• <tr id="yyy80"></tr>
  • <sup id="yyy80"></sup>
  • <tfoot id="yyy80"><noscript id="yyy80"></noscript></tfoot>
  • 99热精品在线国产_美女午夜性视频免费_国产精品国产高清国产av_av欧美777_自拍偷自拍亚洲精品老妇_亚洲熟女精品中文字幕_www日本黄色视频网_国产精品野战在线观看 ?

    Microstructure Characterization of Bubbles in Gassy Soil Based on the Fractal Theory

    2024-03-12 11:14:18WUChenLINGuoqingLIULeleLIUTaoLIChengfengandGUOZhenqi
    Journal of Ocean University of China 2024年1期

    WU Chen , LIN Guoqing , , LIU Lele , LIU Tao , ,LI Chengfeng and GUO Zhenqi

    1) Shandong Provincial Key Laboratory of Marine Environment and Geological Engineering, Ocean University of China, Qingdao 266100, China

    2) Key Laboratory of Gas Hydrate, Ministry of Natural Resources, Qingdao Institute of Marine Geology,Qingdao 266237, China

    3) College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China

    4) Key Laboratory of Marine Environment and Ecology, Ministry of Education, Ocean University of China,Qingdao 266100, China

    5) Qingdao National Laboratory for Marine Science and Technology, Qingdao 266237,China

    Abstract The microscopic characterization of isolated bubbles in gassy soil plays an important role in the macroscopic physical properties of sediments and is a key factor in the study of geological hazards in gas-bearing strata. Based on the box-counting method and the pore fractal features in porous media, a fractal model of bubble microstructure parameters in gassy soil under different gas contents and vertical load conditions is established by using an industrial X-ray CT scanning system. The results show that the fractal dimension of bubbles in the sample is correlated with the volume fraction of bubbles, and it is also restricted by the vertical load. The three-dimensional fractal dimension of the sample is about 1 larger than the average two-dimensional fractal dimension of all the slices from the same sample. The uniform porous media fractal model is used to test the equivalent diameter, and the results show that the variation of the measured pore diameter ratio is jointly restricted by the volume fraction and the vertical load. In addition, the measured self-similarity interval of the bubble area distribution is tested by the porous media fractal capillary bundle model, and the fitting curve of measured pore area ratio in a small loading range is obtained in this paper.

    Key words gassy soil; bubble microstructure parameters; fractal dimension; vertical load

    1 Introduction

    Due to many natural and human causes (e.g., global warming, oil and gas exploitation), natural gas hydrates in the submarine reservoir can decompose and release free gas(mainly methane). The free gas will temporarily stay in the marine sediments and then migrate upward to the seabed surface, normally occurring in a discrete form. This kind of sediments with discrete gas bubbles is called gassy soil.Not all the gases within gassy soil in nature come from natural gas hydrates, they can also be directly produced by microbial degradation of organic matter under anaerobic conditions and thermogenic methanogenesis (Liet al.,2019, 2021a). Gassy soil or gassy sediment is widely distributed in the coastal areas of continents (Fleischeret al.,2001; Liet al., 2021b). Gassy soil has characteristics of large porosity, under compaction, poor cementation, and partial non-uniformity, which easily lead to insufficient bearing capacity of the overlying strata. Under the external load, it is easy to deform and lead to subsidence after gas evolution, causing threats to the stability of seabed equipment and the safety of marine engineering projects (Liuet al., 2022). For example, in the Quaternary deposit along the coastal region of Shanghai, plenty of methane gas released during urbanization and leaded to burning, poisoning,and instability of submarine structures (Xuet al., 2017).Therefore, mechanical properties of gassy soil and the disaster-causing mechanism have become increasingly important in the field of marine geotechnical engineering.

    At present, there are a lot of studies focusing on the macroscopic mechanics of gassy soil. Wheeler (1988) and Honget al. (2017) observed the microstructure within two samples of typical fine-grained gassy soil by using scanning electron microscope (SEM). It is shown that the undissolved gas in the saturated matrix occurs in the form of large discrete bubbles, and the size of bubbles is much larger than those of soil particles and pores in the matrix.This not only changes the compression characteristics of pore fluids but also significantly alters the microstructure of soil, affecting mechanical properties of gassy soil. Thomas (1987) carried out a series of one-dimensional consolidation tests on remolded gassy soil (undrained when loaded, then drained), and found that, with the increase of gas contents, the compressibility of gassy soil increases,and the compression curve of gassy soil will eventually coincide with the compression curve of saturated soil. Honget al. (2017) systematically studied the undrained shear characteristics of remolded gassy silt under the condition of large initial pore water pressure. The results show that the existence of bubbles will significantly affect the undrained shear behavior of aerated soil, and the shearing process may produce excess pore water pressure, which depends on the initial pore water pressure and the initial gas content. Sultanet al.(2012) studied the effects of gas evolution and bubble expansion on the consolidation and undrained shear characteristics of gassy soil during undrained unloading processes. The test results showed that the gas evolution and bubble expansion caused by the pressure unloading would enhance the compressibility of gassy soil but reduce its pre-consolidation pressure. The undrained shear strength was significantly reduced, and the structural changes caused by the gas evolution would affect the effective stress path. At the microscopic level, Honget al.(2019) conducted the experiments under one-dimensional consolidation conditions and found that, with the increase of vertical load, bubbles were mainly compressed along the direction of vertical load, while there is basically no compression in the horizontal direction. However, the distribution of isolated bubbles in gassy soil is very complex.Understanding of the evolved microstructure of gassy soil under different external conditions is still insufficient, and the microscopic response mechanism of macroscopic mechanical properties remains elusive. There are limitations in the application and promotion of relevant constitutive models, which seriously restrict the accurate prediction on mechanical properties of gassy soil and the effective prevention and control of engineering accidents.

    The fractal theory is proposed and created by Mandelbrot (1967), which can describe disordered chaos phenomena and irregular shapes without the limitation of cross scale. The fractal theory has been widely used in the field of sediment particle and pore distribution (Katz and Thompson, 1985; Rieu and Sposito, 1991; Yu, 2001; Yu and Cheng,2002a; Shenget al., 2020; Wood, 2021) and hydrate features (Liuet al., 2020a, 2021). It is found that the pore space of sediment samples has obvious fractal characteristics in a certain scale range. Fractal parameters such as pore size fractal dimension, tortuosity fractal dimension, and maximum pore diameter are usually used to quantify the pore structure of porous materials. Based on the pore structure characterization, constitutive models for hydraulic and electrical properties of porous media have achieved well prediction performances (Liuet al., 2020b; Zhanget al.,2021).

    Therefore, in this paper, the fractal theory is used to quantitatively characterize the bubble distribution in gassy soil remolded by using sediments from the Yellow River Delta. The fractal parameters to describe the bubble distribution are extracted from X-ray computed tomography (CT)scanning images under different gas-content and load conditions, and characteristics of the bubble distribution in gassy soil and its influence on mechanical properties of gassy soil are discussed. It provides basic support for the prevention and controlling of marine engineering accidents in the offshore area.

    2 Methodology

    2.1 Test Equipment and Experimental Material

    In this paper, all the X-ray CT images were obtained by using a Phoenix v | tome | x industrial CT scanner produced by GE. The scanner has a 180 kV / 15 W high-power nanofocus X-ray tube and three 240 kV / 320 W micro-focus X-ray tubes, which are described in detail by Zhanget al.(2020). The images collected in the experiment are 1000 pixels × 1000 pixels, and each pixel represents 21 μm in this study. The device after consolidation was fixed on the rotary table in the X-ray CT scanning room, and the rotation step was set to 0.3? s?1. A miniature X-ray CT experimental device (Guoet al., 2021) with one-dimensional consolidation and multi-stage loading function is installed on the internal rotary table of the X-ray CT scanner to apply different vertical loads, as shown in Fig.1.

    Fig.1 Phoenix v | tome | x industrial CT scanner and loading device.

    The silt used in the experiment was collected from the Yellow River Delta. The sediment sample was placed in a ventilated and cool environment to air dry, and then the impurities were removed by using a 0.25 mm soil sieve. According to the method of ‘Geotechnical Test Method Standard’, the physical index experiment of the silt sample was carried out, and the measured parameters such as water content, dry density, specific gravity, and porosity were listed in Table 1.

    Table 1 Basic physical property parameters of the experimental material

    2.2 Preparation of the Gassy Soil Sample

    Due to the pressure release caused by deep-water sampling, the gas in silt will dissolve and expand which will change the soil skeleton structure and even produce cracks.Porous media introduction technology was used to prepare remolded gassy soil samples (Honget al., 2019). Due to the strong adsorption of zeolite powder, the small hole continuously absorbs nitrogen (N2) gas, which will exchange the water in the slurry in the next step, forming a porous medium filled with bubbles. And it is easy for small bubbles to form at the edges and corners of the porous medium,which will change the soil skeleton structure, closely resembling the bubbles in the sediments under marine environment. The detailed steps are described as follows:

    The porous media materials (zeolite powder: average particle size of 0.8 μm – 3 μm) were dried at a high temperature (100℃, 36 h) and kept in a vacuum saturation instrument (?100 kPa, 36 h); then, the N2gas was pressed into porous media under high pressure (250 kPa, 48 h). The dry silt and stagnant water were mixed according to the ratio of 1:2wL, stirred evenly, and also kept in a vacuum saturated instrument (?100 kPa, 24 h). Finally, the N2saturated zeolite powder is mixed with the watery mud to exchange the N2gas with the water in the slurry, so that bubbles are formed in the silt. Then, carefully pour the slurry into the cylindrical chamber and apply various vertical stresses until the initial consolidation is completed.

    Eight samples in two groups with different contents (10%and 20%) of zeolite powder were prepared. The vertical loads of 0 kPa, 2 kPa, 4 kPa, and 6 kPa were applied respectively, and the labels were S10-0, S10-2, S10-4, S10-6,S20-0, S20-2, S20-4, and S20-6, respectively. After 48 h consolidation, X-ray CT scanning experiments were carried out to observe the distribution of bubbles in the air-bearing soil samples under different air contents and loads.

    The sample was rotated at a constant speed along the XY plane to complete the scanning process. Each scan takes about 22 min to obtain 1000 slices of original X-ray CT images, and these images are exported by using VG Studio MAX 2.1 software, followed by reconstruction and analyses by using Avizo 9.0 software.

    2.3 Image Processing and Fractal Dimension Acquisition of Gas Bubbles

    For noise reduction, the median filter method is used to minimize the signal distortion of sharp edges in the original gray images. Then, the optimal segmentation range of gas(Fig.2a) and matrix (Fig.2b) is found by threshold segmentation. The gas is expanded (Fig.2c) by Precise Dilation, and then the matrix part is subtracted by an algorithm.At the same time, the connected pores are subtracted to achieve the best bubble threshold segmentation effect (Fig.2d). After the segmentation, the Label Analysis module is used to extract the segmented bubbles, and the microscopic parameters of the bubble distribution are extracted after three-dimensional reconstruction, as shown in Fig.3.

    Fig.2 Segmentation process. (a), gas (red) threshold segmentation; (b), matrix (white) threshold segmentation; (c), gas (blue)dilation; (d), final segmentation effect.

    Fig.3 3D reconstruction effect of segmented gas phase extracted by using the Label Analysis module.

    The fractal dimension is usually measured by box-counting method, that is, a series of boxes with the same scale are used to cover the object, and the number of boxes intersected with the measured object is calculated. Then the number of intersecting boxes is recalculated by changing the length of the box. Finally, the trendline of the box number with the length of the box is drawn in the double logarithmic coordinate system. The absolute value of the slope of the straight line is the ‘box dimension’ of the measured object.Dfis the fractal dimension of the porous media,which ranges from 0 to 2 in two dimensions (Df2) and 0 to 3 in three dimensions (Df3). In this paper, Fractal Dimension module in Avizo software is used to extract three-dimensional and two-dimensional fractal dimensions of the bubble distribution after segmentation.

    3 Results and Analysis

    3.1 Fractal Dimension and Volume Fraction of Gas

    Fig.4 shows the relationship between the bubble volume fraction in gassy silt and the vertical load under different zeolite powder contents. The experimental data show that the bubble volume fraction decreases non-linearly with the increase of the vertical load. The bubble volume fraction decreased about 29.5% in S10 group, and 32.6% in S20 group when the vertical load increased from 0 kPa to 6 kPa.The upper limit of threshold segmentation is set to 19500 and 20000, and the results show that the three-dimensional fractal dimension numbers of bubble distribution change with the vertical loads under different segmentation conditions, as shown in Fig.5. In this paper, the upper limit of threshold segmentation of 20000 is selected for the better effect. It can be seen that the fractal dimension of bubble distribution decreases linearly with the increase of vertical load in general. Under the same vertical loading condition,values of the fractal dimension numbers of the bubble distribution in S10 samples are significantly smaller than those in S20 samples because of the bubble volume difference.

    Fig.4 Effect of vertical loads on bubble volume fractions under different contents of zeolite powder.

    Fig.5 Comparison of three-dimensional fractal dimensions of bubbles with different segmentation thresholds in the sample group of (a) S10 and (b) S20.

    The average value of two-dimensional fractal dimensions for all slices of each sample and the three-dimensional fractal dimension under different vertical load conditions are shown in Fig.6. It shows that the fractal dimension decreases with the increase of the vertical load. Combined with Fig.4,the fractal dimension decreases with the decrease of bubble volume fraction. The three-dimensional fractal dimension is about 1 larger than the mean value of two-dimensional fractal dimension of all slices from the same sample.

    Fig.6 Differences between mean value of Df 2 and Df 3 for the same sample under various vertical loads. (a), S10; (b), S20.

    The normalizedDf2(Two-dimensional fractal dimension divided by the maximum value) and the normalized?(volume fraction divided by the maximum value) are plotted against the normalized slice number (slice number divided by the total number) for the slices 50 – 950 in Fig.7. It shows the relationships of fractal dimension and volume fraction in single slice are similar to the results of the whole sample, but the difference is more obvious in S20 group.The variation amplitude of bubble volume fraction in different slices is much higher than that of fractal dimension,and the variation amplitude in the slices from the sample S10-6 is particularly obvious. The analysis of single slice image shows that there are more irregular large bubbles in this sample, and most of bubble are flat, which will cause the fluctuations of bubble volume fractions obtained by our methods, but does not affect the measured fractal dimension.

    Fig.7 Variations of normalized fractal dimension and volume fraction in all slices from one sample. (a), S10; (b), S20.

    It can be seen from Fig.7 that the variation trends of fractal dimension and volume fraction are different. In the S20 group, the overall fractal dimension of the sample with the load of 2 kPa is greater than that of 0 kPa. Therefore,the slices at different normalized positions of samples 20-0 and 20-2 were analyzed, that is, the bubble equivalent diameter distribution in the slices at the abnormal normalized positions with inconsistent variations in fractal dimension and volume fraction were compared. By extracting the threshold segmentation effect maps from the slices at the normalized position of 0.55 and 0.65. It was found that the equivalent diameter distribution of the slices with higher two-dimensional fractal dimension was more uniform.

    3.2 Microscopic Parameters of Large Bubbles

    Because the mechanical properties of gassy soil are mainly affected by large bubbles (Wanget al., 2018; Gaoet al.,2020; Honget al., 2020, 2021), in this paper, only the bubbles with the equivalent diameter larger than 0.3 mm are analyzed, and the results are shown in Figs.8 and 9.

    From Fig.8 and Fig.9, we can find that the distribution of bubbles with equivalent diameter greater than 1 mm is not correlated with the load and gas content, but when the larger bubbles with low sphericity increase, the equivalent diameter increases. The variation of bubble sphericity with loads in different samples for the bubbles with diameters greater than 1 mm and greater than 0.3 mm is shown in Fig.10. It can be seen that with the increase of loads, the spherical values generally show the downward trend. In the compression process, the volume change is mainly composed of two parts: gas compression and consolidation drainage. The overall spherical value did not change significantly in S10 because the gas content was low and the compression effect of gas in soil skeleton was not obvious.

    Fig.8 Bubble extraction images with specific sizes in S10. (a), equivalent diameter > 1 mm (from left to right the vertical loads are 0, 2, 4, 6 kPa, respectively); (b), 1 mm > equivalent diameter > 0.3 mm (from left to right the loads are 0, 2, 4, 6 kPa, respectively).

    Fig.9 Same as Fig.8, but for S20.

    Fig.10 Sphericity variation of large bubbles.

    3.3 Inspection of Unified Fractal Model for Porous Media

    According to Yu (2001), a unified model describing the fractal characteristics of porous media is proposed as follow:

    wheredis the Euclidean dimension and equals to 3 in this study, is volume fraction (i.e., volume porosity),λminandλmaxare minimum and maximum pore diameters, respectively. The ratioλmin/λmaxis the equivalent pore diameter.According to Eq. (1), the volume fraction and fractal dimension of the gassy soil are calculated, and the theoretical value ofλmin/λmaxis obtained, which is compared with the measured value of all bubbles extracted in Label Analysis.

    As shown in Fig.11, according to the measured volume fraction and fractal dimension, the values ofλmin/λmaxcalculated by Eq. (1) change little and are stable at about 0.006. However, the actual measured values ofλmin/λmaxare generally higher than the theoretical values, and there is no obvious law with the change of volume fractions. With the increase of the load, the gap between the two values is narrowing, and the difference reaches the minimum at 6 kPa. According to Figs.8 and 9, with the increase of the load, the probability of larger bubbles increases, resulting in the decrease of the measured value ofλmin/λmax. For the equivalent pore diameters obtained by Label Analysis, the minimum values of all samples are basically the same,stable at about 0.037, which is related to the equivalent method of pore size (Liuet al., 2020a).

    Fig.11 Comparison between the measured values and the theoretical values of λmin / λmax. Note that, values illustrated in the coordinates are all for the parameter λmin / λmax.

    3.4 Relationship Between the Area Distribution and the Fractal Dimension of Bubbles

    The fractal capillary bundle model of porous media proposed by Yu and Cheng (2002b) conforms to the following rules: the cumulative number of pores with diameter greater than a certain scale obeys the fractal scaling relationship in Eq. (2). Eq. (3) can be obtained by replacing the pore sizeλwith the bubble areaAobtained in Label Analysis.Nrepresents the cumulative numbers under different independent variables.

    According to Eq. (3), the obtained overall bubble area distribution is plotted in a double logarithmic coordinate system (Fig.12). There are obvious self-similar scaling intervals in the overall pore area distribution for S10 and S20 groups. The minimum value of the self-similar interval is basically fixed at about 0.06, while the maximum value of the interval increases roughly with the volume fraction of bubbles.

    Fig.12 Double logarithmic curves of the bubble area distribution. (a), S10; (b), S20.

    Then the maximum value of the obtained interval is set asAmaxand the minimum value is set asAmin, which are substituted into Eq. (3) to replaceλminandλmax, respectively.The results are shown in Fig.13. The ratio ofAmin/Amaxgradually approaches the theoretical value with the increase of volume fraction, but the relationship with the variation of load is not obvious. Therefore, in the range of small loads,the area distribution of bubbles in gassy soil changes regularly with the volume fraction.

    Fig.13 Comparison between measured values and theoretical values of Amin / Amax. Note that, values illustrated in the coordinates are all for the parameter Amin / Amax.

    4 Conclusions

    In this paper, the microstructure within gassy soil samples with different gas contents is observed by using an X-ray CT scanner at different vertical stress levels. X-ray CT images are processed and used to extract gas bubble related microstructure parameters based on the fractal theory. Main conclusions are drawn as follows:

    Bubble volume fractions in gassy soil samples decreases nonlinearly with increasing vertical load stress when zeolite powder contents in the samples are the same. Both the three-dimensional fractal dimension and the average of all the two-dimensional fractal dimensions decrease with increasing vertical load stress. In addition, value of the threedimensional fractal dimension for each sample is about unit larger than the average of all the two-dimensional fractal dimension values.

    Sphericity of gas bubbles with large sizes generally decreases with increasing vertical loading stress. This indicates that the gas bubble will become more ellipsoidal due to vertical loading. When the gas content is small, the sphericity tends to change little during vertical loading.

    Measured values of the equivalent pore diameterλmin/λmaxin gassy soil sample are generally larger than the theoretical values, and the difference between measured and theoretical values becomes small when the vertical loading stress increases. Self-similar scaling intervals are obvious in the gas bubble area distribution, and the upper limit of the scaling intervals is positively correlated with the volume fraction. The measured value of the bubble area ratioAmin/Amaxgradually approaches the theoretical value when the volume fraction of gas bubbles increases.

    Acknowledgements

    The study is supported by the Open Research Fund Program of State Key Laboratory of Hydroscience and Engineering (No. sk lhse-2022-D-03), the National Natural Science Foundation of China (Nos. U2006213, 42277139),and the Taishan Scholars Program (No. tsqn202306297).

    国产一区二区三区在线臀色熟女| 啪啪无遮挡十八禁网站| 精品久久久久久久末码| a在线观看视频网站| 亚洲色图 男人天堂 中文字幕| 在线观看免费午夜福利视频| 99久久精品国产亚洲精品| 国产单亲对白刺激| 国产aⅴ精品一区二区三区波| 黄色毛片三级朝国网站| 一本综合久久免费| 亚洲专区国产一区二区| 国产精品综合久久久久久久免费| 日本五十路高清| 亚洲18禁久久av| 少妇裸体淫交视频免费看高清 | 韩国av一区二区三区四区| 99久久久亚洲精品蜜臀av| 国产蜜桃级精品一区二区三区| 中文字幕熟女人妻在线| 国产亚洲欧美98| 一级毛片高清免费大全| 国内少妇人妻偷人精品xxx网站 | 亚洲成人久久性| 两人在一起打扑克的视频| 亚洲avbb在线观看| 欧美久久黑人一区二区| 日韩大尺度精品在线看网址| 国语自产精品视频在线第100页| 亚洲精品中文字幕在线视频| 国产在线观看jvid| 国产黄a三级三级三级人| 免费人成视频x8x8入口观看| aaaaa片日本免费| 国产高清videossex| 国产亚洲精品av在线| www日本在线高清视频| 妹子高潮喷水视频| 久久久久国产精品人妻aⅴ院| 女同久久另类99精品国产91| 三级国产精品欧美在线观看 | 岛国在线观看网站| 国产亚洲av高清不卡| 日韩欧美国产一区二区入口| 18禁国产床啪视频网站| 久久久久久大精品| 久久久久久免费高清国产稀缺| 在线十欧美十亚洲十日本专区| 国产精品免费视频内射| 亚洲第一电影网av| 91大片在线观看| 免费在线观看日本一区| 香蕉久久夜色| 无限看片的www在线观看| 全区人妻精品视频| 一a级毛片在线观看| 九九热线精品视视频播放| 久久久水蜜桃国产精品网| 久久久国产精品麻豆| 亚洲国产精品成人综合色| 成人手机av| 国产成人一区二区三区免费视频网站| www.精华液| 日日夜夜操网爽| 99国产精品一区二区三区| 日本成人三级电影网站| 18禁观看日本| 97人妻精品一区二区三区麻豆| 在线免费观看的www视频| 精品久久久久久久毛片微露脸| 欧美黑人巨大hd| 亚洲成人久久爱视频| www.精华液| 又黄又粗又硬又大视频| 丰满的人妻完整版| 欧美成狂野欧美在线观看| 亚洲在线自拍视频| 人人妻,人人澡人人爽秒播| 91成年电影在线观看| 老司机午夜十八禁免费视频| 亚洲欧美日韩东京热| 美女大奶头视频| 亚洲av第一区精品v没综合| 精品日产1卡2卡| 亚洲av五月六月丁香网| 久久精品国产清高在天天线| 国产成人aa在线观看| 一级毛片高清免费大全| 国产在线观看jvid| 最近最新中文字幕大全免费视频| 国产aⅴ精品一区二区三区波| 久久精品91蜜桃| 岛国视频午夜一区免费看| 亚洲欧美日韩高清专用| 亚洲av中文字字幕乱码综合| 巨乳人妻的诱惑在线观看| 欧美在线一区亚洲| 男女那种视频在线观看| 国产精品影院久久| 免费看美女性在线毛片视频| 成人国语在线视频| 观看免费一级毛片| 国产精品电影一区二区三区| 国产精品久久视频播放| 他把我摸到了高潮在线观看| 亚洲九九香蕉| a在线观看视频网站| 欧美成人免费av一区二区三区| 国产激情偷乱视频一区二区| 国产午夜福利久久久久久| 两个人免费观看高清视频| 亚洲九九香蕉| 亚洲成人久久爱视频| 亚洲国产中文字幕在线视频| 一级毛片精品| 成人永久免费在线观看视频| 老司机在亚洲福利影院| 亚洲全国av大片| 黄片小视频在线播放| 午夜亚洲福利在线播放| 日韩有码中文字幕| 中文字幕最新亚洲高清| 欧美乱色亚洲激情| 成人av一区二区三区在线看| 色综合亚洲欧美另类图片| 香蕉丝袜av| 可以在线观看的亚洲视频| 午夜久久久久精精品| 国内精品一区二区在线观看| 午夜免费成人在线视频| 亚洲精品粉嫩美女一区| 欧美日韩福利视频一区二区| 欧美日本视频| 黄片小视频在线播放| 欧美日韩福利视频一区二区| 午夜激情av网站| 久久中文看片网| 欧美人与性动交α欧美精品济南到| 亚洲av片天天在线观看| 一区福利在线观看| 亚洲一卡2卡3卡4卡5卡精品中文| 亚洲一区中文字幕在线| 88av欧美| 亚洲欧美精品综合久久99| 小说图片视频综合网站| 国产精品精品国产色婷婷| 色av中文字幕| 天天躁夜夜躁狠狠躁躁| 最近最新免费中文字幕在线| 国产激情欧美一区二区| 婷婷六月久久综合丁香| 亚洲欧美激情综合另类| 一二三四在线观看免费中文在| 国产成年人精品一区二区| 精品无人区乱码1区二区| 欧美精品啪啪一区二区三区| 国产精品,欧美在线| 老司机在亚洲福利影院| 久久精品影院6| av福利片在线| 国产精品98久久久久久宅男小说| 亚洲精品国产精品久久久不卡| e午夜精品久久久久久久| 手机成人av网站| 国产精品一区二区三区四区久久| 美女 人体艺术 gogo| 欧美激情久久久久久爽电影| 亚洲中文av在线| 欧美一级毛片孕妇| 三级男女做爰猛烈吃奶摸视频| 久久久水蜜桃国产精品网| 久久久久久亚洲精品国产蜜桃av| 一区二区三区激情视频| 日日干狠狠操夜夜爽| 日本一本二区三区精品| 亚洲成人中文字幕在线播放| 日韩有码中文字幕| 小说图片视频综合网站| 成在线人永久免费视频| 欧美一级a爱片免费观看看 | x7x7x7水蜜桃| 日本黄色视频三级网站网址| 我要搜黄色片| 国产精品电影一区二区三区| 少妇被粗大的猛进出69影院| 久久久国产成人精品二区| 国产精品久久久久久久电影 | 久久亚洲精品不卡| 日韩有码中文字幕| 熟女电影av网| 国产亚洲精品久久久久5区| 午夜久久久久精精品| 此物有八面人人有两片| 国产精品久久视频播放| 久久久久免费精品人妻一区二区| 一二三四社区在线视频社区8| xxxwww97欧美| 999精品在线视频| 琪琪午夜伦伦电影理论片6080| 校园春色视频在线观看| 999久久久国产精品视频| 亚洲aⅴ乱码一区二区在线播放 | 亚洲aⅴ乱码一区二区在线播放 | 久久香蕉国产精品| 成人三级做爰电影| 波多野结衣高清无吗| 一个人观看的视频www高清免费观看 | 久久亚洲真实| 精品久久久久久久人妻蜜臀av| 国内揄拍国产精品人妻在线| 免费在线观看成人毛片| 在线观看www视频免费| 极品教师在线免费播放| 高清在线国产一区| 亚洲欧美日韩无卡精品| 久99久视频精品免费| 成人高潮视频无遮挡免费网站| 精品乱码久久久久久99久播| 中出人妻视频一区二区| 亚洲一区二区三区色噜噜| 亚洲精品中文字幕一二三四区| 国产精品一区二区免费欧美| 一a级毛片在线观看| 1024手机看黄色片| 亚洲专区国产一区二区| 久久精品国产亚洲av高清一级| 99热这里只有是精品50| 亚洲片人在线观看| 又爽又黄无遮挡网站| 成人特级黄色片久久久久久久| 露出奶头的视频| 欧美国产日韩亚洲一区| 日韩欧美精品v在线| 亚洲五月婷婷丁香| 国语自产精品视频在线第100页| 国产午夜精品久久久久久| 午夜福利成人在线免费观看| 人人妻,人人澡人人爽秒播| 国模一区二区三区四区视频 | 男女午夜视频在线观看| 亚洲一卡2卡3卡4卡5卡精品中文| 三级男女做爰猛烈吃奶摸视频| 午夜福利免费观看在线| 脱女人内裤的视频| 香蕉av资源在线| e午夜精品久久久久久久| 全区人妻精品视频| 中亚洲国语对白在线视频| 国产1区2区3区精品| 免费av毛片视频| 久久这里只有精品19| 午夜两性在线视频| 亚洲黑人精品在线| 亚洲va日本ⅴa欧美va伊人久久| 免费高清视频大片| 丰满人妻熟妇乱又伦精品不卡| 国产男靠女视频免费网站| 一本久久中文字幕| 久热爱精品视频在线9| 欧美日韩中文字幕国产精品一区二区三区| 淫妇啪啪啪对白视频| 巨乳人妻的诱惑在线观看| 操出白浆在线播放| 久久久久久免费高清国产稀缺| 舔av片在线| 国产成人av激情在线播放| www日本黄色视频网| 久9热在线精品视频| 成人国产综合亚洲| 亚洲av第一区精品v没综合| 精品国内亚洲2022精品成人| 久久中文看片网| 又爽又黄无遮挡网站| 两个人的视频大全免费| 欧美乱妇无乱码| 欧美绝顶高潮抽搐喷水| 亚洲狠狠婷婷综合久久图片| 国产在线精品亚洲第一网站| 久久99热这里只有精品18| 欧美中文日本在线观看视频| 人人妻,人人澡人人爽秒播| 91国产中文字幕| 亚洲专区字幕在线| av在线天堂中文字幕| 夜夜躁狠狠躁天天躁| 一区福利在线观看| 91麻豆av在线| 亚洲成人精品中文字幕电影| 国产亚洲av嫩草精品影院| 中文字幕高清在线视频| 欧美在线黄色| 真人一进一出gif抽搐免费| 欧美高清成人免费视频www| 国产野战对白在线观看| 日本一区二区免费在线视频| 老汉色∧v一级毛片| 中国美女看黄片| 欧美绝顶高潮抽搐喷水| 亚洲人成77777在线视频| 制服人妻中文乱码| 国内揄拍国产精品人妻在线| 一卡2卡三卡四卡精品乱码亚洲| 伊人久久大香线蕉亚洲五| 18美女黄网站色大片免费观看| 久久精品国产综合久久久| 深夜精品福利| 午夜成年电影在线免费观看| 亚洲片人在线观看| 欧美日韩亚洲国产一区二区在线观看| 日韩成人在线观看一区二区三区| 国内精品久久久久久久电影| 亚洲全国av大片| 一本一本综合久久| 久久香蕉精品热| 亚洲av熟女| 中文资源天堂在线| 久久精品国产综合久久久| 国产成年人精品一区二区| 国产av一区在线观看免费| 无遮挡黄片免费观看| 在线观看免费午夜福利视频| 亚洲精品在线美女| 国产av又大| 成年版毛片免费区| 亚洲七黄色美女视频| 一级毛片女人18水好多| 亚洲国产欧洲综合997久久,| 精品国产乱子伦一区二区三区| 国产精品av视频在线免费观看| 国产成人欧美在线观看| 久久国产乱子伦精品免费另类| 久久这里只有精品19| 亚洲成人久久性| 黄片大片在线免费观看| 精品国产超薄肉色丝袜足j| 国产精品久久久久久人妻精品电影| 午夜日韩欧美国产| 19禁男女啪啪无遮挡网站| 夜夜躁狠狠躁天天躁| 午夜免费观看网址| 九色国产91popny在线| 国产精品av视频在线免费观看| www国产在线视频色| 午夜福利18| 国内精品久久久久久久电影| 婷婷精品国产亚洲av在线| 无人区码免费观看不卡| 成人国产一区最新在线观看| 国产精品美女特级片免费视频播放器 | 久久精品91蜜桃| 麻豆av在线久日| 成人国产综合亚洲| 中亚洲国语对白在线视频| 欧美激情久久久久久爽电影| 69av精品久久久久久| 天堂av国产一区二区熟女人妻 | 免费观看精品视频网站| 香蕉久久夜色| 国产又色又爽无遮挡免费看| 国产av又大| 久久精品亚洲精品国产色婷小说| 18禁黄网站禁片免费观看直播| 啪啪无遮挡十八禁网站| 99热这里只有是精品50| 亚洲 国产 在线| 岛国在线免费视频观看| 男女那种视频在线观看| 精品人妻1区二区| 亚洲国产欧美一区二区综合| 天堂av国产一区二区熟女人妻 | 国产伦人伦偷精品视频| 高清在线国产一区| 久久精品人妻少妇| 亚洲国产精品成人综合色| 国产精品野战在线观看| 亚洲国产精品sss在线观看| 麻豆国产av国片精品| 亚洲人成网站在线播放欧美日韩| 嫁个100分男人电影在线观看| 在线a可以看的网站| 久久久久久久精品吃奶| 国产精品一区二区三区四区免费观看 | 国语自产精品视频在线第100页| 国产黄色小视频在线观看| 亚洲国产日韩欧美精品在线观看 | 亚洲片人在线观看| 国内久久婷婷六月综合欲色啪| 久久精品aⅴ一区二区三区四区| 99热这里只有精品一区 | 18禁国产床啪视频网站| 国产在线精品亚洲第一网站| 88av欧美| 国产av麻豆久久久久久久| 亚洲精品国产精品久久久不卡| 中文在线观看免费www的网站 | 久久久久性生活片| 久久久国产欧美日韩av| 无人区码免费观看不卡| 国产亚洲精品久久久久久毛片| 最近最新中文字幕大全免费视频| 免费无遮挡裸体视频| 久久精品91无色码中文字幕| 日本成人三级电影网站| 日韩大码丰满熟妇| 亚洲成人久久性| 国产真实乱freesex| 午夜视频精品福利| 夜夜夜夜夜久久久久| 无遮挡黄片免费观看| 性欧美人与动物交配| 亚洲国产看品久久| 国产片内射在线| 99热只有精品国产| 国产在线精品亚洲第一网站| 久久精品综合一区二区三区| 无限看片的www在线观看| 男女之事视频高清在线观看| 国产精品98久久久久久宅男小说| 国产成人影院久久av| 不卡一级毛片| 狂野欧美白嫩少妇大欣赏| 婷婷精品国产亚洲av在线| e午夜精品久久久久久久| 一级a爱片免费观看的视频| 老司机福利观看| 久久婷婷人人爽人人干人人爱| 国产片内射在线| 免费在线观看完整版高清| 国产探花在线观看一区二区| 露出奶头的视频| 久久精品亚洲精品国产色婷小说| 男女视频在线观看网站免费 | av福利片在线| 国产男靠女视频免费网站| 亚洲欧美精品综合久久99| 午夜a级毛片| 中文在线观看免费www的网站 | 久久久久免费精品人妻一区二区| 亚洲七黄色美女视频| 亚洲精品一卡2卡三卡4卡5卡| 久久久久国内视频| 国内少妇人妻偷人精品xxx网站 | 亚洲avbb在线观看| 动漫黄色视频在线观看| 老司机在亚洲福利影院| 深夜精品福利| 亚洲一区高清亚洲精品| av福利片在线观看| a级毛片a级免费在线| 窝窝影院91人妻| 露出奶头的视频| 亚洲专区字幕在线| 老鸭窝网址在线观看| 在线观看www视频免费| 一级作爱视频免费观看| 精品人妻1区二区| 亚洲av电影不卡..在线观看| 久久天堂一区二区三区四区| 看免费av毛片| 久久中文字幕人妻熟女| 婷婷精品国产亚洲av| 男人的好看免费观看在线视频 | 高清毛片免费观看视频网站| 国产精品综合久久久久久久免费| e午夜精品久久久久久久| 精华霜和精华液先用哪个| 国产人伦9x9x在线观看| 黄色视频不卡| 91九色精品人成在线观看| 亚洲七黄色美女视频| 在线观看免费视频日本深夜| av福利片在线| 日韩欧美精品v在线| 黄色丝袜av网址大全| 亚洲熟妇中文字幕五十中出| netflix在线观看网站| 亚洲七黄色美女视频| 日韩中文字幕欧美一区二区| 亚洲人与动物交配视频| 国产精品久久久av美女十八| xxx96com| 一个人免费在线观看的高清视频| 亚洲国产精品合色在线| 国产精华一区二区三区| 久久这里只有精品中国| 亚洲精品av麻豆狂野| 免费看美女性在线毛片视频| 国产精品98久久久久久宅男小说| av福利片在线| 丁香欧美五月| 久久国产精品人妻蜜桃| 听说在线观看完整版免费高清| 国内精品一区二区在线观看| 91国产中文字幕| 婷婷精品国产亚洲av在线| 欧美极品一区二区三区四区| 国内揄拍国产精品人妻在线| 午夜精品一区二区三区免费看| 欧美性猛交╳xxx乱大交人| 国内精品一区二区在线观看| 国产亚洲av嫩草精品影院| 精品人妻1区二区| 欧美另类亚洲清纯唯美| 天堂动漫精品| 国产伦一二天堂av在线观看| 俺也久久电影网| www.自偷自拍.com| 日本三级黄在线观看| 国产欧美日韩精品亚洲av| 搡老熟女国产l中国老女人| 免费看十八禁软件| 又粗又爽又猛毛片免费看| 亚洲avbb在线观看| 免费高清视频大片| 亚洲欧美日韩东京热| 高清毛片免费观看视频网站| 人人妻人人澡欧美一区二区| 国内久久婷婷六月综合欲色啪| 女生性感内裤真人,穿戴方法视频| 在线十欧美十亚洲十日本专区| 桃红色精品国产亚洲av| av天堂在线播放| 黄色丝袜av网址大全| 久久久久久国产a免费观看| 国产精品一区二区三区四区免费观看 | 最好的美女福利视频网| svipshipincom国产片| 床上黄色一级片| 日韩精品中文字幕看吧| 1024手机看黄色片| 中文字幕人成人乱码亚洲影| 午夜精品一区二区三区免费看| 国产伦人伦偷精品视频| 日本黄色视频三级网站网址| 欧美黄色淫秽网站| 丰满人妻一区二区三区视频av | xxxwww97欧美| 日韩欧美一区二区三区在线观看| 波多野结衣巨乳人妻| 亚洲精华国产精华精| ponron亚洲| 老司机福利观看| 亚洲精品美女久久久久99蜜臀| 不卡av一区二区三区| 两性夫妻黄色片| 午夜福利18| 91老司机精品| 午夜亚洲福利在线播放| 妹子高潮喷水视频| 亚洲欧美精品综合久久99| 国产高清视频在线观看网站| 成人高潮视频无遮挡免费网站| tocl精华| 啦啦啦免费观看视频1| 亚洲 欧美一区二区三区| 日日干狠狠操夜夜爽| 三级国产精品欧美在线观看 | 又黄又爽又免费观看的视频| 好男人在线观看高清免费视频| 亚洲国产精品999在线| 精品久久久久久久久久免费视频| 亚洲欧美一区二区三区黑人| 999精品在线视频| 99久久综合精品五月天人人| 麻豆国产97在线/欧美 | 亚洲九九香蕉| 亚洲国产高清在线一区二区三| 欧美黄色淫秽网站| 欧美黑人欧美精品刺激| 两性午夜刺激爽爽歪歪视频在线观看 | 99国产精品一区二区三区| 成年人黄色毛片网站| 美女大奶头视频| 日日夜夜操网爽| 99久久无色码亚洲精品果冻| 91字幕亚洲| svipshipincom国产片| a级毛片a级免费在线| 精品不卡国产一区二区三区| 首页视频小说图片口味搜索| 欧美黑人欧美精品刺激| 婷婷亚洲欧美| 久99久视频精品免费| 国产高清激情床上av| 亚洲av成人一区二区三| a在线观看视频网站| 午夜福利18| 精品国内亚洲2022精品成人| cao死你这个sao货| 18禁观看日本| 91大片在线观看| 我要搜黄色片| 999精品在线视频| 法律面前人人平等表现在哪些方面| 亚洲av日韩精品久久久久久密| 欧美成人午夜精品| 久久久国产成人精品二区| 亚洲av成人av| 一二三四在线观看免费中文在| 老司机午夜十八禁免费视频| 男女床上黄色一级片免费看| 亚洲国产精品合色在线| 黄色片一级片一级黄色片| 免费电影在线观看免费观看| 国产免费男女视频| 别揉我奶头~嗯~啊~动态视频| 久久99热这里只有精品18| 好看av亚洲va欧美ⅴa在| 久久九九热精品免费| 久久精品夜夜夜夜夜久久蜜豆 | 天堂动漫精品| 欧美不卡视频在线免费观看 | 少妇被粗大的猛进出69影院| 欧美乱码精品一区二区三区| 99在线视频只有这里精品首页|