共查询到20条相似文献，搜索用时 250 毫秒
1.
The impact load (equivalent impact height) applied to deep-sea sediment by a walking mining machine was first deduced by the energy conservation principle, and the simulative soil was prepared based on the deep-sea sediment collected from the Pacific C-C mining area. The self-designed impact compressive creep tests of the simulative soil were conducted under different ground stresses and impact heights, in order to determine impact compressive creep parameters using a K-H rheological model. Test results show that the impact compressive creep curves have three similar creep stages (transient creep, unstable creep, and stable creep) to static compressive creep curves, where the transient creep deformation and total deformation at the unstable creep stage decrease with the impact load. Among the three impact compressive creep parameters (K1, K2, β) of the simulative soil, K1 is first increased with impact height and finally fluctuated to a certain stable value, while K2 and β are approximately linearly increased with impact height. The maximum subsidence of the mining machine under a specific designed ground stress and walking velocity predicted by the impact compressive creep constitutive equation can be used for safety assessment of the mining machine. 相似文献
2.
In deep-sea mining engineering, the compression–shear coupling effect of the sediment on the moving tracked mining vehicle must be considered, since it is proved to be existing in compression–shear creep test of the sediment simulant. Based on the endochronic theory, the compression–shear coupling rheological model is established by the definition of intrinsic time and calculation of deviatoric tensor, where the coupling rheological parameters can be obtained by the compression–shear creep test. For simulating sinkage and traction force of the moving tracked mining vehicle, the compression–shear coupling rheological model as well as compressive rheological model and direct shear rheological model (regardless of coupling rheological effect) is programmed and introduced into RecurDyn software (with only traditional elastic–plastic constitutive model) for comparison. Research results show that the sinkage is the largest, and the traction force is the smallest under the compression–shear coupling rheological model, which could better reflect the worse working situation. The compression–shear coupling rheological model could provide theoretical basis for optimal design and safety assessment of the tracked mining vehicle. 相似文献
3.
AbstractDue to the low shear strength of deep-sea sediment, crawled mineral collector is easily slips in the deep-sea mining process, therefore, high-traction bionic grouser is needed to be studied to improve the working efficiency. Based on the rate-dependent characteristics of deep-sea sediment, a rate-dependent extended Drucker-Prager material constitutive model is used to define the deep-sea sediment. The Arbitrary Lagrange-Euler finite element (LEA-FE) was used to simulate the cutting process of different bionic grousers at different speeds. By comparing the simulation of different grousers, it was found that the maximum traction of grouser is related to the grouser parameters (distance L from the top to the curvature change point and curvature radius R). By analyzing the traction characteristics of different bionic grousers, the binary quadratic regression equation between maximum traction and bionic grouser parameters was established and the best bionic grouser parameters were obtained by the optimization algorithm. Based on the rate-dependent properties of deep-sea sediment, the traction characteristics at different speeds were analyzed and the relationship between maximum traction and speeds was established, the best bionic grouser walking speed was obtained, which can provide the theoretical basis for the crawled mineral collector. 相似文献
4.
海底底质的物理力学参数不同于陆地土壤,其极低的抗剪强度和承压强度对深海采矿车的行走性能提出高要求。分析基于车辆地面力学理论,开展了底质土力学特性试验研究,建立了深海底质力学模型。根据深海重载作业采矿车样机结构参数,在大型动力学仿真软件Recurdyn中建立了仿真模型。通过直线行走多体动力学仿真与直线行走海试试验的对比,验证了仿真模型的准确性。在此基础上开展了采矿车样机在深海软底质上的多种行走工况动力学仿真,分析与评价其行走性能。结果表明,采矿车样机可以顺利完成转弯、爬坡、越障等基本功能。该研究成果可为深海采矿车海底行走性能评估提供理论参考,为深海采矿车和软底质的相互作用力学研究提供借鉴。 相似文献
5.
Nansha clay is an interactive marine and terrestrial deposited soft clay that is widely spread in Guangzhou, Pearl River Delta, China. To avoid excessive settlement after construction, there is a need for better quantifying the time-dependent deformation of the soft clay. This paper presents a preliminary study to predict the one-dimensional compression of Nansha clay using fractional derivatives. A fractional Merchant model was introduced to describe the time-dependent settlement, and analytical solutions were obtained in terms of the Mittag-Leffler function. The oedometer test results were presented to validate this model. Compared with classical rheological models, the fractional derivative-based model enabled close estimation of the one-dimensional compression with fewer parameters. The meaning of the order of fractional derivative and its relationship with the clay physical properties were explored. It shows that a smaller value of this order corresponded to a higher coefficient of consolidation and a lower coefficient of secondary consolidation. The amplitude of both the primary and secondary consolidation of clay may be estimated quantitatively by the order of fractional derivative. Taken together, these results may open up new avenues for theoretical and empirical modeling of rheological phenomena in clay using fractional derivatives. 相似文献
6.
将衬砌分别视为多孔柔性材料和弹性介质,在频率域内研究内水压力作用下饱和分数导数黏弹性土-深埋圆形隧洞多孔柔性或弹性衬砌系统的耦合简谐振动。土体的宏观力学特性采用多孔介质理论来模拟。通过引入与土体体积分数相关的应力系数,利用衬砌和土体界面处位移连续,分别得到饱和黏弹性土和衬砌的位移、应力和孔隙水压力等的解析表达式。在此基础上,分析了多孔柔性衬砌和弹性衬砌结构的差异,并考察了应力系数、渗透系数、分数阶导数本构参数等对系统动力响应的影响,结果表明:多孔柔性衬砌材料条件下系统的动力响应明显大于弹性衬砌材料条件下系统的动力响应;随着分数导数阶数和材料参数比的增加,系统共振效应明显减弱;衬砌边界透水和不透水只是反映边界渗透性的两种极限状态。 相似文献
7.
Wisam R. Muttashar 《Marine Georesources & Geotechnology》2020,38(8):896-910
AbstractThe mechanical response of a sediment to an applied stress is significantly affected by variations of material properties, state conditions, and stress states. These stress state and conditions are utilized to infer input parameters for advanced soil constitutive models. Parameters such as void ratio and effective stresses have been readily inferred from shear-wave velocities under low-strain conditions. Thus, this research aimed to develop a shear-wave velocity-based constitutive model within a critical state soil mechanics framework to predict the undrained triaxial behavior of fine-grained sediments. Laboratory tests were performed for sediment samples ranging from silt-predominant to clay-predominant sediments. As result, a new two-term power function was developed that determined mean effective stress as a function of shear-wave velocity. By virtue of this new power function, the Original Cam Clay and Modified Cam Clay critical state models were adapted to estimate the stress-strain behavior and stress paths under undrained conditions, in terms of shear velocity. In addition, correlations were developed using the state and material properties to predict the input model parameters. The developed correlations allow broad application of the proposed framework to different sediment types in which clay and silt are the dominant deposits. 相似文献
8.
采用现代技术配制自密实混凝土,能有效拓展水泥基材料在现代海洋、交通以及水利等工程领域的应用范围。采用坍落扩展度等指标对钢纤维自密实混凝土的传统工作性能进行表征,使用流变仪对拌合物的流变特性进行了测试,并对硬化后的钢纤维自密实混凝土的抗压强度进行了测试。结果表明,对于钢纤维自密实混凝土,使用幂律型的Herschel-Bulkley方程获得的屈服应力、黏度系数和流动指数这三项流变参数能够很好地反映拌合物的流变性能。 相似文献
9.
实现高精度的定位导航是深海采矿车完成海底工作任务的基础条件。在采矿车行进过程中,声呐设备生成的图像信息能够反映海底场景的变化,从而体现采矿车本身的运动,由此建立了一种声呐图像里程计,并将其与轮式里程计和USBL测量数据相结合提出了一种深海采矿车组合定位导航算法。首先对多波束前视声呐图像进行预处理,然后使用Canny算法进行特征检测并对特征点云进行配准,再结合声呐成像原理构建了声呐图像里程计运动模型,最后通过轮式里程计运动模型推导预测方程、声呐图像里程计运动模型和USBL测量数据推导更新方程,利用EKF（extended Kalman filter）算法实现基于多传感器融合的定位与姿态估计。海试数据验证了该组合定位算法能实现轮式里程计、声呐里程计和超短基线在速度、位置、艏向角估计、定位速率的精度互补,具有一定的有效性和精确性,该算法为深海采矿车的定位与导航算法研发提供了参考。 相似文献
10.
海底滑坡会对海洋工程结构物造成严重破坏。滑移速度和距离是量化和分析海底滑坡的两个重要参数。目前BING等计算方法在模拟水下土体流动方面存在局限性,因此通过建立考虑土体固结和侵蚀效应的控制方程,选用摩擦流变模型,采用SPH深度积分算法,对海底滑坡进行了模拟研究。对比不同水深、坡度、接触摩擦系数和侵蚀率条件下的滑移体的速度、高度、长度的时程曲线,整理了最大滑移距离和速度,讨论变化规律。研究成果可为海底滑坡灾害预警和海底管线路由选址提供技术参考。 相似文献
11.
为研究深海能源土在负压开采过程中含气储层的力学特性,基于含气土赋存理论,提出一种能够控制含气量及气泡大小的制样方法,通过GDS标准应力路径三轴试验系统,开展深海能源土含气储层的固结排水试验研究,分析深海能源土在不同黏土含量及不同含气量下的力学响应规律。研究结果表明：围压变化对深海能源土含气储层的抗剪强度峰值大小影响显著,围压越大抗剪强度峰值越高;黏土含量是决定应力应变曲线变化趋势的关键影响因素,黏土含量越高试样抗剪强度越低,试样抵抗应变软化效应的能力越强;含气土比饱和土体承载能力更低,且承载能力随含气量的增大呈衰减趋势;黏土含量和含气量是深海能源土含气储层抗剪强度指标的重要影响因素,黏土含量、含气量越高,土体自身的总抗剪强度值越低。 相似文献
12.
Huayang Lei Haibin Lu Xuechao Wang Qian Ren Bin Li 《Marine Georesources & Geotechnology》2016,34(4):365-375
The accelerated rheological properties of natural soft clay are the external power and predisposing factors of geological and geotechnical disasters. To determine the changes in soil micro-structure for natural soft clay under accelerated creep condition, a detailed study has been carried out using consolidated undrained tri-axial tests under static and cyclic loads, as well as experimental data from mercury intrusion porosimetry and a scanning electron microscope. In the tri-axial tests, creep of the soft clay would be accelerated under dynamic loads, the sample would be destroyed faster, and the strain-rate would increase clearly along with the increase of the vibration frequency. Based on a comparison of micro-structure behaviors between the intact sample and the test soil samples under static and dynamic loads in the creep condition, an interpretation of the changes in soil micro-structure for natural soft clay under an accelerated creep condition was proposed. The research indicated that the large pores of the soil sample gradually changed into small pores, the large particles continuously changed into tiny particles, and the pore distribution gradually became uniform under dynamic loads. It was found that the fractal dimension of the pores decreased with the increase of the vibration frequency. The test results not only showed that the accelerated creep characteristics depended on the vibration frequencies of the applied dynamic loads, but the accelerated creep was actually an unceasingly self-adjusting and reengineering process of the internal structure in soil under dynamic loads. In addition, these results revealed that there was a close relationship between the vibration frequencies and the micro-structure parameters. 相似文献
13.
In this article, the mechanical behavior of a Jiangsu marine clay was investigated by drained triaxial tests, traixial rheological tests, and one-dimensional compression and swelling tests. A visco-plastic model, the Bingham model combining two yield surfaces model, was proposed to describe the time-dependent deformation behaviors of the marine clay. The governing equation of Biot's consolidation theory for the visco-plastic soil is solved using a finite element code which incorporates the visco-plastic model. Using the finite element method, settlements of a typical embankment on the Lianxu expressway in China are calculated. Settlement calculations using the visco-plastic model are in agreement with the measured settlements in the field. The results demonstrate that the visco-plastic model is appropriate for calculating the visco-plastic deformations of Jiangsu marine clay. Theoretical and experimental studies show that the visco-plastic deformation of Jiangsu marine clay is substantial. 相似文献
14.
深海采矿尾矿排放产生的细颗粒羽状流会对海底生态环境造成影响,预测尾矿排放羽状流行为及其对环境影响具有工程意义。基于欧拉多相流方法,采用欧拉双流体模型对深海采矿细颗粒羽状流开展数值模拟研究,分析近海底排放的羽状流演化和发展过程,探究羽状流初始排放质量浓度、排放速度对羽状流扩散过程的影响。结果表明：初始排放条件对羽状流演化性质有重要影响。主射流区被稀释的程度随着初始入射速度的增大而减小,随着入射质量浓度的增大而增大;初始羽状流入射速度和质量浓度越大,撞击海底后的水平方向流动速度越快,影响区域越广;水平速度的峰值随着初始入射速度的增大呈对数增长;当初始质量浓度和速度高于50 g/L和 0.5 m/s 时可能会导致颗粒在海底撞击点附近堆积成坡状,影响底流的后续发展。研究结果可以为深海采矿尾矿排放参数选择提供参考。 相似文献
15.
海底沉积物取样的扰动机理研究 总被引：3，自引：0，他引：3
海底沉积物取样技术对大洋诸多科学研究来说非常重要,各种研究目标的实现与沉积物样品的质量息息相关.在使用常规管状取样器对松软或轻微固结的沉积物取样时,沉积物样品的扰动总是不可避免的.以机械手持式沉积物取样器为原型机,建立了管状取样器的取样过程模型,分析了沉积物样品的扰动机理;采用球形孔扩张理论获得了沉积物土体受到取样管挤压扩张的理论解;结合太平洋具体沉积物土体物理力学参数,对管状取样器取样造成沉积物扰动的状况给出了一个定量描述,并且提出取样管壁的厚度是减小沉积物扰动的关键参数. 相似文献
16.
Settlement Analysis for An Embankment Considering Visco-Elasto-Plastic Characteristics 总被引：1，自引：0，他引：1
SHI Jianyong 《中国海洋工程》2000,14(3):349-360
—In the paper.a visco-elasto-plastic constitutive model and a method for determining modelparameters for soft clay are presented.In this model total strain of soft clay is assumed to be divided intothree parts:instantaneous elastic.visco-elastic and visco-plastic.The characteristics of instantaneous andvisco-elastic deformation of soft clay are simulated by Merchant's model.the plastic is by a model withtwo yield surfaces.And related constitutive equation is conducted,A number of stress-controlled triaxialtests are performed to calculated the model parameters The visco-elasto-plastic model is used for analysisof the displacement of an embankment on soft ground by use of three-dimensional finite element method.The predicted settlements agree well with the measured data.It is indicated that the viscous characteristicsshould be taken into account in deformation analysis for soft clay. 相似文献
17.
采用Laplace数值反演的Stehfest算法研究了分数阶Oldroyd-B粘弹性流体在两平板间非定常的Poiseuille流动问题.首先,通过数值解与近似解析解的比较验证了Stehfest算法的有效性.其次,运用Stehfest算法对平板Poiseuille流动进行了研究,揭示了分数阶黏弹性平板流的速度过冲和应力过冲现象,指出这些现象对分数导数的阶数存在明显的依赖性.同时,数值结果表明,整数阶本构方程仅仅是分数阶本构方程的特例,分数阶本构方程较整数阶本构方程具有更广泛的适用性. 相似文献
18.
Rheological Properties and Incipient Motion of Cohesive Sediment in the Haihe Estuary of China 总被引：2，自引：1，他引：2
The Haihe cohesive sediment, which is typical in China, is studied systematically for its basic physical and incipientmotion properties. Following the requirements of dredging works in the Haihe Estuary, cohesive sediment samples weretaken from three locations. Laboratory experiments were conducted to determine the rheological properties of these sam-ples and to examine the incipient motion of the cohesive sediment. It is found that the cohesive sediment has an obviousyield stress τb, which increases with the mud density in a manner of an exponential function, and so does the viscosityparameter η. The cohesive sediment behaves like a Bingham fluid when its density is below 1.38 ～ 1.40 g/cm3, andwhen denser than these values, it may become a power-law fluid. The incipient motion experiment also revealed that theincipient velocity of the cohesive sediment increases with the density in an exponential manner. Therefore, the incipientmotion is primarily related to the density, which is different from the case for non-cohesive sediment in which the incipi-ent motion is correlated with the diameter of sand particles instead. The incipient motion occurs in two different ways de-pending on the concentration of mud in the bottom. For sufficiently fine particles and a concentration lower than1.20 g/cm3, the cohesive sediment appears as fluidized mud, and the incipient motion is in the form of instability of aninternal wave. For a higher concentration, the cohesive sediment appears as general quasi-solid-mud, and the incipientmotion can be described by a series of extended Shields curves each with a different porosity for newly deposited alluvial mud. 相似文献
19.
R. Sharma 《Marine Georesources & Geotechnology》2013,31(4):331-338
In recent years, several experiments to assess the potential impacts due to deep-sea mining in the Pacific as well as the Indian Oceans have indicated the immediate changes and restoration patterns of environmental conditions in the marine ecosystem. The large volume of sediment(~ 500 × 107 m3 per year) estimated to be resuspended would be the major influencing factor in environmental impact in the mining area, leading to changes in availability of certain nutrients and composition of biomass, followed by gradual restoration. Important results have been obtained from these experiments, but in order to have a better understanding of the impacts and restoration processes, it will be necessary to improvise future experiments to resemble actual deep-sea mining in terms of scale and methodology. 相似文献
20.
潮汐河口断面悬沙通量组分模式及其在长江口的应用 总被引：2，自引：5，他引：2
断面泥沙通量估算的误差主要来源于计算方法、测点布局等,通量模式应该建立在通量估算统计误差最小的原则基础之上.在断面网格设计中采用统计误差最小的等面积单元网格,在泥沙通量估算中采用泥沙组分浓度,在流速变量插值上垂向采用对数函数插值,横向采用第一边界三次方样条函数插值.这样建立的潮汐河口悬沙断面通量组分模式较以往的任何模式更完善,断面通量估算的误差最小.将该模式应用于长江河口南港断面悬沙通量估算及其输移机制分析,断面泥沙通量表现为大潮期大进大出、大出大于大进;小潮期小进小出、小出大于小进;主要输移机制是拉格朗日输移和潮泵. 相似文献