Abstract-We have investigated the porosity of a large number of chondritic interplanetary dust particles (IDPs) and meteorites by three techniques: standard liquidgas flow techniques, a new, noninvasive ultrasonic technique, and image processing of backscattered images. The latter technique is obviously best-suited to subkilogram sized samples. We have also measured the gas and liquid permeabilities of some chondrites by two techniques: standard liquidgas flow techniques, and a new, nondestructive pressure release technique. We find that chondritic IDPs have a somewhat bimodal porosity distribution. Peaks are present at 0 and 4% porosity; a tail then extends to 53%. Type 1-3 chondrite matrix porosities range up to 30%, with a peak at 2%. The bulk porosities for type 1-3 chondrites have the same approximate range as exhibited by the matrix, which indicates that other components of the bulk meteorites (including chondrules and aggregates) have the same average porosity as the matrix. These results reveal that the porosities of primitive materials at scales ranging from nanogram to kilogram are similar, which implies that similar accretion dynamics operated through 12 orders of size magnitude. Permeabilities of the investigated chondrites vary by several orders of magnitude, and there appears to be no simple dependence of permeability with degree of aqueous alteration, chondrite type or porosity.

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Dynamic loading of embankment, foundation and pavement structures results in particle breakage of the constituent granular materials, when the stresses imposed on their particles exceed their strength. This paper presents the results of a number of drained cyclic triaxial tests on loose, uniformly graded samples of Dogs bay carbonate sand. It is observed that particle breakage is dependent on stress level, cyclic stress ratio, and creep and is directly related to volumetric strain. Drained cycling increases volumetric strain and therefore more breakage occurs when larger numbers of cycles are imposed. The increase in particle breakage from one cycle to the next indicates that while particles may not be loaded to their full capacity in a given cycle, they can be crushed in subsequent cycles without any variation in the amplitude of cyclic loading.

This paper attempts to synthesise available information in parallel with recent work by Skipper et al (2005), who provide an updated understanding of the geology of the DBC.Having assessed the effects of sampling disturbance, the paper characterises the various formations and sub-units of the DBC. The interpreted material behaviour is related to observed engineering performance. It was found from the behaviour of earth retained structures that intact, clayey, DBC formations are 2 to 3 times stiffer than assessed from high quality laboratory tests on block samples. DBC is shown to be significantly stiffer than other well-characterised tills. Relatively inexpensive Multi Channel Surface Wave techniques (MASW) can give very reliable estimates of in situ small strain stiffness. High undrained triaxial compression strengths were measured and it appears that simple UU tests on high quality specimens give good results. Significant strength anisotropy was suggested by undrained triaxial extension strengths that were only 30% to 50% of the triaxial compression strengths. Field horizontal permeability values of the intact clayey till units have a representative mean of about 10 -9 m/s and when compared to laboratory values suggest that the material may exhibit some degree of anisotropy of permeability.Overall, the measured engineering parameters for the DBC are favourable for many construction projects. Further work is required in order to understand the in situ horizontal stress profile and the stiffness anisotropy of the till. From an associated wealth of borehole investigations, in-situ tests, laboratory tests, excavation exposures and monitored field performance, these projects have provided much more detailed information on the superficial deposits in Dublin.Technical data are now available from a concentration of such projects in Dublin, but these are not in the public domain and have not been interpreted and correlated on a (geological) formation-level scale. There are significant economic benefits in understanding the characteristics of the DBC as it underlies much of the city, see Figure 1. A parallel study is reported by Skipper et al (2005), which provides a more detailed understanding of the geology of the DBC, and serves as a backdrop to this paper.Much of the data are from the Dublin Port Tunnel Project (DPT, Site 1), which has been augmented by information from other important developments, as listed below and shown in Figure 1. Site 1: Dublin Port TunnelThe central part of the DPT project comprises 12m external diameter twin bored tubes, with lengths of cut and cover tunnel at either end. The project involves the excavation of about 1.5 million cubic metres of soil and rock. Although project wide information is 4 considered, focus in this paper is placed on experience gained at the northern cut and cover section and shaft WA2, where excavations were carried out in the superficial deposits to about 25m depth, see Figure 1. Further details of the project and a review of case histories associated with it ar...

Abstract:Recent

Publication informationMarine Geology, 226 (1-2): 145-165Publisher Elsevier A cost efficient way of investigating shallow sediments and for collecting soils data for 2 many offshore geotechnical problems, e.g. anchoring of floating structures with suction 3 piles or evaluation of submarine slope stability, is to carry out seabed sampling to say 4 25 m below seabed and in addition perform seabed CPTUs to say 40 m. Based on a 5 review of data collated from the literature and from in house project experience at the 6 Norwegian Geotechnical Institute it was found that Kullenberg type piston core samples 7give poor recovery and samples, which are increasingly disturbed as penetration 8increase. This means that laboratory tests on these samples will give results that are not 9 representative of in situ conditions and will give incorrect parameters for foundation 10 design. Many different factors control the quality of the samples recovered but the need 11 for an effectively stationary piston a core retainer and improvements to the physical 12 sampler parameters, e.g. diameter / wall thickness ratio, cutting edge angle, inside and 13 outside friction are perhaps the most critical. The importance of each of these factors is 14 discussed in detail in addition to the need for instrumentation and the way to penetrate 15 the sampler. Recommendations are given in terms of criteria for the design of a new 16 sampler, which the authors feel will give better results than most samplers used in 17 practice today.

Publication information Landslides, 3 (1): 51-61Publisher Springer were used to model the slide and it was found that the features observed on site could easily be reproduced. These included confirmation that thin layers of peat could be stable on steep slopes but the margin of safety reduces rapidly under elevated pore pressure conditions. As was observed in the field, the analyses suggested the most vulnerable zone was the upper layer of weathered rock but that slides could occur in the peat if its thickness was appreciable. Careful site characterization is vital in such studies. Here efforts have been made to understand the effect of fibres on the peat strength and some sensitivity analyes have been performed to assess the critical engineering parameters of the peat.

Publication informationGéotechnique, 60 (11) (Kleven et al., 1986), and the normalised change in void ratio, Δe/e 0 (Lunne et al., 1997). Most of these approaches, however, require reconsolidation back to in-situ stresses, a process that may require a number of days of testing. This is a particular problem for offshore sampling, where rapid assessment of sample quality could significantly improve efficiency.A number of studies in recent years have observed that laboratory determined shear wave velocities (V s ), and corresponding small strain shear modulus, G max :are generally lower than the in-situ equivalent, and have attributed this difference to sampling disturbance (Shiwakoti et al. 2000; Porcino & Ghionna 2004). These studies involved reconsolidation of laboratory specimens back to their in-situ stress, before measurement of V s . For a quick assessment of sample quality, Hight & Leroueil (2003), Nash (2003) and Landon & DeGroot (2007) used portable bender element kits to measure V s , immediately after removal from the subsurface on unconfined samples. Hight & Leroueil (2003) also suggested simultaneous soil suction (u r ) measurements, enabling differences between unconfined and in-situ stress state to be taken into account.The use of suction measurements for sample quality evaluation was introduced by Ladd & Lambe (1963), who proposed using the ratio u r /σ' ps to evaluate disturbance, where σ' ps is the effective stress for a "perfect" sample. Calculation of σ' ps is, however, not straightforward and requires knowledge of Skempton's pore pressure parameter, A u 3 (consequent to the release of deviatoric stress), and K 0 (coefficient of earth pressure at rest). Authors such as Tanaka et al. (1996) DESCRIPTION OF SITES AND TECHNIQUESThe soft soils investigated during this study were located at Onsøy in Norway and at Ballinasloe and Bogganfin in Ireland (Table 1). A number of samplers of varying quality were used, the dimensions and features of which are given in Table 2. Onsøy, NorwayThe Onsøy test site is the main soft clay research site used by the Norwegian Geotechnical Institute (NGI). Onsøy is underlain by an extensive deposit of uniform marine clay, as described by Lunne et al. (2003). 4In this paper comparisons are made between Sherbrooke block, 76mm steel and 54mm composite piston samples at two depths (approximately 10m and 13m). The Scandinavian displacement approach was adopted for the piston sampling, wherein the sampler (with the piston in front of the sampling tube) was pushed down to the desired depth without preboring. Ballinasloe and Bogganfin, IrelandThe Ballinasloe and Bogganfin test sites (Donohue, 2005), located in the midlands of Ireland, are both underlain by post glacial lacustrine clay. Although generally uniform, the soils contain some thin silt laminations (1mm to 2mm). Testing TechniquesIn-situ V s measurements were obtained from the seismic cone (SCPT -Eidsmoen et al., 1985) Measurements of V s and u r were performed on all samples either immediately after extrusion...