Newly developed technique and analysis solution to accelerate consolidation of ultrasoft soil     

Chen Geng  Shi Jiangwei  Chen Long 《Marine Georesources & Geotechnology》2017,35(2):292-299

Plastic vertical drainage is widely used in vacuum preloading for soft soil treatment. However, plastic vertical drainage has a number of disadvantages such as it only provides drainage paths in vertical directions and the distribution of soil strength is not uniform. A new technique, prefabricated vertical–horizontal drainage, was developed in this study to shorten the consolidation time of ultrasoft soil. Using one vertical drainage tube and four horizontal drainage tubes, prefabricated vertical–horizontal drainage provides drainage paths not only in vertical but also in horizontal directions. An analytical solution was derived to calculate the degree of soil consolidation when using the prefabricated vertical–horizontal drainage technique. Field tests were conducted to evaluate the effectiveness of prefabricated vertical–horizontal drainage and to verify the proposed analytical solution. It was found that consolidation time of soft clays using prefabricated vertical–horizontal drainage was 50% lower than plastic vertical drainage. Moreover, the average undrained shear strength of soil treated by the prefabricated vertical–horizontal drainage technique was approximately 30% larger than that treated by the plastic vertical drainage technique. The degree of soil consolidation estimated from the proposed analytical solution showed good agreement with field measurements. This implies that the proposed analytical solution can be used to directly estimate the degree of consolidation when the soil is treated by prefabricated vertical–horizontal drainage.  相似文献   

Numerical study of nonlinear freak wave impact underneath a fixed horizontal deck in 2-D space     

《Applied Ocean Research》2017

Freak waves are extreme and unexpected surface waves with huge wave heights that may lead to severe damage to ships and offshore structures. However, few researches have been conducted to investigate the impact underneath fixed horizontal decks caused by freak waves. To study these phenomena, a 2-D numerical wave tank is built in which nonlinear freak waves based on the Peregrine breather solution are generated. As a validation, a regular-wave-induced underneath impact is simulated and compared to the existing experimental measurements. Then the nonlinear freak-wave-induced impact is investigate with different values of deck clearance above the mean free surface. In addition, a comparative simulation of a “large” regular wave based on the 2nd-order Stokes wave theory with the same crest height and wave length of the nonlinear freak wave is carried out to reveal the unique features of the nonlinear freak-wave-induced impact. By applying a fluid–structure interaction (FSI) algorithm in which the bottom deck and front side wall are simplified as Euler beams in 2-D and discretized by the finite element method (FEM), the hydroelastic effects are considered during the impact event. The vertical force acting underneath the bottom deck, the transversal force acting on the front side wall, the structural displacements of the elastic deck and wall are analyzed and discussed respectively, from which meaningful conclusions are drawn.  相似文献   

Impact of climate change on dynamic behavior of offshore wind turbine     

Swagata Bisoi 《Marine Georesources & Geotechnology》2017,35(7):905-920

Global warming is expected to change the wind and wave patterns at a significant level, which may lead to conditions outside current design criteria of monopile supported offshore wind turbine (OWT). This study examines the impact of climate change on the dynamic behavior and future safety of an OWT founded in clay incorporating dynamic soil–structure interaction. A statistical downscaling model is used to generate the time series of future wind speed and wave height at local level. The responses and fatigue life of OWT are estimated for present and future periods and extent of change in design is investigated at offshore location along the west coast of India. Wind speed, wave height, and wave period data are collected from the buoy deployed by Indian National Centre for Ocean Information Services and the future climate for the next 30 years is simulated using the general circulation model corresponding to Special Report on Emission Scenarios A1B scenario. The OWT is modeled as Euler–Bernoulli beam and soil–structure interaction is incorporated using nonlinear p-y springs. This study shows that changes in design of OWT are needed due to increased responses owing to the effect of climate change. Fatigue life is found to be decreased because of climate change.  相似文献   

Process and cause of urban-rural development transformation in the Bohai Rim Region,China   总被引：2，自引：2，他引：0  

Yansui Liu  Zhichao Hu  Yuheng Li 《地理学报(英文版)》2014,24(6):1147-1160

China＇s reform and opening-up policy has brought the country a great development opportunity. The high-speed growth of the economy not only led China to a period of industrialization, urbanization, informatization and agricultural modernization, but also exacerbated the situation of the urban–rural dual structure. Based on the review of current studies, we first used the analytic hierarchy process（AHP） method to evaluate the urban–rural development and transformation level by population transformation index, land transformation index, industrial transformation index and social transformation index between 1996 and 2012 around the Bohai Rim Region. Then, based on the results of each index, we used the exploratory spatial data analysis（ESDA） method to investigate the spatial autocorrelation of the change in the urban–rural development transformation index during the 16-year period using Global Moran＇s I index and Local Moran＇s I index. Finally, we investigated the mechanism of change of the urban–rural development transformation index at county level, summarizing five main factors：（1） the radiation from the surrounding big cities,（2） the acceleration of the urbanization process,（3） the upgrading of the industrial structure,（4） the publishing and implementation of a macro development strategy and regional policy, and（5） natural factors such as topology.  相似文献   

云冈石窟砂岩循环冻融试验研究     

方云  乔梁  陈星  严绍军  翟国林  梁亚武 《岩土力学》2014,35(9):2433-2442

风化是云冈石窟目前所面临的严重的地质病害之一,温度和水分的变化是造成石窟岩体风化的重要原因,尤其是在循环冻融条件下岩体更易风化,因此,利用室内试验研究循环冻融条件下云冈石窟砂岩的物理力学性质,对于石窟岩体的稳定性评价和保护具有重要的意义。将取自云冈石窟的砂岩岩样分为饱水组、干燥组和对比组3组,通过对饱水组和干燥组岩样进行35次循环冻融试验,模拟云冈石窟砂岩的风化过程。在冻融循环开始前以及每5次冻融循环结束后,量测岩样的质量、体积,并利用超声检测分析仪对各岩样进行超声纵波测试;利用INSTRON－1346岩石伺服试验机对上述3组砂岩岩样进行单轴压缩试验,并对试验后的岩样进行SEM微观结构分析。通过试验研究,得到不同含水状态下云冈石窟砂岩岩样的冻融破坏特征以及不同循环冻融次数后岩样体积、质量、超声波纵波波速、砂岩的单轴应力-应变全过程曲线、抗压强度、抗冻系数以及微观结构的变化,分析归纳出循环冻融条件下云冈石窟砂岩的主要物理力学特性。  相似文献   

小波分频分析法在沉积层序划分及等时对比中的应用     

王贵文  徐敬领  杨宁  赖锦  赵显令 《高校地质学报》2013,19(1):70-77

为了提高沉积层序旋回自动划分对比的精度和准确度,解决高频层序旋回划分难、人为性、多解性等问题,在厘定 前人研究成果的基础上,以国内陆相拉张型盆地沉积层序旋回特征为切入点,以实际测井资料为依托,开展小波分频分析 方法的研究,查明了小波分频分析方法研究不同级别沉积层序旋回的基础理论,建立了表征不同类型沉积层序旋回的量化 标准和响应标准模式,实现了小波分频分析方法在层序界面拾取、层序单元划分、复杂地层精细划分及等时对比中的应用, 为提高沉积层序旋回划分及等时对比的精度提供有力的证据。  相似文献   

改良粉土强度的冻融循环效应与微观机制   总被引：2，自引：0，他引：2  

谈云志  吴翩  付伟  万智  张华  张振华 《岩土力学》2013,34(10):2827-2834

为了研究冻融循环对改良粉土强度的影响规律及其作用机制,开展了不同初始压实度和初始含水率试样的冻融循环试验。对经历不同冻融循环次数作用后的试样进行无侧限抗压强度试验,探讨了冻融循环作用对改良粉土的长期强度的影响规律。试验结果表明,随着冻融循环次数增加,改良粉土的抗压强度下降,最终在6次冻融循环后趋于稳定;相同的冻融循环次数条件下,初始含水率越大,改良粉土的抗压强度衰减幅度越大。为了寻找冻融循环作用对改良粉土孔隙结构的影响规律,进而揭示冻融循环对试样结构损伤的机制,开展了改良粉土的细观孔隙结构试验。试验结果表明,不同的冻融循环次数和初始含水率对小孔径孔隙（ 10 nm）之间的结构影响不大;冻融循环作用主要损伤了大孔径孔隙（0.01～100 μm）之间的结构,从而降低了改良粉土的强度。  相似文献   

粉砂土反复冻胀融沉特性试验研究   总被引：3，自引：0，他引：3  

严晗  王天亮  刘建坤 《岩土力学》2013,34(11):3159-3165

针对深季节冻土区的特殊环境,通过室内试验研究了粉砂土在不同初始含水率、干密度、荷载、冻融次数条件下的反复冻胀、融沉特性。研究结果表明：粉砂土的冻结温度为-1.03 °C;其冻胀融沉变形随冻融次数的增加呈现波浪式起伏变化,并最终趋于稳定状态;经历多次冻融后,干密度较大试样整体表现为膨胀,干密度较小试样整体表现为压密;上部荷载在抑制冻胀的同时加大了试样的整体融沉变形,却降低了每次冻融的冻胀率和融沉系数;存在一个最优初始含水率,该含水率条件下,试样经历多次冻融后的高度不发生变化;由于外界水源的补给,冻融后试样内部含水率均大于初始含水率;干密度和顶端荷载的增大均有效地抑制了外界水源的补给;4次冻融循环后,粉砂土的冻胀率、融沉系数均逐渐趋于稳定。  相似文献   

An efficient approach for frequency-domain and time-domain hydrodynamic analysis of dam–reservoir systems     

Gao Lin  Yi Wang  Zhiqiang Hu 《地震工程与结构动力学》2012,41(13):1725-1749

An efficient procedure is developed for the hydrodynamic analysis of dam–reservoir systems. The governing equations of hydrodynamic pressure in the frequency as well as time domain are derived in the framework of the scaled boundary finite element method. The water compressibility and absorption of reservoir sediments can be conveniently taken into consideration. By extending the reservoir to infinity with uniform cross-section, only the dam–reservoir interface needs to be discretized to model the fluid domain, and the hydrodynamic pressure in the stream direction is solved analytically. Several numerical examples including a gravity dam with an inclined upstream face and an arch dam with a reservoir of arbitrary cross-section are provided to demonstrate the computational efficiency and accuracy of the proposed method. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

差分干涉SAR冻土形变检测方法研究   总被引：12，自引：4，他引：8  

李震  李新武  刘永智  任鑫 《冰川冻土》2004,26(4):389-396

季节性冻融导致的地表形变是冻土地区工程建设的主要病害,冻土的冻胀和融沉是影响青藏公路以及目前建设的青藏铁路路基稳定的重要因素.近年来,差分干涉测量技术已成为地表形变测量和监测的重要工具.基于重复轨道的ERS 1/2雷达图像,研究了利用干涉SAR技术探测冻土形变的方法,经过对引入DEM差分干涉SAR技术的处理和分析,得到研究区冻土形变结果.通过与实测数据比较,表明重轨差分干涉测量可以精确地探测冻土表面形变,可用于青藏铁路冻土形变监测.  相似文献