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沉积方向对饱和密砂力学特性的影响 预览
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作者 罗强 汤振 +1 位作者 马可栓 王奎阳 《长江科学院院报》 CSCD 北大核心 2020年第1期113-118,共6页
沉积方向对土体强度的影响对于研究初始各向异性而言具有重要意义。基于砂土颗粒的毛细效应提出一种试样制备方法,制备若干组具有不同沉积方向的密砂试样。通过系列三轴固结排水剪切试验研究沉积方向对强度、体变的影响,并拟合得到沉积... 沉积方向对土体强度的影响对于研究初始各向异性而言具有重要意义。基于砂土颗粒的毛细效应提出一种试样制备方法,制备若干组具有不同沉积方向的密砂试样。通过系列三轴固结排水剪切试验研究沉积方向对强度、体变的影响,并拟合得到沉积方向和峰值强度的关系公式。研究表明:沉积方向夹角在0°~90°范围内对峰值强度和体变的影响比较显著,当沉积方向夹角与试样破坏面方向(45°+?/2)接近时,剪切带形成得更早,试样更容易达到破坏,所对应的峰值强度更低,达到峰值和残余状态更早。依据试验结果拟合得到沉积方向夹角和峰值强度的关系公式,公式预测结果与试验结果吻合度在不同围压条件下均较高。研究结果为研究砂土的初始各向异性力学特性提供了有益的方法。 展开更多
关键词 砂土 毛细效应 沉积方向 固结排水 剪切试验 峰值强度
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多功能沙地播种机的设计 预览
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作者 邱毅清 武建新 +1 位作者 陈强 张涵 《农机化研究》 北大核心 2020年第3期138-142,共5页
随着沙漠地区种植技术的发展,且因目前播种机存在结构功能单一、体积大、播种效果差等问题,一般的播种机已经无法满足现状。为此,设计开发了沙漠专用的多功能播种机,主要介绍了总体设计方案、主要技术参数及关键零部件的确定与设计。该... 随着沙漠地区种植技术的发展,且因目前播种机存在结构功能单一、体积大、播种效果差等问题,一般的播种机已经无法满足现状。为此,设计开发了沙漠专用的多功能播种机,主要介绍了总体设计方案、主要技术参数及关键零部件的确定与设计。该机由地轮、开沟圆盘、覆土器、镇压轮、机架、种箱及肥料箱等组成,一次性完成开沟、施肥、播种、镇压等作业,机具结构设计合理,为中国的沙漠地区作业提供了技术支持。 展开更多
关键词 沙地 播种机 夹持式 开沟器
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非等向固结砂土极小应变刚度的超弹性模型 预览
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作者 张帅 程晓辉 王天麟 《工程力学》 EI CSCD 北大核心 2020年第1期145-151,共7页
反映砂土极小应变刚度的 Hardin-Richart 公式主要是基于等向固结的实验数据,但是天然土体基本都是处于非等向固结状态。实验研究表明,随着非等向程度的加深,Hardin-Richart 公式对土体刚度的估算偏差越大,误差最大可超过 20%。3 种类... 反映砂土极小应变刚度的 Hardin-Richart 公式主要是基于等向固结的实验数据,但是天然土体基本都是处于非等向固结状态。实验研究表明,随着非等向程度的加深,Hardin-Richart 公式对土体刚度的估算偏差越大,误差最大可超过 20%。3 种类型的超弹性模型能够反映土体极小应变刚度随应力水平增大而增大的幂律关系,但仅有 HE1 模型具有弹性剪胀等特殊的正剪耦合特性,对土体非等向固结状态下的刚度规律趋势预测正确。HE1 模型对土体非等向固结状态下的刚度规律预测结果受到其参数取值的影响,但总体而言与实验结果总结的规律一致。 展开更多
关键词 非等向固结 极小应变刚度 Hardin-Richart公式 超弹性模型 砂土
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Influence of Aggregate Grain Size on the Formulation of Sand Concrete in the Construction Industry in Congo 预览
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作者 Charlène Bassolokidi Nkengue Narcisse Malanda +2 位作者 Gilbert Ganga Paul Louzolo-Kimbembe Guy Richard Mouengue 《地质材料(英文)》 2019年第4期81-96,共16页
The main objective of this study is to contribute to the optimization of the formulation of sand concretes and its valorisation according to natural sands from different quarries or extraction sites. Physical characte... The main objective of this study is to contribute to the optimization of the formulation of sand concretes and its valorisation according to natural sands from different quarries or extraction sites. Physical characteristics of natural sands have been determined and improved by the addition of crushing sand, taking into account the too fine elements of the sand. Four types of sand were used (Congo River, Djiri, Mfilou, crushed sand). The concrete formulations proposed from improved sands (30% crushed sand and 70% natural sand) reveal an increase in mechanical strength. Thus, it appeared that this improvement of the natural fine sands by the crushing sand has brought a clear increase in the maneuverability of the concretes and the physico-mechanical characteristics of nearly 50%, although this crushing sand has a sand equivalent value of less than 70%. These results augur well for the durability of structures in the construction industry in Congo. 展开更多
关键词 SAND FORMULATION RECOVERY Materials SAND CONCRETE Physico-Mechanical Characteristics Construction
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铸造砂型3D打印设备混砂均匀性分析 预览
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作者 冯兵 王志刚 +1 位作者 赵龙 闫小龙 《科技视界》 2019年第14期88-89,共2页
本文针对3D打印设备混砂机在混砂过程中影响混砂均匀性的因素进行分析,通过对各类影响因素的控制,彻底解决偶尔出现的混砂不均匀的问题,从而提升了混砂过程的稳定性及混砂质量。
关键词 3D打印 砂子 固化剂 砂型
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白刺灌丛沙堆的生态位构建作用 预览
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作者 王俊杰 《甘肃林业科技》 2019年第3期36-37,共2页
白刺沙包是白刺削弱风速滞留风沙形成的灌丛沙堆。分析指出,沙包发育是白刺的生态位构建过程,通过积沙覆沙蓄水保墒,提高降水有效性;梭梭、沙拐枣则更新覆沙层以构建生态位。砂田和红沙洋芋与之原理相同。
关键词 白刺沙包 生态位构建 风沙 粒径 覆沙层 透水保墒
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The Feasibility of Basalt Rock Powder and Superfine Sand as Partial Replacement Materials for Portland Cement and Artificial Sand in Cement Mortar 预览
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作者 Hongxia Qiao Desire Ndahirwa +1 位作者 Yuanke Li Jinke Liang 《材料科学与应用(英文)》 2019年第1期1-9,共9页
The research gap on the feasibility of basalt rock powder(BRP)and superfine sand(SS)in preparation of cement mortar is significant.This study examines probable changes occurred in the modified cement mortar due to inc... The research gap on the feasibility of basalt rock powder(BRP)and superfine sand(SS)in preparation of cement mortar is significant.This study examines probable changes occurred in the modified cement mortar due to incorporation of certain quantity of basalt rock powder and superfine sand in mixture proportion.The cement mortar included Portland cement,artificial sand and water as principal mixture constituents.Then,basalt rock powder and superfine sand were added as partial replacement materials for Portland cement and artificial sand respectively.Therefore,replacement percentages were 10%,15%,20%,25%and 30%when the basalt rock powder replaced Portland cement and in case the artificial sand was replaced by superfine sand,10%,20%,30%,40%and 50%.Then,the strength indexes such as flexural strength,compressive strength,ultrasonic pulse velocity and dynamic elastic modulus were investigated.The results show that the presence of basalt rock powder in mixture proportion increased the flexural and compressive strengths of cement mortar however the cement mortar that contained superfine sand illustrated inadequate mechanical performance as flexural and compressive strengths decreased remarkably.Moreover,when basalt rock powder and superfine sand were included together in mixture proportion,the cement mortar’s mechanical performance declined compared to that of the reference cement mortar.Despite the fact that basalt rock powder and superfine sand weakened the cement mortar’s mechanical properties,it was found that they can be added into the cement mortar as partial replacement of Portland cement and artificial sand in the following ratios:from 10%to 25%when basalt rock powder replaces Portland cement and from 10%to 20%when artificial sand is replaced by superfine sand. 展开更多
关键词 basalt rock powder superfine sand artificial sand cement mortar mechanical properties
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Impact of repeated loading on mechanical response of a reinforced sand 预览
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作者 Aida Mehrpazhouh Seyed Naser Moghadas Tafreshi Mehdi Mirzababaei 《岩石力学与岩土工程学报:英文版》 CSCD 2019年第4期804-814,共11页
Pavements constructed over loosely compacted subgrades may not possess adequate California bearing ratio (CBR) to meet the requirements of pavement design codes,which may lead to a thicker pavement design for addressi... Pavements constructed over loosely compacted subgrades may not possess adequate California bearing ratio (CBR) to meet the requirements of pavement design codes,which may lead to a thicker pavement design for addressing the required strength.Geosynthetics have been proven to be effective for mitigating the adverse mechanical behaviors of weak soils as integrated constituents of base and sub-base layers in road construction.This study investigated the behaviors of unreinforced and reinforced sand with nonwoven geotextile using repeated CBR loading test (followed by unloading and reloading).The depth and number of geotextile reinforcement layers,as well as the compaction ratio of the soil above and below the reinforcement layer(s) and the compaction ratio of the sand bed,were set as variables in this context.Geotextile layers were placed at upper thickness ratios of 0.3,0.6 and 0.9 and the lower thickness ratio of 0.3.The compaction ratios of the upper layer and the sand bed varied between 85% and 97% to simulate a dense layer on a medium dense sand bed for all unreinforced and reinforced testing scenarios.Repeated CBR loading tests were conducted to the target loads of 100 kgf,150 kgf,200 kgf and 400 kgf,respectively (1 kgf=9.8 N).The results indicated that placing one layer of reinforcement with an upper thickness ratio of 0.3 and compacting the soil above the reinforcement to compaction ratio of 97% significantly reduced the penetration of the CBR piston for all target repeated load levels.However,using two layers of reinforcement sandwiched between two dense soil layers with a compaction ratio of 97% with upper and lower thickness ratios of 0.3 resulted in the lowest penetration. 展开更多
关键词 GEOSYNTHETICS GEOTEXTILE Reinforced soil California bearing ratio (CBR) ELASTIC behavior Repeated loading DENSE SAND Medium DENSE SAND
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砂土中大直径开口桩打入过程的有限元模拟 预览
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作者 高尤毅 《低温建筑技术》 2019年第7期97-100,共4页
文中采用Abaqus软件中的耦合欧拉-拉格朗日法(CEL)模拟了砂土中大直径开口桩的打入过程。通过数值分析得到的土塞变化规律与现场试验结果较为一致,表明了CEL方法能够较好地模拟打桩过程。同时还得到了桩侧砂土的应力分布规律,并验证了... 文中采用Abaqus软件中的耦合欧拉-拉格朗日法(CEL)模拟了砂土中大直径开口桩的打入过程。通过数值分析得到的土塞变化规律与现场试验结果较为一致,表明了CEL方法能够较好地模拟打桩过程。同时还得到了桩侧砂土的应力分布规律,并验证了应力的h/R效应。 展开更多
关键词 砂土 开口桩 打入过程 有限元模拟 土塞 应力
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Heterogeneous tide-surge interaction during co-occurrence of tropical and extratropical cyclones in the radial sand ridges of the southern Yellow Sea 预览
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作者 XIONG Mengjie ZHANG Jinshan +1 位作者 ZHANG Weisheng YIN Chengtuan 《海洋湖沼学报(英文)》 SCIE CAS CSCD 2019年第6期1879-1898,共20页
The Radial Sand Ridges(RSRs)area in the southern Yellow Sea are subject to tropical and extratropical cyclone activities frequently,in which the special geometry feature and moving stationary tidal system result in co... The Radial Sand Ridges(RSRs)area in the southern Yellow Sea are subject to tropical and extratropical cyclone activities frequently,in which the special geometry feature and moving stationary tidal system result in complex storm-induced hydrodynamic processes,especially the tide-surge interactions.We studied a rare weather event influenced simultaneously by an extratropical cyclone EX1410 and Typhoon Vongfong as an example to investigate the characteristics of storm surges,wave-surge,and tide-surge interaction in the RSRs area,and applied a high-resolution integrally-coupled ADCIRC+SWAN model,in which the meteorological forcing inputs are simulated by the WRF-ARW model.The model is validated by records from 4 tide gauges and 2 wave buoys along the Yellow Sea coast.Results show that the tide-surge interactions are of considerable regional heterogeneousness.The surge curves at Lüsi(in south RSRs)and Jianggang(in middle RSRs)have abrupt falls near the time of low tide,where the peak occurrence time of interaction residuals tend to shift towards the mid-ebb period.Significant increase of bed shear stress in shallow waters was proved the dominant factor to affect the tide-surge interaction in broad tidal flats of the RSRs area.Differently,the interaction pattern in the Xiyang Trough(in north RSRs),showed a unique rising in mid-flood period due to the phase advances of real surge waves in relatively deep waters.Therefore,we suggested to the local flood risk management that the tide-surge interaction tends to alleviate the flooding risk in the RSRs area around the time of high tide,but aggravate the risk on the rising tide in the Xiyang Trough and on the falling tide in large-scale tidal flats of the southem RSRs area. 展开更多
关键词 ADCIRC+SWAN model Radial Sand RIDGES Jiangsu coast extratropical cyclone tide-surge interaction
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Influence of sand content on the flow characteristics of soft soil under cyclic and high-frequency vibration 预览
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作者 Zhuang Zhongxun Yin Deshun +1 位作者 Bai Chunyu Zhou Chao 《地震工程与工程振动:英文版》 SCIE EI CSCD 2019年第3期487-496,共10页
The flow characteristics of foundation soils subjected to train loads can present engineering hazards in highspeed railways. In order to verify the feasibility of blending coarse sand in modifying soft subsoil, undrai... The flow characteristics of foundation soils subjected to train loads can present engineering hazards in highspeed railways. In order to verify the feasibility of blending coarse sand in modifying soft subsoil, undrained pulling sphere tests were carried out and the train loads were simulated through localized and cyclic vibration at various frequencies. Laboratory testing results indicate that the fl ow characteristics of soft soil can be signifi cantly enhanced by high-frequency vibration;meanwhile the continuous increase in fl ow characteristics caused by cyclic vibration may be an important reason for the long-term settlement of soft subsoil. The infl uence of sand content on fl ow characteristics is also studied in detail, and it is shown that the addition of coarse sand can weaken the fl ow characteristics of soft soil induced by sudden vibration at lower than 50 Hz. Under the condition of cyclic vibration, the growth of the fl ow characteristics of sand-clay mixtures is mainly caused by the fi rst-time vibration in the cycle, and the increase in sand content can make the fl ow characteristics present a faster convergent tendency. 展开更多
关键词 SAND content FLOW characteristics PULLING SPHERE tests SOFT soil
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砂与黏土混合物强度特性环剪试验研究 预览
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作者 吕玺琳 张滨 章澎 《工程地质学报》 CSCD 北大核心 2019年第5期1110-1115,共6页
为分析砂和黏土混合物的强度特性,将石英砂和高岭土按不同质量比配制试验土样,开展了一系列固结排水条件下的环剪试验。通过设置轴压为75 k Pa、150 k Pa、300 k Pa和600 k Pa状态下开展试验,得到土样剪切角与剪切应力的关系曲线。根据... 为分析砂和黏土混合物的强度特性,将石英砂和高岭土按不同质量比配制试验土样,开展了一系列固结排水条件下的环剪试验。通过设置轴压为75 k Pa、150 k Pa、300 k Pa和600 k Pa状态下开展试验,得到土样剪切角与剪切应力的关系曲线。根据试验曲线的峰值剪应力,通过莫尔-库仑准则得到土样的黏聚力和摩擦角。结果表明,砂和黏土混合物的黏聚力在5~18 k Pa范围内波动,当高岭土含量为50%时黏聚力值达到最小值。当高岭土含量小于50%时,摩擦角随高岭土含量增加略有减小;当高岭土含量超过50%时,摩擦角随高岭土含量增加而减小的趋势更明显。 展开更多
关键词 砂土 高岭土 环剪试验 抗剪强度
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不同低温温度下砂土物理力学特性试验研究 预览
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作者 孙杰龙 任建喜 +2 位作者 李盛斌 曹雪叶 武雯利 《延安大学学报:自然科学版》 2019年第3期38-44,共7页
以白垩系富水砂层砂土为研究对象,对其在不同低温温度下的物理力学特性进行了分析。结果表明:砂土比热容随冻结温度降低呈现出先减小后增大再减小最终趋于稳定的变化规律,砂土导热系数随冻结温度降低而逐渐增大最终趋于稳定,其变化过程... 以白垩系富水砂层砂土为研究对象,对其在不同低温温度下的物理力学特性进行了分析。结果表明:砂土比热容随冻结温度降低呈现出先减小后增大再减小最终趋于稳定的变化规律,砂土导热系数随冻结温度降低而逐渐增大最终趋于稳定,其变化过程主要分为3个阶段,即:缓慢增大阶段、迅速增大阶段和基本稳定阶段;随冻结温度降低人工冻结砂土粘聚力、内摩擦角、弹性模量和单轴抗压强度会逐渐增大,但增大的幅度会随着冻结温度的降低而逐渐减小;在同一加载速率下,不同冻结温度下人工冻结砂土变形均表现为应变软化,人工冻结砂土试样破坏时应变较小,一般介于6%~10%之间。 展开更多
关键词 人工冻结 砂土 热物性 力学特性
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机器人单足系统-沙土塑性接触力学建模及验证
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作者 杨传潇 丁亮 +2 位作者 唐德威 高海波 邓宗全 《机器人》 EI CSCD 北大核心 2019年第4期473-482,506共11页
为了更好地实现足式移动机器人在柔软流动性地面的仿真以及反馈控制,提出了机器人单足系统与沙土(柔性地面环境)接触力学的模型.该模型讨论并继承了部分经典土力学中极限承载力理论的假设条件,并加以拓展和深化,分别建立了机器人硬质足... 为了更好地实现足式移动机器人在柔软流动性地面的仿真以及反馈控制,提出了机器人单足系统与沙土(柔性地面环境)接触力学的模型.该模型讨论并继承了部分经典土力学中极限承载力理论的假设条件,并加以拓展和深化,分别建立了机器人硬质足、柔性足与沙土环境的接触力学模型.与其他模型相比,该模型充分考虑了接触面和滑裂面的外形特征,且参数均为常用已测物理参数而不需要在线的辨识过程.设计、加工并搭建了机器人单足式移动平台,完成了单足系统移动平台与沙土环境准静态和动态冲击状态下的相互作用实验.实验和仿真预测结果的对比表明,预测结果与样本数据结果的总误差为8.97%,验证了塑性接触力学模型的准确性和预测足地接触变形时力学行为的有效性. 展开更多
关键词 塑性接触力学 机器人单足系统 硬质足 柔性足 沙土
基于电阻率的砂土渗透系数测试方法 预览
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作者 袁志华 王炳辉 +2 位作者 彭超 梅岭 王丽艳 《扬州大学学报:自然科学版》 CAS 北大核心 2019年第3期60-64,共5页
为了实现土体渗透系数的实时检测,利用电阻率测试无损和快速的优点,对砂土的电阻率及常水头渗透进行了检测试验,研究了砂土渗透系数和结构因子随孔隙率的变化规律,讨论了渗透系数与结构因子的关系.试验结果表明:渗透系数随着孔隙率的增... 为了实现土体渗透系数的实时检测,利用电阻率测试无损和快速的优点,对砂土的电阻率及常水头渗透进行了检测试验,研究了砂土渗透系数和结构因子随孔隙率的变化规律,讨论了渗透系数与结构因子的关系.试验结果表明:渗透系数随着孔隙率的增加而增加,均值粒径越大,渗透系数增加越快;结构因子随孔隙率的增大而减小,结构因子越小,渗透系数越大;并给出了渗透系数与结构因子的关系式,由结构因子换算得到的渗透系数与常水头测试的结果一致. 展开更多
关键词 渗透系数 电阻率测试 结构因子 孔隙率 砂土
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基于CPTU状态参数的无黏性土最大剪切模量评价方法 预览
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作者 段伟 蔡国军 刘松玉 《西南交通大学学报》 EI CSCD 北大核心 2019年第4期801-807,共7页
土体最大剪切模量是动力基础设计和地震场地响应分析的重要参数,目前该参数的确定主要来源于室内试验,但室内试验值难以反应现场土层的真实情况,因而采用原位测试技术确定土体最大剪切模量的方法备受关注.以宿迁-新沂高速公路为工程背景... 土体最大剪切模量是动力基础设计和地震场地响应分析的重要参数,目前该参数的确定主要来源于室内试验,但室内试验值难以反应现场土层的真实情况,因而采用原位测试技术确定土体最大剪切模量的方法备受关注.以宿迁-新沂高速公路为工程背景,利用地震波孔压静力触探(SCPTU)对现场场地进行测试,在总结已有的最大剪切模量确定方法研究成果的基础上,以实测剪切波速计算得到的最大剪切模量作为参考值,研究了孔压静力触探(CPTU)测试参数与最大剪切模量之间的关系;基于临界状态土力学理论,研究了联合CPTU测试参数和状态参数与最大剪切模量的关系.结果表明:最大剪切模量与CPTU测试参数存在良好的相关关系,可通过锥尖阻力和孔压参数来近似估计最大剪切模量值;将状态参数作为孔隙比或孔压参数比的有效代替参数,能够同时考虑围压应力与孔隙比双重因素,所估算的最大剪切模量与参考值基本一致.因此,CPTU原位状态参数可作为一种新方法来初步评价无黏性土的最大剪切模量. 展开更多
关键词 地震波孔压静力触探 砂土 最大剪切模量 剪切波速 状态参数
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Heavy Oils and Oil Sands:Global Distribution and Resource Assessment 预览
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作者 LIU Zuodong WANG Hongjun +7 位作者 Graham BLACKBOURN MA Feng HE Zhengjun WEN Zhixing WANG Zhaoming YANG Zi LUAN Tiansi WU Zhenzhen 《地质学报:英文版》 SCIE CAS CSCD 2019年第1期199-212,共14页
Gl obal recoverable resources of heavy oil and oil sands have been assessed by CNPC using a geology-based assessment method combined with the traditional volumetric method,spatial interpolation method,parametric-proba... Gl obal recoverable resources of heavy oil and oil sands have been assessed by CNPC using a geology-based assessment method combined with the traditional volumetric method,spatial interpolation method,parametric-probability method etc.The most favourable areas for exploration have been selected in accordance with a comprehensive scoring system.The results show:(1)For geological resources,CNPC estimate 991.18 billion tonnes of heavy oil and 501.26 billion tonnes of oil sands globally,of which technically recoverable resources of heavy oil and oil sands comprise 126.74 billion tonnes and 64.13 billion tonnes respectively.More than 80%of the resources occur within Tertiary and Cretaceous reservoirs distributed across 69 heavy-oil basins and 32 oil-sands basins.99%of recoverable resources of heavy oil and oil sands occur within foreland basins,passive continental-margin basins and cratonic basins.(2)Since residual hydrocarbon resources remain following large-scale hydrocarbon migration and destruction,heavy oil and oil sands are characterized most commonly by late hydrocarbon accumulation,the same basin types and source-reservoir conditions as for conventional hydrocarbon resources,shallow burial depth and stratabound reservoirs.(3)Three accumulation models are recognised,depending on basin type:degradation along slope;destruction by uplift;and migration along faults.(4)In addition to mature exploration regions such as Canada and Venezuela,the Volga-Ural Basin and the Pre-Caspian Basin are less well-explored and have good potential for oil-sand discoveries,and it is predicted that the Middle East will be an important region for heavy-oil development. 展开更多
关键词 HEAVY OIL OIL SAND RESIDUAL hydrocarbons GLOBAL RESOURCE assessment
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砂土隧道开挖引起的地表及深层土体变形研究 预览 被引量:1
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作者 张天奇 葛隆博 郑刚 《天津大学学报:自然科学与工程技术版》 CSCD 北大核心 2019年第A01期113-119,共7页
城市地铁线路网络渐趋密集,经常出现隧道近接既有建、构筑物施工的情况,变形控制要求严格,故精细预测隧道施工引起的地表及深层土体变形尤为必要.相较于黏土地层,砂土地层中隧道开挖引起的地表及深层土体变形十分复杂,具体表现为:隧道... 城市地铁线路网络渐趋密集,经常出现隧道近接既有建、构筑物施工的情况,变形控制要求严格,故精细预测隧道施工引起的地表及深层土体变形尤为必要.相较于黏土地层,砂土地层中隧道开挖引起的地表及深层土体变形十分复杂,具体表现为:隧道开挖过程中,地表以下土体的体积将随隧道土体损失率 Vt 的改变而发生改变,之前所提出的土体变形模式均不能很好地解释砂土中隧道开挖引起的土体体积变化行为.以之前的砂土隧道模型试验为研究对象,建立数值模型,对试验过程中地表以下土体的体积响应进行分析.研究发现,隧道开挖时,隧道周围土体的体积响应与应力路径密切相关,不同应力路径下的土体体积响应有所不同.数值结果表明,根据不同位置处应力路径特点,地表以下土体可被分成 4 个特征区域,地表及地表以下不同深度位置处获得的土体损失率(Vs 和Vsub)与隧道土体损失率 Vt 之间的差异均可通过 4 个特征区域的土体体积变化来解释. 展开更多
关键词 砂土 隧道 地表 深层土体 沉降 体积变化行为 应力路径
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含水层砂土压缩变形特性及数学描述 预览
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作者 王雅平 王旭东 罗东娜 《南京工业大学学报:自然科学版》 CAS 北大核心 2019年第4期480-484,共5页
基于 FlowTracⅡ增量固结试验系统,通过控制孔隙水压力设计模拟符合承压含水层砂土应力状态和满足抽水条件应力路径的压缩试验,得到了砂土应变与时间关系曲线,探讨分析不同抽水模式作用对含水层砂土压缩变形特性的影响。试验结果表明:... 基于 FlowTracⅡ增量固结试验系统,通过控制孔隙水压力设计模拟符合承压含水层砂土应力状态和满足抽水条件应力路径的压缩试验,得到了砂土应变与时间关系曲线,探讨分析不同抽水模式作用对含水层砂土压缩变形特性的影响。试验结果表明:在抽水作用下,砂土压缩变形具有非线性和时效性特征;在相同前期固结压力下,砂土压缩变形量随着抽水强度的增加而增大,且变形稳定所需时间也越长;在稳压抽水作用下,砂土的应变率与时间在双对数坐标中呈现较明显的线性关系,其斜率受抽水强度和抽水速率的影响。建立了考虑抽水强度和抽水速率影响的砂土压缩变形与时间、应力的归一化经验公式。研究成果揭示了不同抽水模式下含水层砂土的压缩变形特性,为合理评价抽水引起的地面沉降提供试验依据。 展开更多
关键词 承压含水层 砂土 抽水模式 压缩变形
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Polyacrylamide hydrogel application in sand control with compressive strength testing
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作者 Mahsa Baghban Salehi Asefe Mousavi Moghadam Samira Zargari Marandi 《石油科学:英文版》 SCIE CAS CSCD 2019年第1期94-104,共11页
Sand production is one of the major problems in sandstone reservoirs.Different mechanical and chemical methods have been proposed to control sand production.In this paper,we propose a chemical method based on using po... Sand production is one of the major problems in sandstone reservoirs.Different mechanical and chemical methods have been proposed to control sand production.In this paper,we propose a chemical method based on using polyacrylamide/chromium triacetate hydrogel to investigate sand production in a synthetic sandpack system.To this end,a series of bulk experiments including the bottle test and rheological analysis along with compression tests were conducted.Experimental results indicated that the compressive strength of the sandpack was increased as much as 30 times by injecting 0.5 pore volume of hydrogel.Also,it was found that the increases in cross-linker and polymer concentrations exhibited a positive impact on the compressive strength of the sandpack,mostly by cross-linker concentration(48 psi).Hydrogel with a higher value of cross-linker could retain its viscoelastic properties against the strain which was a maximum of 122%for 0.5 weight ratio of cross-linker/polymer.The presence of salts,in particular divalent cations,has a detrimental effect on the hydrogel stability.The maximum strain value applied on hydrogel in the presence of CaCl2 was only about 201%as compared to 1010%in the presence of distilled water.Finally,thermogravimetric analysis and its derivative showed that the hydrogel could retain its structure up to 300°C.The results of this study revealed the potential application of the hydrogel to control sand production. 展开更多
关键词 SAND CONTROL - RHEOLOGY HYDROGEL STRENGTH COMPRESSIVE STRENGTH Sandpack
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