Efficacy of preloading combined with prefabricated vertical band drains in improving a clayey silt stratum in situ

2006 ◽  
Vol 10 (4) ◽  
pp. 147-152
Author(s):  
V. K. Chakravarthi ◽  
B. R. Phanikumar
Keyword(s):  
Vertical Band ◽  
Clayey Silt

Tassement et consolidation au dégel d'un silt argileux à Kangiqsualujjuaq

1991 ◽  
Vol 28 (5) ◽  
pp. 678-689
Author(s):  
Serge Leroueil ◽  
Guy Dionne ◽  
Michel Allard
Keyword(s):  
Key Words ◽  
Physical Characteristics ◽  
Pore Pressures ◽  
Clayey Silt ◽  
Excess Pore Pressures ◽  
Excess Pore

The physical characteristics, the compressibility, and the consolidation of a permafrost clayey silt of Kangiqsualujjuaq, Quebec, have been studied, in the laboratory and in the field, by melting the permafrost in the foundation of an excavation. It appears that the values of the thawing settlement parameter (A0) obtained in the laboratory and in the field coincide perfectly with one another, and with those found in the literature for the same type of soil. It has also been observed, on that site, that the thawing of the permafrost, even though ice-rich, does not generate excess pore pressures. Key words: permafrost, compressibility, consolidation, laboratory, in situ. [Journal translation]

scholarly journals Accelerated gravity testing of aquitard core permeability and implications at formation and regional scale

2015 ◽  
Vol 12 (3) ◽  
pp. 2799-2841
Author(s):  
W. A. Timms ◽  
R. Crane ◽  
D. J. Anderson ◽  
S. Bouzalakos ◽  
M. Whelan ◽  
...  
Keyword(s):  
Hydraulic Conductivity ◽  
Preferential Flow ◽  
Fluid Velocity ◽  
Regional Scale ◽  
Geotechnical Centrifuge ◽  
Regional Flow ◽  
Clayey Silt ◽  
Vertical Hydraulic Conductivity ◽  
Core Permeability

Abstract. Evaluating the possibility of leakage through low permeability geological strata is critically important for sustainable water supplies, the extraction of fuels from strata such as coal beds, and the confinement of waste within the earth. The current work demonstrates that relatively rapid and reliable hydraulic conductivity (K) measurement of aquitard cores using accelerated gravity can inform and constrain larger scale assessments of hydraulic connectivity. Steady state fluid velocity through a low K porous sample is linearly related to accelerated gravity (g-level) in a centrifuge permeameter (CP) unless consolidation or geochemical reactions occur. The CP module was custom designed to fit a standard 2 m diameter geotechnical centrifuge (550 g maximum) with a capacity for sample dimensions of 30 to 100 mm diameter and 30 to 200 mm in length, and a maximum total stress of ~2 MPa at the base of the core. Formation fluids were used as influent to limit any shrink–swell phenomena which may alter the permeability. Vertical hydraulic conductivity (Kv) results from CP testing of cores from three sites within the same regional clayey silt formation varied (10−7 to 10−9 m s−1, n = 14). Results at one of these sites (1.1 × 10−10 to 3.5 × 10−9 m s−1, n = 5) that were obtained in < 24 h were similar to in situ Kv values (3 × 10−9 m s−1) from pore pressure responses over several weeks within a 30 m clayey sequence. Core scale and in situ Kv results were compared with vertical connectivity within a regional flow model, and considered in the context of heterogeneity and preferential flow paths at site and formation scale. More reliable assessments of leakage and solute transport though aquitards over multi-decadal timescales can be achieved by accelerated core testing together with advanced geostatistical and numerical methods.

scholarly journals Accelerated gravity testing of aquitard core permeability and implications at formation and regional scale

2016 ◽  
Vol 20 (1) ◽  
pp. 39-54 ◽  
Author(s):  
W. A. Timms ◽  
R. Crane ◽  
D. J. Anderson ◽  
S. Bouzalakos ◽  
M. Whelan ◽  
...  
Keyword(s):  
Preferential Flow ◽  
Fluid Velocity ◽  
Regional Scale ◽  
Geotechnical Centrifuge ◽  
Clayey Silt ◽  
Vertical Hydraulic Conductivity ◽  
Geochemical Reactions ◽  
Set Up ◽  
Core Permeability

Abstract. Evaluating the possibility of leakage through low-permeability geological strata is critically important for sustainable water supplies, the extraction of fuels from coal and other strata, and the confinement of waste within the earth. The current work demonstrates that relatively rapid and realistic vertical hydraulic conductivity (Kv) measurements of aquitard cores using accelerated gravity can constrain and compliment larger-scale assessments of hydraulic connectivity. Steady-state fluid velocity through a low-K porous sample is linearly related to accelerated gravity (g level) in a centrifuge permeameter (CP) unless consolidation or geochemical reactions occur. A CP module was custom designed to fit a standard 2 m diameter geotechnical centrifuge (550 g maximum) with a capacity for sample dimensions up to 100 mm diameter and 200 mm length, and a total stress of  ∼  2 MPa at the base of the core. Formation fluids were used as influent to limit any shrink–swell phenomena, which may alter the permeability. Kv results from CP testing of minimally disturbed cores from three sites within a clayey-silt formation varied from 10−10 to 10−7  m s−1 (number of samples, n = 18). Additional tests were focussed on the Cattle Lane (CL) site, where Kv within the 99 % confidence interval (n = 9) was 1.1 × 10−9 to 2.0 × 10−9 m s−1. These Kv results were very similar to an independent in situ Kv method based on pore pressure propagation though the sequence. However, there was less certainty at two other core sites due to limited and variable Kv data. Blind standard 1 g column tests underestimated Kv compared to CP and in situ Kv data, possibly due to deionised water interactions with clay, and were more time-consuming than CP tests. Our Kv results were compared with the set-up of a flow model for the region, and considered in the context of heterogeneity and preferential flow paths at site and formation scale. Reasonable assessments of leakage and solute transport through aquitards over multi-decadal timescales can be achieved by accelerated core testing together with complimentary hydrogeological monitoring, analysis, and modelling.

Seismic strengthening of diatom-rich sediments: A comparison of slope sediments from Chilean lakes and the Japan Trench margin

2020 ◽  
Author(s):  
Jasper Moernaut ◽  
Gauvain Wiemer ◽  
Ting-Wei Wu ◽  
Ariana Molenaar ◽  
Achim Kopf ◽  
...  
Keyword(s):  
Shear Strength ◽  
Sediment Cores ◽  
Hollow Structure ◽  
Japan Trench ◽  
Submarine Landslides ◽  
Compression Tests ◽  
Seismic Strengthening ◽  
Active Margins ◽  
Clayey Silt

&lt;p&gt;Earthquakes are a main trigger of subaqueous landslides and surficial sediment remobilization at ocean margins and lake basins. If the earthquake loading is insufficient to lead to sediment failure, the subsequent dewatering and inherent compaction may enhance the shear strength of sedimentary slopes, a process termed &amp;#8222;seismic strengthening&amp;#8220;, which is believed to be especially relevant for the upper 10s of meters. This mechanism has been suggested to explain the observed paucity of submarine landslides on active margins when compared to the short recurrence of strong earthquakes in such settings. However, only few field studies were dedicated on this topic and little is known about which settings are especially prone to seismic strengthening.&lt;/p&gt;&lt;p&gt;Here, we present geotechnical data from diatom-rich sedimentary slopes in Chilean lakes and at the Japan Trench margin. We use the overburden-normalized undrained shear strength as an indicator of consolidation state. In Chile, this data is derived from in-situ dynamic cone penetrometer measurements, whereas the Japan data is obtained by lab vane shear tests on sediment cores. Both settings show extremely elevated shear strength of about ~5-10 times higher than expected for normally-consolidated sediment in the upper meters of a sequence. Significant overconsolidation is confirmed by one-dimensional compression tests, providing overconsolidation ratios of ~2-8 (Chilean lakes) and 4-9 (Japan Trench). For each setting, the shear strength profiles of sites with different sedimentation rates show very similar trends when they are normalized over the sediment age instead of over overburden stress. As older sediments experienced more earthquakes, this apparent age-dependency may form a new argument supporting the hypothesis of seismic strengthening. Following previous lab experiments on mixtures of diatoms and clayey-silt, we postulate that a high susceptibility to seismic strengthening in both settings is caused by the abundance of diatom frustules which are typically characterized by a high particle interlocking and surface roughness. On the Japan Trench margin, biogenic opal forms ~15% in dry weight, and given the hollow structure of diatom frustules, we infer that diatoms take up a considerable space in the in-situ sediment texture. We conclude that seismically active margins with diatom-rich sediments have a reduced susceptibility to submarine landslide hazards.&lt;/p&gt;

Laboratory and in situ studies on a compacted clayey silt fill

2012 ◽  
Vol 165 (2) ◽  
pp. 107-119 ◽  
Author(s):  
Marcio S. S. Almeida ◽  
Marcelo G. Rios Filho ◽  
Marcos M. Futai ◽  
Mario Riccio Filho
Keyword(s):  
In Situ Studies ◽  
Clayey Silt

scholarly journals Vertical hydraulic conductivity of a clayey-silt aquitard: accelerated fluid flow in a centrifuge permeameter compared with in situ conditions

2014 ◽  
Vol 11 (3) ◽  
pp. 3155-3212 ◽  
Author(s):  
W. A. Timms ◽  
R. Crane ◽  
D. J. Anderson ◽  
S. Bouzalakos ◽  
M. Whelan ◽  
...  
Keyword(s):  
Hydraulic Conductivity ◽  
Centrifugal Force ◽  
Stress Conditions ◽  
K Value ◽  
Geotechnical Centrifuge ◽  
In Situ Conditions ◽  
Clayey Silt ◽  
Vertical Hydraulic Conductivity ◽  
Permeameter Tests

Abstract. Evaluating the possibility of leakage through low permeability geological strata is critically important for sustainable water supplies, extraction of fuels from strata such as coal beds, and confinement of waste within the earth. Characterizing low or negligible flow rates and transport of solutes can require impractically long periods of field or laboratory testing, but is necessary for evaluations over regional areas and over multi-decadal timescales. The current work reports a custom designed centrifuge permeameter (CP) system, which can provide relatively rapid and reliable hydraulic conductivity (K) measurement compared to column permeameter tests at standard gravity (1g). Linear fluid velocity through a low K porous sample is linearly related to g-level during a CP flight unless consolidation or geochemical reactions occur. The CP module is designed to fit within a standard 2 m diameter, geotechnical centrifuge with a capacity for sample dimensions of 30 to 100 mm diameter and 30 to 200 mm in length. At maximum RPM the resultant centrifugal force is equivalent to 550g at base of sample or a total stress of ~2 MPa. K is calculated by measuring influent and effluent volumes. A custom designed mounting system allows minimal disturbance of drill core samples and a centrifugal force that represents realistic in situ stress conditions is applied. Formation fluids were used as influent to limit any shrink-swell phenomena which may alter the resultant K value. Vertical hydraulic conductivity (Kv) results from CP testing of core from the sites in the same clayey silt formation varied (10−7 to 10−9 m s−1, n = 14) but higher than 1g column permeameter tests of adjacent core using deionized water (10−9 to 10−11 m s−1, n = 7). Results at one site were similar to in situ Kv values (3 × 10−9 m s−1) from pore pressure responses within a 30 m clayey sequence in a homogenous area of the formation. Kv sensitivity to sample heterogeneity was observed, and anomalous flow via preferential pathways could be readily identified. Results demonstrate the utility of centrifuge testing for measuring minimum K values that can contribute to assessments of geological formations at large scale. The importance of using realistic stress conditions and influent geochemistry during hydraulic testing is also demonstrated.

Lacustrine ostracodes in the Late Pleistocene Sunnybrook diamicton of southern Ontario, Canada

1987 ◽  
Vol 24 (11) ◽  
pp. 2330-2335 ◽  
Author(s):  
J. A. Westgate ◽  
F.-J. Chen ◽  
L. D. Delorme
Keyword(s):  
Late Pleistocene ◽  
Laurentide Ice Sheet ◽  
Silty Clay ◽  
Southern Ontario ◽  
Quaternary Stratigraphy ◽  
Clayey Silt ◽  
Low Diversity ◽  
Excellent Preservation

Two opposing interpretations have been made on the depositional origin of the Late Pleistocene Sunnybrook diamicton in the Metro-Toronto region of southern Ontario. The traditional view holds this deposit to be a till, but more recent arguments advocate a glaciolacustrine origin by suspension deposition and ice rafting.The discovery of a low-diversity ostracode fauna consisting of Candona subtriangulata, Candona caudata, and Darwinula stevensoni in the Sunnybrook diamicton suggests a lacustrine origin. Excellent preservation of thin, fragile shells and a mixture of juveniles and adults in sediments of varying texture—clayey silt to silty clay—indicate that there has been little winnowing or selective sorting and that the ostracodes are in situ. Indications are that the Sunnybrook diamicton was deposited in a large, deep, and cold lake.These new palaeontological observations call for a reassessment of the Quaternary stratigraphy of the Ontario Basin and suggest that the Laurentide Ice Sheet in the eastern Great Lakes region was less extensive during the early part of the Wisconsin Glaciation than previously assumed.

Hydraulic conductivity and diffusion monitoring of the Keele Valley Landfill liner, Maple, Ontario

1993 ◽  
Vol 30 (1) ◽  
pp. 124-134 ◽  
Author(s):  
K. S. King ◽  
R. M. Quigley ◽  
F. Fernandez ◽  
D. W. Reades ◽  
A. Bacopoulos
Keyword(s):  
Hydraulic Conductivity ◽  
Major Ions ◽  
Geometric Mean ◽  
Actual Performance ◽  
Landfill Liner ◽  
Monitoring Programs ◽  
Field Diffusion ◽  
Clayey Silt ◽  
Sand And Gravel

The 99-ha Keele Valley Landfill is located in a former sand and gravel pit at Maple, Ontario. The base and sides of the pit are lined with a minimum of 1.2 m of excavated clayey silt till recompacted to achieve a design hydraulic conductivity of 1 × 10−8 cm/s or less. Extensive construction controls and monitoring programs have been implemented to determine the hydraulic conductivity and advective performance of the liner. A total of 267 postcompaction laboratory hydraulic conductivity (k) tests indicated that the first two stages of the liner had a geometric mean k of 7.7 × 10−9 cm/s. Calculations of in situ hydraulic conductivity based on lysimeter effluent collection rates show decreases in k to field values close to the laboratory values. In situ electrical conductivity sensors and lysimeter effluent chemistry measurements have monitored the advance of leachate-derived chemicals into the liner. Concurrent field verification by liner exhumation and chemical analysis has confirmed the importance of diffusion as the dominant migration mechanism through this low-k liner. Similar concentration trends for major ions have been observed in the field lysimeter effluents, effluents from laboratory liner–leachate compatibility tests, and pore water extracted from core samples of sections of exhumed liner exposed to leachate. The multicomponent field and laboratory testing and monitoring programs have shown good cross-agreement, and the actual performance of the liner has been close to preconstruction predictions. Key words : landfill, clayey liner, field hydraulic conductivity, field diffusion, municipal solid waste leachate, field lysimeter test, laboratory hydraulic conductivity, liner–leachate compatibility.

Behavior of Instrumented Omega Pile in Porous Soil

2014 ◽  
Vol 1030-1032 ◽  
pp. 732-735
Author(s):  
Paulo J.R. Albuquerque ◽  
Osvaldo de Freitas Neto ◽  
Jean R. Garcia
Keyword(s):  
Tropical Soils ◽  
Soil Parameters ◽  
Silty Clay ◽  
Geometric Conditions ◽  
Viable Solution ◽  
Clayey Silt ◽  
Load Tests ◽  
Numerical Finite Element ◽  
Experimental Values

Results obtained from in-situ load tests carried out on omega displacement piles sunk in a porous, lateritic and unsaturated soil deposit, are analyzed in this paper. Three slow-maintained load tests were performed on deep instrumented piles with a diameter of 0.37 m and around 12 m long. The soil deposit consists of a superficial, silty clay “porous” layer 6 m thick. Under this layer there is a lateritic stratum 10 m thick, geotechnically consisting of a residual clayey silt. The results of the field load tests yielded a maximum pile load (average for the tests) of 1428 kN, which is twice as high as corresponding experimental values from standard bored piles with similar geometric conditions. Numerical finite element analyses, were performed in order to back-analyze the geotechnical soil parameters for a post-execution pile condition. The results permitted a better understanding of the improvement of the subsoil given the intrinsic execution characteristics of this particular pile. It was also possible to note that omega displacement piles have great potential to become an economically viable solution in tropical soils, given the enhanced behavior of such piles when compared to alternative techniques.

Rendez vous with Saturn's rings

1984 ◽  
Vol 75 ◽  
pp. 743-759 ◽  
Author(s):  
Kerry T. Nock
Keyword(s):  
Solar Energy ◽  
Electric Propulsion ◽  
Power Source ◽  
Propulsion System ◽  
Low Thrust ◽  
Ring Plane ◽  
The Earth ◽  
Total Impulse ◽  
Saturn's Rings

ABSTRACTA mission to rendezvous with the rings of Saturn is studied with regard to science rationale and instrumentation and engineering feasibility and design. Future detailedin situexploration of the rings of Saturn will require spacecraft systems with enormous propulsive capability. NASA is currently studying the critical technologies for just such a system, called Nuclear Electric Propulsion (NEP). Electric propulsion is the only technology which can effectively provide the required total impulse for this demanding mission. Furthermore, the power source must be nuclear because the solar energy reaching Saturn is only 1% of that at the Earth. An important aspect of this mission is the ability of the low thrust propulsion system to continuously boost the spacecraft above the ring plane as it spirals in toward Saturn, thus enabling scientific measurements of ring particles from only a few kilometers.

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