J. David Rogers

Subsurface Exploration Using the Standard Penetration Test and the Cone Penetrometer Test

The Standard Penetration Test (SPT) and Cone Penetrometer Test (CPT) have become industry standards for subsurface geotechnical investigations using small diameter (<8-in. [20-cm]) borings and soundings. Both procedures have evolved over a period of 100 and 70 years, respectively, and have been adopted as ASTM standards. Each procedure has certain advantages over the other, but both can elicit incorrect data under particular subsurface conditions that are often overlooked, depending on the experience of field personnel operating or logging the tests. This paper seeks to explain the operative assumptions employed in both procedures, highlight the various corrections that are commonly employed, and warn the reader of common errors in interpretation. The article concludes by stating that, under most conditions, the joint employment of SPT and CPT together has the greatest potential for characterizing sites correctly.

Interpolations of Groundwater Table Elevation in Dissected Uplands

The variable elevation of the groundwater table in the St. Louis area was estimated using multiple linear regression (MLR), ordinary kriging, and cokriging as part of a regional program seeking to assess liquefaction potential. Surface water features were used to determine the minimum water table for MLR and supplement the principal variables for ordinary kriging and cokriging. By evaluating the known depth to the water and the minimum water table elevation, the MLR analysis approximates the groundwater elevation for a contiguous hydrologic system. Ordinary kriging and cokriging estimate values in unsampled areas by calculating the spatial relationships between the unsampled and sampled locations. In this study, ordinary kriging did not incorporate topographic variations as an independent variable, while cokriging included topography as a supporting covariable. Cross validation suggests that cokriging provides a more reliable estimate at known data points with less uncertainty than the other methods. Profiles extending through the dissected uplands terrain suggest that: (1) the groundwater table generated by MLR mimics the ground surface and elicits a exaggerated interpolation of groundwater elevation; (2) the groundwater table estimated by ordinary kriging tends to ignore local topography and exhibits oversmoothing of the actual undulations in the water table; and (3) cokriging appears to give the realistic water surface, which rises and falls in proportion to the overlying topography. The authors concluded that cokriging provided the most realistic estimate of the groundwater surface, which is the key variable in assessing soil liquefaction potential in unconsolidated sediments.

Seismically Induced Lateral Spread Features in the Western New Madrid Seismic Zone

Between December 1811 and March 1812, the largest series of earthquakes recorded in United States struck the Upper Mississippi Embayment, centered near New Madrid, MO. The region was subjected to repeated episodes of wide-scale liquefaction, ground subsidence and uplift, as well as landslides and earth movement towards stream channels. In his 1912 report on the New Madrid earthquakes, Myron Fuller described numerous features that exhibited characteristics and morphology similar to lateral spread features associated with the 1964 Alaska earthquake. However, before this report, no lateral spread features were substantially verified and characterized within the New Madrid Seismic Zone (NMSZ). The authors have used topographic mapping protocols to identify areas of seismically induced landslippage, including lateral spread features, along Crowley9s Ridge in the western NMSZ. It is thought that the lateral spread features formed in response to liquefaction of underlying confined sand layers during ground shaking associated with the New Madrid earthquakes. Lateral spreads, like other types of landslippage, exhibit fairly specific topographic signatures that can be identified on contour maps. The authors used digital map products in combination with Geographic Information Systems programs to find and delineate areas with topographic signatures representative of lateral spread features. For verification of the features, the authors are using geophysical and field methods, including ground penetrating radar (GPR) and electrical resistivity, to determine whether the suspect features are indeed lateral spreads.

Simplified Method for Spatial Evaluation of Liquefaction Potential in the St. Louis Area

As a part of an earthquake hazard mapping program being undertaken by the U.S. Geological Survey in the St. Louis metropolitan area, surficial geologic mapping and subsurface geotechnical data have been compiled into a three-dimensional geographic information system (GIS). The potential for soil liquefaction was then spatially evaluated by using subsurface information from 562 boreholes for an assumed M7.5 earthquake emanating from the New Madrid Seismic Zone. Geotechnical data (standard penetration test N-values, overburden pressure, and depth-to-groundwater) and the scenario peak ground accelerations (PGA=0.1, 0.20, and 0.30  g) were applied to evaluate the factor of safety (FS) against earthquake-induced liquefaction. The liquefaction potential index (LPI) method was used in these evaluations because it allows for calculations of FS with depth for 10–25 discrete stratigraphic horizons overlying the bedrock across the St. Louis metropolitan area. LPI values were derived from the correlation between calc...

Unstable ground: landslide policy in the United States

Introduction ................................................. 941 I. The Landslide Problem in the United States ............... 942 A. Physical Characteristics and Extent of Damages ....... 942 B. Social Issues ......................................... 948 C. Roadblocks to Resolution-Limited Availability of Landslide Information and Inaccurate Perceptions of Landslide Risks ...................................... 949 II. Policy Strategies .......................................... 950 A. Research and Education-Prerequisites to Effective Reduction of Landslide Hazards ...................... 950 1. G oals ............................................ 950 2. Example-USGS-HUD Work in the San Francisco Bay A rea ......................................... 951 3. Mapping Programs of the California Division of Mines and Geology ............................... 952 4. Programs and Legislation in Other States .......... 953 5. National-Scale Landslide Research ................ 954 6. Effect of Landslide Information on Public Behavior ......................................... 955 7. Research and Education Summary ................ 956 B. Land Use Planning-Controlling Development on Unstable Lands ....................................... 956

A Regional Level Preliminary Landslide Susceptibility Study of the Upper Indus River Basin

Abstract The major goal of this research was to explore low cost means by which large tracts of mountainous terrain (∼75000 km2) can be screened for landslide-related hazards. For upper Indus watershed study, landslide susceptibility index maps were generated by coupling two main indicators groups: 1) environmental risk factors, which mainly contain slope angle, slope aspect, elevation, lithology maps; and 2) the causative factors, which include seismicity and rainfall. GIS based expert driven weighted overlay and fuzzy logic techniques were adopted to generate susceptibility maps for this preliminary landslide hazard study. The results obtained from this study were validated with landslide inventory mapping and other landslide historic data scattered throughout the upper Indus watershed. This kind of regional level landslide susceptibility mapping can play a vital role in identifying those areas where more detailed assessments of landslide hazards should be undertaken.

Creep parameters of rocks on an engineering scale

Vertical shafts of 137 cm diameter were excavated to measure creep deformations of carbonate shale, weathered limestone and tuff. Changes of diameter at successive time intervals were recorded under constant, radial pressure. Three typical models were chosen for a regression analysis of the experimental data and their fitness were compared to one another in a statistical approach.The introduction of a steady state flow term improves the data fit considerably, and the power law was found to yield an even better result. It was also determined that rock masses in the field contain numerous discontinuities which increase the plasticity of the three types of rock tested. The viscosities determined in-situ were found to be much lower than those derived from small intact specimens by up to several orders of magnitude.

Hydrogeophysical Investigation at Luxor, Southern Egypt

Over the past 35 years , the exposed stone foundations of the ancient Egyptian monuments at Luxor have deteriorated at an alarmingly accelerated rate. Accelerated deterioration is attributable to three principal factors: 1) excavation and exposure of foundation stone; 2) construction of the Aswan High Dam; and 3) changes in the regional groundwater regime. In an effort to better elucidate the hydrostratigraphy in the Luxor study area that extends from the River Nile to the boundaries of the Nile Valley and covers about 70 km2 , a geophysical∕hydrological investigation was conducted. Forty Schlumberger vertical electrical soundings (VES), two approximately 6 km long seismic refraction profiles and a total number of 39 groundwater and surface water samples were acquired. Based on the integrated interpretation of the acquired geophysical∕hydrological data, the main contributions of this study were the geophysical definition of the hydrostratigraphy using resistivity (seven distinct geologic∕ hydrologic units...

Adapting to Change in the Lowermost Mississippi River: Implications for Navigation, Flood Control and Restoration of the Delta Ecosystem

The Lowermost Mississippi River (LMMR), from the Gulf of Mexico to 520 km above Head of Passes, remains critical for flood conveyance and transport of agricultural and industrial bulk products from the central United States. The US Army Corps of Engineers (USACE) has managed it with little change for 80 years using the levees and spillways constructed under the Mississippi River and Tributaries project (MR&T). At the same time, public demand for reconnection of the Mississippi to the deteriorating delta ecosystem has grown. Significant sediment diversion projects have been authorized downstream of New Orleans to restart deltaic wetland building to conserve fish and wildlife resources and reduce hurricane flood risk to delta communities. Recent research and observations from the back-to-back record 2011 high-, and 2012 low-discharge events indicate that LMMR hydraulics have changed significantly, and that sea level rise, subsidence and a reduction in sand transport through the Plaquemines-Balize birdsfoot delta (PBD) now favor formation of new, unregulated outlets upstream. During the peak of the 2011 flood, only 27 % of the 65,000 m3-s−1 discharge entering the LMMR reached the Gulf via Head of Passes, compared to 36 % passing through the two outlets of the shorter Atchafalaya distributary. About 20 % of the water lost from the LMMR occurred through unregulated flow overbank and through small, but growing, distributaries between New Orleans and Head of Passes. Adding delta restoration to existing USACE missions will require adjusting the MR&T but has potential to lower flood flow lines and reduce navigation dredging costs sufficiently to allow LMMR ports to accommodate larger, Post-Panamax ships.

Seismic Site Response Modeling for Three Missouri River Highway Bridges

Three highway bridges spanning the Missouri River flood plain were selected for evaluation of seismic site response for moderate size earthquakes emanating from the New Madrid Seismic Zone (NMSZ) in the Midwestern United States. The NMSZ is known to be capable spawning earthquakes larger than magnitude (M) 7.0, four of which occurred in a three-month period between 1811 and 1812, and the Mw 6.0 earthquake of October 1895 centered near Charleston, Missouri. This study evaluated the likely impacts of long period motion of these historic earthquakes on three long-span highway bridges using geotechnical data obtained from recent investigations. Our results suggest site amplification between 6× and 9×, depending on the magnitude and epicentral distance. We believe that threshold magnitude for serious foundation failure and damage to these bridges is between Mw 6.5 and 6.6. Above these magnitudes widespread liquefaction is predicted, which would effect the peak horizontal acceleration and spectral accelerations, causing the ground motions to be different than predicted. Increase in amplification of the response spectra also should be expected where the periods are higher than 1.0 sec. Therefore, Mw 6.5+ earthquakes at ranges 210–260 km could be expected to engender resonant frequency problems for multiple span bridges and tall buildings (10 to 25 stories) in channel corridors containing 20 to 46 m of unconsolidated sediment.