By adopting the F in ite E lementMethod, a conceptualmode l is set up to ana lyze groundw ater flow and sea w ater transportation w ith a mathem atica lmode.l The conclusions are ( 1) in annual average precip itation years, the sea w ater invasion w ill persist in one year after the pro ject is fin ished, and ( 2) seaw ater levelw ill be c lose to adjacent place on the lakeside. Consequently, theremay be, in low w ater years, reverse supply o f seaw ater to lake w ater through g roundw ater f low, w hich w ill cause salinity rise, w a ter quality decline, and deterio ration of drink ing w ater sources o f som e areas
D rastically in fluenced by hum an activ ities, the w ater qua lity of theM iddle Lake of X iamen Island has been seriously polluted. In order to allev iate w ater pollution of the lake, a projectw as planned. It is the sea wa ter diversion pro ject from w est to eas.t The pro ject w ill change groundw ater environm en.t The most important the im pact in on the g round w ater environm ent o f the who le island. W ill the pro ject improvew ater qua lityw ithout causing ex tra prob lem s? W ill it decrease sea w ater invasion, groundw ater- seaw ater interaction, and nutriment reciproca t ion betw een freshw ater bodies and seaw ater as w el?l By adopting the F in ite E lementMethod, a conceptualmode l is set up to ana lyze groundw ater flow and sea w ater transportation w ith a mathem atica lmode.l The conclusions are ( 1) in annual average precip itation years, the sea w ater invasion w ill persist in one year after the pro ject is fin ished, and ( 2) seaw ater levelw ill be c lose to adjacent place on the lakeside. Consequently, theremay be, in low w ater years, reverse supply o f seaw ater to lake w ater through g roundw ater f low, w hich w ill cause salinity rise, w a ter quality decline, and deterio ration of drink ing w ater sources o f som e areas
2008, 16(5): 694-698.
The landslide thrust is the important evidence for the designed thrust of anti - slide p ile. It is often cal2 culated with the residual thrustmethod. On the basis of residual thrustmethod, a new method to find the designed thrust of anti - slide p ile is p roposed for an accurate and reasonable result. On the condition of limit equilibrium state and safety requirement, the residual thrust is calculated and reasonable p ile position is determined to make it locate the anti - slide segment of landslide. Residual thrust of landslide lies behind the p ile is adjusted to ensure not only that adjustment quantity can meet safety requirement, but also it can be modify on the basis of the designed thrust of anti - slide p ile. All of this consideration is realized with p rocedure. The method is verified with exam2 p les. It also p rovides reference function for reasonable value of the designed thrust of anti - slide p iles in the future.
The landslide thrust is the important evidence for the designed thrust of anti - slide p ile. It is often cal2 culated with the residual thrustmethod. On the basis of residual thrustmethod, a new method to find the designed thrust of anti - slide p ile is p roposed for an accurate and reasonable result. On the condition of limit equilibrium state and safety requirement, the residual thrust is calculated and reasonable p ile position is determined to make it locate the anti - slide segment of landslide. Residual thrust of landslide lies behind the p ile is adjusted to ensure not only that adjustment quantity can meet safety requirement, but also it can be modify on the basis of the designed thrust of anti - slide p ile. All of this consideration is realized with p rocedure. The method is verified with exam2 p les. It also p rovides reference function for reasonable value of the designed thrust of anti - slide p iles in the future.
2008, 16(5): 699-702.
Digitalmodeling of comp lex three - dimensional geological body is always a difficulty in p re - p rocessing of FLAC3D. Therefore, a new modelingmethod is put forward in this paper. The three - dimensional geological information of ground surface and strata interfaces are extracted and transformed in the Surfer software. Using Surfer as a transitional p latform, the information can be exported from Surfer and then is retransformed by p rogram made by Fish language embedded in FLAC3D. According to above p rocess, the model data for FLAC3D is generated and comp lex three - dimensional geologicalmodel can be created quickly and accurately in p re - p rocessing of FLAC3D. The feasibility and simulating effect of the method is verified by combining p ractical p roject. The result shows that the modeling method is simp le, p ractical and with bettermaneuverability. Thereby the method is a new, good approach in pre - processing of FLAC3D.
Digitalmodeling of comp lex three - dimensional geological body is always a difficulty in p re - p rocessing of FLAC3D. Therefore, a new modelingmethod is put forward in this paper. The three - dimensional geological information of ground surface and strata interfaces are extracted and transformed in the Surfer software. Using Surfer as a transitional p latform, the information can be exported from Surfer and then is retransformed by p rogram made by Fish language embedded in FLAC3D. According to above p rocess, the model data for FLAC3D is generated and comp lex three - dimensional geologicalmodel can be created quickly and accurately in p re - p rocessing of FLAC3D. The feasibility and simulating effect of the method is verified by combining p ractical p roject. The result shows that the modeling method is simp le, p ractical and with bettermaneuverability. Thereby the method is a new, good approach in pre - processing of FLAC3D.
2008, 16(5): 703-709.
Reverse Engineering, as a new discip line, has unique advantages in comp lex modeling. It has been widely used in many fields. This paper firstly uses the reverse engineering technique to build the refined modeling of a comp lex geological body. The established model is viewable and computable. As the universal finite element simulation system, such as ABAQUS, AD INA and ANSYS have a good function in mesh generation and have a good interface with many CAD /CAM software systems. Using the method, geometrical body ismeshed in FEM system, then the mesh can be translated into the format that can be received by FLAC3D. By this, the comp lex geology body can be built in FLAC3D , and the p re - p rocess shortage of FLAC3D can be overcame. For this purpose, an interface p rogram between AND INA and FLAC3D is developed, and the methods are expounded. Above techniques are used in an engineering p roject. The results are validated.
Reverse Engineering, as a new discip line, has unique advantages in comp lex modeling. It has been widely used in many fields. This paper firstly uses the reverse engineering technique to build the refined modeling of a comp lex geological body. The established model is viewable and computable. As the universal finite element simulation system, such as ABAQUS, AD INA and ANSYS have a good function in mesh generation and have a good interface with many CAD /CAM software systems. Using the method, geometrical body ismeshed in FEM system, then the mesh can be translated into the format that can be received by FLAC3D. By this, the comp lex geology body can be built in FLAC3D , and the p re - p rocess shortage of FLAC3D can be overcame. For this purpose, an interface p rogram between AND INA and FLAC3D is developed, and the methods are expounded. Above techniques are used in an engineering p roject. The results are validated.
2008, 16(5): 710-714.
The second subway line in Xian city crosses 10 ground fissures, and these ground fissureswill influence the safety of subway line. Using the three - dimensional ( 3D) distinct element code ( 3DEC) , a computational model is built. The effect of ground fissure dislocation on the shield p ipeline of running tunnel of subway is exam2 ined. The deformations and stresses under different dislocations of tunnel lining is obtained. The calculated results show that, If the dislocation is changed from 10 to 93 cm, the deformation will be changed from 0. 712 to 13. 99 cm, and the maximum deformation will occur at 35 to 36 m along longitudinal direction about 9. 5 to 8. 5 m distance to ground fissures. The maximum tensile stresswill be changed from 0. 65 to 18. 43Mpa, and the maximum com2 p ression stresswill be changed from 0. 611 to 16. 9MPa. The maximum deformation and stress zones are uniform. The findings can p rovide effective design parameters and scientific evidences for quantify the effect of ground fis2 sures dislocation on running tunnel of subway.
The second subway line in Xian city crosses 10 ground fissures, and these ground fissureswill influence the safety of subway line. Using the three - dimensional ( 3D) distinct element code ( 3DEC) , a computational model is built. The effect of ground fissure dislocation on the shield p ipeline of running tunnel of subway is exam2 ined. The deformations and stresses under different dislocations of tunnel lining is obtained. The calculated results show that, If the dislocation is changed from 10 to 93 cm, the deformation will be changed from 0. 712 to 13. 99 cm, and the maximum deformation will occur at 35 to 36 m along longitudinal direction about 9. 5 to 8. 5 m distance to ground fissures. The maximum tensile stresswill be changed from 0. 65 to 18. 43Mpa, and the maximum com2 p ression stresswill be changed from 0. 611 to 16. 9MPa. The maximum deformation and stress zones are uniform. The findings can p rovide effective design parameters and scientific evidences for quantify the effect of ground fis2 sures dislocation on running tunnel of subway.
2008, 16(5): 715-720.
urban ground subsidence is of nonlinear dynamic character and its quantity in time series is analyzed in this paper. Then it is assumed that there is chaos in the urban ground subsidence in time series. Based on this as2 sump tion and using the chaos neural network theory, a p rediction model of urban ground subsidence quantity was built with phase space reconstruction. The ground subsidence quantity in Gao - qiao analyzed and p redicted with thismode1. The observed data are compared with the p redicted data. The largest absolute p rediction error is 1. 7 and the average forecast error is 0. 0833. The results indicate that the chaos neural network theory is reasonable and accurate to p redict the urban ground subsidence.
urban ground subsidence is of nonlinear dynamic character and its quantity in time series is analyzed in this paper. Then it is assumed that there is chaos in the urban ground subsidence in time series. Based on this as2 sump tion and using the chaos neural network theory, a p rediction model of urban ground subsidence quantity was built with phase space reconstruction. The ground subsidence quantity in Gao - qiao analyzed and p redicted with thismode1. The observed data are compared with the p redicted data. The largest absolute p rediction error is 1. 7 and the average forecast error is 0. 0833. The results indicate that the chaos neural network theory is reasonable and accurate to p redict the urban ground subsidence.
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