滑帶土動(dòng)力學(xué)性質(zhì)試驗研究

1049665201(03)031805 Journal of Engineering Geology工程地質(zhì)學(xué)報滑帶土動(dòng)力學(xué)性質(zhì)試驗研究晏鄂川①劉漢超②唐輝明①(①中國地質(zhì)大學(xué)武漢430074)(②成都理工大學(xué)成都610059)摘要為了研究地震高烈度區老滑坡的復活變形原因,本文對滑坡滑帶土的動(dòng)力學(xué)特性進(jìn)行了系列研究。本次試驗采用擾動(dòng)土樣,制樣基本物理指標按滑帶土的現場(chǎng)測試指標確定在不固結不排水條件下,運用MTS810 Teststar程控液壓伺服土動(dòng)軸儀對單個(gè)樣品逐級放大動(dòng)應力的分級試驗方法進(jìn)行。側向壓力(圍壓)分別采用10Fa200Pa,0kPa三級,通過(guò)施加軸向振動(dòng)荷載(力模擬地震作用振動(dòng)波形為正弦波頻率為1H,振幅隨試樣性質(zhì)確定。研究結果表明滑帶土在動(dòng)荷載作用下的動(dòng)力學(xué)性質(zhì)與其靜荷載作用下的力學(xué)性質(zhì)有著(zhù)較大的差異主要表現在滑帶土的動(dòng)應力與動(dòng)應變關(guān)系的非線(xiàn)性滯后性及變形積累特點(diǎn)動(dòng)彈性模量與動(dòng)強度的顯著(zhù)降低以及動(dòng)阻尼比的顯蓍增大特性。這揭示了動(dòng)力作用下的滑坡復活原因之一同時(shí)為滑坡穩定性評價(jià)和動(dòng)力作用下的變形機制模擬分析提供了基礎資料也為分析滑帶土動(dòng)力本構模型提供了基本內容。關(guān)鍵詞滑帶土動(dòng)力學(xué)特性動(dòng)彈性模量阻尼比動(dòng)強度中圖分類(lèi)號:F642.11·6文獻標識碼:AEXPERIMENTAL STUDY ON THE DYNAMIC PROPERTIES OF SOIL INSLIDE ZONE OF LANDSLIDEYAN Chuan LIU Hanchao TANG huiming o(O Engineering Faculty, China University of Geosciences, Wuhan 430074)((2 Chengdu institute of Technology, Chengdu 610059)Abstract In order to study the deformation cause of reactivated landslide in a high seismic intensity area, the authors firstly systematically analyze the dynamic properties of soil in slide zone in cyclic triaxial test. The disturbedsoil samples, physical properties of which are prepared to be field test index are tested on triaxial compressor underunconsolidated-undrained condition, with confining pressure of 100kPa, 200kPa and 300k Pa and a step by stepincreasing dynamic load. Analyzing the environmental condition of the landslide in combination with high seismicintensity in the region, the seismic response properties of soil in slide zone are systematically sdutied. The resultshows that there is a lot of difference between the dynamic and the static properties, for example, the nonlinear re-lation between dynamic stress and strain, dynamic elasticity modulus and dynamic strength of the soil markedly re-duce, but damping ratio increases. The study provides an important theoretical basis for evaluating the sliding of theKey words The slide zone, Dynamic property, Dynamic elasticity modulus, Damping ratio, Dynamic strength*收稿日期:2002-12-20;收到修改稿日期:2003-02-12第一作者簡(jiǎn)介:鄂川(1969-),男博士副教授,從事巖土工程和工中國煤化工CNMHG要鄂川等:滑帶土動(dòng)力學(xué)性質(zhì)試驗研究319滑坡穩定性計算與評價(jià)。引言衰1代表性地震崩滑統計大量歷史地震資料表明(表1),在地震烈度達Table 1 Statistics of collapses and landslidesⅦ度時(shí)就可以產(chǎn)生崩滑地質(zhì)災害。這些崩塌滑坡多representative是在山體地震(裂)縫的基礎上發(fā)展而成的,如1933震級崩滑總數/個(gè)年8月25日岷江上游疊溪發(fā)生75級強震觸發(fā)爐霍7.25大小滑坡幾十處,其中三處大型山崩滑坡將岷江堵19338.25疊溪7.5斷達4天之久。地震引起的崩塌與滑坡給人類(lèi)帶19554.14康定195923會(huì )理20來(lái)了巨大的危害許多重要工程如水電工程位于高1973.224甘孜-爐霍烈度區,這些地區山高坡陡,斜坡(含老滑坡)的地196816松播-平武72震穩定性關(guān)系到整個(gè)工程的成敗,這使得斜坡地震動(dòng)力響應研究具有重要意義滑帶土在滑坡的發(fā)生和老滑坡的復活過(guò)程中均1滑帶土常規物理力學(xué)性質(zhì)起著(zhù)十分重要的作用。除了其物質(zhì)組成和結構特征對滑坡穩定性狀況有重要影響外,更為重要的是滑據室內土工試驗,滑帶土的物理力學(xué)性質(zhì)及有帶土的物理力學(xué)性質(zhì)。目前對大量滑坡的穩定關(guān)參數見(jiàn)表2。由表2可知,從天然狀態(tài)到飽水狀性分析仍主要采用靜荷載作用下的強度指標進(jìn)行,態(tài)滑帶土的抗剪強度指標變化較大這是滑坡易于但眾多事例中遇到了因動(dòng)荷載而導致復活的滑坡的在連續降雨之后變形復活加劇的原因之穩定性問(wèn)題。為此,本文就某滑坡滑帶土動(dòng)力學(xué)特性2進(jìn)行研究,以探討其動(dòng)力響應特性,從而指導表2滑帶土物理力學(xué)性質(zhì)及有關(guān)參數表Table 2 Physical and mechanical properties of soil in sliding zone天然含水率天然密度飽和密度天然快剪飽水快剪壓縮模量w/(%)/kN3內聚力內摩擦角內聚力內摩擦角Es/MPac/kPa17.0-24220.5~24.222.I-24.75-17257-32815-4313.9-19.952-9.2樣制成直徑50mm,高為100mm的圓柱形樣共兩組2滑帶土動(dòng)力學(xué)性質(zhì)(C1、G2,計20個(gè)樣品)。試驗在不固結不排水條件下進(jìn)行。側向壓力由于歷史上多次強震都對該滑坡所在區造成了(圍壓)分別采用a3=100kPa,200kPa和300三級,嚴重災害同時(shí)引發(fā)了無(wú)數山崩、滑坡以及地面裂縫在試驗過(guò)程中側向壓力保持不變。試樣裝畢后根等地質(zhì)災害。為了查明該區地震作用影響山體斜坡?lián)﨟.B.Sed理論3,模擬地震動(dòng)荷載作用確定如巖土體力學(xué)特性變化的規律對該老滑坡滑帶土進(jìn)下:在各向等壓狀態(tài)下開(kāi)始施加軸向振動(dòng)荷載控制行了動(dòng)力學(xué)條件下的力學(xué)特性試驗。方式采用力控制,振動(dòng)波形為正弦波,頻率為1Hz2.1實(shí)驗測試條件振幅隨試樣性質(zhì)確定。2.2滑帶土動(dòng)彈性模量測試試驗是參照水電部《土工試驗規程》(SDS0179)在MIS8l0 Teststar程控液壓伺服土動(dòng)三軸儀上本次試驗采用單樣逐級放大動(dòng)應力的分級試驗進(jìn)行的。本次試驗采用擾動(dòng)土樣,制樣基本物理指方法。分別在圍壓(側向壓力)為100kPa,20kPa標按滑帶土的現場(chǎng)測試指標確定:即制樣含水率30中國煤化工彈性模量測定,測19%,容重13kN·m3。根據制樣要求滑帶土定CNMHG關(guān)系曲線(xiàn)(圖1和Journal of Engineering Geology工程地質(zhì)學(xué)報200311(3)圖2)。由圖可知,4-E關(guān)系具有明顯的非線(xiàn)性0.0025特征,曲線(xiàn)態(tài)與雙曲線(xiàn)近似-200kPa300kFa +b上映=0.00050.05P 300kPa圖3G1滑帶土動(dòng)應變-動(dòng)彈模倒數擬合曲線(xiàn)Fig 3 Dynamic stress- elasticity modulus reciprocalhit curve of soil in GI sliding zone0.0500.008動(dòng)應變/(%圖1G1滑帶土動(dòng)應力-動(dòng)應變曲線(xiàn)0.006Fig. 1 Dynamic stress-strain curve of0.soil in Gl sliding zone0.002圖4G2滑帶土動(dòng)應變-動(dòng)彈模倒數擬合曲線(xiàn)Fig 4 Dynamic stress-elasticity modulus reciprocalbit curve of soil in G2 sliding zone動(dòng)應變/(%)圖2C2滑帶上動(dòng)應力-動(dòng)應變曲線(xiàn)Fig 2 Dynamic stress- strAin curve ofC200k Pssoil in G2 sliding zone-+300kPa上式表明動(dòng)(割線(xiàn))彈性模量E4的倒數與動(dòng)彈性應變c近似為線(xiàn)性關(guān)系。圖3和圖4為線(xiàn)性回歸后的-E曲線(xiàn)直線(xiàn)與軸的截距a=(動(dòng)應變/(%)此時(shí)的E4為最大值E-m常為初始切線(xiàn)模量。而圖5G1滑帶土動(dòng)應變-動(dòng)彈模倒數擬合曲線(xiàn)6a直線(xiàn)的斜率b則為:當E4→∞時(shí),on=Fig 5 Dynamie strain- elasticity modulusit curve af soil in GI sliding zone即為動(dòng)應力的最大值σ如m,同時(shí)也是a4-6a曲線(xiàn)的漸近線(xiàn)。表3列出滑帶土樣在不動(dòng)周次的a=E曲線(xiàn)形成滯回圈滯回圈面積大小表示加、卸荷過(guò)程中能量損失的大小,即表示了土體同圍壓下的a、b、Edm、O-,值。同樣,可擬合動(dòng)彈模E與動(dòng)應變6關(guān)系曲線(xiàn)的阻尼大小。阻尼A是土體振動(dòng)中材料阻尼與臨界(圖5和圖6)由圖可知,E隨Et的增大而非線(xiàn)性地阻尼的比值。降低。本次試樣的動(dòng)應變E4與阻尼比A4的關(guān)系曲線(xiàn)見(jiàn)圖7和圖8由圖可知,滑帶土的阻尼比均有隨動(dòng)由于滑帶土體內阻尼,在振動(dòng)過(guò)程中應變的變?yōu)榘诵脑黾佣龃蟮内厔?但更為明顯的特征是:2.3阻尼比測試應變中國煤化工0.38%(G2樣)時(shí)化相對于應力的變化有一事實(shí)上的滯后,在同一振阻CNMHG增長(cháng),此后,曲線(xiàn)趨晏鄂川等:滑帶土動(dòng)力學(xué)性質(zhì)試驗研究2000200kPa300kPa00.0.20.30.40.50.60.700.120.240.360.480.60.72動(dòng)應變/(%)圖8C2滑帶土動(dòng)應變-阻尼比曲線(xiàn)圖6G2滑帶土動(dòng)應變一動(dòng)彈模擬合曲線(xiàn)Fig8 Dynamic strain-damping ratioFig6 Dynamic strain-elasticity moduluscurve of soil in G2 sliding zonebit curve of soil in G2 sliding zone于平緩。這說(shuō)明滑帶土體的阻尼比隨動(dòng)應變增加而2.4動(dòng)強度測試增大,但在應變到達一定值的條件下,這種變化不顯滑帶土動(dòng)強度指在一定應力循環(huán)次數下使試樣著(zhù)即振動(dòng)過(guò)程中應變的變化滯后于應力的變化是達到破壞應變時(shí)的振動(dòng)應力。據相關(guān)規范和工程要有一極限值的,相應地加卸荷過(guò)程在土體中的能求確定本次試樣的破壞標準為:應變達到25%時(shí)量損失也是有一定域值。為破壞標準。每個(gè)試樣按選定的動(dòng)應力振動(dòng)直至破壞,動(dòng)應力的選值為盡量使土樣振動(dòng)破壞的周次N表3滑帶土初始切線(xiàn)模量及動(dòng)應力實(shí)驗值小于10周、20周、30周(分別對應于H.B.Sed根Table 3 The test results of tangent modulus據強震記錄資料分析中的7級75級、8級地震)。and dynamic stress in sliding zone soil試驗結果如圖9。由圖可知,在相同圍壓下隨動(dòng)應x 10kPa力σ增加,破壞振次N減小;在相同的破壞振N次0.71428.570.143下,圍巖σ3越大,所需施加的動(dòng)應力σ4越大。854909.10.125】0.20←100kPa振次/N圖9滑帶土破壞時(shí)動(dòng)應力與破壞振次的關(guān)系曲線(xiàn)100kP2200kPacurve of soil sliding zone in failure process莫爾-庫侖理論仍然適用于土動(dòng)力學(xué),通過(guò)動(dòng)應變/(%)動(dòng)強度測試可求出動(dòng)抗剪強度參數c4和q在圖9圖7G1滑帶土動(dòng)應變一阻尼比曲線(xiàn)中,按一定振次分別在4條曲線(xiàn)上截取4個(gè)不同圍壓Fig 7 Dynamic strain-damping ratioo3對應的動(dòng)應力σ4,即得最大主應力σ1=σ3+σa,curve of soil in Gl sliding zone在s-t座標中(s=(σ1+σ3)2,t=(a1-a2)2)對實(shí)驗點(diǎn)進(jìn)行線(xiàn)性回歸分析(圖10)得出:t=a+s中國煤化工(wg)求得滑帶CNMHG一結果計算隨破壞322Journal of Engineering Geology工程地質(zhì)學(xué)報200311(3)(2)滑帶土的動(dòng)割線(xiàn)模量隨動(dòng)應變增加而降00515+41.6(=x9T低(3)滑帶土的阻尼比隨動(dòng)應變增加而增大,但應變達到一定范圍時(shí),阻尼比增加不顯著(zhù);0.058s+38.298(r=0.958)20}=0030+3振動(dòng)10次(4)振次越高滑帶土的抗剪強度cφa降低幅(r=0.956)度較大;振動(dòng)30(5)動(dòng)荷載如強震對斜坡或滑坡的巖土體力學(xué)400500性質(zhì)影響顯著(zhù),可以加速斜坡失穩破壞或滑坡變形復活進(jìn)程圖10滑帶土動(dòng)強度擬合曲線(xiàn)參考文獻of soil in G1 sliding zone振次的增加,動(dòng)內聚力c比動(dòng)內摩擦角φ的下降幅[1]韓愛(ài)果聶得新任光明大型滑坡滑帶土剪切流變特性研究[]工程地質(zhì)學(xué)報2001,9(4):22~25度更大,分別達6~10%和1%。Han Aiguo, Nie Dexin, Ren Guangming. 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