Effects of pore fluids on quasi-static shear modulus caused by pore-scale interfacial phenomena

It is evident from the laboratory experiments that shear moduli of different porous isotropic rocks may show softening behaviour upon saturation. The shear softening means that the shear modulus of dry samples is higher than of saturated samples. Shear softening was observed both at low (seismic) frequencies and high (ultrasonic) frequencies. Shear softening is stronger at seismic frequencies than at ultrasonic frequencies, where the softening is compensated by hardening due to unrelaxed squirt flow. It contradicts to Gassmann's theory suggesting that the relaxed shear modulus of isotropic rock should not depend upon fluid saturation, provided that no chemical reaction between the solid frame and the pore fluid. Several researchers demonstrated that the shear softening effect is reversible during re-saturation of rock samples, suggesting no permanent chemical reaction between the solid frame and the pore fluid. Therefore, it is extremely difficult to explain this fluid–rock interaction mechanism theoretically, because it does not contradict to the assumptions of Gassmann's theory, but contradicts to its conclusions. We argue that the observed shear softening of partially saturated rocks by different pore fluids is related to pore-scale interfacial phenomena effects, typically neglected by the rock physics models. These interface phenomena effects are dependent on surface tension between immiscible fluids, rock wettability, aperture distribution of microcracks, compressibility of microcracks, porosity of microcracks, elastic properties of rock mineral, fluid saturation, effective stress and wave amplitude. Derived equations allow to estimate effects of pore fluids and saturation on the shear modulus and mechanical strength of rocks.     

Numerical studies on saltwater intrusion in a coastal aquifer in northwestern Germany

Saltwater intrusion in coastal aquifers depends on the distribution of hydraulic properties, on the climate, and on human interference such as land reclamation. In order to analyze the key processes that control saltwater intrusion, a hypothetical steady-state salt distribution in a representative cross-section perpendicular to the coastline was calculated using a two-dimensional density-dependent solute transport model. The effects of changes in groundwater recharge, lowering of drainage levels, and a rising sea level on the shape and position of the freshwater/saltwater interface were modeled in separate simulations. The results show that the exchange of groundwater and surface water in the marsh areas is one of the key processes influencing saltwater intrusion. A rising sea level causes rapid progression of saltwater intrusion, whereas the drainage network compensates changes in groundwater recharge. The time scale of changes resulting from altered boundary conditions is on the order of decades and centuries, suggesting that the present-day salt distribution does not reflect a steady-state of equilibrium.     

污水资源化与中国的水环境

本文从我国当前水环境面临的问题,阐述了污水资源化的必要,可能与效益,以及将污水转化为资源的措施,从而得出污水资源化是解决水危机的重要途径。     

建立罗非鱼保鲜期实验方程及其应用性探讨

根据实验数据和采用王怡评定罗非鱼感官的评分标准，建立０℃、８℃和１５℃三个温度水平的罗非鱼保鲜期实验方程；同时．实验表明：在温度０℃～５℃下无论采用感官检定或ＴＶＢ－Ｎ，或细菌总数和Ｋ值的指标检定其鲜度，所得的结果均相同。因此．在实际应用时，以０℃温度水平下的实验方程其可靠性较大。     

水准网平差系统介绍

本文介绍的水准网平差系统采用全新的图形化操作界面,输入原始数据更方便、更直观,按间接平差方法进行严密平差,系统自动判断节点,整个平差过程无需人工干预。平差成果可预览查看或打印输出,水准网图形可打印输出或保存为位图文件。     

Distribution,characteristics and influencing factors of fresh groundwater resources in the Loess Plateau,China

The fresh groundwater in the Loess Plateau serves as a major source of water required for the production and livelihood of local residents and is greatly significant for regional economic and social development and ecological protection. This paper analyzes the hydrogeological conditions and groundwater characteristics in the Loess Plateau, expatiates on the types and distribution characteristics of the fresh groundwater in the plateau, and analyzes the influencing factors and mechanisms in the formation of the fresh groundwater in the plateau as a priority. Based on this, it summarizes the impacts of human activities and climatic change on the regional fresh groundwater. The groundwater in Loess Plateau features uneven temporal-spatial distribution, with the distribution space of the fresh groundwater closely relating to precipitation. The groundwater shows a distinct zoning pattern of hydrochemical types. It is fresh water in shallow parts and is salt water in deep parts overall, while the fresh water of exploration value is distributed only in a small range. The storage space and migration pathways of fresh groundwater in the loess area feature dual voids, vertical multilayers, variable structure, poor renewability, complex recharge processes, and distinct spatial differences. In general, the total dissolved solids (TDS) of the same type of groundwater tends to gradually increase from recharge areas to discharge areas. Conditions favorable for the formation of fresh groundwater in loess tablelands include the low content of soluble salts in strata, weak evaporation, and special hydrodynamic conditions. Owing to climate change and human activities, the resource quantity of regional fresh water tends to decrease overall, and the groundwater dynamic field and the recharge-discharge relationships between groundwater and surface water have changed in local areas. Human activities have a small impact on the water quality but slightly affect the water quantity of the groundwater in loess.© 2021 China Geology Editorial Office.     

长江河口浮泥形成机理及变化过程

1976年以来，在长江河口盐水楔和最大浑浊带活动的河道进行了20余次现场观测，本文在现场观测资料基础上，确认长江河口浮泥由细颗粒泥沙组成，中值粒径在8－11.5um,小于2um的粘土占28.18%-36.39%,长江河口浮泥是悬沙在盐水混合环境中絮凝沉降于近义廾风暴潮再悬浮泥沙形成的高浓度浑水层，在成因类型上分为憩流浮泥，盐水楔浮泥和风暴潮浮泥，第1种在涨或落潮转流期低流时形成，规模大，厚度薄，第2种在盐水楔发育时形成，规模较小，厚度较大，第3种在大风后形成，规模大，厚度薄，第2种在盐水楔发育时形成，规模较小，厚度较大，第3种在大风后形成，规模大，范围广，若三者相遇，则浮泥厚度和范围最大，浮泥具有枯季，大小潮秽暴周期变化规律，长江河口河道多的浮泥层，浮泥层的变化与河口拦门沙的冲淤有良好的正相关。     

B码设备中的GPS时间信号接口

ＰＯ９７型ＧＰＳ／Ｂ码解调器把ＧＰＳ技术融入Ｂ码设备中,用于自动定时定位和精密时间同步。该设备的ＧＰＳ时码接口解出ＧＰＳ时间信号,并同步所有的时标信号和时间码信号。主要介绍了该接口的硬件和软件的实现过程。     

Motorola VP OnCore接收机的GPS数据接收软件

总结了Motorola VP OnComm接收机的几种数据格式。采用MAX232作为计算机串口和接收机输出口之间的电平转换接口器件，在MicrosoftVisualC 6．0平台上，利用MSComm控件开发了MotorolaVP OnCoreGSP接收机的数据接收软件。最后给出了数据拉媚的实例。 利用多通道共视实现纳秒量级时间传递系统的基础性工作，对于研制该系统具有重要意义。另外，该软件通用性较强，对于各种OEM板的GPS数据接收也具有实用意义或参考价值。     

Effect of saltwater intrusion on groundwater environment in Weihe River downstream,Shandong Province,China

Based on the geological and hydrogeological conditions along with dynamic changes of groundwater level,this paper analyzes the hydrodynamic characteristics of saltwater intrusion in the study area.According to monitoring data of groundwater quality,the distribution characteristics of macro component are analyzed,and then fuzzy comprehensive evaluation method is adopted to evaluate the impact of saltwater intrusion on groundwater environment.Concerning the influence degree of groundwater environment,the study area is divided into brine area,seriously influenced area,moderately influenced zone,slightly influenced zone and uninfluenced zone.The results can offer references for prevention and control of saltwater intrusion as well as the protection of water resources.