Migration of induced-infiltrated stream water into nearby aquifers due to seasonal ground water withdrawal

Analysis of stream-aquifer interaction due to ground water extraction has traditionally focused on the determination of the amount of water depleted in the stream. Less attention has been paid to the movement of infiltrated stream water inside aquifer, particularly for agricultural areas. This paper presents a method of using particle-tracking techniques to evaluate the transport of the leaked stream water in the nearby aquifers. Simple stream-aquifer conditions are used to demonstrate the usefulness of the analysis. Travel times, pathlines, and influence zones of stream water were determined between a stream and nearby pumping wells for seasonal ground water extraction areas. When water quantity is a concern, the analyses provide additional information about stream depletion; when water quality is an issue, they offer information for wellhead protection. Analyses were conducted for transient conditions, and both pumping and nonpumping periods were considered. According to the results from the simulation examples, migration of infiltrated stream water into the nearby aquifers is generally slow and most infiltrated stream water does not arrive at the pumping well at the end of a 90-day irrigation season. Infiltrated stream water may remain in the aquifer for several years before arriving at the pumping well. For aquifers with a regional hydraulic gradient toward streams, part of the infiltrated stream water may discharge back to streams during a recovery period.     

A note on permeability changes in geologic material due to stress

Summary Stress produces framatic changes in fluid permeability of geologic materials. An increase of nearly threefold occurred in granite at high stress, an increase of 20 percent in sandstone, and a hundredfold decrease in compacted sand. Permeability of sand and sandstone did not follow the effective stress law. Flow along joints was very sensitive to effected stress changes, a fourfold change being caused by as little as 1.0 MPa.     

Underground pipeline response to earthquake-induced ground deformation

The principal causes of earthquake-induced ground deformation are identified and their interaction with underground infrastructure, primarily pipelines and conduits, is described. The coupled forces normal and parallel to underground pipelines arising from earthquake-induced ground movement are evaluated, including a review of measured stresses on pipe surfaces during large-scale testing, evaluation of frictional forces related to soil-pipe interaction, and the resolution of interaction forces along and across pipelines. Methods for characterizing soil reaction to pipe lateral and vertical movements are presented. The maximum downward pipe force is only about one-third the maximum force determined with conventional bearing capacity equations, thus requiring changes in current analytical and design practice. The analytical results for pipeline response to strike-slip and normal fault rupture are shown to compare favorably with the results of both large-scale and centrifuge tests of soil-pipeline interaction simulating these types of severe ground deformation.     

蓄水池塘放水对昆明地震台形变观测影响

监控昆明地震台观测山洞附近蓄水池塘的放水过程,掌握放水对水管倾斜、洞体应变观测造成的干扰形态,计算观测数据的卸载响应比,根据干扰类型,选用合理方法处理数据,更好地提升水管倾斜、洞体应变潮汐观测质量;对于未来地震异常落实,可用于类似干扰因素的排除及干扰量的计算。     

Earthquake-induced soft-sediment deformation structures in the Mesoproterozoic Wumishan Formation,North China,and their geologic implications

Soft-sediment structures are key to defining seismites. Two soft-sediment deformation horizons, bounded by undeformed carbonate strata, have been found in the Wumishan Formation in the Jumahe region, 175 km southwest of Beijing. One is in the lowest part of Wumishan Formation; and the other is in the uppermost part of Litho-member I. The soft-sediment structures in these two horizons fall into three categories: mould-and-sag structures, hydraulic shatterings and liquefaction dikes. The mould-and-sag structures are divided into two types: one developed in tidal-flat sediments, accompa-nied by many liquefaction-related structures and characterized by autochthonous post-earthquake sediments in sags, and the other type developed in deep-water environments, is not associated with liquefaction structures, and is overlain immediately by seismogenic tsunamites. The hydraulic shat-terings are composed of pockets of fluidization conglomerate, sand intrusions, and syndepositional faults. The liquefaction dikes fall into two categories: hydraulic-fracturing dikes and lateral-spreading dikes. The former are steep, planar, and pinch out upwards. The latter are snake-like and characterized by no diapir-related drag structures in surrounding rocks. Examination of the attitudes and strati-graphic positions of these structures suggests that these soft-sediment structures are seismogenic, and consequently, are seismites. Most seismites in the Wumishan Formation are developed near the former western, margin fault of Yanliao rift. This occurrence suggests that they could be related to movements on this fault. Other geological implications are discussed.     

Measuring streambank erosion due to ground water seepage: correlation to bank pore water pressure,precipitation and stream stage

Limited information exists on one of the mechanisms governing sediment input to streams: streambank erosion by ground water seepage. The objective of this research was to demonstrate the importance of streambank composition and stratigraphy in controlling seepage flow and to quantify correlation of seepage flow/erosion with precipitation, stream stage and soil pore water pressure. The streambank site was located in Northern Mississippi in the Goodwin Creek watershed. Soil samples from layers on the streambank face suggested less than an order of magnitude difference in vertical hydraulic conductivity (K_s) with depth, but differences between lateral K_s of a concretion layer and the vertical K_s of the underlying layers contributed to the propensity for lateral flow. Goodwin Creek seeps were not similar to other seeps reported in the literature, in that eroded sediment originated from layers underneath the primary seepage layer. Subsurface flow and sediment load, quantified using 50 cm wide collection pans, were dependent on the type of seep: intermittent low‐flow (LF) seeps (flow rates typically less than 0·05 L min^?1), persistent high‐flow (HF) seeps (average flow rate of 0·39 L min^?1) and buried seeps, which eroded unconsolidated bank material from previous bank failures. The timing of LF seeps correlated to river stage and precipitation. The HF seeps at Goodwin Creek began after rainfall events resulted in the adjacent streambank reaching near saturation (i.e. soil pore water pressures greater than ?5 kPa). Seep discharge from HF seeps reached a maximum of 1·0 L min^?1 and sediment concentrations commonly approached 100 g L^?1. Buried seeps were intermittent but exhibited the most significant erosion rates (738 g min^?1) and sediment concentrations (989 g L^?1). In cases where perched water table conditions exist and persistent HF seeps occur, seepage erosion and bank collapse of streambank sediment may be significant. Copyright © 2007 John Wiley & Sons, Ltd.     

基于地壳分层的唐山地震断层震后变形分析

本文利用球体粘弹性地球模型研究唐山地震断层基于地壳分层的震后变形影响，计算四种不同类型的地球分层模型（均匀模型和三种地壳分层模型）产生的震后变形场，分析不同模型对地表变形的影响异同，定量研究了实际地壳分层模型与均匀地壳模型计算的地表变形差异.计算结果显示，相对均匀粘弹性地球模型，利用分层的地壳结构模型，计算的唐山地震断层附近区域震后28年积累的变形，两者最大差值水平方向可达20mm，垂直变形相差10mm左右.计算的结果显示地壳结构的差异对震后地表变形的影响很大，超过现有高精度测量技术的精度.如果利用该区的实测资料进行反演研究，必须根据实际地壳构造情况考虑地壳分层的影响.     

打桩引起的地面振动的研究

为了对打桩引起的地面振动进行研究,应用一维应力波理论建立了粘弹性成层土中等截面弹性桩的力学模型,得到了桩中任意一点处位移的半解析解。利用桩与土的相互作用将桩对土的作用力简化到各土层面上。在复阻尼理论和纳维方程的基础上,利用分层法得到了任意荷载作用下土的位移、速度和加速度的解。从而得到了打桩引起的地面振动的衰减特性。通过实测结果和计算结果的比较说明了该方法的可行性。     

三维竖向断层场地对地面运动的影响

实际工程场地中的断层通常具有三维尺寸,应进行三维分析。本文考虑均匀弹性半空间内存在不同长度、深度的三维断层,由下向上垂直入射一个脉冲波,主要采用三维时域显式有限元结合透射人工边界的方法及相应编写的三维显示有限元波动程序DSI3,计算断层附近地震地面运动的时程反应,研究含有三维断层场地地面运动的一些特点,并与自由场反应对比,以说明三维竖向断层对地震波传播的特点和对断层附近地面运动的影响。     

The effects of torsional ground motion on thin cylindric shell structures

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Attenuation of ground vibrations due to different technical sources

The attenuation of technically induced surface waves is studied theoretically and experimentally.In this paper, nineteen measurements of ground vibrations induced by eight different technical sources including road and rail traffic, vibratory and impulsive construction work or pile driving, explosions, hammer impulses and mass drops are described, and it is shown that the technically induced ground vibrations exhibit a power-law attenuation v～r-q where the exponents q are in the range of 0.5 to 2.0 and depend on the source types.Comparisons performed demonstrate that the measured exponents are considerably higher than theoretically expected.Some potential effects on ground vibration attenuation are theoretically analyzed.The most important effect is due to the material or scattering damping.Each frequency component is attenuated exponentially as exp(-kr), but for a broad-band excitation, the sum of the exponential laws also yields a power law but with a high exponent.Additional effects are discussed, for example the dispersion of the Rayleigh wave due to soil layering, which yields an additional exponent of 0.5 in cases of impulsive loading.     

In-plane response of two-story structures to near-fault ground motion

Linear and non-linear responses of a two-story structural model excited by near-source fault-normal pulse and fault-parallel displacement are investigated. For the considered linear system, the multi-component differential-motion effects amplify the first-story drifts 3.0–4.0 times relative to the excitation by synchronous horizontal ground motion only. The contribution of horizontal differential ground motion to the total drift is about two thirds, and the contribution of vertical and rocking differential ground motions is about one third. For the considered nonlinear system, the effects of vertical and rocking differential ground motions become more significant for the second-story drifts. The horizontal differential ground motion amplifies the first-story drifts, but the simultaneous action of horizontal, vertical, and rocking differential ground motions can amplify the first- and second-story drifts by more than 2.0 times relative to the drifts computed for uniform horizontal ground motion only.     

地幔对流拖曳力对中国大陆岩石层变形的影响

采用较为符合实际岩石层变形的非线性幂指数本构关系,基于ANSYS有限元平台, 模拟了近20万年来中国大陆地区地表运动及演化过程,探讨了印度板块挤压作用和地幔对流拖曳力各自对于中国大陆地区地表形变运动格局的影响.模拟结果与观测数据的比较表明：在印度板块的挤压和地幔拖曳力联合作用下,中国及东亚大陆岩石层运动形变模式能够和现代GPS观测有较好的吻合; 印度大陆和欧亚大陆的碰撞以及印度大陆的持续向北推进、挤压所产生的应力环境,一直主导了以青藏高原为核心的我国西部地域岩石圈构造、运动和演化,但其影响随着远离青藏高原地区而逐渐变小;地幔对流产生的作用于岩石层底部的拖曳力是中国大陆（特别是远离碰撞带）岩石层运动构造变形的重要驱动力.然而在构造复杂和东部靠近太平洋板块的区域,模型预测结果和GPS观测还存在一定的差距,这说明在未来的中国大陆岩石层变形运动的数值模拟中,应当采用更为复杂的构造模型和驱动力因素.     

The effects of water interactions on engineering structures

ABSTRACT

The intended performance of hydraulic structures such as dams built on soluble rock or soil foundations may depend upon rates of dissolution caused by water seeping through joints, fissures or granular zones. Previous papers by one author and collaborators have defined the rates of dissolution for soluble rocks by means of a simple equation: dM/dt = K A (C_s—C)^θ. This relationship may be used as an aid to prediction of enlargement of joints and fissures in rocks, settlements of granular foundation strata, the deterioration of filters, risks to shallow but intensely loaded foundations, and durability of underground storage caverns in soluble rocks. The relationship requires a knowledge of the solution potentials of groundwater associated with these features of engineering structures. They in turn require an understanding of the relevant hydrochemistry and hydrology which is discussed in this paper.     

The effect of the earth's rotation on ground water motion

The average pore velocity of ground water according to Darcy's law is a function of the fluid pressure gradient and the gravitational force (per unit volume of ground water) and of aquifer properties. There is also an acceleration exerted on ground water that arises from the Earth's rotation. The magnitude and direction of this rotation-induced force are determined in exact mathematical form in this article. It is calculated that the gravitational force is at least 300 times larger than the largest rotation-induced force anywhere on Earth, the latter force being maximal along the equator and approximately equal to 34 N/m(3) there. This compares with a gravitational force of approximately 10(4) N/m(3).     

The piezomagnetic computation of magnetic anomalies due to ground loading by a man-made lake

Summary A method has been developed to determine the stress distribution and resultant piezomagnetic surface anomaly field due to the load imposed on the earth's crust from filling man-made lakes of variable depths and arbitrary geometries but uniform elastic properties. The dam-magnetic effect observed byDavis andStacey [1] on Talbingo reservoir in the Snowy Mountains of SE Australia is adequately explained in terms of the piezomagnetic effect if more highly magnetic rock than that measured on the surface is present at depth.     

The inverse problem and ground water management

The response of groundwater basins to natural and anthropogenic inputs depends on many interrelated factors such as the values of groundwater flow and mass transport parameters. This work presents a theoretical analysis of the impact of parameter uncertainty on groundwater management decisions. It is shown that under classical, Bayesian, and deterministic assumptions about the parameter structure, the resulting management decisions could be very different. This underscores the importance of adopting the proper parameter structure and the need for using consistent methods to solve the inverse problem.