Groundwater Locations Research Articles

Development of seismic design criteria for category I cofferdams

Gravity-type cellular cofferdams are widely used as waterfront retaining structures. Static design of these structures is generally performed by considering several modes of static failure. The experience gained from post-construction observation of cofferdam behavior has greatly enhanced the postulation of admissible failure mechanisms that should be considered in design. In nuclear power plant operation, assuring the safety and stability of waterfront embankments is important in providing an undisturbed supply of cooling water under all seismic and flood conditions. In moderate to highly seismic areas, the protection of the waterfront with an economic class I embankment may be quite difficult or impractical as the area required to develop the relatively flat slope construction that is required for seismic stability is often unavailable. Therefore, more attention should be directed toward the design and construction of cellular cofferdams as waterfront earth retaining structures. However, in the absence of data on dynamic behavior of cofferdams under seismic conditions, the methods for design and construction of structures which meet the current regulatory requirements are not well documented. Because static methods of cofferdam design have become somewhat standardized and have been verified through observations of performance, a promising approach to the seismic design of such structures is centered about the development of consistent pseudo-static failure mechanisms. This paper illustrates such extensions of the static design techniques, and compares the factors of safety obtained from static and pseudo-static (seismic) analyses. Certain design criteria, which have been modified to account for dynamic action, are explained. Local soil, rock and hydrostatic conditions, liquefaction and hydrodynamic forces are considered. Design/analysis parameters are suggested for evaluating extreme condition seismic loading, i.e., the Safe Shutdown Earthquake (SSE). Included among the parameters are; active and passive dynamic earth pressure coefficients; location of groundwater and free water surfaces to be used in conjunction with the SSE; the coefficient of friction acting at the interface between the fill material within the cell and the material on which the cell is founded; dynamic pressure distributions due to groundwater and free-standing water adjacent to the structure; vertical and horizontal coefficients of seismic acceleration. In addition, the consequences of postulated liquefaction of adjacent materials are investigated, and measures are suggested to adjust the analysis to accommodate such an occurrence. Among the postulated failure conditions which are considered under seismic loading are the following: • sliding, • overturning, • slippage between the sheeting and the cell fill, • shear failure along the centerline of the cell, • Cummings method of horizontal shear, and • interlock strength. The method of analysis admits various assumptions that are based on the static failure modes of the analytical models; for example, the postulated sliding failure condition assumes an inflexible rigid body type of behavior while the Cummings method of horizontal shear considers the structure to be flexible and the soil to be capable of developing failure planes. By extending these postulated failure modes for the dynamic analysis, the same modeling assumptions are admitted for the pseudo-static case. The methodology proposed is suggested as a means of conservatively performing design checks, using simplified procedures, and not as a replacement for a dynamic, state-of-stress response analysis.

Determination of Groundwater Inflow to Prairie Lakes Using Remote Sensing

This study was designed to find the locations in Big Quill Lake, Saskatchewan, where the transfer of surficial and aquifer ground-water occurs in the lake bed. Using the findings of a geological survey done between 1966 and 1969, and combining the results of the remote sensing techniques of LANDSAT-1 airborne radio phase detection (EPHASE) and infrared line-scanning, it proved possible to locate nine areas at which inflow of groundwater is assumed to take place. Together these nine locations comprise an area of four square kilometers (1.5 mi2) in a lake that covers 250 square kilometers (100 mi2). In addition it was possible to separate these nine groundwater locations from such dynamic events as spiral currents (a tenth anomaly zone) and peninsula building bottom currents.

Earth Resistivity Surveys — A Method for Defining Ground‐Water Contaminationa

ABSTRACTAn important part of every investigation of ground‐water pollution is to locate and define the extent of the contaminated body of ground water. The usual method for accomplishing this is to install and sample numerous test wells, a costly and time‐consuming procedure. A much faster and less costly method, which has proven to give accurate results, is the earth resistivity survey. Because earth resistivity is inversely proportional to ground‐water conductivity, the location of ground water that has been contaminated by a relatively high concentration of conductive industrial wastes, for example, may be quickly and accurately traced.In order for the resistivity method to give useful results, resistivity contrasts must exist in the subsurface. For example, if the contaminant does not have a significantly greater conductivity than the natural ground water, or if the ground water is naturally highly conductive itself, a large enough resistivity contrast may not exist, and the method may not work. In addition, if depth to water is too great, the thickness of the unsaturated sediments can mask any contrasts between contaminated and natural ground water. The geologic environment must be relatively uniform so that the resistivity values and profiles can be compared with one another. At most industrial plant sites and landfills, these conditions are met. That is, the area of investigation is usually limited to a few hundred acres, where the geology and depth to water tend to be uniform.Four case histories of industrial and landfill sites are discussed in this paper. The areas underlain by the contaminated ground‐water bodies ranged from 25 to 100 acres. The depths to the contaminated water were relatively shallow, ranging from 5 to about 60 feet below land surface. In three of the cases, the results of the earth resistivity studies, which were verified by installing test wells in and around the area being investigated, proved to be remarkably accurate. In the fourth study, the conditions mentioned were not met, and the survey was unsuccessful.

Factors controlling the location of the groundwater divide in Northern Israel

The location and formation of the regional groundwater divide in the Cenomanian-Turonian carbonate aquifer of Galilee, which today is situated west of the structural axial region, is controlled by two factors: 1. the shifting of the ancient groundwater divide from the structural axis zone westward, due to tectonic movements and formation of new base levels since the Neogene. 2. facies changes within the carbonate aquifer and differences in permeability between its lower and upper subaquifers. As a result, an upconing of the water table may occur during the process of natural recharge, and thus, regional or local groundwater divides may be formed.

Electrical resistivity and seismic refraction studies for groundwater in the Jodhpura area, Rajasthan

The results of geophysical investigations carried out for groundwater employing seismic refraction and electrical resistivity methods near Jodhpura (27o47′30″N:75o42′40″E) in the Jhunjhunu District, Rajasthan, are presented. Prominent resistivity low zones, revealed by the resistivity profiles, are indicative of deeper section of unconsolidated sediments overlying the bedrock and are usually favourable locations for groundwater. An equiresistivity and water-level contour map based on well data is furnished, indicating the fresh water zone boundary deduced geophysically. Longitudinal velocities for the various rock types occurring in and around the area are tabulated for general interest. A bedrock map prepared on the basis of depths estimated geophysically is incorporated. The depths to bedrock computed from electrical and/or seismic data compare well with those obtained from borehole data.

Location and Evaluation of Ground Water Resources

■■PHE location and evaluation of X ground water resources require the application of both geological and engineering techniques. Typical examples of the coordinated efforts of geologists and engineers in dealing with ground water problems exist in the Ground Water Branch of the USGS, the parallel agencies of many states, and a few consulting firms. Most of the quantitative evaluation methods in common use are the products of such group effort. The USGS is usually given credit for the pioneer efforts and for the training of most ground water experts. The purpose here is to discuss some of the principles of ground water location and evaluation in terms that will be meaningful to those who are not trained experts but are vitally concerned with adequate ground water supplies. For the sake of illustration, use will be made of a survey and evaluation problem for the area around the city of Wooster in Wayne County, Ohio. The Wooster survey is not unique but does represent a problem of greater than average complexity and interest which covered an area of several hundred acres.

Application of Air Photo Interpretation in the Location of Ground Water

THE technique of air photo interpreta ion has been em loyed for some time in the performance f soil surveys (1) and th analysis of soils and engineeri g materials (2, 3). As report d in the literature, air photo studies have been used to determine the origin and nat re of soils, kinds of rock, nature of the geologic structure, land use, drainage, and even ce tain hydrographic characteristics of an area (4-7). Basically, the technique of interpreting air photos involves the recognitio of vari us ground features and the logical deduction of their geologic and engineering significance. To study ground water locations, the analyst must also have a thorough background in geology, hydrology, geomorphology, and pedology. The work of the air photo analyst in appraising the geologic and engineering characteristics of an area might be compared to that of a doctor in interpreting an X-ray film to appraise the condition of a patient: a thorough background in physiology, biology, and bone structure is necessary to interpret and evaluate X-ray photographs properly. Of the few tools used by the air photo analyst the most essential is the stereoscope, shown in Fig. 1. This simple instrument is much like that employed in a parlor pastime in the early 1900's, or the more modern devices used for