岩石破裂过程渗透性质及其与应力耦合作用研究

为了分析岩石细观结构特性变化引起渗透性演化对宏观力学行为的影响,并进行渗流应力耦合作用下岩石破裂机制的研究。基于细观损伤力学和Biot经典渗流力学,建立了岩体损伤非线性本构方程和渗透率关系模型,开发出岩石破裂过程渗流-应力耦合分析系统(coupling system of flow and solid in rock failure process analysis,简称F-RFPA2D),拓宽了原有程序RFPA2D的研究领域。这个系统能够对裂纹在萌生、扩展过程中渗透率演化规律及其渗流-应力耦合机制进行模拟分析,把流固耦合问题的研究从应力状态深入到破坏过程。围绕岩石破裂过程中渗透性的演化规律及其渗流-应力耦合作用机理这一课题,开展以下方面的研究工作: (1) 对经典Biot渗流力学做了进一步的考察,验证了建立耦合渗流方程的主要假设,讨论了各种渗流与应力耦合方程及数学模型的适用条件,通过不同深度岩体渗透率工程试验研究,分析了连续介质模型耦合渗流方程参数的物理意义、适用性和测试方法。 (2) 通过岩石应力应变-渗透率全过程实验研究,从细观结构特征揭示出岩石应力峰值前后的渗透性演化规律。基于逾渗理论,通过引入突跳系数这一概念,建立了描述岩石破裂过程的渗流-应力-损伤关系方程。 (3) 秉承RFPA2D关于岩石材料的细观非均匀性的基本思想。

粘土的结构对渗透性质影响的试验研究

天然沉积的粘性土都具有一定的结构性 ,根据研究粘土的渗透性能与土体的结构性具有密切的关系。土体的渗透性是土力学中主要的研究课题之一 ,对某些工程问题具有重要的意义。本文对粘土在不同压力下进行原状土与重塑土的渗透试验 ,并根据试验结果探讨了粘土结构性对渗透性的影响 ,得出一些有意义的结论 。

砂柱微生物注浆的水力渗透性质试验研究

为了有效实现防渗堵漏,对砂柱微生物注浆的水力渗透性质进行试验研究。砂柱微生物注浆采用巴氏芽孢杆菌菌种,向试验装置中注入胶结液与菌液,静置完成微生物注浆。对实际工程问题物理模型进行简化处理,构造满足工程特性的数学模型,对模型赋予参数、初始条件及边界条件,为砂柱微生物注浆水利渗透性质试验提供依据。构造均质高孔隙率砂岩非稳定达西渗流数学模型,计算可体现砂柱微生物注浆水力渗透性质的孔隙率与渗透率。将已有实验结果和数值模拟结果进行比较,对数值模型合理性进行验证。通过观察孔隙率与渗透率对砂柱微生物注浆的水利渗透性质进行试验分析。结果发现,砂柱微生物注浆可降低砂柱孔隙率与渗透率,提高砂土水力渗透性质。

安哥拉梅农盖水田农场有机质粉质粘土渗透性质初探

在安哥拉梅农盖水田农场勘测过程中,在LONGA河漫滩部位具有一种黑色～棕褐色有机质粉质粘土层,该种土类以砂土作为构架,具有机质含量高、渗透性质不均匀、退化快等特点.在农场开发种植过程中,该类土的渗透性质成为制约其使用的关键要素,本文结合对该类土的进行的常规、单、双环渗透,试坑渗透试验,对其的相关性质,尤其是渗透性质进行了初步探索,结合试验结果对后期施工提出了一些结论和建议,为类似地层条件的工程提供了一定的设计和施工依据.

柱状节理岩体渗透性模型试验研究

针对柱状节理岩体渗透性质的研究较少,开展了柱状节理岩体相似材料的模型试验,研究了柱状节理岩体相似材料在多次围压循环加卸载作用下的渗透性质,分析得出柱状节理岩体存在表征单元体积,可以采用等效连续介质模型分析柱状节理岩体的渗流性质,提出了计算柱状节理岩体渗透率张量的方法,基于张量不变性理论,推导出了柱状节理岩体渗透张量的主渗透系数的计算公式。研究表明:在围压初次加载阶段,柱状节理岩体渗透张量的主渗透系数随围压加载显著降低,在随后的围压循环加卸载阶段主渗透系数保持较低值,围压的加卸载对柱状节理岩体的主渗透系数影响较少,且在每个围压加卸载阶段,柱状节理岩体渗透张量的主渗透系数与围压均呈幂函数关系;柱状节理岩体渗透张量的主方向随着围压加卸载逐渐增大,在初次围压加卸载阶段增长显著,在此后的围压加卸载阶段缓慢增长;柱状节理岩体在低围压下渗透各向异性较为显著,且随着柱体倾角增大渗透各向异性逐渐减弱,在第一次围压加载阶段,随围压增大柱状节理岩体的渗透各向异性迅速减弱,当加载到高围压时,柱体倾角对柱状节理岩体的渗透各向异性几乎没有影响,在此后的围压循环加卸载阶段,柱状节理岩体的渗透各向异性稳定在较低水平,柱体倾角对渗透各向异性的影响很微弱;柱状节理岩体的渗透性质均是在第一次围压加载阶段发生显著变化,且围压卸载后渗透性质不能恢复,此后的围压循环加卸载对其渗透性质影响很小。

Effects of Drought Stress on Osmotic Regulation Substances of Five Catalpa bungei Clones

[Objective] This study aimed to investigate the effects of drought stress on osmotic regulation substances of Catalpa bungei clones. [Method] Potting experimental was carried out with plastic film sealing method, to differentiate the degrees of drought stress based on changes in soil water content and leaf water potential and investigate variations in contents of osmotic regulation substances（free proline,soluble sugar and soluble protein） in leaves of five Catalpa bungei clones under different degrees of drought stresses. [Result] According to changes in soil water content and leaf water potential, the whole process of drought stress was divided into normal level（CK, with soil water content of 97.49% and leaf water potential of-0.54MPa）, light drought（LD with soil water content of 59.96% and leaf water potential of-1.28 MPa）, mediate drought（MD with soil water content of 34.19% and leaf water potential of-2.32 MPa） and severe drought（SD with soil water content of 14.52%and leaf water potential of-2.99 MPa）. The soil water content and leaf water potential of five Catalpa bungei clones reached the highest correlation in exponential fitting, with an average R2of 0.989 3（P0.001）. The free proline content in leaves of five Catalpa bungei clones increased rapidly with the increasing degree of drought stress（P 0.001）. To be specific, free proline contents of Catalpa bungei clones015-1 and 7080 were 34.39 and 33.41 times of the normal level under severe drought conditions, which reached an extremely significant level（P0.001）; the free proline content of Catalpa bungei clone 1-3 rapidly increased to（855.46±227.52） μg/g Fw under light drought conditions. The soluble protein content in leaves showed different variation trends. To be specific, the soluble protein content of Catalpa bungei clone 7080 was the lowest at various drought stages and reached（1.644 ±0.137）mg/g Fw under normal conditions; the soluble protein content of Catalpa bungei clone 1-3 was relatively high under normal conditions and was reduced rapidly under light drought conditions, showing different response patterns. [Conclusion] Osmotic regulation substances in leaves of five Catalpa bungei clones all have certain response to drought stress. Free proline is the most important osmotic regulation substance, followed by soluble protein, while soluble sugar makes no significant contribution. According to changes in content of osmotic regulation substances, Catalpa bungei clone 7080 has relatively high capacity and good drought resistance, while Catalpa bungei clone 1-3 has the rapidest response to drought stress.

微生物灌浆的颗粒流细观力学数值模拟研究

基于流固耦合原理的PFC2D颗粒流数值模拟程序,运用其内置FISHTANK函数库和FISH语言,分别定义流体域的流动方程和压力方程,对微生物灌浆过程中菌液在地层中的扩散过程和形态进行了数值模拟计算。通过调节PFC命令流中的注浆压力p、时步step、水力传导系数perm等参数对菌液的注浆过程进行了模拟计算。数值模拟计算表明,灌浆过程中菌液与地基土的作用形式与灌浆压力大小密切相关,过高的注浆压力会对地层结构造成一定的破坏。对钻孔周围土体的应力状态进行了理论推导和分析,理论推导结果与数值模拟结果相符。劈裂灌浆作用发生时,孔隙率和应变率均增加。

砂土注浆的颗粒流细观力学数值模拟

灌浆工程隐蔽性较强,浆液扩散机理远不成熟。基于细观力学理论的PFC2D数值仿真试验技术,可以从细观角度研究灌浆过程中土颗粒的位移、变形运动及与浆液的耦合作用过程,为注浆机理研究开辟了一条新的途径。基于流固耦合原理的PFC2D颗粒流数值模拟程序,运用其内置FISHTANK函数库和FISH语言,分别定义流体域的流动方程和压力方程,对灌浆过程中浆液在地层中的扩散过程和形态进行了数值模拟计算。通过调节PFC命令流中的注浆压力、时间步长、水力传导系数等参数对浆液的注浆过程进行了模拟计算。模拟结果表明,灌浆过程中浆液与地基土的作用形式与灌浆压力大小密切相关,为达到理想的劈裂灌浆效果需要适当提高注浆压力,但过高注浆压力会对地层结构造成一定的破坏。对钻孔周围土体的应力状态进行了理论推导和分析,指出土体环向拉应力的增加导致钻孔周围产生劈裂缝,浆液由渗透作用方式向劈裂作用方式转变,数值模拟结果与理论推导结果相符。劈裂灌浆作用发生时,孔隙率和应变率均增加。流动性能差的稠浆适于压密灌浆和劈裂灌浆,流动性能好的稀浆则适于渗透性灌浆,而浆液的渗透性能对高压劈裂灌浆的作用效果影响不明显。

Effects of Nitric Oxide on the Germination of Wheat Seeds and Its Reactive Oxygen Species Metabolisms Under Osmotic Stress

Effects of sodium nitroprusside (SNP), a nitric oxide (NO) donor, on the germination and metabolism of reactive oxygen species were surveyed in wheat (Triticum aestivum L.) seeds. Germination of wheat seeds and even the elongation of radicle and plumule were dramatically promoted by SNP treatments during the germination under osmotic stress. Meanwhile, activities of amylase and EP were enhanced, thus leading to the degradation of storage reserve in seeds. After osmotic stress was removed, higher viability of wheat seeds was also maintained. In addition, the activities of CAT, APX and the content of proline were increased by SNP treatment simultaneously, but activities of LOX were inhibited, and both of which were beneficial for improving the antioxidant capacity during the germination of wheat seeds under osmotic stress. It was also shown that the increase of the activity of amylase induced by SNP in embryoless half-seeds of wheat in the beginning period of germination (6 h) might be indirectly related to GA(3).

砂土注浆颗粒流数值模拟研究

基于流固耦合原理的PFC2D颗粒流数值模拟程序,运用其内置FISHTANK函数库和FISH语言,分别定义流体域的流动方程和压力方程,对灌浆过程中浆液在地层中的扩散过程和形态进行了数值模拟计算.通过调节PFC命令流中的注浆压力p、时步step、水力传导系数perm等参数对浆液的注浆过程进行了模拟计算.数值模拟计算表明,灌浆过程中浆液与地基土的作用形式与灌浆压力大小密切相关,过高的注浆压力会对地层结构造成一定的破坏.对钻孔周围土体的应力状态进行了理论推导和分析,理论推导结果与数值模拟结果相符.劈裂灌浆作用发生时,孔隙率和应变率均增加.而浆液的渗透性能对高压劈裂灌浆的作用效果影响不明显.

Influences affecting the soil-water characteristic curve

The soil-water characteristic curve (SWCC) is the primary partially saturated soil information as its behavior and properties can be derived from it. Although there have been many studies of unsaturated soils and the SWCC, there is still no combined constitutive model that can simulate soil characteristics accurately. In cases when hydraulic hysteresis is dominant (e.g. under cyclic loading) it is particularly important to use the SWCC. In the past decades, several mathematical expressions have been proposed to model the curve. There are various influences on the SWCC as a source of information, so the curves obtained from conventional tests often cannot be directly applied; and the mathematical expressions from one scenario cannot be used to simulate another situation. The effects of void ratio, initial water content, stress state and high suction were studied in this work revealing that water content and stress state are more important than the other effects; but that the influences tend to decrease when suction increases. The van Genuchten model was modified to simulate better the changes in the degree of saturation at low values of suction. Predictions were compared with experimental results to determine the simulation capability of the model.

Effect of absorption boundary layer on nonlinear flow in low permeability porous media

Taking low permeability cores of Daqing oilfield for example,the flow characteristics at low velocity were studied with the self-designed micro-flux measuring instrument.Considering the throat distribution and capillary model,the thickness of fluid boundary layer under different pressure gradients was calculated,and the mechanism and influencing factors of nonlinear percolation were discussed.The results show that the percolation curve of ultra-low rocks is nonlinear,and apparent permeability is not a constant which increases with pressure gradient.The absorption boundary layer decreases with the increase of pressure gradient,and changes significantly especially in low pressure gradient,which is the essence of nonlinear percolation.The absorption boundary layer is also found to be impacted by the surface property of rocks.

Increased paracellular permeability of tumor-adjacent areas in 1,2-dimethylhydrazine-induced colon carcinogenesis in rats

Objective: The morphology and functions of the proximal and distal large intestine are not the same. The incidence of colorectal cancer in these regions is also different, as tumors more often appear in the descending colon than in the ascending colon.Inflammatory bowel disease and colorectal cancer can increase transepithelial permeability, which is a sign of reduced intestinal barrier function. However, there is not enough evidence to establish a connection between the difference in colorectal cancer incidence in the proximal and distal colon and intestinal permeability or the effects of carcinogenesis on the barrier properties in various areas of the colon. The aim of the study was to assess the permeability of different segments of the large intestine according to a developed mapping methodology in healthy rats and rats with 1,2-dimethylhydrazine(DMH)-induced colon adenocarcinoma.Methods: The short circuit current, the transepithelial electrical resistance and the paracellular permeability to fluorescein of large intestine wall of male Wistar rats were examined in the Ussing chambers. The optical density of the solution from the serosa side to assess the concentration of the diffused fluorescein from mucosa to serosa was analyzed by spectrophotometry. The morphometric and histological studies were performed by optical microscopy.Results: Rats with DMH-induced colon adenocarcinomas showed elevated transepithelial electrical resistance in the areas of neoplasm development. In contrast, there was no change in the electrophysiological properties of tumor adjacent areas, however,the paracellular permeability of these areas to fluorescein was increased compared to the control rats and was characterized by sharply reduced barrier function.Conclusions: The barrier properties of the colon vary depending on tumor location. The tumors were less permeable than the intact intestinal wall and probably have a negative influence on tumor-adjacent tissues by disrupting their barrier function.

Penetration grouting reinforcement of sandy gravel

To study the relationship between grouting effect and grouting factors, three factors （seven parameters） directionless pressure and small cycle grouting model experiment on sandy gravel was done, which was designed according to uniform design method. And regressing was applied to analysis of the test data. The two models test results indicate that when the diffusing radius of grout changes from 26 to 51 cm, the grouted sandy gravel compressing strength changes from 2.13 to 12.30 MPa; the relationship between diffusing radius（R） and water cement ratio（m）, permeability coefficient（k）, grouting pressure（p）, grouting time（t） is R=19.953m^0.121k^0.429p^0.412t^0.437; the relationship between compressing strength（P） and porosity（n）, water cement ratio, grouting pressure, grouting time is P =0.984n^0.517m6-1.488p^0.118t^0.031. So the porosity of sandy gravel, the permeability coefficient of sandy gravel, grouting pressure, grouting time, water cement ratio are main factors to influence the grouting effect. The grouting pressure is the main factor to influence grouting diffusing radius, and the water cement ratio is the main factor to influence grouted sandy gravel compressing strength.

Finite element simulation on percolation of low permeability reservoir with permeability anisotropy

In low permeability porous media which permeability anisotropy is ubiquitous,the percolation of fluid no longer follows linear Darcy’s Law.Oil-water two phase flow equation of low permeability reservoir with permeability anisotropy is established based on generalized Darcy’s law and starting pressure gradient,corresponding finite element program is developed and simulated based on the Finite Element Program Generator system (FEPG).The results show that energy-gathering exists in the flow event of flowing area front in low permeability reservoir.In the process of energy-gathering,the flow velocity changed little but increased rapidly as soon as the pressure gradient exceeded the starting pressure gradient of the reservoir,then gradually stabilized.The greater the starting pressure gradient is,the greater the near wellbore pressure drop is,the smaller the area influenced by the reservoir pressure changes caused by water injection and oil recovery.The greater the starting pressure gradient is,the lower the water saturation in same point of the reservoir is,the smaller the water flood swept area is.There will be more difficulties in water injection to the same extent.

Microstructural insight into permeability and water retention property of compacted binary silty clay

The durability of silty clay embankments is partially controlled by the moisture migration, which depends on soil hydraulic properties. This paper presents an experimental study of hydraulic properties of compacted binary silty clay. Specimens with different mixing ratios and dry densities were prepared. Scanning electron microscopy and mercury intrusion porosimetry were used to characterise the microstructure of silty clay. Thereafter, falling-head permeability tests and water retention tests were conducted to study the permeability and water retention property, respectively. The results demonstrate that clay particles are dispersed and show preferred arrangements after compaction when the clay content is 100%. As the clay content decreases, the arrangement of clay particles is gradually disturbed because of the existence of silt particles, causing the formation of large pores around silt particles. When the dry density increases, the pores around silt particles significantly decrease. Moreover, the permeability of silty clay decreases but the water retention capacity increases with increasing clay content and dry density. This is because the silty clay with larger clay content and dry density has fewer large pores, which greatly restrains the flow of water. Both the permeability and water retention property of silty clay can be predicted from pore size distribution parameters.

Changes of Resistance During Polyelectrolyte-enhanced Stirred Batch Ultrafiltration

The permeation flux or the resistance in the ultrafiltration process is mainly limited by osmotic pressure, and it may originate from various kinds of polymer interactions. However, the real origin of permeation resistance hasn＇t been clarified yet in the light of polymer solution nature. The removal of nitrate contamination by polyelectrolytes was carried out with stirred batch ultrafiltration. The polyelectrolyte concentrations both in permeate and retentate were analyzed with total organic carbon analyzer and permeate mass was acquired by electronic balance connected with computer. The total resistance was calculated and interpreted based on the osmotic pressures in three concentration regimes. In the dilute region, the resistance was proportional to polymer concentration; in the semidilute region, the resistance depended on polymer concentration in the parabolic relationship; in the highly concentrated solution regime, the osmotic pressure factor （OPF） would dominate the total resistance; and the deviation from OPF control could come from the electrostatic repulsion between the tightly compacted and charged polyelectrolyte particles at extremely concentrated solution regime. It was first found that dilute and semidilute concentration regions can be easily detected by plotting the leg-log curves of the polymer concentration versus the ratio of the total resistance to polymer concentration. The new concept OPF was defined and did work well at highly concentrated regime.

Research on Permeability of Multiphase Medium of Middle to High-Rank Coals

The permeability of coal of middle to high ranks were tested using He,CH 4 and H 2O in single phase medium and using CH 4 and H 2O in double phase medium. The relation between adsorption and permeability of those media was discussed, and the seepage flow characteristics of methane-water medium in coals were analyzed. The result shows that the coalbed methane resource of high-rank coal reservoirs in China is still recoverable.

Multi-functional forward osmosis draw solutes for seawater desalination

Forward osmosis(FO), as one of the emerging desalination technologies, has the potential to produce fresh water from a variety of water sources by utilizing the osmotic pressure gradient across a semi-permeable membrane.Draw solution, as an essential component of any FO process, can extract water molecules from seawater or wastewater. An ideal draw solution should meet three essential requirements, namely high osmotic pressure, low reverse flux, and facile regeneration mechanism. The selection of proper draw solutes is especially critical for an energy-efficient FO process since the energy consumption mostly arises from the separation or regeneration of the draw solution. Recently, we developed a few multi-functional FO draw solutes, mainly aiming to enhance the FO water flux and to explore facile re-concentration methods. This review summarizes these draw solutes,including Na^+_- functionalized carbon quantum dots, thermoresponsive copolymers, hydrophilic magnetic nanoparticles, and thermoresponsive magnetic nanoparticles.

Quantitative Estimation of Directional Permeability Barrier as Reservoir Heterogeneity A New Approach Using Synthetic Core

One of the major challenges in reservoir characterization is to estimate the effective porosity and the permeability of the reservoir due to reservoir heterogeneity. Often, the vertical and the horizontal permeabilities are not considered separately in 3D geo-cellular models and in the reservoir simulations. Conventional reservoir modeling extrapolates all of the small-scale data to full-field scale data without considering the impact of the small-scale geological details, and therefore carries forward inherent errors into the reservoir predictions as a consequence of ignoring the reservoir heterogeneity. Most reservoirs are geologically complex and heterogeneous and that greatly influences reservoir performance. A case study is taken from a CHOPS （cold heavy oil production with sands） field. An innovative method of reservoir heterogeneity estimation has been introduced to illustrate the complex reservoir heterogeneity honouring all of the small-scale geological details in the 3D geological model. This detailed near-wellbore modeling through a synthetic core can provide the realistic quantitative volumetric assumption of the production prediction and improve the EOR （enhanced oil recovery） processes.