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1.
A comprehensive study of the data profiles, including the 2D seismic data, single channel seismic data, shallow sections,
etc., reveals that gas hydrates occur in the East China Sea. A series of special techniques are used in the processing of seismic
data, which include enhancing the accuracy of velocity analysis and resolution, estimating the wavelet, suppressing the multiple,
preserving the relative amplitude, using the DMO and AVO techniques and some special techniques in dealing with the wave impedance.
The existence of gas hydrates is reflected in the subbottom profiles in the appearance of BSRs, amplitude anomalies, velocity
anomalies and AVO anomalies, etc. Hence the gas hydrates can be identified and predicted. It is pointed out that the East China Sea is a favorable area of
the gas hydrates resource, and the Okinawa Trough is a target area of gas hydrates reservoir. 相似文献
2.
《中国海洋湖沼学报》2018,(6)
Numerous isolated shallow seabed domes with depressions were discovered in the North Yellow Sea in a high-resolution multibeam echosounder survey. Twelve domes were located within a 11 km by 17 km survey area. The domes in this area were between 0.1 m and 1.0 m high with diameters ranging from 250 to 1 700 m. They were surrounded by corresponding depressions and displayed characteristic shapes ranging from circular to elliptical. The acoustic anomalies displayed on the high resolution sub-bottom profile images demonstrated that shallow gas accumulated just beneath these domes, suggesting that the migration and accumulation of the shallow gas caused the formation of these features. Accumulation atop the seabed domes and erosion within the depressions, as indicated by the lithological features of the sediment cores, suggested that seabed bottom currents also played a role in the formation and evolution of these features. In addition, the simultaneous decrease in the chlorite and sulfate content in core d pore water samples confirmed the presence of submarine fresh/brackish groundwater, which is of interest for hydrological budgets and may be a significant component of the regional hydrologic balance. Our findings suggested that shallow gas accumulation and migration are likely coupled to localized groundwater discharge at this domed site. 相似文献
3.
强对流或台风等极端天气下乔木坡地发生浅层滑坡灾害往往是暴雨和强风共同作用的结果。以皖南山区一处暴雨型浅层滑坡——畈章组滑坡为例, 通过现场调查和气象资料的分析表明, 除暴雨外风荷载也有可能促进滑坡的启动。为揭示该滑坡启动与破坏后这一完整运动过程的演化机制, 首先基于无限斜坡模型分析了实际降雨条件下的滑坡稳定性, 然后对取自于滑坡体内乔木根系周围和滑动面附近的两种土样利用DPRI型环剪仪, 分别开展了不排水循环剪切试验和自然排水残余剪切试验。结果表明: ①降雨入渗引起滑动面孔隙水压力的上升, 并导致稳定性的降低是畈章组滑坡启动的直接原因; ②乔木根系周围的饱和土在风振作用产生的动剪切荷载下易形成高的超孔隙水压力, 并导致浅表层的局部失稳滑动, 增加了畈章组滑坡整体破坏的可能性; ③滑动面土体的残余强度具有强烈的"正速率效应", 从而控制了畈章组滑坡启动后不会表现出高速远程的运动特征, 与现场调查结论一致。研究结果可以为暴雨协同风振作用下富乔木坡地浅层滑坡的预警预报研究提供参考。 相似文献
4.
5.
X气田位于东海盆地西湖凹陷中央反转构造带,主要目的层H4层为浅水三角洲沉积环境,气田地震资料主频较低（25 Hz）,而H4层埋深较大（3 300~3 400 m）,储层低孔低渗,常规地震反演预测砂体厚度吻合度较低。针对X气田三维地震资料全覆盖及钻井较少的特点,通过地质模式指导下的正反演结合设置虚拟井来弥补SVR（Support Vector Regression）算法中样本点的不足,通过提取地震属性并优选表征砂体厚度的敏感属性,利用SVR算法进行多属性融合,完成了H4层砂体的定量预测。基于储层预测成果,提出H4层为浅水三角洲曲流型分流河道沉积,并进一步完成了砂体沉积模式解剖,成功指导了开发调整井部署,实钻砂体厚度与预测砂体厚度吻合度高达84%以上。探索得到了海上少井条件下地质模式约束的SVR算法储层定量预测方案,对X气田中深层分流河道储层完成了精准预测,亦对同类型油气田的储层描述具有一定指导意义。 相似文献
6.
Cracks in rock or soil slopes influence the stability and durability of the slopes. Seismic forces can trigger slope disasters, particularly in the cracked slopes. Considering the nonlinear characteristics of materials, the more generalized nonlinear failure criterion proposed by Baker is adopted. The influence of non-dimensional strength parameters on the stability of cracked slopes under earthquakes is performed using the upper bound limit analysis. The seismic displacement is calculated by adopting the logarithmic spiral failure surface according to the sliding rigid block model. Based on the existing studies, two methods for the stability analysis of cracked slopes under earthquakes are introduced: the pseudo-static method(with the factor of safety(Fs) as an evaluation index), and the displacement-based method(with the seismic displacement as an evaluation index). The pseudo-static method can only determine the instantaneous stability state of the cracked slope, yet the displacement-based methodreflects the stability variation of cracked slopes during earthquakes. The results indicate that the nondimensional strength parameters affect the factor of safety and seismic displacement of slopes significantly. The non-dimensional strength parameter(n) controlling the curvature of strength function shapes on the slope stability is affected by other parameters. Owing to cracks, the effect of non-dimensional strength parameters on seismic displacement becomes more significant. 相似文献
7.
《山地科学学报》2018,(11)
Shallow slope failures induced by rainfall infiltration occur frequently, and the relevant triggering mechanisms have been widely studied.Rainfall-induced landslides are widely recognized to be caused by increases in soil weight, seepage force and pore water pressure or decreases in soil mechanical properties. However, even when all these factors are considered, some landslides still cannot be explained well. The increased pore water pressure in a slope reduces the effective stress of the soil and may trigger slope failure. Similarly, the pore gas pressure in a slope also reduces the effective stress of the soil but has been neglected in previous studies. As the viscosity of air is nearly negligible when compared with that of water, the pore gas pressure spreads faster, and its influence is wider, which is harmful for the stability of the slope. In this paper, the effects of pore gas pressure are considered in a shallow slope stability analysis, and a self-designed experiment is conducted to validate the force transfer mechanism.Numerical simulation results show that the pore gas pressure in the slope increases sharply at different locations under heavy rainfall conditions and that the pore gas pressure causes a rapid decrease in the slope safety factor. Laboratory experimental results show that the pore gas pressure throughout the whole unsaturated zone has the same value, which indicates that the gas pressure could spread quickly to the whole sample. 相似文献
8.
水库蓄水后, 滑坡体碎石土经受长时期的浸泡, 力学性质发生改变, 从而影响滑坡整体稳定性。为探究浸泡对碎石土力学性质的影响规律, 选取三峡库区马家沟滑坡后缘未经受长期浸泡作用的碎石土进行大型直剪试验, 分析了不同浸泡天数下碎石土的剪切力学性质。试验结果表明: 浸泡40 d后, 碎石土黏聚力下降幅度达39%, 内摩擦角下降幅度为8.3%;碎石土黏聚力在浸泡前期快速下降, 下降速率随浸泡天数增加而降低, 浸泡20 d后, 黏聚力基本达到稳定。为探究碎石土抗剪强度降低的原因和机理, 对粉质黏土(碎石土细粒成分)进行了三轴剪切试验、激光粒度分析及浸出液阳离子分析等试验, 揭示了碎石土抗剪强度的衰减机理为: 浸泡作用下, 碎石土中的粉质黏土发生矿物溶解、离子交换与吸附作用, 土体中大颗粒细化, 胶结作用减弱, 进而导致碎石土整体抗剪强度降低。研究结果对库区碎石土滑坡评价与治理具有一定的指导意义。 相似文献
9.
Large-scale shaking table tests were conducted to study the dynamic response of a slope reinforced by double-row anti-sliding piles and prestressed anchor cables. The test results show that the reinforcement suppressed the acceleration amplification effectively. The axial force time histories are decomposed into a baseline part and a vibration part in this study. The baseline part of axial force well revealed the seismic slope stability, the peak vibration values of axial force of the anchor cables changed significantly in different area of the slope under seismic excitations. The peak lateral earth pressure acting on the back of the anti-sliding pile located at the slope toe was much larger than that acting on the back of the anti-sliding pile located at the slope waist. The test results indicate an obvious load sharing ratio difference between these two anti-slide piles, the load sharing ratio between the two anti-sliding piles located at the slope toe and the slope waist varied mainly in a range of 2-5. The anti-slide pile at the slope waist suppressed the horizontal displacement of the slope surface. 相似文献
10.
In recent major earthquakes, the researchers have found the need for consideration of vertical seismic acceleration for the stability analysis of the man-made and natural slopes. However, in most past studies, the performance of slopes has been assessed by accounting only the horizontal seismic component of the ground motion, without giving due weightage to the effect of vertical component. In the present study, analytical expressions are derived to determine the factor of safety, yield seismic coefficient and consequently the seismic displacement of cohesionless soil slope under combined horizontal and vertical components of the ground motion. The derivation uses the Newmark’s sliding block approach, in which the soil slope with a planar failure surface within the framework of conventional pseudo-static analysis is assumed to follow the Mohr-Coulomb failure criterion. The effects of vertical seismic coefficient on the stability of cohesionless slope have been studied through a set of graphical presentations for a specific range of soil parameters. It is observed that overlooking the effect of the vertical component of the ground motion on factor of safety and the displacement while designing the slope may be detrimental, resulting in the slope failure. The general expressions presented in this paper may be highly useful in the field of earthquake geotechnical engineering practice for designing the cohesionless soil slopes under combined horizontal and vertical seismic loads. 相似文献
11.
沿山脊走向的长输油气管道在我国西部山区常有分布,强震作用下其动力响应直接关系到管道的安全运营,实际管道工程建设中亟需相关研究结果提供指导。依托云南玉溪龙马槽村段此类输油管道工程,考虑山坡的工程地质特征,对管道与坡体进行整体三维数值建模,采用有限差分方法FLAC3D进行数值模拟,基于汶川地震波,计算得到了水平地震加速度峰值、震后等典型时刻的管道位移、轴力、剪力和弯矩及坡体稳定性等地震动力响应特征。结果表明,管道内力最大值出现于震后时刻,地震作用使管道轴力达到较高水平,而剪力与弯矩值的量级仅占最大轴力的约1%;竖向地震波对管道内力影响较小,管道受力的不利部位出现在其与断层交界附近。地震过程中管道水平方向存在较多的弹性变形,竖向则存在较多的塑性变形,管道累计变形是影响其内力的主要因素,管道内力最大值出现于震后时刻。 相似文献
12.
Achieving reliable underwater communication in shallow water acoustic channels is a difficult because of the random time-varying nature of multipath propagation,severe amplitude fluctuation,and spatial variability of the channel conditions.This paper describes a new signal processing technique-frequency coding and decoding by means of real-time measurement of signal width,jamming and suppressing multipath interference and using redundant coder.The application of the technique to thd model ZTY-1 status monitor for underwater system of seabed is introduced in this paper.The main principle,the technique specifications and the key techniques of the system are discussed here.Theoretical estimations and experimental results proved that the performance of the system is excellent.The method can be used for some other related low-data-rate data transmission detecting in shallow water acoustic channel. 相似文献
13.
研究不同环剪条件下库岸堆积层滑坡滑带土强度特性对滑坡稳定性评价具有重要意义。针对目前在库岸堆积层滑坡滑带土力学特性方面研究薄弱的问题, 以三峡库区童家坪滑坡滑带土为研究对象, 采用ARS-E2环剪仪开展了不同剪切速率下的剪切试验, 研究了等速剪切、加速剪切以及减速剪切作用下滑带土强度变化特征。试验结果表明: 滑带土试样在恒定的低速剪切条件下更容易得到稳定的残余强度, 并且达到峰值强度后易出现"应变软化"现象; 在相同剪切应力条件下, 滑带土加速环剪和减速环剪的剪应力变化趋势基本一致, 与法向应力均呈正相关关系; 剪切速率的变化会显著影响滑带土峰值黏聚力的大小。研究成果揭示了不同环剪条件下滑带土力学特性, 可以为揭示库岸堆积层滑坡变形破坏的力学机制提供理论依据。 相似文献
14.
This study aims at exploring the void space gas effect of earthquake-triggered slope instability and providing a new method for studying the formation mechanism of earthquake-triggered landslides. We analysed the basic characteristics, kinematic characteristics, initiation mechanisms and physical mechanical parameters of the Daguangbao landslide, generalized a landslide prototype, and established a geological model and performed simulation tests. Based on the seismic wave propagation theory of rock-soil mass, rock fracture mechanics and the effective stress principle, we found that the void space gas effect is due to the occurrence of excess void space gas pressure when the dynamic response of seismic loads impacts the void space gas in weak intercalated layers of the slope. The excess void space gas pressure generated by the vibration(earthquake) damages the rock mass around the void space with a certain regularity. The model test results show that the effective shear strength of the rock mass can be reduced by 4.4% to 21.6% due to the void space gas effect. 相似文献
15.
Predicting the rainfall-triggered landslides in a forested mountain region using TRIGRS model 总被引：3，自引：0，他引：3
Landslides are natural disasters which can pose a serious threat to human and property in many areas around the world. The
Transient Rainfall Infiltration and Grid-based Regional Slope-stability (TRIGRS) model was used to investigate the rainfall-induced
shallow landslides in a forested mountain region, Korea. Various input data for TRIGRS model include time-varying rainfall,
topographic characteristics, soil depth, material strength, and hydraulic properties. A series of calculations were conducted
in determining the slope stability over the Jangheung region in Korea during the storm occurred on August 6, 1998. The results
show that TRIGRS model captured about 64.1% of landslides that were extracted from the IKONOS2 imageries. The model demonstrated
how the factor of safety changed with time during a storm considering both the transient and spatial responses of pore water
pressure in its slope stability calculation. 相似文献
16.
The bearing capacity of interfering footings located near the slope face suffers from reduced bearing capacity due to the formation of the curtailed passive zone. Depending upon the position of the footing, their spacing and steepness of the slope, different extents of bearing capacity reduction can be exhibited. A series of finite element investigation has been done with the aid of Plaxis 3D vAE.01 to elucidate the influence of various geotechnical and geometrical parameters on the ultimate bearing capacity of interfering surface strip footings located at the crest of the natural soil slope. Based on the large database obtained from the numerical simulation, a 6-8-1 Artificial Neural Network architecture has been considered for the assessment of the ultimate bearing capacity of interfering strip footings placed on the crest of natural soil slope. Sensitivity analyses have been conducted to establish the relative significance of the contributory parameters, which exhibited that for the stated problem, apart from shear strength parameters, the setback ratio and spacing of footing are the prime contributory parameters. 相似文献
17.
The stability of submarine geological structures has a crucial influence on the construction of offshore engineering projects and the exploitation of seabed resources. Marine geologists should possess a detailed understanding of common submarine geological hazards. Current marine seismic exploration methods are based on the most effective detection technologies. Therefore, current research focuses on improving the resolution and precision of shallow stratum structure detection methods. In this article, the feasibility of shallow seismic structure imaging is assessed by building a complex model, and differences between the seismic interferometry imaging method and the traditional imaging method are discussed. The imaging effect of the model is better for shallow layers than for deep layers because coherent noise produced by this method can result in an unsatisfactory imaging effect for deep layers. The seismic interference method has certain advantages for geological structural imaging of shallow submarine strata, which indicates continuous horizontal events, a high resolution, a clear fault, and an obvious structure boundary. The effects of the actual data applied to the Shenhu area can fully illustrate the advantages of the method. Thus, this method has the potential to provide new insights for shallow submarine strata imaging in the area. 相似文献
18.
It is difficult to obtain reliable shear strength parameters for the stability analysis and evaluation of high loess slopes.Hence,this paper determines slope elements and physical parameter of 79 slopes with heights of[40,120]m based on the measured loess slopes in the Ganquan and Tonghuang subregions of northern Shaanxi Province,China.In the limit state of the loess slope(stability factor Fs is 1.0),a fitting equation for the slope height and width is established.Then,the model is developed by stability analysis software-SLOPE/W,and the comprehensive shear strength parameters corresponding to different slope heights of the high slope in the study area are obtained by inversion using the Morgenstern-Price method.The results show that when the height of the slope increases,the cohesion c increases in the soil,and the internal friction angle j decreases.This change is consistent with the characteristics reflected in the composition and physical properties of the slopes,and the comprehensive strength parametric curves are very similar between the Ganquan subregion and the Tonghuang subregion.A landslide that occurred in Miaodian-zaitou of Jingyang County,Shaanxi Province,is selected to verify this inversion method,and the results show that the calculated shear strength parameters of the inversion are consistent with the measured value of the actual slope. 相似文献
19.
No matter from the perspective of slope protection, landscape effect and construction cost, or from the perspective of ecological benefit, the development of original ecological tridimensional vegetation has become the inevitable trend for slope vegetation in pursuit of protecting ecological condition, decreasing soil erosion, maintaining ecological balance and beautifying environment of slope. The concept of original ecological tridimensional slope vegetation is proposed in this paper, and the original ecological tridimensional slope vegetation is studied through theoretical analysis and experiments. Specifically, the mechanical effect of slope vegetation in reinforcing the cohesion and shear strength of soil mass is firstly discussed, and then experiments are performed to study the water interception and containing function of slope under various vegetation conditions. Moreover, the relation between soil moisture and cohesion, the relation between root distribution density and cohesion, and the relation between root distribution density and soil shear strength are also studied based on experiments. Finally, based on field observation, the soil erosion states of slope under various vegetation conditions are comparatively studied. It is found that the original ecological tridimensional slope, which combines grass,shrub and tree, can generate comprehensive slope protection effects, and hence strengthen the slope protection ability and bring multiple slope protection benefits. Thereby, the theoretical foundation for developing original ecological tridimensional slope vegetation is established. 相似文献
20.
Seepage-induced fines migration under rainfall infiltration is a main cause leading to shallow failures in loose colluvial slopes. To describe the full process of fines migration within unsaturated soils during rainfall infiltration and the associated hydro-mechanical behaviors, a seepage-erosion-deformation coupled formulation is proposed in this paper. The governing equations proposed are implemented into a finite element code and used to investigate the influences of skeleton deformation on the rainfall infiltration process through unsaturated soil columns. The numerical results were presented in detail for a better understanding of the rainfall-induced fines migration process within unsaturated soils. Further, the obtained results are integrated into an infinite slope model for slope stability analysis. The results show that, the skeleton deformation will affect the rainfall infiltration rate and hence the timing of slope failures; meanwhile their influences are more evident if the fines deposition process is taken into account. Moreover, the slope stability could be reduced gradually due to the soil strength loss along with loss of fine particles. Therefore, particular attentions should be paid to analyzing the stability of soil slopes susceptible to internal erosion. 相似文献