对黄土地区钻孔和探井试样试验指标的分析评价

通过对济南地区次生黄土所采集的钻孔和探井土样进行浸水试验,并对其主要物理力学指标进行了分析评价,得出探井试样比钻孔试样所具有的试验指标更为真实可靠,因此次生黄土分布区采集探井试样进行湿陷性浸水试验是十分必要的。     

西宁地区次生盐渍土的分布特征及地基处理方法

西宁地区次生盐渍土主要分布于山麓斜坡带高阶地和河谷高漫滩,前者属中～弱硫酸、亚硫酸盐渍土,且多具中等～强烈湿陷性,盐份主要来自斜坡后缘含盐碎屑岩风化物及易溶盐;后者为中等亚氯、亚硫酸盐渍土,溶于土中的盐份系浅层咸地下水常年毛细上升蒸发所致。其次生盐渍土的松胀性、溶陷性、腐蚀性较强,工程建设要引起重视。     

天津滨海绿地土壤水分特征曲线的拟合与比较分析

土壤水分特征曲线是定量研究土壤水运动和溶质运移的重要参数,对滨海地区盐碱土绿化建设有重要的作用。通过对天津滨海盐碱地绿化土进行脱水试验,选取Gardner模型和VG模型对实测数据进行拟合。运用对数简化方法对Gardner模型变形后进行回归分析,另外,采用软件Matlab的非线性拟合函数lsqcurvefit对VG模型进行了参数求解。结果表明:Gardner模型和VG模型都可以用于天津滨海盐碱地绿化土水分特征曲线的拟合。Gardner模型的参数求解过程简单,但用VG模型计算出的残差平方和较Gardner模型小,拟合效果优于Gardner模型。同时,该区绿地土断面上各层之间的拟合曲线相近,持水能力相当,说明了该区绿化土断面上各土层的土壤质地和结构差异不大。     

论三亚地区标贯试验锤击数与地基承载力的关系

通过对三亚华宇度假酒店项目场地运用普通碎石桩地基处理后进行复合地基的静载荷试验和对应的浅层0～3m深度范围内桩间土标准贯入试验建立关系,得到海南三亚地区标贯击数和地基承载力的相关关系散点图及对应表.可以用标贯试验手段检验整个场地的地基承载力,减少了载荷试验的数量,为整个三亚地区沿海的地基承载力的评定提供经验参数,节约检测成本,缩短检测工期.建立了海南三亚地区标贯击数和地基承载力的相关关系,填补了该地区运用标贯试验确定地基土承载力值的空白.     

高山湖盆区特殊性工程岩土

研究了国道219线新疆接西藏段阿克赛钦湖区新生代高山湖盆的构造演化及沉积物岩相分带,利用地质调查、钻探、物探、试验等工作成果,对公路展布带及地基影响深度范围内的特殊性工程盐渍土的盐渍化类型、程度、盐胀性,冻土的类型、融沉性、盐渍化冻土进行了研究与分类。综合评价了特殊土的工程性能和对公路工程的影响程度,为改建公路的选线和路基设计提供了依据,并提出了经济合理、可行的特殊土工程整治措施。     

黄河三角洲盐渍土区土地整理实施及绩效评价

该文以垦利县永安镇五村片省级土地整理项目为例,在对土地整理规划设计、实施管理和效益评价的基础上,提出了黄河三角洲盐渍土区土地整理项目绩效评价的重点内容、主要指标和基本思路,对于丰富黄河三角洲盐渍土区土地整理理论,规范和指导黄河三角洲盐渍土区土地整理实践具有重要的指导和现实意义。     

山东省黄河下游地区盐渍土地球化学特征

山东省黄河下游地区盐渍土受地质构造、地形地貌、水资源、气象等因素控制。盐渍土的形成与水体地球化学作用等密切相关。根据盐渍土地球化学元素分布规律、植物群落分布状况,将本区域划分成3个不同自然环境类型的地球化学分区和盐渍分区。为合理治理土壤盐渍化和系统规划农业布局提供信息。     

浸泡作用下碎石土剪切强度衰减规律及机理

水库蓄水后, 滑坡体碎石土经受长时期的浸泡, 力学性质发生改变, 从而影响滑坡整体稳定性。为探究浸泡对碎石土力学性质的影响规律, 选取三峡库区马家沟滑坡后缘未经受长期浸泡作用的碎石土进行大型直剪试验, 分析了不同浸泡天数下碎石土的剪切力学性质。试验结果表明: 浸泡40 d后, 碎石土黏聚力下降幅度达39%, 内摩擦角下降幅度为8.3%;碎石土黏聚力在浸泡前期快速下降, 下降速率随浸泡天数增加而降低, 浸泡20 d后, 黏聚力基本达到稳定。为探究碎石土抗剪强度降低的原因和机理, 对粉质黏土(碎石土细粒成分)进行了三轴剪切试验、激光粒度分析及浸出液阳离子分析等试验, 揭示了碎石土抗剪强度的衰减机理为: 浸泡作用下, 碎石土中的粉质黏土发生矿物溶解、离子交换与吸附作用, 土体中大颗粒细化, 胶结作用减弱, 进而导致碎石土整体抗剪强度降低。研究结果对库区碎石土滑坡评价与治理具有一定的指导意义。      

西宁地区盐渍土盐胀特性及其地基处理方法探讨

针对西宁地区盐渍土的特殊工程地质性质,就其地基处理方法通过数个工程实例从场地的盐渍土特点及其地基处理进行了分析探讨,提出了该类地基通过碎石桩及碎石垫层等处理方法和经验。     

鲁西石炭、二叠系沉积矿床成矿系列

石炭、二叠系是我国主要含煤地层,它广泛分布于鲁西隆起区。该区上石炭统由本溪组和太原组组成,二叠系下统由山西组和下石盒子组组成,二叠系上统由上盒子组组成。石炭系和二叠系划分出五个成矿系列。本溪组成矿系列主要有 G 层铝土矿,其次是山西式铁矿、硬质耐火粘土矿、软质耐火粘土矿和伴生镓元素。太原组成矿系列主要有煤,其次是膨胀粘土矿、陶瓷“大同土”。山西组成矿系列主要有煤,其次是膨胀粘土矿、菱铁矿。石盒子组万山段成矿系列主要有 A 层硬质耐火耐土矿和铝土矿,其次是铝土矿中伴生镓,石盒子组奎山段成矿系列主要有石英砂岩。这些矿床应归属于“滨海相→滨海沼泽相→内陆沼泽相→内陆湖泊相→内陆河湖相的化学→碎屑岩建造沉积成矿系列”。     

Influences of soil moisture and salt content on loess shear strength in the Xining Basin,northeastern Qinghai-Tibet Plateau

Moisture and salt content of soil are the two predominant factors influencing its shear strength. This study aims to investigate the effects of these two factors on shear strength behavior of loess in the Xining Basin of Northeast Qinghai-Tibet Plateau, where such geological hazards as soil erosion, landslides collapse and debris flows are widespread due to the highly erodible loess. Salinized loess soil collected from the test site was desalinized through salt-leaching in the laboratory. The desalinized and oven-dried loess samples were also artificially moisturized and salinized in order to examine how soil salinity affects its shear strength at different moisture levels. Soil samples prepared in different ways(moisturizing, salt-leaching, and salinized) were measured to determine soil cohesion and internal friction angle. The results show that salt-leaching up to 18 rounds almost completely removed the salt content and considerably changed the physical components of loess, but the soil type remained unchanged. As salt content increases from 0.00% to 12.00%, both the cohesion and internal friction angle exhibit an initial decrease and then increase with salt content. As moisture content is 12.00%, the salt content threshold value for both cohesion and internal friction angle is identified as 3.00%. As the moisture content rises to 16.0% and 20.00%, the salt content threshold value for cohesion is still 6.00%, but 3.00% for internal friction angle. At these thresholds soil shear strength is the lowest, below which it is inversely related to soil salinity. Beyond the thresholds, however, the relationship is positive. Dissimilar to salinity, soil moisture content exerts an adverse effect on shear strength of loess. The findings of this study can provide a valuable guidance on stabilizing the engineering properties of salinized loess to prevent slope failures during heavy rainfall events.     

PRIMARY ANALYSIS ON GROUNDWATER, SOIL MOISTURE AND SALINITY IN FUKANG OASIS OF SOUTHERN JUNGGAR BASIN

１INTRODUCTIONSoilandlandformarethemoreimportantenviron－mentalfactorsaffectingthedistributionofvegetationinabasinwhenthemeteorologicconditionissimilaronalargescale，especiallyspatialandtemporalvariationsofthesoilmoistureandsaltcontent．Inaridareasthesoil…     

Characteristics and causes of the preconsolidation stress of soils in the Yellow River Delta

Preconsolidation stress ( σ P') is the maximum effective stress that a soil has suffered throughout its life. From a geotechnical point of view, pre-consolidation stress has great importance because it separates elastic and reversible deformations from inelastic and only partially irreversible deformations and marks the starting point of high compressibility. In this study we calculated the preconsolidation stress for 72 undisturbed soil samples from the Yellow River Delta, using the oedometer tes...     

冻土地基中锥管板条装配式基础抗拔承载性能试验研究

为了分析冻土地基中输电线路基础发生冻拔破坏的科学问题, 以锥管板条装配式基础为研究对象, 采用室内模型试验测试及分析的研究方法, 开展了不同环境温度下, 冻土地基的冻结试验和基础的上拔加载试验, 分析了地基温度场、位移场的分布特征以及基础抗拔承载力与温度之间的关系, 揭示出上拔荷载作用下冻土地基的破坏模式。研究结果表明: 冻结试验中, 模型基础的冻拔位移均小于周围地基土体的冻胀位移, 基础对地基土体的冻胀存在反约束作用, 距离基础越近, 约束作用越明显; 不同冻结环境温度下基础的上拔加载试验中, 抗拔极限承载力均随环境温度的降低近似呈线性增大, 增加速率接近1.8 kN/℃; 在冻结与上拔力双重作用下, 地基土体首先出现局部张拉破坏, 随着上拔荷载的不断增加, 地基土体逐渐由局部张拉破坏过渡为整体剪切破坏。研究成果可为这种形式的基础在冻土地基中的应用提供理论依据和实践经验。      

Effects of topography on dynamic responses of single piles under vertical cyclic loading

This paper describes model tests of single piles subjected to vertical cyclic compressive loading for three kinds of topography: sloping ground, level ground, and inclined bedrock. Comprehensive dynamic responses involving cyclic effects and vibration behaviours are studied under various load combinations of dynamic amplitude, mean load,frequency and number of cycles. Test results show that permanent settlement can generally be predicted with a quadratic function or power function of cycles.Sloping ground topography produces more pronounced settlement than level ground under the same load condition. For vibration behaviour,displacement amplitude is weakly affected by the number of cycles, while load amplitude significantly influences dynamic responses. Test results also reveal that increasing load amplitude intensifies nonlinearity and topography effects. The strain distribution in a pile and soil stress at the pile tip are displayed to investigate the vibration mechanism accounting for sloping ground effects. Furthermore, the dynamic characteristics among three kinds of topography in the elastic stage are studied using a three-dimensional finite method. Numerical results are validated by comparing with experimental results for base inclination topography. An inclined soil profile boundary causes non-axisymmetric resultant deformation, though a small difference in vertical displacement is observed.     

土质参数变异性研究

研究岩土参数的变异特征是将概率统计方法应用于岩土工程的一项基础性工作。本文研究了西安地区粉质粘土的三个重要实测参数,即天然容量γ、抗剪指标C和Φ值、压缩系数a_v的变异特征及其规律,最后讨论了取土扰动对以上土质参数变异性的影响。     

L波段对不同盐类土壤的微波介电特性分析

 土壤盐碱化是世界面临的一大难题。微波遥感探测土壤具有优势,L波段对土壤含水量和含盐量较为敏感。为了分析不同盐类对土壤介电特性的影响,本文利用L波段(1.43 GHz)微波谐振腔测量了我国盐碱土中普遍存在的3种盐类(NaCl,Na₂SO₄,NaHCO₃)土壤样品的介电常数,研究了土壤介电常数与含水量、含盐量和盐种类的关系。得出结论:实部主要由土壤的含水量决定,含盐量对实部的影响无明显规律;虚部值随含水量和含盐量的增加而增大;3种盐类土壤介电常数虚部随含盐量变化呈现不同的递增趋势,在含盐浓度一定的条件下,虚部值是ε″ _NaCI>ε″ _NaHCO3>ε″ _Na2SO4;在某一含盐量点3种盐类土壤虚部随含水量变化的斜率不同,以此能将3种盐类区分。该研究为建立含不同盐类土壤介电常数模型和微波遥感监测土壤盐碱化提供了实验的依据。     

Practical method and application study for predicting cyclic accumulative deformations of the saturated soft clay

The distribution of saturated soft clay is greatly wide in China. The current main measures adopted to deal with soft soil foundations may lead to environmental pollution, even some engineering accidents may happen on soft soil foundations. In order to solve engineering problems of saturated soft soil foundations well, researches of mechanical properties of them are necessary. One of the most important mechanical characteristics of saturated soft clay is its cyclic accumulative deformation under cyclic loadings. For saturated soft clay, the cyclic accumulative deformation is similar to the creep behavior under static loadings. Therefore, the cyclic accumulative deformation is equivalent to the creep, the number of loading cycles is seen as the time, and this study develops a practical method for predicting the cyclic accumulative deformation of saturated soft clay with the creep theory. The method is a pseudostatic elasto-plastic finite element method implemented by ABAQUS software. A fitted equation between cyclic accumulative strain and number of loading cycles and the empirical relationship of parameters of fitted equation were established with a series of cyclic triaxial compression tests. Then with this empirical relationship of parameters, the method developed by this study was employed to predict the cyclic accumulative deformation under cyclic triaxial tension tests. Predicted results were in good agreement with test results, and the effectiveness of this method was thus validated for different stress states. The method was then applied in analyzing the cyclic accumulative deformation for soft soil foundation of a pile-supported wharf structure.     

泗河冲洪积扇松散岩土体地温场自恢复能力研究

泗河冲洪积扇区域分布厚层松散岩土体,浅层地温能开发利用潜力巨大,查明地温场的温度自恢复能力并分析其影响因素,对地源热泵工程换热器的设计具有重要参考价值。笔者开展了多组现场热响应试验,并采用高精度测温线缆,长期监测地埋管换热器周边不同岩性、不同深度岩土体温度变化情况,以查明其变化规律。研究表明:在同种工况下,砂性土的温度恢复能力要远强于粘性土,地温的恢复主要发生在负荷停止的初期。研究区粘性土温度自恢复能力差,岩土体热物性参数、地下水径流条件、埋管循环水温度、气温及变温带深度是影响地温场恢复能力的因素。     

Study on deformation law of circular foundation under combined loading

The foundations of some ocean engineering structures are built to withstand not only the vertical gravity load V, but also the horizontal load H induced by sea waves and current. The horizontal load includes the concentrated force load, the moment load M, and the torque load T termed also as combined loading. It is of academic and engineering significance to study the deformation law of submarine seabed due to combined loading. On the basis of the three-dimensional elastic mechanics solution of circular foundation, numerical methods are used to analyze the deformation law of submarine soil under circular foundation with six degrees of freedom. The finite element analysis results give the elastic deformation law of soil in three dimensional spaces, modify the theoretical elasticity solution, and presents nonlinear soil deformation mechanism under the circular foundation with six degrees of freedom.