Environmental and Engineering Geoscience

Published by Geological Society of America
Print ISSN: 1078-7275
Publications
One of the most common and effective means of slope stabilization is lowering the water level within a soil mass. Frequently, horizontal drains are installed for this purpose. Computer-aided slope stability analyses are then used to evaluate the increase in factor of safety produced by drain installation. Critical to these analyses is the location and shape of the water table surface above the drain field. However, evaluation of the water table surface is complicated by its complex corrugated shape, with troughs corresponding to drain locations and ridges at the midpoints between drains. The objective of this research was to accurately describe the water table surface within a drain field using easily measured field and laboratory parameters. To accomplish this, physical and computer modeling of the water table along and between drains was conducted. The results of these analyses were compared to an analytical solution of the water table profile between drains that was derived by modifying groundwater equations developed for agricultural engineering applications. Based on these comparisons, a method was developed to describe the water table surface using the analytical solution and an experimentally derived correction factor. The method was confirmed by comparisons to field data. As a result of this research, water table surface heights can be approximated along and between drains. Additionally, an average water table surface height may be calculated and used in stability analyses, allowing accurate substitution of two-dimensional analyses for more complex three-dimensional situations.
 
Debris flows originating in colluvial deposits within hillside swales cause significant property damage and loss of life in steep, soil-mantled environments and will continue to do so for as long as mitigation measures are not adopted for both new and existing development. Colluvium-filled swales constitute mappable debris flow source areas and should be identified routinely as potential hazards in geotechnical feasibility and design-level investigations. Toward this end, we propose a swale classification system that incorporates the state of activity, slope, and depth of colluvial fill within a swale. Recognition and siting considerations allow for debris flow hazard mitigation by avoiding locations downslope of colluvium-filled swales, along low-order channelways, or on debris fans. Alternative mitigations, particularly appropriate for areas of existing development, include removal of colluvial deposits, subdrain installation, or downslope intervention to reduce the impact of a debris flow.
 
The importance of locating the slip surfaces of landslides is emphasized in connection with their investigation and instrumentation, their analysis and their stabilization. The available methods are divided into two groups, those applicable only to moving landslides and those applicable to stationary ones. The first group comprises inferences from surface movement observations, direct measurements of sub-surface displacements, and geoacoustic sensing. In the second group the methods reviewed include in situ observations from access holes, observations on recovered samples and surface and sub-surface geophysical techniques. It is concluded that it is advisable to employ a variety of methods and to pursue first the more easily accessible and hence more cheaply gained information. It should also be borne in mind that multiple slip surfaces often exist and that it is important to ensure that the lowest of these is found. An extensive list of references is provided.
 
Geotechnical Investigations at the site of ancient Ayla in Aqaba, Jordan, show that soils are predominantly granular, with archaeological fill overlying beach sand, which in turn overlies a coarser sand and gravel. Except for the wadi area, ground water occurs about 3 m below the existing ground level. The bearing capacity of the foundation is 3.5 kg/cm(2) for the dense granular materials that represent the probable founding layer of the existing walls, and 2.0 kg/cm(2) for the weaker silty/clayey zone. Back analysis yields a safe wall height of at least 6.0 m. Therefore, no stability problems are present. Tilting and sinking were noted in some portions of the exterior malls as a result of dynamic lateral earth pressures caused by a major earthquake incident in 1067 A.D. Thus, wall-foundation support is recommended during archaeological excavations; and permanent excavations for exposing the walls should be limited to about 3 m by the western wall, and about 2.5 m by the eastern wall. Stones used in the construction of ancient Ayla consist of precut sandstone, siltstone, mudstone and granite. Weathering effects were clearly noted on the exposed stones on the walls. The replacement stone should consist of sandstone blocks located 35 km north of Aqaba. Wall restoration includes replacement of mortar in the inner walls and disintegrated stone pieces in the external walls. Existing mortars consist primarily of a brown silty mixture and a gray mixture, but also a mixture of fine gravel, and a lime/gypsum binder. The major chemical constituents of the original mortar are 18 percent SiO2, 23 percent CaO, and 34 percent SO3. X-ray diffraction peaks indicate the presence of gypsum, calcite and quartz. Comparative analysis data gave 7 percent CaCO3, 53 percent sand, and 40 percent solubles as average values for the constituents. Two sand sources were identified for the mortar mix; recommended mortar for restoration was a mix of lime, sand, and ash, with ratios of 1:3:1.5.
 
Geotechnical Investigations at the site of ancient Ayla in Aqaba, Jordan, show that soils are predominantly granular, with archaeological fill overlying beach sand, which in turn overlies a coarser sand and gravel. Except for the wadi area, ground water occurs about 3 m below the existing ground level. The bearing capacity of the foundation is 3.5 kg/cm2 for the dense granular materials that represent the probable founding layer of the existing walls, and 2.0 kg/cm2 for the weaker silty/clayey zone. Back analysis yields a safe wall height of at least 6.0 m. Therefore, no stability problems are present. Tilting and sinking were noted in some portions of the exterior walls as a result of dynamic lateral earth pressures caused by a major earthquake incident in 1067 A.D. Thus, wall-foundation support is recommended during archaeological excavations; and permanent excavations for exposing the walls should be limited to about 3 m by the western wall, and about 2.5 m by the eastern wall. Stones used in the construction of ancient Ayla consist of precut sandstone, siltstone, mudstone and granite. Weathering effects were clearly noted on the exposed stones on the walls. The replacement stone should consist of sandstone blocks located 35 km north of Aqaba. Wall restoration includes replacement of mortar in the inner walls and disintegrated stone pieces in the external walls. Existing mortars consist primarily of a brown silty mixture and a gray mixture, but also a mixture of fine gravel, and a lime/gypsum binder. The major chemical constituents of the original mortar are 18 percent SiO2, 23 percent CaO, and 34 percent SO3. X-ray diffraction peaks indicate the presence of gypsum, calcite and quartz. Comparative analysis data gave 7 percent CaCO3, 53 percent sand, and 40 percent solubles as average values for the constituents. Two sand sources were identified for the mortar mix; recommended mortar for restoration was a mix of lime, sand, and ash, with ratios of 1:3:1.5.
 
Surface movement is suspected in the pier foundation of the Neveille H. Colson Bridge based on historical aerial photography, past movement of the foundation, and recent geomorphic evidence. Aerial photography dating back to the 1940's suggest this earthslide has formed as a result of the Brazos River meandering. The earthslide is located on a cutbank of the river and aerial photography indicates the presence of a landslide scarp prior to bridge construction. Initial construction was completed by the Texas Department of Highways and Public Transportation (TDHPT) in 1954. Since this time the TDHPT has performed numerous bridge pier adjustments to the structure including a complete pier replacement in 1979 as a result of pier rotation. Various mitigation procedures have been recommended by a local engineering consultant, one which was carried out included the excavation of soil at the head of the earthslide. Surveys since the excavation show that the earthslide has stabilized in the area of the replaced pier. Geomorphic features in other areas of the earthslide, however, suggest active surface movement and include the following: three well developed movement scarps, surface tension cracks, irregular topography, sag ponds and rotated trees. Subsurface geology indicates that this earthslide may have a rotational failure plane in Brazos River alluvium changing to a translational failure plane at depth within the underlying Oakville Formation.
 
By the mid-1700s, the parts of British colonies along the eastern seaboard of North America were settled, safe and civilized. This was by no means the case not very far inland in the Allegheny Mountains and at The Forks of The Ohio, now the site of Pittsburgh, from which the Ohio River flows west, Virginia claimed The Forks but was driven out by the French. In 1754, Lieutenant Colonel George Washington of the Virginia Militia tried and failed to reverse this, bringing on the French-British Seven Years War, the French and Indian War of American history. A second British attempt in 1755 via Washington's route, Virginia, Maryland and to The Forks, was crushed. In 1758, the invalid General Sir John Forbes was ordered to try again. He concluded to go from Carlisle, Pennsylvania to The Forks as directly as possible. There was no through road, but in five months his 6,000-man army, managed for Forbes by Colonel Henry Bouquet, cut a road capable of carrying wagons and artillery through the mountainous, heavily forested Alleghenies. Late in the year the outnumbered French abandoned The Forks and retreated to Canada. This paper examines the setting of the 217 mi of Forbes Road and the physical obstacles facing Forbes' army. Adding only the most significant climbs and descents, construction of Forbes Road was the equivalent of conquering a single obstacle more than 8,000 ft high, something that might have given even Hannibal pause. It was a remarkable job, done with very few of the tools we now have.
 
This study assesses the relationship between coronavirus (COVID-19) and the spread of various heavy metal contaminants across Iraq. The study collects all confirmed, recovered, and death cases of the COVID-19 virus at its onset in Iraq until May 2, 2020, comparing Iraq with the top three infected countries in the world (the United States Spain, and Italy). In addition, numerous heavy metal contamination in different Iraqi cities have been summarized and associated with the allowable upper and lower worldwide standard limits. Furthermore, the study introduces a hierarchical predictive approach for the relationship between confirmed infected cases and deaths due to the COVID-19 virus and heavy metal contamination in various Iraqi cities. It is concluded that all the studied Iraqi cities have heavy metal contamination for different chemical elements exceeding the allowable standard limits. Extreme contents of copper, nickel, lead, and zinc are concentrated in Al-Qadisiyah, Al-Sulaimaniyah, Erbil, and Baghdad with limits of 160 µg/g, 240.9 µg/g, 378 µg/g, and 1,080 µg/g, respectively. Based on the hierarchical prediction approach, a linear positive relationship between both confirmed cases and deaths due to COVID-19 with different heavy metal contamination was obtained with a maximum coefficient of determination (R2) of 0.97.
 
The San Andreas dam and associated water distribution system were built in 1868–70 to collect, store, and distribute domestic water for use in San Francisco. Although the dam and reservoir are situated in the valley of the same name in close proximity to the San Andreas fault, they were constructed before the San Andreas fault was recognized. Following the earthquake of April 18, 1906, it was discovered that a brick forebay and other parts of the reservoir outlet system were in the slip zone of the San Andreas fault. The original outlet through which water was directed to San Francisco consisted of two tunnels joined at the brick forebay; one tunnel extends 2,820 ft to the east under Bald Hill on Buri Buri Ridge, and the other tunnel intersects the lake bottom about 250 ft west of the forebay. In 1897 a second intake was added to the system, also joining the original forebay. No major damage to this outlet system was reported in 1906, even though offsets of 7 to 10 ft were reported short distances to the southeast and northwest along the fault. During the present study the accessible parts of this original outlet system were examined with the hope of learning how the system had been affected by fault slip in 1906. The west end of the accessible tunnels was found to have been displaced at least 8.3 ft right laterally, along with a small component of east-side-down vertical movement. The tunnels are deformed over a width of at least 75 ft, and it is possible that the zone of deformation may be more than twice that width. It appears that sections of the rigid tunnels bent and rotated in the zone of deformation rather than shearing along a single fracture.
 
The 1929 Attica earthquake, the largest recorded shock in the region of Buffalo, New York, occurred two years before the appearance of the Modified Mercalli Scale of Intensity. Since this represents the controlling shock for the region, a method was required to derive accelerations at rock for the design of important contemporary structures. A program consisting of field geological and geophysical explorations, laboratory testing and mathematical modeling was developed whereby accelerations at the buried rock surface could be derived using as input the well-documented surface effects of the shock. Dynamic models utilizing data such as thickness and density of strata, shear moduli and damping ratios were constructed. Site response was modeled using records from well-documented shocks elsewhere, and an ultraconservative synthetic earthquake. Evaluation indicated that maximum acceleration is only one of several factors involved in earthquake damage and that different intensities and frequencies could have different effects on different structures. Seismic impedance between the uppermost two strata, and between the rock and average soil system was shown to have the greatest effect on ground motion. It is concluded that damage from the 1929 Attica earthquake could have resulted from ground accelerations in the range 0.13–0.23g. Bedrock accelerations compatible with these ground motions were calculated in the range 0.05–0.15g using historical data, and less than 0.1g using the conservative synthetic data.
 
On March 20, 1941, more than 110,000 yd3 (84,000 m3) of rock slumped from Brilliant Cut in Pittsburgh, Pennsylvania. Failure was triggered by water pressure buildup due to ice blockage of drainage outlets on the slope face. I investigated this slide as part of my Ph.D. research at the University of Pittsburgh in 1968–1969 and have continued to study it. Historical photographs discovered in 1997 provided new insights on the construction and failure of Brilliant Cut and led to this re-evaluation. In this paper, my 1968–1969 work is summarized and then additional geological and historical information is presented along with key observations from the historical photographs. These photographs reveal that slope excavation at Brilliant Cut in 1930–1931 removed lateral support, in turn initiating stress release and progressive failure that loosened or broke bedrock adjacent to the cut. This fractured rock mass remained marginally stable for a decade but then collapsed in March 1941. The 1941 failure was triggered by water held back in rock fractures by a frozen crust over talus and fractured rock on the slope face. A progressive failure mechanism by Brooker and Peck explains the behavior of Brilliant Cut from 1931 to 1941. Sliding Block stability analyses demonstrate the mechanism of progressive failure and suggest that friction angles were reduced gradually to near-residual values along the failure surface, with low water levels in the slope. With drainage blocked in 1941, a water level developed about 30 ft (9 m) above the basal failure surface to initiate the catastrophic failure. This water level is below that previously inferred to have existed at the time of failure.
 
A large landslide failed catastrophically along steep, 90-m (300-ft) high bluffs overlooking the waters of Puget Sound at Tacoma, Washington, in April of 1949, three days after the region was struck by a magnitude 7.1 earthquake. The area of failure was investigated to estimate the static and seismic stability of the pre-earthquake slope and to identify factors that contributed to the failure. Results of static analyses suggest that the slope was marginally stable and that high ground-water conditions would have significantly reduced slope stability. The Newmark analysis of dynamic (seismic) slope stability was used to calculate predicted inertial displacements for the landslide for a range of possible material property and ground-water conditions. Comparison of predicted displacements with a reported displacement suggests that the ground motion could have initiated the large-scale failure. Results of the study provide a basis for discussion and comparison of similar bluffs in the Puget Sound region that may be susceptible to catastrophic, earthquake-induced slope failure.
 
The Good Friday earthquake of 1964 brought unexpected destruction to the city of Anchorage, Alaska. In the Anchorage area, the quake registered 8.5 on the Richter scale. Though the seismic vibrations were ruinous, the major cause of damage to the city was slab slides. These slides were related to the quick clay properties of Bootlegger Cove Clay which underlies most of Anchorage. Prolonged seismic activity triggered huge masses of earth, initially bounded on one side by a bluff, to move laterally upon a horizontal and planar shear surface within the clay. The lateral displacement of many slides was extensive, and one major slide transported earth more than half a mile. Grabens formed as a result of faulting and collapsing of the sediments within the slab slide. Although the Bootlegger Cove Clay bed is shallow, its presence greatly augmented the destructiveness of the earthquake.
 
Top-cited authors
Stephen George Evans
  • University of Waterloo
Michael Bovis
  • University of British Columbia - Vancouver
Oldrich Hungr
  • University of British Columbia - Vancouver
John E Mccray
  • Colorado School of Mines
William C. Haneberg
  • University of Kentucky