巖體滲透結(jié)構(gòu)類(lèi)型及其滲透特征

巖體滲透結(jié)構(gòu)類(lèi)型及其滲透特征李清波閆長(zhǎng)斌（黃河勘測(cè)規(guī)劃設(shè)計(jì)有限公司，河南鄭州450001）摘要分析了控制巖體滲透特征的主要因素，提出了巖體滲透結(jié)構(gòu)類(lèi)型的劃分原則以及不同滲透結(jié)構(gòu)的宏觀滲透特征，并給出了工程實(shí)例，對(duì)水庫(kù)滲漏問(wèn)題評(píng)價(jià)及防滲、排水工程設(shè)計(jì)具有重要意義。關(guān)鍵詞裂隙巖體；滲透結(jié)構(gòu)類(lèi)型；滲透特征；防滲排水1引言在水利水電工程建設(shè)中，經(jīng)常遇到與巖體滲流相關(guān)的水文地質(zhì)問(wèn)題。由于巖體中通常發(fā)育有裂隙或溶蝕管道，受裂隙、溶蝕管道分布的方向性和不均勻性控制，地下水在巖體中的滲流狀態(tài)遠(yuǎn)較在土體中復(fù)雜，一般具有明顯的各向異性和不均一性。如對(duì)其認(rèn)識(shí)不足，則可能導(dǎo)致防滲、排水工程的低效甚至失誤。國(guó)內(nèi)外學(xué)者在裂隙巖體的滲透特性研究方面取得的成果?⑸表明，巖性、斷裂構(gòu)造、風(fēng)化卸荷作用及巖溶作用是控制巖體滲透結(jié)構(gòu)及其宏觀滲透特征的主要因素。谷德振先生⑺以地質(zhì)體結(jié)構(gòu)為基礎(chǔ)，將巖體劃分為不透水體、統(tǒng)一含水體、層狀含水體、脈狀含水體、管道含水體等水文地質(zhì)結(jié)構(gòu)類(lèi)型。孫廣忠先生⑻提出了以透水體（層）和隔水體（層）為基本單元?jiǎng)澐謳r體水力學(xué)結(jié)構(gòu)的概念，將透水體劃分為孔隙透水體（層）、裂隙透水體（層）和管道透水體三種類(lèi)型，將隔水體劃分為塊狀隔水體、夾層或帶狀隔水體、層狀隔水體三種類(lèi)型。萬(wàn)力［1］等研究了砂泥巖互層裂隙地層的滲透性特征，指出砂泥巖互層地層具有層狀、帶狀和殼狀三種滲透結(jié)構(gòu)。周志芳⑵等則提出了塊狀巖體的水文地質(zhì)結(jié)構(gòu)類(lèi)型劃分意見(jiàn)。本文在上述研究的基礎(chǔ)上，系統(tǒng)地提出了巖體滲透結(jié)構(gòu)類(lèi)型的劃分原則及各類(lèi)滲透結(jié)構(gòu)所具有的宏觀滲透特征，對(duì)水庫(kù)滲漏問(wèn)題評(píng)價(jià)及防滲、排水工程設(shè)計(jì)具有重要意義。2控制巖體滲透特征的主要因素一般情況下，完整巖塊的滲透性很小，多在10-7?10-6cm/s以下。相比之下，巖體的滲透性比巖塊大得多，二者相差可達(dá)幾個(gè)數(shù)量級(jí)。導(dǎo)致這種差異的主要原因，在于巖體中除包含各種尺度的巖塊外，還發(fā)育有不同成因類(lèi)型的裂隙或溶蝕管道（灰?guī)r中）。總體上看，巖體的滲透性大小及宏觀滲透特征主要受巖性、斷裂構(gòu)造、風(fēng)化卸荷作用及巖溶作用等因素控制。巖性對(duì)巖體滲透性的影響非常明顯。在裂隙巖體中，裂隙是地下水滲流的唯一通道，而裂隙的發(fā)育規(guī)律則嚴(yán)格受巖性控制。大量調(diào)查統(tǒng)計(jì)結(jié)果表明，脆性巖（如砂巖、石英巖等）中裂隙的發(fā)育程度一般遠(yuǎn)大于塑性巖（如粘土巖、頁(yè)巖等）中裂隙的發(fā)育程度。相應(yīng)地，脆性巖的滲透性一般也遠(yuǎn)大于塑性巖，構(gòu)成透（含）水層（體），塑性巖則多構(gòu)成相對(duì)隔水層（體）。斷裂構(gòu)造是影響裂隙發(fā)育的重要因素。一般說(shuō)來(lái)，在斷裂兩側(cè)常發(fā)育有裂隙密集帶，從而使斷裂影響區(qū)內(nèi)的巖體在平面和剖面上均表現(xiàn)為一個(gè)滲透性相對(duì)較強(qiáng)的帶狀區(qū)域。另一方面，較大規(guī)模的斷裂帶內(nèi)多發(fā)育有低滲透性的斷層泥等物質(zhì)，從而使斷裂帶在橫向上往往具有一定的阻（隔）水性。風(fēng)化卸荷作用對(duì)巖體滲透性也有比較明顯的影響。對(duì)花崗巖等侵入巖體而言，其全強(qiáng)風(fēng)化帶通常類(lèi)似于各向同性的孔隙介質(zhì)，弱、微風(fēng)化帶巖體的滲透性則有不同程度的增強(qiáng)；對(duì)脆性沉積巖及火山巖而言，其風(fēng)化卸荷帶內(nèi)巖體的滲透性一般會(huì)有明顯增加。巖溶發(fā)育程度對(duì)灰?guī)r等可溶巖類(lèi)的滲透特征具有突出的控制作用。巖溶不發(fā)育的灰?guī)r，其滲透特征與一般裂隙巖體相同；僅發(fā)育溶蝕裂隙的灰?guī)r，其滲透特征仍與一般裂隙巖體類(lèi)似，地下水運(yùn)動(dòng)以層流為主，但透水性和富水性有所增大；發(fā)育有溶蝕管道的灰?guī)r，透水性和富水性強(qiáng)，地下水運(yùn)動(dòng)狀態(tài)復(fù)雜。需要指出的是，到目前為止，人們?cè)诖蠖鄶?shù)實(shí)際工程中仍習(xí)慣于把裂隙巖體視為各向同性的孔隙介質(zhì)來(lái)處理，并通常采用常規(guī)的垂直鉆孔壓水試驗(yàn)獲取巖體的透水性指標(biāo)，進(jìn)而評(píng)價(jià)巖體的滲透特性以及庫(kù)水滲漏問(wèn)題。事實(shí)上，對(duì)高傾角裂隙發(fā)育的巖體來(lái)說(shuō)，由于垂直鉆孔揭露高傾角裂隙的幾率較小，巖體透水性試驗(yàn)結(jié)果往往比實(shí)際情況明顯偏低。小浪底工程對(duì)比試驗(yàn)表明，采用水平鉆孔壓水試驗(yàn)獲取的高傾角裂隙巖體的透水性指標(biāo)一般要比垂直鉆孔壓水試驗(yàn)所得指標(biāo)高出2?5倍。工作中如對(duì)此認(rèn)識(shí)不足，可能導(dǎo)致較大失誤。3巖體滲透結(jié)構(gòu)類(lèi)型及其滲透特征所謂巖體滲透結(jié)構(gòu)，是指透（含）水層（體）和相對(duì)隔水層（體）的空間分布及組合規(guī)律。合理劃分巖體滲透結(jié)構(gòu)類(lèi)型，有助于從宏觀上把握巖體的滲透特征，為巖體滲流計(jì)算及防滲、排水工程設(shè)計(jì)提供科學(xué)依據(jù)。巖體滲透結(jié)構(gòu)一般可劃分為5類(lèi)，即散體狀滲透結(jié)構(gòu)、層狀滲透結(jié)構(gòu)、帶狀滲透結(jié)構(gòu)、網(wǎng)絡(luò)狀滲透結(jié)構(gòu)、管道狀滲透結(jié)構(gòu)。3.1散體狀滲透結(jié)構(gòu)散體狀滲透結(jié)構(gòu)主要由侵入巖類(lèi)全強(qiáng)風(fēng)化帶巖體構(gòu)成。其滲透介質(zhì)類(lèi)型以孔隙介質(zhì)為主，具均質(zhì)各向同性滲透特征，透水性一般相對(duì)較強(qiáng)。3.2層狀滲透結(jié)構(gòu)層狀滲透結(jié)構(gòu)主要由透水層與相對(duì)隔水層互層的緩傾巖層、平緩的多層結(jié)構(gòu)的噴出巖以及平緩的斷層破碎巖等構(gòu)成。其滲透介質(zhì)類(lèi)型以裂隙介質(zhì)為主，地下水主要賦存、運(yùn)移于各透水層中，其補(bǔ)、徑、排嚴(yán)格受透水層上下的相對(duì)隔水層控制，常具多層水位。宏觀上看，順層方向滲透性遠(yuǎn)大于垂層方向滲透性，具有明顯的各向異性滲透特征。3.3帶狀滲透結(jié)構(gòu)帶狀滲透結(jié)構(gòu)主要由產(chǎn)狀較陡的斷層破碎帶、裂隙密集帶、巖脈裂隙帶以及透水層與相對(duì)隔水層互層的陡傾巖層、河谷岸邊強(qiáng)卸荷帶等構(gòu)成。其滲透介質(zhì)類(lèi)型以裂隙介質(zhì)為主，透水性一般較強(qiáng)，多與層狀、網(wǎng)絡(luò)狀等滲透結(jié)構(gòu)相通，構(gòu)成地下水集中滲漏通道，亦可構(gòu)成不同透水層地下水間的水力聯(lián)系通道。宏觀上看，順帶方向滲透性明顯大于垂帶方向滲透性，具有明顯的各向異性滲透特征。3.4網(wǎng)絡(luò)狀滲透結(jié)構(gòu)網(wǎng)絡(luò)狀滲透結(jié)構(gòu)主要由弱風(fēng)化?新鮮的塊狀巖體及巖性單一、裂隙（包括溶蝕裂隙）較發(fā)育的沉積巖等構(gòu)成。其滲透介質(zhì)類(lèi)型為裂隙介質(zhì)，透水性一般較差，地下水運(yùn)動(dòng)主要受裂隙網(wǎng)絡(luò)發(fā)育特征及其滲透性控制，具有明顯的非均質(zhì)各向異性滲透特征。賦存于同一巖層中的裂隙水不一定具有統(tǒng)一的地下水位。3.5管道狀滲透結(jié)構(gòu)管道狀滲透結(jié)構(gòu)主要由溶蝕洞穴、管道發(fā)育的灰?guī)r構(gòu)成。其滲透介質(zhì)類(lèi)型主要為溶穴介質(zhì)，常形成大水量集中滲漏通道。地下水主要沿巖溶管道流動(dòng)并以泉的方式排泄，分布不均一，動(dòng)態(tài)變化大，流態(tài)較復(fù)雜。需要強(qiáng)調(diào)的是，多數(shù)情況下工程區(qū)的巖體滲透結(jié)構(gòu)類(lèi)型不是單一的，而是多種滲透結(jié)構(gòu)類(lèi)型的疊加。而不同類(lèi)型滲透結(jié)構(gòu)交叉疊加的部位，往往形成透水性較強(qiáng)的地下水集中滲漏通道，也是防滲、排水工程需要關(guān)注的重點(diǎn)。此外，層狀滲透結(jié)構(gòu)中的透水巖層，局部而言亦具有網(wǎng)絡(luò)狀滲透結(jié)構(gòu)的滲透特征。4工程實(shí)例4.1實(shí)例1小浪底壩址區(qū)巖體滲透結(jié)構(gòu)類(lèi)型劃分4.1.1基本地質(zhì)條件壩址區(qū)出露地層主要為二疊系上統(tǒng)及三疊系下統(tǒng)，巖性為硅鈣質(zhì)砂巖、泥質(zhì)粉砂巖、粉砂質(zhì)粘土巖互層。砂巖為硬巖，性脆，裂隙發(fā)育，屬透（含）水層；泥質(zhì)粉砂巖與粘土巖為軟巖，裂隙不發(fā)育，屬相對(duì)隔水層。壩址區(qū)巖層產(chǎn)狀平緩，傾向北東（下游方向），傾角8°?12。。出露的斷層主要有規(guī)模較大的F1、F28、F461以及F236、F238等，均為陡傾角。F1分布在右岸河床部位，走向與黃河近平行；F28沿左岸風(fēng)雨溝展布，走向?yàn)?0。?60。；F461分布在左岸小南莊一帶，走向290°?310°；F236、F238穿過(guò)左岸洞群區(qū)呈近東西向展布，貫穿水庫(kù)上下游。壩址區(qū)砂巖中發(fā)育有3?4組陡傾角裂隙，泥質(zhì)粉砂巖與粘土巖中裂隙不發(fā)育。風(fēng)化卸荷帶內(nèi)的裂隙張開(kāi)寬度相對(duì)較大。4.1.2滲透結(jié)構(gòu)類(lèi)型劃分通過(guò)對(duì)小浪底壩址區(qū)基本地質(zhì)條件的分析，可以確定其滲透結(jié)構(gòu)類(lèi)型主要表現(xiàn)為層狀及帶狀（圖1）。水庫(kù)蓄水后，庫(kù)水將主要沿分布于不同高程的透水砂巖層及貫穿水庫(kù)上下游的斷層破碎帶向下游滲漏?？紤]防滲、排水工程處理措施時(shí)，應(yīng)對(duì)主要透水砂巖層以及透水砂巖層與斷層破碎帶交叉部位巖體予以重點(diǎn)關(guān)注。圖1小喂底壩址區(qū)砂”泥巖地層滲透始輜典型剖面示意圖4.2實(shí)例2三峽壩址區(qū)巖體滲透結(jié)構(gòu)類(lèi)型4.1.1基本地質(zhì)條件三峽工程壩址區(qū)出露的主要巖石為閃云斜長(zhǎng)花崗巖，并有多期酸一基性巖脈侵入。巖體表部存在較厚的風(fēng)化殼，可劃分為全、強(qiáng)、弱、微四個(gè)風(fēng)化帶。全風(fēng)化帶以疏松但略具聯(lián)結(jié)力的碎屑狀巖石為主，強(qiáng)風(fēng)化帶由疏松、半疏松狀巖石夾堅(jiān)硬、半堅(jiān)硬狀巖石組成，弱風(fēng)化帶為堅(jiān)硬、半堅(jiān)硬狀巖石為主，微風(fēng)化帶巖石風(fēng)化輕微。壩址區(qū)發(fā)育有北北西、北北東向等四組斷層，均以陡傾角為主。相對(duì)發(fā)育的四組裂隙大部分為陡傾角，少部分為中等傾角及緩傾角。巖脈與圍巖多呈斷層或裂隙接觸。4.1.2滲透結(jié)構(gòu)類(lèi)型劃分通過(guò)對(duì)三峽壩址區(qū)基本地質(zhì)條件的分析，可以確定其滲透結(jié)構(gòu)類(lèi)型主要表現(xiàn)為散體狀（全強(qiáng)風(fēng)化巖體）、網(wǎng)絡(luò)狀（裂隙巖體）及帶狀（斷層及巖脈）3種（圖2）。其中帶狀滲透結(jié)構(gòu)可構(gòu)成滲流場(chǎng)的主干網(wǎng)絡(luò)，對(duì)地下水起著類(lèi)似于集水、輸水廊道的作用，在防滲排水工程設(shè)計(jì)時(shí)需予以注意。一弓KN匚-f七IT-I白 ,或0HF!笙寫(xiě)煩此止Ml玉起：吒夫’荏十字*“族*htH；HC1無(wú)心：芯X攻（據(jù)周志芳修改）5結(jié)論（1） 巖性、斷裂構(gòu)造、風(fēng)化卸荷作用及巖溶作用是控制巖體滲透結(jié)構(gòu)及其宏觀滲透特征的主要因素。（2） 巖體滲透結(jié)構(gòu)系指透（含）水層（體）和相對(duì)隔水層（體）的空間分布及組合規(guī)律。巖體滲透結(jié)構(gòu)類(lèi)型一般可劃分為散體狀、層狀、帶狀、網(wǎng)絡(luò)狀以及管道狀5類(lèi)。（3） 工程區(qū)的巖體滲透結(jié)構(gòu)類(lèi)型一般不是單一的，而是多種滲透結(jié)構(gòu)類(lèi)型的疊加。不同類(lèi)型滲透結(jié)構(gòu)交叉疊加的部位，往往形成透水性較強(qiáng)的地下水集中滲漏通道，也是防滲、排水工程需要關(guān)注的重點(diǎn)。（4） 合理劃分巖體滲透結(jié)構(gòu)類(lèi)型，有助于從宏觀上把握巖體的滲透特征，為巖體滲流計(jì)算及防滲、排水工程設(shè)計(jì)提供科學(xué)依據(jù)。參考文獻(xiàn)：萬(wàn)力，李清波等.砂泥巖互層裂隙地層的滲透性特征[J].水利學(xué)報(bào)，1993,（9）.劉光堯.砂巖業(yè)頁(yè)巖和泥巖的含水條件及含水層分類(lèi)[J].水文地質(zhì)工程地質(zhì)，1990，（5）.周志芳，王錦國(guó).裂隙介質(zhì)水動(dòng)力學(xué)[M].北京：中國(guó)水利水電出版社，2004.Snow，D.T.Anisotropicpermeabilityoffracturedmedia[J].Waterresourcesresearch,Vol.5,No6,1969.Withspoon,P.A.Newapproachesofproblemsoffluidflowinfracturedrockmass[J].Proc.22ndU.S.Symp.RockMech.,1981.BearJ，Tsangchin-FuandGhislaindeMarsily.Flowandcontaminanttransportinfracturedrock[M].AcademicPress,Inc.California,1993.谷德振.工程地質(zhì)力學(xué)基礎(chǔ)[M].北京：科學(xué)出版社，1978.孫廣忠.地質(zhì)工程理論與實(shí)踐[M].北京：地震出版社，1996.PermeabilityCharacteristicsLIQing-boYanChang-bin(YellowRiverEngineeringConsultingCo.,Ltd,HenanZhengzhou450001)Abstract：Keyfactorsthatcontrolpermeabilitycharacteristicsofrockmassareanalyzed.Dividedprinciplesofrockmasspermeabilitystructuretypesandmacroscopicpermeabilitycharacteristicsofdifferentpermeabilitystructuresareputforward.Andengineeringexamplesarepresent.Itismostsignificantforseepagecontrolanddrainagedesignofwaterconservancyandhydropowerengineering.Keywords：fracturedrockmasses；permeabilitystructuretypes；permeabilitycharacteristic；seepagecontrolanddrainageIntroductionProblemsofhydrogeologicrelatedwithrockmassseepagearemetfrequentlyinwaterconservancyandhydropowerengineeringconstruction.Cranniesandkarstpassagesaredevelopedinrockmasscommonly.Controlledbyorientationandnon-uniformityofcranniesandkarstpassagesdistribution,seepagestateofgroundwaterinrockmassisfarmorecomplexthanthatinsoilandtakesonobviousanisotropyandnon-uniformitygenerally.Theseepagecontrolanddrainageengineeringmaybelowefficiency,evenbemistaken,withoutenoughcognition,Researchachievements[1]~[5]forpermeabilitycharacteroffracturedrockmassesobtainedbyscholarsathomeandabroadshowthatlithology,faultedstructure,weatheringandunloadingandkarsteffectarekeyfactorsthatcontrolpermeabilitystructuresanditsmacroscopicpermeabilitycharacteristicsofrockmass.RockmassisdividedintohydrogeologicstructuretypesbyMr.GUDezhen[7],suchasimperviousmass,uniformaquifer,layeredaquiferandveinaquifer,basedonstructureofgeologicbody.TheconceptionofrockmasshydraulicsstructureisputforwardbyMr.SUNGuangzhong[8],inwhichpermeablemass(layer)andimperviousmass(layer)areconsideredasbasicunit.Itdividespermeablemassintothreetypes,whichareholepermeablemass(layer),fracturepermeablemass(layer)andpipepermeablemass(layer),andalsodividesimperviousmassintothreetypes,whichareblockyimperviousmass,interlayerorzonalimperviousmass,layeredimperviousmass.WANLi[1]studiedthepermeabilitycharacteristicsofinterbeddedandfracturedsandstoneandmudstonestrata,andpointedoutthattherewerethreepermeabilitystructures,whichwerelayered,zonalandshell-perm,ininterbeddedandfracturedsandstoneandmudstonestrata.ZHOUZhifang⑵putsforwardtheideastodividethehydrogeologicstructureofblockyrockmass.Onthegroundofaboveresearches,dividedprinciplesofrockmasspermeabilitystructuretypesanditsmacroscopicpermeabilitycharacteristicsofallkindsofpermeabilitystructuresaresystematicallyputforwardinthepaper.Itismostsignificantforseepagecontrolanddrainagedesignofwaterconservancyandhydropowerengineering.KeyfactorsofcontrollingrockmasspermeabilitycharacteristicsInageneralway,thepermeabilityofintactrockisverylow,mostlylowerthan10-710-6cm/s.Comparedwiththeintactrock,thepermeabilityofrockmassisfarhigher.Thediscrepancybetweenthemcanbeseveralmagnitudes.Themainreasonswhichinducethisdiscrepancyarethattherearemanyfracturesandkarstpassages(inlimestone)ofdifferentcausesinrockmass,inadditiontoblockyrockofallkindsofscale.Asawhole,thepermeabilityandmacroscopicpermeabilitycharacteristicsofrockmassismostlycontrolledbylithology,faultedstructure,weatheringandunloadingandkarsteffect,etc.Theinfluenceoflithologyonrockmasspermeabilityisveryobvious.Thefractureistheuniquechannelforseepageofgroundwaterinfracturedrockmass,whilethedevelopmentruleoffracturesiscontrolledbylithologystrictly.Resultsfromaboundofinvestigationandstatisticshowthatthedevelopmentdegreeoffracturesinbrittlerock,suchassandstoneandquartzite,isfarbetterthanthatinplasticrock,forexampleclaystoneandshale.Thepermeabilityofbrittlerockiscommonlyfarhigherthanthatofplasticrockaccordingly.Thebrittlerockmakesupofpermeablemass(layer)oraquifer,whiletheplasticrockmakesupofrelativeimperviouslayer(mass)mostly.Faultsareimportantfactorsthatinfluencethedevelopmentoffractures.Fracturesconcentrationzonesexistonthebothsidesoffaultscommonly.Therebytherockmassinfaultsinfluencedzonesbehavesfromplaneandsectionasthezonalareawhosepermeabilityisrelativehigher.Ontheotherhand,lowpermeabilitysubstancesuchasgougedevelopsinrelativelarge-scalefaultzonesfrequently,andthenthefaultzoneswillformtransversewater-resistingpropertytosomeextent.Theinfluenceofweatheringandunloadingonrockmasspermeabilityisalsorelativeobvious.Forintrusiverocksuchasgranite,itsfullandhighlyweatheredzoneisgenerallysimilarwithisotropicporousmedia,whileitspermeabilityofweaklyandslightlyweatheredzoneincreasesinvariousdegrees.Forbrittlesedimentaryrockandvolcanicrock,theirrockmasspermeabilityinweatheringandunloadingzonewillincreaseobviouslyinageneralway.Karstdevelopmentdegreecanobservablycontrolthepermeabilitycharacteristicsofsolublerocksuchaslimestone.Thepermeabilitycharacteristicsoflimestonewherekarstdoesnotdeveloparethesameasthoseofcommonfracturedrockmass.Thepermeabilitycharacteristicsoflimestonewhereonlycorrodedfracturesdeveloparesimilarwiththoseofcommonfracturedrockmass.Inthecircumstances,stratifiedflowismainmovementstateofgroundwater,whilepermeabilityandyieldingpropertywillincrease.Forthelimestonewherecorrodedpassagesdevelop,itspermeabilityandyieldingpropertyarestrong,andmovementstateofgroundwateriscomplex.Itisnecessarytopointoutthatpeopleareusedtotakefracturedrockmassforisotropicporousmediamostlyinpracticebyfar,andgetpermeabilityindexesofrockmasswithgeneralverticalwaterpressuretestinborehole,thenevaluatethepermeabilitycharacteristicsofrockmassandseepageofreservoir.Infact,asfarastherockmasswherehighdipangledfracturesdevelop,theresultsobtainedbythepermeabilitytestofrockmassareusuallylowerthanthoseinengineeringpractice,becauseoflessprobabilitywithverticalboreholediscoveringhighdipangledfractures.ContrasttestofXiaolangdiprojectshowsthatpermeabilityindexesofhighdipangledfracturesrockmassobtainedbyhorizontalwaterpressuretestinboreholearethreetosixtimeshigherthanthoseobtainedbyverticalwaterpressuretestinboreholecommonly.Itwillinducerelativebigmistakesinwork,withoutenoughrecognition.PermeabilitystructuretypesofrockmassanditspermeabilitycharacteristicsSo-calledpermeabilitystructuresofrockmassarespatialdistributionandcombinationlawofpermeablemass(layer)oraquifer,andrelativeimperviouslayer(mass).Todividepermeabilitystructurestypesofrockmassinreasonishelpfulforgraspingpermeabilitycharacteristicsofrockmassfrommacro-scale,andcanprovidebasicreferenceforseepagecalculationandseepagecontrolanddrainageengineeringdesign.Thepermeabilitystructuresofrockmasscanbedividedintofiveclasses,whicharediscretemasspermeabilitystructure,layeredpermeabilitystructure,zonalpermeabilitystructure,netlikepermeabilitystructureandduct-likepermeabilitystructure.DiscretemasspermeabilitystructureDiscretemasspermeabilitystructureismainlymadeupoffullandhighlyweatheredzoneofintrusiverock.Itspermeabilitymediatypeisporousmediabasically,andtakesonhomogeneousisotropicpermeabilitycharacteristics.Itspermeabilityisrelativestrongcommonly.LayeredpermeabilitystructureLayeredpermeabilitystructureismainlyformedbygentlydippingstrataofinter-layersbetweenpermeablelayersandrelativeimperviouslayers,gentlyeruptiverockwithmultilayerstructureandgentlyfaultfragmentizedzone,etc.Itspermeabilitymediatypeiscrannymediabasically.Groundwatergenerallyhosts,transportsineachpermeablelayer.Itsrecharge,runoffanddrainagearecontrolledbytherelativeimperviouslayersaboveandunderpermeablelayers,andtakesonmultilayerwaterlevelfrequently.Itcanfoundfrommacro-scalethatthepermeabilityincataclinallayerdirectionisfarhigherthanthatinverticallayerdirection,andtakesonobviousanisotropicpermeabilitycharacteristic.ZonalpermeabilitystructureZonalpermeabilitystructureismainlymadeupofthefaultfragmentizedzonewithhighdiporientation,fracturesconcentrationzone,dikefracturedzone,highlydippingstrataofinter-layersbetweenpermeablelayersandrelativeimperviouslayers,strongunloadingzonebesiderivervales,etc.Itspermeabilitymediatypeiscrannymediabasicallyanditspermeabilityisrelativestrongcommonly.Itoftenconnectswithlayeredandnetlikepermeabilitystructures,andformsconcentrativeseepagepassagesofgroundwater,andalsocanformhydraulicrelationchannelsofgroundwaterbetweenvariouspermeablelayers.Itcanfoundfrommacro-scalethatthepermeabilityincataclinalzonedirectionisfarhigherthanthatinverticalzonedirection,andtakesonobviousanisotropicpermeabilitycharacteristic.NetlikepermeabilitystructureNetlikepermeabilitystructureismainlymadeupofslightlyweatheredtofreshblockyrockandsedimentaryrockwhoselithologyissingleandfracturesincludingkarstcranniesrelativedevelop,etc.Itspermeabilitymediatypeiscrannymediaanditspermeabilityisrelativeweak.Themovementofgroundwaterismainlycontrolledbydevelopmentcharacteristicsoffracturenetworkanditspermeability,andtakesonobviousinhomogeneousandanisotropicpermeabilitycharacteristic.Fracturedgroundwaterhostinginthesamestratadoesnotalwayshaveuniformgroundwaterlevel.Duct-likepermeabilitystructureDuct-likepermeabilitystructureismainlymadeupofkarstcavesandlimestonewherepipelinesdevelop.Itspermeabilitymediatypeiskarstcavemediaandoftenformsconcentrativeseepagepassagesoflargewaterquality.Groundwatergenerallyflowsalongkarstpassagesanddrainagesbywayofspring.Thedistributionofgroundwaterisinhomogeneous,andgroundwaterdynamicschangegreatly.Itsflowingstateisrelativecomplex.Itisnecessarytoemphasizethatpermeabilitystructureofrockmassisnotsingletypeundermostconditions,butthesuperpositionofmanypermeabilitystructuretypes.Thepositionwherevariouspermeabilitystructurescrossandfoldwillformconcentrativeseepagepassagesofgroundwater.Soitistheemphasesthatneedpaymoreattentiontoforseepagecontrolanddrainageprojects.Inaddition,layeredpermeabilitystructurealsohasthepermeabilitycharacteristicsofnetlikepermeabilitystructure,intermsoflocalscope.EngineeringcasesCase1divisionofrockmasspermeabilitystructuretypesforXiaolangdidamsiteBasicgeologicconditionsOutcroppingstrataatdamsitearemainlyupperPermiansystemandlowerTriassic,itslithologyissiliceousandcalcareoussandstone,muddysiltstone,andinterlayerofsiltyclayrock.Thesandstoneishardandbrittlerock,wherefracturesdevelop.Itbelongstopermeablelayeroraquifer.Muddysiltstoneandclayrockwherefracturesdonotdevelopbelongtoimperviouslayer.Theorientationofstrataatdamsiteisgently,thedipdirectionisNE(downstreamdirection),andthedipangelis8°?12°.Theoutcroppingfaultsaremainlyrelativelarge-scale,whichareF1、F28、F461andF236、F238,etc.Theyareallhighdipangel.F1faultdistributesatriverbedofrightbank,whosestrikeisclosetotheparallelofYellowRiver.F28faultdistributesalongwindandrainravineofleftbank,whosestrikeis30°?60°.F461faultdistributesatXiaonanvillageofleftbank,whosestrikeis290°?310°.F236andF238faultstraversetheareaofchambersgroupatleftbank,andwhosedistributionisclosetoeastandwestdirection,andpasstroughupstreamanddownstreamofreservoir.Thereare3?4grouphighdipfracturesdevelopedatdamsitesandstone.Thefracturesdonotdevelopatmuddysiltstoneandclayrock.Thepatulouswidthoffracturesatweatheringandunloadingzoneisrelativelarge.DivisionofpermeabilitystructuretypesThepermeabilitystructuretypescanbeconfirmedtobelayeredandzonal(Fig1.),byanalyzingbasicgeologicconditionsofXiaolangdidamsite.Thereservoirwaterseepstodownstreamalongpermeablesandstonedistributingatvariousheightandfaultfragmentizedzonewhichpassesthroughupstreamanddownstreamofreservoir.Theemphaticattentionshouldbetakentothepermeablesandstoneandtherockmasswherepermeablesandstoneandfaultfragmentizedzonecross,whentreatmentsofseepagecontrolanddrainageengineeringareconsidered.l Z.O1inipeiiiiien iy^rniciuieF236Fig.1ThetypicalpermeabilitystructuresectionofsandstoneandclayrockstrataatXiaolangdidamsiteCase2thepermeabilitystructuretypesofrockmassattheThreeGorgesdamsiteBasicgeologicconditionsOutcroppingrockattheThreeGorgesengineeringdamsitearemainlyporphyriticgranite,andintrusiveacid-maficdikesofmorethanoneperiod.Thereisrelativethickweatheredshellatsurfacelayerofrockmass.Itcanbedividedintofourweatheredzones,whicharefull,highly,weaklyandslightlyweatheredzonesrespectively.Thefullweatheredzoneconsistsofloosenclasticrockwhichhassomejointedforce.Thehighlyweatheredzoneismadeupofinterlayerbetweenloosen,halfloosenrockandhard,halfhardrock.Theweaklyweatheredzoneishardandhalfhardrockmainly.TheweathereddegreeofslightlyweatheredzonerockisslightTherearefourgroupsoffaultsdevelopingatdamsite,whosestrikesareNNWandNNE,etc.Theirdipangelsarehighgenerally.Thefourgroupsoffractureswhichdevelopwellrelativelyhavehighdipangelmostly,andfewofmiddleandgentledipangel.Thedikecontactswithsurroundingrockthroughfaultsorfracturesfrequently.DivisionofpermeabilitystructuretypesThepermeabilitystructurecanbeconfirmedtothreetypes,whicharediscretemass(fullweatheredrockmass),netlike(fracturedrockmass)andzonal(faultsanddikes)byanalyzing

basicgeologicconditionsoftheThreeGorgesdamsite.ItcanbeseeninFig.2.Thezonalpermeabilitystructurecanformthechiefnetworkofseepagefield,anditseffectsareclosetocatchmentsandfilling&emptyingculvert.Itisnecessarytopayattentiontowhenthedesignofseepagecontrolanddrainageengineeringiscarriedout.Fig.2ThetypicalpermeabilitystructuresectionofblockyrockmassattheThreeGorgesengineeringdamsite(accordingtorevisionbyZHOUZhifang)霎一切履辛一-fiussFig.2ThetypicalpermeabilitystructuresectionofblockyrockmassattheThreeGorgesengineeringdamsite