不同回填土条件下软土区强夯加固效果测试与对比分析

为了探讨在软土区山皮土与细砂2种不同回填土土质条件下的强夯加固效果,在同一滨海区开展了2种回填土土质条件下的现场强夯对比试验。并对现场不同试验区强夯前后标准贯入试验（SPT）与浅层平板载荷试验结果进行分析与对比研究。根据所得出的结论,提出了进一步提高强夯后地基处理效果的建议。     

Neotectonic state of stress in the Jura Mountains

Abstract

For the determination of the tectonic stress field in the region of the Jura Mountains, three different relief techniques have been used in 18 test sites. In six test sites measurements have been carried out in horizontal boreholes using the doorstopper method. In the remaining test sites measurements were made in vertical boreholes by the doorstopper method (8), triaxial strain cell method (3) and borehole slotter (1). Additionally, analyses of borehole breakouts from six deep wells are presented.

Orientation of maximum horizontal stress clearly deviates from the uniform NW-SE orientated central and western European stress field. Local stress sources, which are probably related to active decollement tectonics in the Jura Mountains, may explain the deviation in stress orientations in comparison to the foreland. Normal stress magnitudes perpendicular to the trend of compressional structures in the Folded Jura are largest in the southeastern Upper Rhine Graben and its southwards prolongation into the Jura Mountains. Low stress magnitudes are characteristic for the eastern termination, intermediate ones for the southern foreland of the Jura Mountains.     

Small-strain constrained elastic modulus of clean quartz sand with various grain size distribution

Approx. 120 resonant column (RC) tests with additional P-wave velocity measurements using piezoelectric elements have been performed on 19 clean quartz sands with piecewise linear, gap-graded, S-shaped or other smoothly shaped grain size distribution curves. For each material different pressures and densities were tested. It is demonstrated that the extended empirical equations for the small-strain constrained elastic modulus proposed by the authors in an earlier paper work well also for most of the more complex grain size distribution curves tested in the present study. These equations considering the influence of the uniformity coefficient of the grain size distribution curve were developed based on the data from tests on linear gradations. A further improvement of the prediction for the more complex grain size distributions can be achieved if the correlation equations are applied with a specially defined average inclination of the grain size distribution curve. Such an improvement is demonstrated not only for the small-strain constrained elastic modulus, but also for small-strain shear modulus, modulus degradation and Poisson's ratio.     

黏性土的动剪切模量比和阻尼比与剪应变关系的统计分析

动剪切模量比和阻尼比是土体重要的动力特性参数,这两种参数取值的合理性对场地地震响应分析的结果有重要影响.为进一步完善黏性土的动剪切模量比和阻尼比随剪应变的变化关系的研究,给出了新的计算模型和推荐曲线.新曲线的计算模型基于Davidenkov模型和新的阻尼比计算模型,通过对搜集的大量黏性土数据进行非线性回归分析后得到.将分析结果与已有国内外学者的成果进行对比,验证了新计算模型具有较好的可靠性和工程实用性.     

Factors affecting shear modulus degradation of cement treated clay

Cement stabilization is often used to improve the bearing capacity and compressibility of soft clays. The present paper aims to investigate the shear modulus degradation of cement treated clay during cyclic loading. A series of cyclic triaxial test was conducted on artificially cement treated marine clay to study the factors affecting the shear modulus degradation. The parameters considered for the study are cement content (2.5–7.5%), curing days (7–28), cyclic shear strain amplitude (0.3–1%), number of loading cycles (1–100) and loading frequency (0.1–0.5 Hz). As in the case of natural clays, cement treated clays exhibit stiffness degradation which depends on mix ratio, curing days and loading conditions. The results show that the shear modulus degradation decreases with increase in the shear strain amplitude, cement content and curing days. It is also noted that irrespective of the mix ratio and curing conditions, the degradation decreases with increase in loading frequency. An empirical relationship is proposed to predict the shear modulus degradation based on Idriss׳s degradation model. The performance of the proposed empirical model is validated with the present experimental results.     

Support vector regression to predict the performance of stabilized aggregate bases subject to wet–dry cycles

Durability is a notion that is integrated with the performance of stabilized pavement materials. Also, because it can be quantified and measured, it carries significant influence on the design of pavements. This study focuses on using support vector machine, a machine learning algorithm, in assessing the performance of stabilized aggregate bases subject to wet–dry cycles. Support Vector Regression (SVR) is a statistical learning algorithm that is applied to regression problems and is gaining popularity in pavement and geotechnical engineering. In our study, SVR was shown to be superior to the least‐squares (LS) method. Results of this study show that SVR significantly reduces the mean‐squared error (MSE) and improves the coefficient of determination (R²) compared to the widely used LS method. Copyright © 2011 John Wiley & Sons, Ltd.     

Numerical characteristics of the full operator hybrid simulation method

The full operator method (FOM) has been proposed to overcome some of the shortcomings of the commonly used operator splitting method (OSM). In particular, the FOM is improved by increasing the accuracy of both the predictor and corrector using the estimated tangent stiffness of the tested structure. The numerical characteristics of the FOM, including stability and accuracy, are investigated in this study. It is shown that FOM is conditionally stable. The stability and accuracy characteristics are dependent on the accuracy of the estimated tangent stiffness and the parameters associated with the acceleration variation in the time-stepping integration method. Mass-spring systems with different types of nonlinearity, including hardening, stiffening, and softening behavior, are used to evaluate the performance of the FOM. It is found that the FOM can capture these types of nonlinearity with satisfactory accuracy. Using a prototype 12-story composite coupled wall system, the influences of the strong nonlinearity of the system as well as the displacement control errors from hydraulic actuators on the performance of the FOM are explored. The results show that the FOM is capable of generating reasonably accurate results despite the presence of strong structural nonlinearity and displacement control errors.     

自适应基质矿物体积模量提取和流体替换验证(英文)

岩石物理学研究中Gassmann方程被广泛应用于预测岩石中的地震波速度,由于输入的基质矿物体积模量参数不准确,极大的影响预测结果的可靠性,特别是复杂基质矿物组合的碳酸盐岩储层。因此本文结合Russell流体因子和Gassmann-Boit-Geertsma方程计算式,通过引入干岩石骨架泊松比,提出了一种基质矿物体积模量提取方法,能够自适应反演岩石基质矿物等效体积模量,提高流体影响预测的可靠性,通过实际资料流体替换验证,该方法的预测结果是可靠的,并且计算效率高、适应性强。     

浅谈GPS-RTK在线路横断面测量的方法

介绍使用GPS-RTK线路横断面测量的基本思路和操作方法,包括适用于GPS-RTK作业的任意中桩点切线方位角的计算和横断面线的确定,提高了横断面测量的工作效率和数据精度。     

下卧软弱岩带变形模量取值研究

软弱岩带的变形模量对于工程建设意义重大,当前变形试验方法难以表征原位条件下软弱岩带的变形模量,导致取值偏于保守.本文基于弹性力学推导了下卧软弱岩带变形模量的解析解,建立了一种新的软弱岩带变形模量的取值方法.在现场试验成果的基础上,采用有限元反演,数值模拟成果与试验计算成果较为吻合,证明该计算方法合理可行,较常规方法直接...