共查询到19条相似文献，搜索用时 115 毫秒
1.
长江入海口原状土动剪切模量预测方法探究 总被引：1，自引：0，他引：1
为探究同一类原状土在各应变范围内动剪切模量G随土层深度H的变化规律,对长江入海口处同一钻孔自地表至基岩深度范围内原状粉质黏土与粉土展开系列共振柱试验。试验发现：原状粉质黏土与粉土在各应变范围内G均随H的增加而规律性增加,最大动剪切模量Gmax随H的增加而线性上升;G衰减关系随H的增加呈现规律性降低。试验结果表明：原状土G与土层深度H存在一定相关,据此提出了分别基于土层深度H和Hardin模型的G预测方法,用以预测各类原状土在不同深度下的Gmax及其在各应变范围内的G。通过3种预测方法的对比分析,得出基于土层深度H的G预测方法最具优势,并且通过对渤海海域原状土数据的重新处理进一步验证了该方法的适用性。 相似文献
2.
通过运用扁铲侧胀仪(DMT)在长江入海口滨海沉积软土中进行的原位测试,获得滨海沉积软土中扁铲侧胀试验各指标参数的变化规律。扁铲侧胀试验与静力触探试验结果一致,试验结果可靠,且扁铲侧胀试验可以快速地获取侧向基床反力系数KH,为桩基础的设计提供可靠的依据。对比旁压试验结果,扁铲侧胀试验得到的KH值常常偏大。在粘土层、粘质粉土夹粉质粘土、淤泥质粉质粘土、粘质粉土、淤泥质粘土等土层中KH与真实值相差较小,可以使用,但实际应用中应同时结合规范使用;而在砂质粉土和粉砂等土层中KH与真实值相差较大,不宜使用。 相似文献
3.
旁压试验广泛应用于岩土工程土体参数测试中。根据旁压试验原理与方法,将其运用于福建某高速公路遂道强风化花岗岩原位测试中。试验结果表明:强风化花岗岩强度参数与表层粘性土相当。对于相同性质的岩土层来说,土层的强度指标随深度的增加呈规律性增强。场区内强风化花岗岩具有较高的抵抗水平向变形能力,但其竖向承载能力相对较低。与部分钻孔原位标贯试验成果对比,两种原位测试结果具很好的相关性。 相似文献
4.
为了揭示黏性土中静压桩贯入过程中桩土界面桩侧土压力的受力特性,依托山东东营某桩工程开展了现场足尺试验,得到了静压桩沉桩过程中桩土界面桩侧土压力随贯入深度的变化规律,分析了贯入过程中不同土层桩侧土压力的分布特性,明确了桩侧土压力在沉桩过程中存在明显的退化效应,探讨了桩土界面桩侧土压力与桩侧上覆土体竖向土压力的比值关系。结果表明：桩土界面桩侧土压力与土层性质密切相关;随着传感器贯入深度的逐渐增加,桩侧土压力逐渐增大,并且增大幅度随土层的不同而不同;在同一贯入深度处,桩土界面桩侧土压力存在明显的退化现象,粉土中的退化幅度明显小于粉质黏土中的退化幅度;同一土层中桩土界面桩侧土压力与桩侧上覆土体竖向土压力的比值为常数,并且粉土中的比值明显大于粉质黏土中的比值。 相似文献
5.
旁压试验广泛应用于岩土工程土体参数测试中。根据旁压试验原理与方法,将其运用于福建某高速公路遂道强风化花岗岩原位测试中。试验结果表明:强风化花岗岩强度参数与表层粘性土相当。对于相同性质的岩土层来说,土层的强度指标随深度的增加呈规律性增强。场区内强风化花岗岩具有较高的抵抗水平向变形能力,但其竖向承载能力相对较低。与部分钻孔原位标贯试验成果对比,两种原位测试结果具很好的相关性。 相似文献
6.
南水北调“穿黄”地基工程勘探,深度大,地层复杂,为获得为可靠,确切的岩土指标,采有了法国ＧＡ型旁压仪对其主要土层进行了原位测试,该试验采用了专门的成孔工艺,试验深度达５７ｍ,最大测试压力为４．８ＭＰａ,通过测试得出和各主要土层的力学性能指标,本文主要介绍该旁压的基本结构和工作原理,成孔工艺,测试及有关计算方法等,并对其有代表性典型成果进行了分析。 相似文献
7.
为了获得红黏土地基承载力和变形参数在横向和垂向上的定量数据及分析它们的变化规律,选取厦门至成都高速公路湖南省郴州段典型横纵断面上的红黏土地层作为试验点,采用平板载荷试验、旁压试验等技术手段进行了原位测试。试验结果表明：红黏土地基承载力和变形模量在横向较小的范围内呈现较大幅度的变化,在垂向上则呈现先增大再减小的变化趋势,与红黏土赋存厚度、地形地貌、含水率等相关;旁压试验所测得的承载力特征值和平板载荷试验测得的承载力特征值之间存在一定的差异性;旁压模量与变形模量可以通过结构性系数联系起来,所得的结构性系数与Menard根据大量黏土试验资料对比所得到的结论较为一致。 相似文献
8.
为探讨在粉土及粉质黏土中桩端阻力随贯入深度的变化规律,通过在试验桩P1的桩端安装轮辐压力传感器,以及在试验桩P1、P2距桩端200 mm处安装光纤光栅（FBG）传感器,采用两种不同的测试技术全程监测了两根闭口预应力高强度混凝土（PHC）管桩现场贯入过程中的桩端阻力。试验结果表明：桩端阻力与土层的变化密切相关,土层越硬,桩端阻力越大,当桩端从粉质黏土层进入粉土层时,桩端阻力明显增大,粉土中的桩端阻力达到粉质黏土层的2倍;整个贯入过程中,同一土层不同位置的差异性对桩端阻力也存在较大影响,在距离地面1.50 m处,P1和P2桩FBG传感器桩端阻力的差值达到了89.29 kN,而在距离地面3.50~4.50 m处,两桩的桩端阻力则相差较小。 相似文献
9.
围压循环变化将引起土体孔压累积,加剧土体累积塑性应变,导致地基灾变事故。为研究围压循环变化对饱和粉质黏土变形特性的影响,利用GDS双向振动三轴仪,进行部分排水时饱和粉质黏土的变围压循环三轴试验,研究不同应力路径斜率和循环动应力比时饱和粉质黏土的孔压、轴向累积塑性应变和体应变发展规律,建立部分排水条件时考虑循环围压和循环动应力耦合作用的地基粉质黏土累积应变数学模型。试验结果表明：部分排水时饱和粉质黏土孔压、轴向累积塑性应变和体应变均随循环动应力比和应力路径斜率的增大而增大;动孔压比随着振动次数的增加明显分为急剧增加、快速下降和持续平稳3个阶段;轴向累积塑性应变和体应变均随振动次数的增加而增大。当加载次数超过2 500次时,粉质黏土孔压趋于平稳,变形速率略有降低,但变形持续增加。补充试验结果表明,所建立模型与试验结果具有较高的一致性。研究结果将为交通循环荷载导致的地基灾变控制技术提供理论依据。 相似文献
10.
《城市地质》2020,(1)
水平基床系数是地下工程设计的重要参数,其数值的准确性关系到工程的安全性和经济性,由于技术原因水平基床系数是比较难确定的参数,旁压试验作为一种原位试验,应力应变关系清晰,估算水平基床系数具有很好的可靠性。在通州地区0～100m深度范围内,针对黏性土及砂土,采用旁压试验法估算水平基床系数。结果表明:通过对0～100m深度范围内粉质黏土及砂土旁压试验,标准贯入试验获取的基床系数和规范经验值进行对比,可以采用旁压试验引进折减系数获取水平基床系数。30m以上可塑粉质黏土,修正系数可取0.23,30～80m密实砂土修正系数可取0.15,80m以下可塑-硬塑粉质黏土修正系数可取0.20。 相似文献
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12.
Radhi M. Alzubaidi 《Geotechnical and Geological Engineering》2016,34(1):155-166
The pressuremeter, used for in situ soil testing, has undergone significant development both in its technical applications and in the interpretation methods employed for a range of parameters. Several methods have been developed to evaluate the undrained strength of a soil using a pressuremeter. Test results based on these methods show distinctive discrepancies. Different methods for evaluating the limit pressure are also presented. The values of these limit pressure evaluations vary based on the evaluation method used. In any given test, the limit pressure results also affect the values deduced for undrained shear strength. The discrepancies in the undrained shear strength values exceeded 80 % for the same test when evaluations were made with different interpretation methods. Because of the large discrepancies in the results of the undrained shear strength when using different analysis methods, the Gibson and Anderson method is recommended as being most reliable in deducing undrained shear strength values from pressuremeter tests, particularly for use in the design of foundations. 相似文献
13.
为了认识冻土旁压试验结果与常规试验结果之间的关系,在室内分别开展了冻结重塑黏土的旁压试验和单轴压缩试验,并对试验结果进行了对比分析。结果表明,在各级荷载作用下旁压曲线一般都呈现应变速率衰减的趋势,而单轴曲线在冻土破坏时会出现渐进流动阶段。旁压试验的应力-应变曲线呈现应变硬化型,而且出现初始拟弹性阶段;而单轴试验的应力-应变曲线则属于应变软化型,并在轴向应变大约为10%时达到剪应力峰值。温度相同时,旁压试验的剪切强度以及初始弹性模量都要大于单轴试验,且温度越低差值越大。 相似文献
14.
Ali Soleimanbeigi 《Geotechnical and Geological Engineering》2013,31(5):1511-1524
Undrained shear strength (su) of foundation soil of Marquette interchange near Milwaukee, Wisconsin was evaluated from the results of a number of pressuremeter tests conducted on normally consolidated (NC) organic silts and overconsolidated (OC) silty clay. The su-values were interpreted from traditional closed-form methods. The pressuremeter geometry and test sequence as well as response of the soil profiles were also simulated using axisymmetric finite element (FE) method with Cam-Clay soil model. The Cam-Clay model parameters were estimated from laboratory tests on undisturbed soil samples. Results show that the su estimated from the rate of cavity pressure change with volumetric strain (referred to as direct traditional method) is almost twice the su estimated from an indirect traditional method that estimates su from shear modulus, in situ horizontal stress, and ultimate cavity pressure obtained from the cavity pressure curves. The su-values predicted from the FE models are lower than those estimated from the traditional methods and shows that the assumption of infinite pressuremeter length in traditional methods results in overprediction of undrained shear strength by a factor of 1.5 for NC clay and 2.2 for OC clay. The results of finite element analysis considering Cam-Clay soil model and finite length for pressuremeters suggest the undrained shear strength of 63 ± 7 kPa for NC organic silt and 259 ± 68 kPa for OC silty clay. 相似文献
15.
高含盐粉土不仅含盐量较高,而且黏粒含量极低,粉粒含量高,级配不均匀,导致难以压实,强度低。为了了解此类特殊粉土的力学特性,在室内物理化学性质分析的基础上,进行原位旁压试验和原状土样的三轴试验,充分分析了高含盐粉土的力学性质。高含盐粉土的可溶性盐含量高达2.9%,主要是高硅、铝,水溶盐以Cl－和Na+为主,属氯盐碱性土。旁压试验结果表明,临塑压力可取350 kPa、极限压力可取500 kPa、旁压模量Em可取1 750 kPa、剪切模量Gm可以700 kPa作为参考值。室内力学试验进一步分析表明,该土体具有较强的剪胀性,在轴向应变达到12%左右时,试样达到稳态状态。围压150 kPa下的峰值强度能达到600～800 kPa,残余强度也能达到450～550 kPa。 相似文献
16.
This paper presents a methodology for identifying soil permeability from pressuremeter test. On the first part we present a numerical analysis of the permeability effects on the test results. We demonstrate that different drainage conditions arise during test, as a function of the loading rate and the soil permeability. We also studied the pore pressure dissipation during strain holding stages. Based on this analysis of these tests, we propose a general procedure to identify simultaneously mechanical parameters and permeability from pressuremeter tests with strain holding test stages. This procedure was applied on tests performed on natural Saint–Herblain clay. An apparatus called pressio‐triax was developed for this purpose. The values of the mechanical parameters as well as of the permeability value were found to agree very well with the values of the same parameters obtained from conventional laboratory tests. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
17.
基于统计分析结果合理布置测点,测试土体力学参数具有测试结果准确和经济快捷等优点。在赣南某稀土矿山非等间距布置6个测点,共计18个测试孔,通过旁压试验和钻孔剪切试验测试了离子型稀土矿体的旁压模量、变形模量、压缩模量、黏聚力和内摩擦角等力学参数,运用经典统计学方法和地质学统计方法分析矿体力学参数的空间变异性。研究结果表明:试验矿块内矿体的黏聚力和旁压模量属于强变异,黏聚力的变异系数为0.48,旁压模量的变异系数为0.36;内摩擦角属于弱变异性,其变异系数为0.067;假设由18个测试孔的测试数据计算得到各力学参数为真值,若15%为工程可接受的误差,运用经典统计学方法分析和地质统计学方法分析结果表明,对于试验矿块,在45 m范围内均匀布置5个测点,测试结果可有效估计矿块内黏聚力和旁压模量的平均值和变异系数。 相似文献
18.
The extreme net pressure resulting from an expansion in a cylindrical or spherical cavity within a limitless medium is studied.
Performing the static and kinematic approaches of yield design theory, analytical solutions of the extreme net pressure are
established for cohesive–frictional as well as for purely cohesive medium. In the case of a cylindrical cavity, the identification
between the analytical extreme net pressure and limit net pressure leads to the prediction of shear strength characteristics
of soil. As useful result, in soil mechanics, the assessment of correlations using pressuremeter data has been discussed.
Also, some assumptions for designing foundations, from pressuremeter data, have been highlighted. 相似文献
19.
The conventional interpretation methods of pressuremeter testing effectively approximate pressuremeter membranes as infinitely long. As a result, the effects of the two‐dimensional geometry of pressuremeters are ignored, leading to an overestimation of soil shear strength by pressuremeter testing, as demonstrated in several previous studies. This paper presents results of a numerical study of two‐dimensional geometry effects on self‐boring pressuremeter tests in undrained clay. The results are obtained using critical state soil models with an effective stress formulation. This is in contrast to most (if not all) existing studies on pressuremeter geometry effects, which were based on perfectly plastic soil models (e.g. Yu (Cavity expansion theory and its application to the analysis of pressuremeters. DPhil Thesis, The University of Oxford, 1990), Yeung and Carter (Proc. 3rd Int. Symp. on Pressuremeters, 1990), and Houlsby and Carter (Géotechnique, 1993; 43 (4):567–576)). The present study suggests that the overestimation of soil strength due to the neglect of finite pressuremeter length is significantly affected by the soil model used in the calculations. It is found that for clays with a high overconsolidation ratio (OCR) the strength overestimation predicted using critical state soil models could be considerably smaller than that predicted using perfectly plastic soil models. The main conclusion of this numerical study is that care must be exercised before directly applying any numerically determined pressuremeter geometry correction factors in practice. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献