Case study of compaction grouting for foundation support in karst terrain: Earth and Marine Sciences Building,University of California at Santa Cruz

Sinkholes were discovered during initial construction of a new science building at the University of California, Santa Cruz campus. The occurrence of such classic karst features in California is typically uncommon, although sinkholes have frequently been encountered at the campus during previous construction projects. Subsequent to the sinkhole collapse, geologic and engineering investigations were conducted to determine the size and extent of the collapsed sinkholes and assess the potential for further failure. An exploratory compaction grouting program was developed and implemented in order to locate, fill, and plug voids and to densify loose soils beneath the structure. Eighty-one injection locations were drilled, totaling 1350 m (4429 ft), and 248.2 m³ (324.4 yd³) of low-slump grout was placed. Grout volumes and pressures were carefully monitored, and these data correlated well with lithology determined during grout pipe drilling. Permitted movement on the structure was kept well within the allowable 0.64 cm (0.25 in) using a combination of manometers and laser levels.     

Bemerkungen zur Hypothese zweier Sturmzeitringströme

Summary For several years the theory of the main phase of geomagnetic storms takes into account the existence of two storm time ring currents which are thought to exist in different altitudes. This hypothesis is supported less by satellite data than by the analysis of recovery effects observed in the geomagnetic records, according to that the recovery phase should exist of two seperate single phases. In our opinion however the observational material seems not convincing enough, especially because material of one station only was used for the hitherto made investigations and no elimination of theSq-part was executed. A critical analysis of the observational material is by all means necessary, especially for the reason that already in literature extensive inferences of theDR2 ring current for the formation and the energy behaviour of theDP part were drawn. For the investigation of recovery effects it is necessary to use additionally to records of equatorial stations those of observatories in higher latitudes. TheSq-part has to be eliminated in the analysis. It is referred that new disturbances after the beginning of the recovery phase can feign two separated ring current effects. Some examples of the recovery phase will be discussed. They show that the observational material gives no necessity for the supposition of two separate strom time ring currents. Furthermore some theoretical considerations are opposite to this hypothesis. The charge exchange with thermical atoms of hydrogen is discussed to be a possible loss process. It is taken into account also the possibility to suppose a wide proton energy spectrum for explaining the recovery phase.

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Mitteilung aus dem Geomagnetischen Institut Potsdam, Nr. 226.     

Deep spectroscopy of distant 3CR radio galaxies: the data

Deep long-slit spectroscopic data are presented for a sample of 14 3CR radio galaxies at redshift z ∼1, previously studied in detail using the Hubble Space Telescope , the Very Large Array, and the UK Infrared Telescope (UKIRT). Analysis of the [O  ii ] 3727 emission-line structures at ∼5 Å spectral resolution is carried out to derive the kinematic properties of the emission-line gas. In line with previous lower resolution studies, a wide variety of kinematics are seen, from gas consistent with a mean rotational motion through to complex structures with velocity dispersions exceeding 1000 km s ⁻¹. The data confirm the presence of a high-velocity gas component in 3C 265 and detached emission-line systems in 3C 356 and 3C 441, and show for the first time that the emission-line gas in the central regions of 3C 324 is composed of two kinematically distinct components. Emission-line fluxes and the colour of the continuum emission are determined down to unprecedentedly low observed wavelengths, λ <3500 Å, sufficiently short that any contribution of an evolved stellar population is negligible. An accompanying paper investigates the variation in the emission-line ratios and velocity structures within the sample, and draws conclusions as to the origin of the ionization and kinematics of these galaxies.     

Pore fluid viscosity effects on P‐ and S‐wave anisotropy in synthetic silica‐cemented sandstone with aligned fractures

Ultrasonic (500 kHz) P‐ and S‐wave velocity and attenuation anisotropy were measured in the laboratory on synthetic, octagonal‐shaped, silica‐cemented sandstone samples with aligned penny‐shaped voids as a function of pore fluid viscosity. One control (blank) sample was manufactured without fractures, another sample with a known fracture density (measured from X‐ray CT images). Velocity and attenuation were measured in four directions relative to the bedding fabric (introduced during packing of successive layers of sand grains during sample construction) and the coincident penny‐shaped voids (fractures). Both samples were measured when saturated with air, water (viscosity 1 cP) and glycerin (100 cP) to reveal poro‐visco‐elastic effects on velocity and attenuation, and their anisotropy. The blank sample was used to estimate the background anisotropy of the host rock in the fractured sample; the bedding fabric was found to show transverse isotropy with shear wave splitting (SWS) of 1.45 ± 1.18% (i.e. for S‐wave propagation along the bedding planes). In the fractured rock, maximum velocity and minimum attenuation of P‐waves was seen at 90° to the fracture normal. After correction for the background anisotropy, the fractured sample velocity anisotropy was expressed in terms of Thomsen's weak anisotropy parameters ε, γ & δ. A theory of frequency‐dependent seismic anisotropy in porous, fractured, media was able to predict the observed effect of viscosity and bulk modulus on ε and δ in water‐ and glycerin‐saturated samples, and the higher ε and δ values in air‐saturated samples. Theoretical predictions of fluid independent γ are also in agreement with the laboratory observations. We also observed the predicted polarisation cross‐over in shear‐wave splitting for wave propagation at 45° to the fracture normal as fluid viscosity and bulk modulus increases.     

Three-dimensional mapping of a landslide using a multi-geophysical approach: the Quesnel Forks landslide

A landslide located on the Quesnel River in British Columbia, Canada is used as a case study to demonstrate the utility of a multi-geophysical approach to subsurface mapping of unstable slopes. Ground penetrating radar (GPR), direct current (DC) resistivity and seismic reflection and refraction surveys were conducted over the landslide and adjacent terrain. Geophysical data were interpreted based on stratigraphic and geomorphologic observations, including the use of digital terrain models (DTMs), and then integrated into a 3-dimensional model. GPR surveys yielded high-resolution data that were correlated with stratigraphic units to a maximum depth of 25 m. DC electrical resistivity offered limited data on specific units but was effective for resolving stratigraphic relationships between units to a maximum depth of 40 m. Seismic surveys were primarily used to obtain unit boundaries up to a depth of >80 m. Surfaces of rupture and separation were successfully identified by GPR and DC electrical resistivity techniques.     

Fluidization pipes in volcaniclastic mass flows, Volcan Hudson, Southern Chile

The presence of fluidization pipes within pyroclastic sediments has been proposed as a criterion for differentiating these volcaniclastic deposits from those of epiclastic mass flows. Observations of pipe structures within low-temperature epiclastic mudflows produced by the 1971 eruption of Volcan Hudson, Southern Chile, demonstrate that this assumption is invalid and that the presence of pipes may only be utilized to interpret the precise mechanics of the fluidization process itself.     

The response of flow duration curves to afforestation

The hydrologic effect of replacing pasture or other short crops with trees is reasonably well understood on a mean annual basis. The impact on flow regime, as described by the annual flow duration curve (FDC) is less certain. A method to assess the impact of plantation establishment on FDCs was developed. The starting point for the analyses was the assumption that rainfall and vegetation age are the principal drivers of evapotranspiration. A key objective was to remove the variability in the rainfall signal, leaving changes in streamflow solely attributable to the evapotranspiration of the plantation. A method was developed to (1) fit a model to the observed annual time series of FDC percentiles; i.e. 10th percentile for each year of record with annual rainfall and plantation age as parameters, (2) replace the annual rainfall variation with the long term mean to obtain climate adjusted FDCs, and (3) quantify changes in FDC percentiles as plantations age. Data from 10 catchments from Australia, South Africa and New Zealand were used. The model was able to represent flow variation for the majority of percentiles at eight of the 10 catchments, particularly for the 10–50th percentiles. The adjusted FDCs revealed variable patterns in flow reductions with two types of responses (groups) being identified. Group 1 catchments show a substantial increase in the number of zero flow days, with low flows being more affected than high flows. Group 2 catchments show a more uniform reduction in flows across all percentiles. The differences may be partly explained by storage characteristics. The modelled flow reductions were in accord with published results of paired catchment experiments. An additional analysis was performed to characterise the impact of afforestation on the number of zero flow days (N_zero) for the catchments in group 1. This model performed particularly well, and when adjusted for climate, indicated a significant increase in N_zero. The zero flow day method could be used to determine change in the occurrence of any given flow in response to afforestation. The methods used in this study proved satisfactory in removing the rainfall variability, and have added useful insight into the hydrologic impacts of plantation establishment. This approach provides a methodology for understanding catchment response to afforestation, where paired catchment data is not available.