冷清公路水库库岸桩锚加固后的渗流变化规律

以云南冷清公路岸坡为研究对象,建立库区边坡二维饱和-非饱和渗流模型,模拟锚杆(索)和桩加固后不同工况下岸坡渗流场演变规律,分析岸坡加固后浸润线及孔隙水压力变化规律。结果表明:相对未加固岸坡而言,由于加固区的渗流阻力增大及其导致的渗流路径改变,加固后岸坡内浸润线形状、位置分布和孔隙水压力分布发生了变化。从桩加固与锚加固的情况对比看,桩加固的阻渗作用较锚加固的阻渗效果差些。岸坡内孔隙水压力受库水位的升降、分析位置到库水或浸润线的距离、加固区渗透系数的降低及其渗透系数降低区的面积和形状等的影响,加固后岸坡滞后效应更明显。离库水面较远处,其孔隙水压力几乎不受库水位变化和加固措施的影响。

低频波动下考虑孔隙度与压力不同程度变化的岩土固结渗流分析

低频波动激励下实际开发储层物性发生改变,开展一维定压或定压力梯度情形岩土固结分析,难以反映具有变化流速、压力梯度的实际储层近井带波动激励效果。推导了低渗孔隙介质固结模型控制方程,建立了考虑不同孔隙度、压力变化程度的3种饱和单相渗流流体孔隙介质固结模型,开展一维、径向物理模型模拟求解,进而评价低频波动在恒定或变压力梯度、不同固结模型下的作用效果及参数影响敏感性。结果表明,考虑低渗储层渗流惯性作用和较强应力敏感性时,波动作用下(恒定压力梯度)一维模型的压力、流速、孔隙度增幅整体减小,(变压力梯度)径向物理模型波诱导作用出现不同变化,压力、孔隙度增幅增加,流速增幅降低;随振动参数增加,径向物理模型物性最大增幅数值波动性变化更为剧烈。研究结论反映了实际储层低频波动激励效果的复杂性及动力学分析的必要性。

基于ABAQUS的地铁深基坑开挖渗流场变化的三维有限元分析

为研究地铁深基坑开挖中的渗流场变化规律,以天津某地铁基坑工程为例,针对大长条深基坑工程开挖规模和特点,结合相关地质资料,运用ABAQUS有限元软件建立三维模型,对深基坑开挖过程中的地下水渗流变化规律进行分析。结果表明,基坑四周边界、角部和地下连续墙底部区域的渗流最大,且开挖越深,渗流影响越大,越易引起基坑破坏,应重点监测并采取有效措施加以防范。

汶川地震对陈村坝基渗流影响分析

汶川地震发生后不久,陈村大坝坝基帷幕后部的浅层扬压力测孔和深部排水测孔水位普遍下降,坝基渗漏量显著增加,表明坝基岩体和帷幕受地震影响微细裂隙张开,渗透性增强。坝基经过丙凝化学加强灌浆的部位,测孔水位下降幅度较小,水位恢复过程较快,显示出丙凝化灌的优异防渗和抗震性能。汶川地震对陈村大坝的稳定以及坝基岩体和帷幕没有产生损坏,震后约9个月坝基整体防渗功能已基本恢复。

低渗透储层水驱油渗流阻力特征

低渗透储层物性差、孔喉细小,水驱油过程中渗流阻力较大,注采井间难以形成有效的驱替压力梯度,建立渗流阻力的描述方法、研究渗流阻力的影响因素和变化特征对低渗透储层注水开发具有重要意义。在油水流动质量守恒定律的基础上,建立了低渗透储层水驱油渗流阻力梯度数学模型,应用水驱油渗流阻力梯度变化率函数分析水驱油渗流阻力梯度的变化特征,为低渗透储层中水驱油渗流阻力梯度的描述提供一种宏观表征方法。理论分析表明:低渗透储层水驱油渗流阻力梯度呈非线性特征,随着含水饱和度的增加水驱油渗流阻力梯度先增加后减小。低渗透储层注水开发存在最大渗流阻力梯度,与油相粘度、储层渗透率和注入速率相关;低渗透储层注水速率越大,需要克服的最大渗流阻力越大;油相粘度越大,最大渗流阻力越大;储层渗透率越低,最大渗流阻力越大。

西霞院水库绕坝渗流分析

绕坝渗流除了影响山体本身的安全外,同时会抬高岸坡部分坝体的浸润面,在坝体和岸坡的接触面上可能产生接触冲刷等不利影响。实际工程大多采用混凝土防渗墙防渗形式,以期增大绕坝渗流渗径来削减绕坝渗流量并减小砂层渗透坡降。本研究以现有76眼民井为基础,分析西霞院水库蓄水前、后近坝区地下水动态变化及续建防渗墙对近坝区地下水影响。结果表明,近坝区地下水位变化与水库水位变化关系密切,水库蓄水对近坝区产生了明显的影响,使地下水位抬升明显、地下水渗流场发生改变。防渗墙续建前后,左岸下游地下水位与库水位响应关系已不明显,渗流方向有所改变,渗流强度明显减小,左岸防渗墙防渗作用明显;右岸渗流方向基本没变,渗流强度有所减小,下游地下水位与库水位仍存在一定的相关关系,右岸防渗墙上下游测井水位差没有左岸明显,说明右岸防渗墙也已经发挥防渗作用,但不如左岸明显。

真空预压法加固软基的地下水位变化探讨

文章分析了真空预压中地下水位变化的研究现状，指出用实测数据进行研究存在误区。在定义地下水位线的基础上，通过土体结构的微观解说，分析了水位变化的机理。得出堆栽预压地下水位线不变，而真空预压在考虑地下水补给的情况下，有下降和不变两种可能。提出了主动渗流和被动渗流以及固结渗流和非固结渗流的概念。

基坑开挖中渗流场与变形稳定分析研究

渗流效应对基坑工程的安全稳定影响很大,研究基坑渗流对指导设计施工具有很强的现实意义。文章基于有限元分析原理,结合实际工程建立数值模型,计算不同开挖深度下的基坑渗流场和地面沉降变形等,与工程实测资料对比分析,得出基坑开挖过程中的渗流场变化。研究成果对指导施工和设计研究具有一定的实际意义。

三峡库区树坪滑坡治理前后渗流场分析

三峡库区地质环境脆弱,滑坡灾害频发,其中少部分滑坡已采取工程措施治理,为研究治理工程对滑坡渗流场的影响,本文以三峡库区树坪滑坡为例,运用岩土软件Geo-studio,根据不同工况条件,分析滑坡采取工程治理前后渗流场变化规律,为库区滑坡工程治理提供经验理论。

基于渗流场-应力场耦合作用下的高大炉渣边坡稳定性分析

边坡的稳定性影响因素较为复杂,而人工堆填的高大炉渣边坡体由于其特殊的化学、物理力学性质,使其应力场及渗流场更加多变,稳定性不易控制。江水位变化引起堆积体变形本质原因是堆积体水岩之间的相互作用,因此本文通过对高炉渣物理力学性质、水文地质条件的初步分析结合渗流场-应力场耦合理论,探究了该边坡前缘江水位的变化对边坡稳定性影响,并得出影响结论,为今后此类边坡工程汛期治理设计提供新思路。

储集层参数动态地质模型的建立——以胜坨油田二区沙二段1^2层为例

胜坨油田二区沙二段12层注水开发38年,含水已高达96％以上,处于特高含水阶段。通过检查井岩心资料分析了不同含水阶段储集层参数的变化,认为渗透率是变化最明显的参数,且有随着含水的上升渗透率升高的规律。通过室内渗流物理模拟实验建立了该层渗透率随含水率变化的定量表达式,并对储集层参数的变化机理进行了研究,最终利用神经网络储集层定量建模技术,建立了渗透率随含水率变化的动态地质模型。

新矿井首采工作面突水预测与实践

针对滕南煤田新井首采工作面多发生突水事故的问题 ,以付村煤矿 2 0 6首采工作面为例 ,讨论了避免新井首采工作面发生突水的预测和监测的方法。

天府机场地下空间建设与地下水环境互馈机制

为研究天府机场地下空间建设与地下水环境的互馈机制,根据长期地下水的监测数据,利用Visual Modflow软件进行模拟,预测建设完成之后不同时间段航站区渗流场的波动状况;并采用水质分析方法以及溶质运移模型预测氯离子的迁移规律。结果表明:地下空间的开挖与地下水环境反馈强烈,尤其是水位变化最为突出,开挖改变了原有的径流路径,并且造成了地下水浮托力不均匀性的产生;通过溶质运移模型分析得出,研究区由于低渗透性,导致氯离子迁移缓慢,但随着时间推移,其迁移范围会随之扩大,对地下空间建筑造成一定威胁。

Influences of strain softening and seepage on elastic and plastic solutions of circular openings in nonlinear rock masses

Considering the influence of strain softening, the solutions of stress, displacement, plastic softening region radius and plastic residual region radius were derived for circular openings in nonlinear rock masses subjected to seepage. The radial stress distribution curve, ground reaction curve, and relation curve between plastic softening region radius and supporting force in three different conditions were drawn respectively. From the comparisons among these results for different conditions, it is found that when the supporting force is the same, the displacement of tunnel wall considering both seepage and strain softening is 85.71% greater than that only considering seepage. The increase values of radial displacement at 0.95 m and plastic softening region radius at 6.6 m show that the seepage and strain softening have the most unfavorable effects on circular opening stability in strain softening rock masses.

Seasonal shifts in the solute ion ratios of vadose zone rock moisture from the Eel River Critical Zone Observatory

One of the greatest challenges in critical zone studies is to document the moisture dynamics, water flux,and solute chemistry of the unsaturated, fractured and weathered bedrock that lies between the soil and groundwater table. The central impediment to quantifying this component of the subsurface is the difficulty associated with direct observations. Here, we report solute chemistry as a function of depth collected over a full year across the shale-derived vadose zone of the Eel River Critical Zone Observatory using a set of novel sub-horizontal wellbores,referred to as the vadose zone monitoring system. The results of this first geochemical glimpse into the deep vadose zone indicate a dynamic temporal and depth-resolved structure. Major cation concentrations reflect seasonal changes in precipitation and water saturation, and normalized ratios span the full range of values reported for the world's largest rivers.

Creep properties and permeability evolution in triaxial rheological tests of hard rock in dam foundation

Triaxial creep tests were carried out under seepage pressure by using rock servo-controlled triaxial rheology testing equipment. Based on experimental results, rock rheological properties influenced by seepage-stress coupling were studied, and variations of seepage rate with time in complete creep processes of rock were analyzed. It is shown that, when the applied stress is less than failure stress level, the creep deformation is not obvious, and its main form is steady-state creep. When applied stress level is greater than or less than but close to fracture stress, it is easier to see the increase of creep deformation and the more obvious accelerative creep characteristics. The circumferential creep deformation is obviously higher than the axial creep deformation. At the stage of steady-state creep, the average of seepage flow rate is about 4.7×10-9 rn/s at confining pressure （tr3） of 2 MPa, and is about 3.9×10-9 m/s at a3 of 6 MPa. It is seen that the seepage flow rate at or3 of 2 MPa in this case is obviously larger than that at tr3 of 6 MPa. At the stage of creep acceleration, the seepage flow rate is markedly increased with the increase of time. The variation of rock permeability is directly connected to the growth and evolution of creep crack. It is suggested that the permeability coefficient in complete creep processes of rock is not a constant, but is a function of rock creep strain, confining pressure, damage variable and pore water pressure. The results can be considered to provide a reliable reference for the establishment of rock rheological model and parameter identification.

Seepage laws of two kinds of disastrous gas in complete stress-strain process of coal

The similarities and differences in seepage flow evolution laws of CH4 and CO2 during complete stress- strain process of samples were comparatively analyzed. The results show that the seepage flow evolution laws of CH4 and CO2 are extremely similar during the stress-strain process, showing that the character- istic first decreased and then increased. A mathematical model was also established according to the rela- tionship of seepage velocity and axial strain. However, due to the strong adsorption ability of CO2, the coal samples generated a more serious ''Klinkenberg effect'' under the condition of CO2. Owing to this, the CO2 seepage flow resulted into occurrence of ''stagnation'' phenomenon during the late linear elastic stage II. In the strain consolidation stage III, the increment rate of CH4 seepage velocity was significantly greater than that of CO2. In the stress descent stage IV, when the axial load reached the peak pressure of coal, the increment rates of CH4 seepage velocity presented a turning point. But the changing rate of CO2 seepage velocity still remained slow and a turning point was presented at one time after the peak of thestrain pressure, which showed an obvious feature of hysteresis.

Time-Dependent Sediment Transport Subjected to Downward Seepage

Experiments were conducted using cohesionless sand particles with median diameter of 0.48 mm to investigate the time variation of sediment transport rate under the influence of local downward seepage.The experimental results show that the bedload transport rate in terms of volumetric sediment transport rate per unit width increased rapidly with time in the presence of suction,eventually reaching a peak beyond which it started to decrease.The trend of reduction was significantly reduced beyond 8 400 s after the test started.The analytical expression was derived in terms of dimensionless sediment transport rate and dimensionless time.The hypothesized relationships were compared with the experimental data,indicating a good agreement with each other.

Deep soil water infiltration and its dynamic variation in the shifting sandy land of typical deserts in China

Soil moisture is the key resource constraint in arid ecosystems, and has been a focus of research on restoration. However, quantitative studies on the contribution of rainfall to deep soil rainfall infiltration are lacking. In this study, we used the YWB-01 Deep Soil Infiltration Water Recorder which had been invented by ourselves to measure the quantity of rain infiltration into deep soil, 150 cm below ground, in four locations in China: Mu Us Sandy Land and Ulan Buh, Tengger, and Badan Jilin deserts over a 2-year period. We found:(1) Deep soil rainfall infiltration decreased progressively from east to west and from semiarid to arid areas, with two locations completely lacking rainfall infiltration. Heavy rain was important to deep soil infiltration in shifting sandy land of arid and semiarid areas.(2) Seasonal variation of infiltration was correlated with rainfall, with a time lag that was less apparent in areas with more rainfall.(3) For single intense rainfall events, infiltration maximums occurred 40–55 h after the rainfall, during which the infiltration rates increased rapidly before reaching a peak, and then decreased slowly. Continuous infiltration could last about 150 h. Rainfall infiltration was determined by the combined action of intensity, quantity and duration. Rainfall with low intensity, long duration, and large quantity was most favorable for deep soil infiltration. Our results can be used in water resource assessments and protection during eco-restoration in the arid and semiarid areas in China.

COMPLEX SYSTEM ANALYSIS OF MARKET RETURN PERCOLATION MODEL ON SIERPINSKI CARPET LATTICE FRACTAL

This paper investigates the statistical behaviors of fluctuations of price changes in a stock market.The Sierpinski carpet lattice fractal and the percolation system are applied to develop a new random stock price for the financial market.The Sierpinski carpet is an infinitely ramified fractal and the percolation theory is usually used to describe the behavior of connected clusters in a random graph.The authors investigate and analyze the statistical behaviors of returns of the price model by some analysis methods,including multifractal analysis,autocorrelation analysis,scaled return interval analysis.Moreover,the authors consider the daily returns of Shanghai Stock Exchange Composite Index,and the comparisons of return behaviors between the actual data and the simulation data are exhibited.