本文選題：固結(jié)比　切入點(diǎn)：彎曲元　出處：《國(guó)際地震動(dòng)態(tài)》2017年05期 　論文類型：期刊論文

【摘要】：黃土液化的判別是工程界長(zhǎng)期存疑的問(wèn)題,現(xiàn)場(chǎng)黃土含水量較低,剪切波速較高,而實(shí)驗(yàn)室對(duì)其飽和,飽和過(guò)程對(duì)其土體結(jié)構(gòu)影響還不確定,又由于固結(jié)比對(duì)土體剛度的影響仍然沒(méi)有定論,這就導(dǎo)致室內(nèi)黃土動(dòng)三軸液化試驗(yàn)結(jié)果與現(xiàn)場(chǎng)力學(xué)指標(biāo)一直無(wú)法建立聯(lián)系。另一方面,黃土從顆粒組成來(lái)說(shuō),屬于細(xì)粒土范疇,細(xì)粒土液化判別方法應(yīng)可為黃土液化判別提供參照,但由于實(shí)驗(yàn)室配制試樣相對(duì)密度、土體骨架強(qiáng)度及細(xì)顆粒賦存形式很難控制,導(dǎo)致細(xì)顆粒對(duì)土體液化勢(shì)影響研究飽含爭(zhēng)議與矛盾。本文緊密結(jié)合工程和科研工作需求,設(shè)計(jì)了一系列原狀黃土在均等固結(jié)與偏壓固結(jié)下的動(dòng)三軸彎曲元試驗(yàn),以及原狀黃土在動(dòng)三軸內(nèi)飽和過(guò)程及飽和后的剪切波速試驗(yàn),并且對(duì)一個(gè)飽和黃土場(chǎng)地進(jìn)行了現(xiàn)場(chǎng)原位測(cè)試,回顧了現(xiàn)有標(biāo)貫液化判別方法,對(duì)含細(xì)粒土體液化判別指標(biāo)進(jìn)行了系統(tǒng)研究,改進(jìn)了細(xì)粒土液化初判準(zhǔn)則以及含細(xì)粒砂性土液化判別式,最后對(duì)CPT液化判別方法的可靠性進(jìn)行了數(shù)據(jù)檢驗(yàn)。具體工作和成果包括:(1)采用動(dòng)三軸彎曲元試驗(yàn)系統(tǒng),對(duì)蘭州市多個(gè)場(chǎng)地原狀黃土進(jìn)行了均等固結(jié)與偏壓固結(jié)下剪切波速測(cè)試,證實(shí)了相關(guān)固結(jié)比對(duì)土體剛度影響的試驗(yàn)研究結(jié)果,進(jìn)一步對(duì)比均等固結(jié)與偏壓固結(jié)下試樣軸向變形,分析了固結(jié)比對(duì)土體剛度影響的機(jī)理。(2)采用動(dòng)三軸彎曲元試驗(yàn)系統(tǒng),首先對(duì)原狀黃土飽和過(guò)程進(jìn)行了剪切波速跟蹤測(cè)試,并進(jìn)一步對(duì)比飽和黃土與原狀黃土在同一逐級(jí)加壓的過(guò)程中剪切波速與軸向變形測(cè)試值,最后通過(guò)與現(xiàn)場(chǎng)飽和黃土場(chǎng)地水位上下黃土層實(shí)測(cè)標(biāo)貫擊數(shù)、剪切波速對(duì)比,分析了原狀黃土遇水及飽和后的軟化特征。(3)通過(guò)對(duì)比唐山、海城地震兩個(gè)液化地區(qū)粉土與砂土的剪切波速與標(biāo)貫擊數(shù)統(tǒng)計(jì)關(guān)系,發(fā)現(xiàn)對(duì)于剪切波速相同的飽和粉土和砂土,由于粉土的觸變性,粉土標(biāo)貫擊數(shù)顯著小于砂土。結(jié)合NCEER推薦的基于SPT與VS的液化判別方法,建立了3個(gè)細(xì)粒含量下臨界剪切波速與臨界標(biāo)貫擊數(shù)的相關(guān)關(guān)系,證實(shí)了含細(xì)粒土體的觸變性。(4)回顧了目前國(guó)內(nèi)外有關(guān)含細(xì)粒土液化研究現(xiàn)狀,結(jié)合1975年海城地震,1976年唐山地震,1999年土耳其Kocaeli地震和臺(tái)灣集集地震液化與非液化土數(shù)據(jù)分析,詳細(xì)對(duì)比了現(xiàn)有液化判別式和初判條件的優(yōu)劣,改進(jìn)了細(xì)粒土液化初判準(zhǔn)則以及含細(xì)粒砂性土標(biāo)貫液化判別式。(5)回顧了NCEER推薦的Robertson的CPT液化判別方法和Olsen的CPT液化判別方法,通過(guò)對(duì)1999年臺(tái)灣集集地震液化與非液化土數(shù)據(jù)分析,并將判別結(jié)果與SPT方法判別結(jié)果進(jìn)行比較,指出了CPT液化判別方法還沒(méi)有達(dá)到SPT方法的準(zhǔn)確性,但是CPT的土分類圖卻是其最大的優(yōu)勢(shì)所在。
[Abstract]:The identification of loess liquefaction is a long-term problem in engineering circles. The loess has low water content and high shear wave velocity in the field, but the laboratory saturation and saturation process have uncertain influence on the soil structure. Because the effect of consolidation ratio on soil stiffness is still uncertain, the results of indoor loess dynamic triaxial liquefaction test can not be related to the field mechanical indexes. On the other hand, loess belongs to the category of fine grained soil in terms of particle composition. The method of liquefaction discrimination of fine grained soil should provide a reference for the identification of loess liquefaction. However, it is difficult to control the skeleton strength and the occurrence form of fine particles because of the relative density of samples prepared in laboratory. The research on the effect of fine particles on soil liquefaction potential is controversial and contradictory. In this paper, a series of dynamic triaxial bending element tests of undisturbed loess under the condition of equal consolidation and partial compression consolidation are designed in combination with engineering and scientific research requirements. The saturated process and shear wave velocity of undisturbed loess in dynamic triaxial are tested. In situ tests are carried out on a saturated loess site, and the existing standard liquefaction identification methods are reviewed. The discriminant index of liquefaction of fine-grained soil was studied systematically, and the criterion of liquefaction of fine-grained soil and the discriminant of liquefaction of fine-grained sandy soil were improved. Finally, the reliability of CPT liquefaction identification method is tested by data. The concrete work and results include: 1) using dynamic triaxial bending element test system, the shear wave velocities of undisturbed loess in many sites in Lanzhou City are tested under the condition of equal consolidation and partial compression consolidation. The experimental results of the influence of the relative consolidation ratio on the soil stiffness are confirmed. The axial deformation of the specimen under equalization consolidation and partial compression consolidation is further compared, and the mechanism of the consolidation ratio affecting the soil stiffness is analyzed. The dynamic triaxial bending element test system is used to test the effect of the consolidation ratio on the soil stiffness. At first, the shear wave velocity of the saturated loess is measured, and the shear wave velocity and the axial deformation of the saturated loess are compared with that of the original loess in the same step by step compression process. Finally, by comparing the measured penetration number and shear wave velocity with the measured penetration number and shear wave velocity of the upper and lower loess layers at the site water level, the softening characteristics of the undisturbed loess under water and after saturation are analyzed. The statistical relationship between shear wave velocity and standard penetration number of silt and sand in two liquefaction areas of Haicheng earthquake shows that for saturated silt and sand with the same shear wave velocity, due to the thixotropy of silt, The standard penetration number of silt is significantly lower than that of sandy soil. Based on the liquefaction discrimination method based on SPT and vs recommended by NCEER, the correlation between critical shear wave velocity and critical standard penetration number at three fine grain contents is established. It is confirmed that the thixotropy of fine-grained soil mass. (4) the present research status of liquefaction of fine-grained soil at home and abroad is reviewed. Combined with the Haicheng earthquake on 1975, Tangshan earthquake in 1976, the Kocaeli earthquake in Turkey on 1999 and the Jiji earthquake in Taiwan, the liquefaction and non-liquefaction soil data are analyzed. The advantages and disadvantages of the existing liquefaction discriminant and initial judgment conditions are compared in detail, and the criterion of initial liquefaction of fine-grained soil and the standard standard liquefaction discriminant of fine-grained sandy soil are improved. The CPT liquefaction discriminant of Robertson recommended by NCEER and the CPT liquefaction discriminant of Olsen are reviewed. By analyzing the data of liquefaction and non-liquefaction soil of Jiji earthquake in 1999, and comparing the discriminant result with that of SPT method, it is pointed out that CPT liquefaction discriminant method has not reached the accuracy of SPT method. But CPT's soil classification map is its biggest advantage.
【作者單位】： 中國(guó)地震局工程力學(xué)研究所;
【分類號(hào)】：TU444

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