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This paper presents a numerical investigation of the effect of foundation size on the response of shallow circular foundations on siliceous and calcareous sands. The study is based on the predictive capabilities of the MIT-S1 soil model for simulating both the compression and shear behaviors of natural sands over a wide range of densities, [K.sub.0] values and confining pressures. The paper highlights the variations in the deformation mechanisms for the siliceous and calcareous sands cases. The assessment of the bearing capacity factor, [N.sub.[gamma]], is examined, showing a dramatic decrease in the values with increasing foundation size for the case of footings on calcareous sands, eventually converging to a terminal [N.sub.[gamma]] value. At this stage the sand resistance is insensitive to variations in initial density and foundation size because the sand tends to loose its initial characteristics due to grain crushing, leading the material rapidly toward ultimate conditions. In the silicious sand case, it is found that, eventually, for extremely large footing diameters, the deformation mechanism progresses toward a punching shear mechanism, rather than the classical rapture pattern accompanied by surface heave as employed in current bearing capacity equations. A dimensional transition between the failure mechanisms can clearly be defined, referred to as a 'critical size' in the [N.sub.[gamma]]-D relationship. CE Database subject headings: Sand; Calcareous soils; Silica; Shallow foundations; Size effect; Finite element method; Numerical analysis.

A CPT-based method is presented for estimating the self-weight penetration and suction required during the installation of suction caissons in medium dense to dense sand. Existing methods, although fundamental in nature, suffer from the difficulty in estimating key input parameters such as an appropriate bearing factor for the tip resistance and frictional coefficients for skirt friction. Instead, the proposed method is based directly on the cone resistance profile, starting with the Det norske Veritas approach for calculating the installation resistance of skirted foundations. The approach is modified to include a simple linear reduction in end beating on the skirt tips and internal friction with the level of suction, with those components of resistance assumed to reduce to zero once the suction reaches the critical level corresponding to hydraulic failure of the soil plug. The method is coupled with a seepage model so that, for a given pumping rate, the penetration and corresponding resistance can both be expressed as a function of time. Results of calculations with this complete model are shown to compare well with data from centrifuge model tests and with published data from suction caisson installations. CE Database subject headings: Suction; Caissons; Sand; Cone penetration; Installation; Pumps; Centrifuge models.

This paper discusses the development of a framework for classifying soil using normalized piezocone test (CPTU) data from the corrected tip resistance ([q.sub.t]) and penetration pore-water pressure at the shoulder ([u.sub.2]). Parametric studies for normalized cone tip resistance (Q = [q.sub.cnet]/[[sigma]'.sub.v0]) and normalized excess pressures ([DELTA][u.sub.2]/[[sigma]'.sub.v0]) as a function of overconsolidation ratio (OCR=[[sigma]'.sub.vy]/[[sigma]'.sub.v0]) during undrained penetration are combined with piezocone data from clay sites, as well as results from relatively uniform thick deposits of sands, silts, and varietal clays from around the globe. The study focuses on separating the influence of yield stress ratio from that of partial consolidation on normalized CPTU parameters, which both tend to increase Q and decrease the pore pressure parameter ([B.sub.q] = [DELTA][u.sub.2]/[q.sub.cnet]). The resulting recommended classification chart is significantly different from existing charts, and implies that assessment of data in Q-[DELTA][u.sub.2]/[[sigma]'.sub.v0] space is superior to Q-[B.sub.q] space when evaluating piezocone data for a range of soil types. Still, there are zones of overlap for silty soils and heavily overconsolidated clays, thus requiring that supplementary information to Q and [DELTA][u.sub.2]/[[sigma]'.sub.v0] be obtained in unfamiliar geologies, including variable rate penetration tests, dissipation tests, CPT friction ratio, or soil sampling. CE Database subject headings: Soil classification; Cone penetration tests; Silts; Sand; Clays; Overconsolidated soils.

The behavior of strip and circular plate anchors during vertical pullout in uniform and normally consolidated clays was studied in this paper by means of small strain and large deformation finite-element analyses. Both fully bonded (attached), and 'vented' (no suction on rear face), anchors were considered. The current numerical results were compared with existing laboratory test data, finite-element results, and analytical solutions. This study showed that, in small strain analysis, the scatter of existing data was mainly due to the effect of soil stiffness. In large deformation analysis, when soil and anchor base were attached with suction, the pullout capacity factor formed a unique curve independent of the soil strength ([s.sub.u]), soil effective unit weight ([gamma]') and anchor size (B=width of strip anchor and D=diameter of circular anchor). The transitional embedment depth ratio, [H.sub.SD]/B or [H.sub.SD]/D, (where [H.sub.SD]=transition depth between shallow and deep embedment) was 1.4 for a strip anchor and 0.75 for a circular anchor. The ultimate pullout capacity factors ([N.sub.c]) for deep embedment were 11.6 and 11.7 for smooth and rough strip anchors and 13.1 and 13.7 for smooth and rough circular anchors, respectively. However, when the anchor base was vented, the soil stayed attached to the anchor base for deep embedment, and the pullout capacity was therefore the same as for the attached anchor. The separation depth ratio, [H.sub.S]/B or [H.sub.S]/D, (where [H.sub.s]=embedment depth at which the soil and anchor base separated) was found to increase linearly with the normalized strength ratio, [s.sub.u]/[gamma]' B or [s.sub.u]/[gamma]'D. CE Database subject headings: Anchors; Pull out resistance; Soil strength; Deep water; Finite element method; Deformation.

The study is on the electrokinetic strengthening of caisson anchors embedded in offshore calcareous sand. The effects of electrode configuration on the effectiveness of electrokinetic treatment are investigated based on electric field analysis and are verified by results from a series of large scale laboratory tests on caisson models of 200 mm diam and 400 mm height, embedded in calcareous sand submerged under seawater. The electrokinetic treatment generates cementation of soil solids as well as bonding between soil and caisson shafts, which leads to increases in the side resistance and overall pullout resistance. The effectiveness of electrokinetic treatment is directly related to the electric field intensity. A linear relationship is observed between the increase in the side resistance and energy consumption. The study shows that the effectiveness of electrokinetic treatments can be maximized by the optimization of the electric field distribution through the electrode configuration. DOI: 10.1061/(ASCE)1090-0241(2008)134:3(352) CE Database subject headings: Soil stabilization; Caissons; Anchors; Cements; Soil-structure interaction; Pull-out resistance.

Suction caissons are increasingly being used for offshore anchors because of their ease of installation. However, for soil profiles that have sand overlain by layers of silt, there are reasons to believe that it may not be possible to install suction caissons. This may happen because the low permeability of the silt will create a hydraulic blockage, and thus diminish the upward hydraulic gradient required to reduce the penetration resistance in the sand to enable caisson penetration. The tendency of the silt to be sucked up, and its effect on the underlying sand, are not clearly understood. Furthermore, the blockage by the silt layer may be less than if a clay layer is present. This is because scouring of the silt may occur, allowing an upward seepage gradient to develop, and hence causing a reduction in penetration resistance. A series of suction caisson installation tests have been conducted in a geotechnical centrifuge to provide data on the penetration resistance and mechanisms for soil profiles where silt layers are present, either on top, or interbedded between layers of sand. In these tests, the thickness of the silt layer and its depth below the sand surface have also been varied. It has been found that if silt overlies the sand, a larger suction force is required for installation than when installation occurs in homogeneous sand, but that this force is still much smaller than the soil resistance when the caisson is pushed into the ground. When a silt layer is present, the suction pressures are observed to follow a similar trend that is independent of the position and thickness of the silt layer. Scouring of silt was evident in the tests, and significant upward movement of the soil plug inside the caisson was observed in all soil profiles when silt layers were present. The plug height was seen to reduce after the suction was turned off, suggesting that the resulting heave was unstable. DOI: 10.1061/(ASCE)1090-0241(2007)133:10(1183) CE Database subject headings: Suction; Caissons; Installation; Offshore structures; Layered soils; Sand; Silts.

Abstract: Large deformation finite element (LDFE) analyses were performed to study the installation of caissons by suction and jacking in normally consolidated clay. The penetration of the caisson wall was [...]

Background: Meniscal tears in the avascular zones do not heal. Although tissue-engineering approaches using cells seeded onto scaffolds could expand the indication for meniscal repair, harvesting autologous cells could cause [...]

This paper discusses the effects of penetration rate on the penetration resistance in soft clay for various shaped penetrometers (cone, T-bar, ball, and plate) and for T-bars with different aspect ratios. Constant rate ('normal') and variable rate ('twitch') penetration tests, where the penetration rate was successively halved over eight steps with the penetrometer advanced by one or two diameters in each step, were undertaken in the beam centrifuge at the University of Western Australia. The tests were conducted on samples reconstituted from clay collected from the Burswood site in Western Australia. The twitch tests showed higher penetration resistance than the corresponding normal tests after the penetration rate had been reduced by a factor of 16 due to cumulative effects of partial consolidation. The penetration rate at which the resistance started to increase due to partial consolidation was used to estimate the consolidation coefficient, [c.sub.v], of the reconstituted clay. The interpreted [c.sub.v] values were similar to values estimated from other consolidation data, both in the centrifuge and from laboratory Rowe cell and constant rate of strain consolidation tests. In addition, results from in situ twitch tests at the Burswood site were examined to evaluate viscous effects on the penetration resistance. DOI: 10.1061/(ASCE)1090-0241(2006)132:9(1188) CE Database subject headings: Centrifuge model; Clays; Loading rate; Penetration resistance; Penetration tests; Viscosity.

Ref.: Can. Geotech. J. 52(6): 682-693 (2015) dx.doi.org/10.1139/cgj-2014-0120. On page 689, right column, eighth line of the second paragraph, replace 'Mmax/B2Lsu = 4.17' with '[M.sub.max]/[B2Ls.sub.u] = 2.05'. Received 20 July [...]

There is little information in the geotechnical literature regarding the influence of the type of cement on the engineering behavior of cemented soils. This paper explores the mechanical behavior of a calcareous soil under triaxial loading after treatment with different types of cement, namely Portland cement, gypsum, and calcite. To identify the specific effects of each cement type a parametric study was undertaken, where factors such as density and unconfined compressive strength were maintained constant for each cementing agent. Samples of the cemented soil were examined under optical and electron microscopy to understand the bond mechanism created by each cement. Results from triaxial testing have shown that, despite having the same unconfined compressive strength and density, the effective stress paths and postyield response are significantly different, mainly because of the different volumetric response upon shearing. Samples prepared using Portland cement showed ductile yield and strong dilation afterwards; calcite and gypsum-cemented samples exhibited brittle yield, generally followed by contractive behavior. The paper discusses the results and explains the reasons behind the differences in the mechanical response. DOI: 10.1061/(ASCE) 1090-0241(2002) 128:6(520) CE Database keywords: Calcareous soils; Portland cements; Contraction; Triaxial tests; Gypsum.

The results of centrifuge modeling of pipe-soil interaction for shallowly embedded offshore pipelines are presented. A non-associated bounding surface model is constructed in vertical-horizontal (V-H) load space on the basis of test data and the theory of plasticity to simulate the response of a pipeline embedded in sandy soil under combined (vertical and horizontal) monotonic loading, taking into account possible pre-loading effects. The model needs nine parameters that can be back calculated from model or field tests and in some cases estimated theoretically. It provides a suitable basis for modeling the load-displacement response of shallowly embedded offshore pipelines. The model reproduces the key features of the load-displacement response of pipelines observed in centrifuge model tests. In particular, the adoption of bounding surface plasticity allows a gradual transition from elastic to plastic response to be simulated and the introduction of a non-associated flow rule allows the model to predict the strain-softening behavior of pipes under horizontal loading. The lateral breakout resistance predicted by the model agrees very well with experimental data. CE Database keywords: Offshore pipelines; Calcareous sand; Bounding surface; Models; Plasticity.