Analysis of the influences of physical parameters on sediment sound speed

Based on the core samples collected in different geological tectonic units in the southern South China Sea, the double parameter equations between sediment sound speed and physical parameters were developed. According to the double parameter equations, the influences of physical parameters (porosity, mean grain size, wet bulk density, and clay content) on sediment sound speed were analyzed. To analyze the sensitivity of each parameter in the double parameter equations, the error norm method was introduced. The most influencing physical parameters with relative order were analyzed using the error norm method. These results show that porosity has a major influence on the sound speed, and the most influential physical parameters on sound speed are as follows: porosity > wet bulk density > clay content > mean grain size.     

Relationship between in situ sound velocity and granular characteristics of seafloor sediments in the Qingdao offshore region

The sound velocity of seafloor sediments from shallow seas can provide important information for harbor design, and ocean and seacoast engineering projects. In this study, in situ measurements were used to obtain accurate sediment sound velocities at 45 stations offshore of Qingdao. The relationships between the sound velocity and granular properties of the seafloor sediments were analyzed. Sound velocity showed an increase with the sand content, sand-clay ratio, and sorting coefficient; and a nonlinear decreasing trend with increasing mean grain size and clay content. We plotted a sound velocity distribution map, which shows that the sound velocity was closely related to the geological environment. Previous empirical equations suggested by Hamilton, Anderson, and Liu were used to calculate the velocity with grain size. A comparison between the measured and calculated velocities indicates that the empirical equations have territorial limitations, and extensive data are essential to establish global empirical equations. Future work includes the calibration of the laboratory acoustic measurements with an in situ technique.     

Relationships between the sound speed ratio and physical properties of surface sediments in the South Yellow Sea

Building empirical equations is an effective way to link the acoustic and physical properties of sediments. These equations play an important role in the prediction of sediments sound speeds required in underwater acoustics.Although many empirical equations coupling acoustic and physical properties have been developed over the past few decades, further confirmation of their applicability by obtaining large amounts of data, especially for equations based on in situ acoustic measurement techniques, is required. A sediment acoustic survey in the South Yellow Sea from 2009 to 2010 revealed statistical relationships between the in situ sound speed and sediment physical properties. To improve the comparability of these relationships with existing empirical equations, the present study calculated the ratio of the in situ sediment sound speed to the bottom seawater sound speed, and established the relationships between the sound speed ratio and the mean grain size, density and porosity of the sediment. The sound speed of seawater at in situ measurement stations was calculated using a perennially averaged seawater sound speed map by an interpolation method. Moreover, empirical relations between the index of impedance and the sound speed and the physical properties were established. The results confirmed that the existing empirical equations between the in situ sound speed ratio and the density and porosity have general suitability for application. This study also considered that a multiple-parameter equation coupling the sound speed ratio to both the porosity and the mean grain size may be more useful for predicting the sound speed than an equation coupling the sound speed ratio to the mean grain size.     

华北盆-山演化和岩石圈转型与煤层气富集的关系

以华北陆块盆-山构造与岩石圈岩浆热结构演化研究为基础,以区内不同富集机制的含煤区域为研究对象,对华北典型地区盆-山演化、岩石圈转型及其与煤层气富集的关系进行了深入探讨。研究表明,华北典型地区盆-山动力学过程从中生代开始经历了挤压盆-山阶段、挤压盆-山向伸展盆-山转换阶段以及伸展盆-山阶段;华北岩石圈结构演化则经历了岩石圈增厚与稳定过程、岩石圈转型过程、岩石圈快速减薄过程等,且自古生代以来至少经历了两次以上具有时空不均一性的岩石圈转型。沁水盆地和两淮煤田的构造—热动力学环境有利于煤层气富集,且在挤压与伸展作用的转换和叠加过程中形成的构造过渡带是煤层气富集的有利构造单元。沁水盆地煤层气富集特征是岩浆—热作用有利于煤层气储集,而一定的构造变形有利于煤层气的渗流和开采;两淮煤田的强构造作用和后期叠加的张性应力场有利于煤层气的富集和储层的增渗,可在构造煤发育区寻找煤层气开发的有利区域。     

运营高铁线路平面控制网复测更新指标研究

基于现有的运营高铁线路平面控制网(route hori-zontal control network,CPⅡ)复测成果更新的双限差法,针对坐标较差与相邻点坐标差之差的相对精度超限严重不匹配的情况,提出改进多限差综合分析判定法进行CPⅡ网复测成果的更新综合分析.结合秩亏自由网平差及尺度变化参数对改进多限差综合分析判定法再...     

Experimental study of the ballast in situ sediment acoustic measurement system in South China Sea

The mechanical structure, the function modules, the working principles, and a sea trial of the newly developed ballast in situ sediment acoustic measurement system are reported in this study. The system relies on its own weight to insert transducers into seafloor sediments and can accurately measure the penetration depth using a specially designed mechanism. The system comprises of an underwater position monitoring and working status judgment module and has two operation modes: self-contained measurement and real-time visualization. The designed maximum working water depth of the system is 3,000?m, and the maximum measured depth of seafloor sediment is 0.8?m. The system has one transmitting transducer with the transmitting frequency band of 20–35?kHz and three receiving transducers. The in situ acoustic measurement system was tested at 15 stations in the northern South China Sea, and repeated measurements in seawater demonstrated good working performance. Comparison with predictions from empirical equations indicated that the measured speed of sound and attenuation fell within the predicted range and that the in situ measured data were reliable.     

云南禄劝地区泥盆系油苗地球化学特征及地质意义

随着四川盆地海相常规天然气和页岩气勘探开发的成功,新区、新层系的油气勘探逐渐提上议程。云南地区泥盆系泥页岩在局部地区广泛分布,有机质丰度较高,但钻井工作很少,研究较为薄弱,油气富集情况不明。通过野外调查,在云南禄劝地区中泥盆统华宁组发现了液态油苗。有机地球化学分析表明:油苗与中泥盆统华宁组三段的泥灰岩亲缘关系较好;中泥盆统华宁组三段的泥灰岩整体沉积于强还原—还原环境,生烃母质主要为藻类等低等水生生物,也有来自高等植物的贡献,已处于成熟阶段,具有较强的油气生成能力,生烃能力与Ⅱ₁型烃源岩相当;康滇古陆西缘泥盆系泥灰岩有过生油气过程,生成的原油以饱和烃和芳香烃为主,且保存条件好的情况下,具有一定的页岩油气和常规油气勘探前景。      

Nonlinear seepage–erosion coupled water inrush model for completely weathered granite

Water inrush from completely weathered granite has presented a significant challenge for tunnel construction, suggesting the urgency and importance of revealing the water inrush mechanism. In this paper, a seepage erosion model is proposed to describe the water inrush. Assuming that completely weathered granite consists of solid grain phase, fluid phase, and fluidized grain phase, the three-phase interaction was constrained by mass balance equations, and the erosion of fluidized grains was described by a modified porosity evolution equation. The fluid flow is governed by a coupled Darcy–Brinkman/Navier–Stokes equation, which responds to the variation of the flow pattern in the evolution process. Then, the validity of the model has been proved, and the superiority has been studied by comparing with the previous models. The comparison results showed that the flow pattern has a significant impact on pore pressure, water velocity, and mutation time, and the proposed model can more accurately predict the development of velocity. Furthermore, this model was used to simulate the development of water inrush and achieved good results in predicting the direction, channel size, and whole evolution process of water inrush. The research findings from the paper can benefit tunnel engineering in the case of water inrush disasters.     

Drag-type in-situ acoustic measurement system: Design,operation, and experimental results

The Drag-type In-Situ Acoustic Measurement System (DISAMS) is a new instrument designed for rapid measurement of seabed sediment acoustic parameters, including the sediment sound velocity and acoustic attenuation coefficient. The DISAMS consists of six independent acoustic probes arranged symmetrically such that each side has one transmitting probe and two receiving probes. The entire operation is controlled and monitored in real time by a deck control unit on board, and the center frequency of the DISAMS is 30?kHz. The DISAMS can record full waveforms to determine the sound velocity and attenuation coefficient in the seabed sediment. In addition to site measurements, the DISAMS can also carry out towing measurements, resulting in improved efficiency compared with existing in-situ acoustic measurement systems. This article presents the configuration, electronics, and tests of the DISAMS in detail. Laboratory tests were conducted in a sediment pool, sea trials were carried out in the Zhoushan Islands, and sound velocity and attenuation coefficient data were obtained. The test results demonstrated that the DISAMS performed well and was able to measure the sound velocity and attenuation coefficient rapidly and accurately in both site measurements and towing measurements.     

广西平果沉积型铝土矿Ga的分布特征与沉积环境关联性探讨

广西平果上二叠统合山组沉积型铝土矿储量大,并以伴生稀散元素Ga为特色。从主量成分和微量元素角度研究平果铝土矿的地球化学特征、形成环境及其与Ga的相互关联性,对综合回收利用和提升矿床经济价值有重要帮助。通过对整个研究区内均匀采集的18件不同类型的矿石及铝土岩样品进行金属Ga和常量、微量元素测试,经统计学方法计算和相关性图解分析,发现样品中Ga平均含量已达到工业品位（0.002×10-2）。但在不同类型矿石中的富集程度不同:豆鲕粒状铝土矿>致密块状铝土矿>铝土岩。而且Ga含量与Al₂O₃含量呈显著正低相关性;与SiO₂含量呈显著负相关关系;与V含量呈显著正低相关关系;与稀土元素相关性不强,无明显规律性。通过对那豆沉积型铝土矿床古地理环境和不同类型样品Sr/Ba比值、Ga的富集、LREE/HREE比值分析发现:区内沉积型铝土矿主成矿期为较稳定、酸性、潮湿的滨海至浅海相环境;而且从二叠纪合山组早期的滨海相氧化环境逐步过渡到二叠纪合山组后期的浅海相还原环境。矿石类型则由早期的紫红色致密块状矿化变化为青灰色至灰黑色鲕粒状矿化。