Thick Clay Deposits Research Articles

Statistical approach to identify variables predicting sulphide clay occurrence in southern Finland

Acid sulphate soil and sulphide-bearing sediments cause various challenges in construction projects and land use planning, as well as harmful environmental effects. Fine-grained sulphide sediments were mainly formed in coastal areas during the Litorina Sea water phase at approximately 7000 BP in the capital region of Finland, but not all these sediments contain sulphide clay. In this study, environmental and material property variables related to the depositional conditions of sulphide clay were selected for statistical analyses to find their association with the occurrence of sulphide. The datasets consisted of sulphide investigations by the City of Espoo, the City of Helsinki, and the Geological Survey of Finland. Statistically significant associations were found in the study area between the occurrence of sulphide and enumerative variables (i.e., sediment organic content, total clay depth, topographic class in the Litorina Sea phase, and water depth) in the Litorina Sea phase. Locations where sulphide clay is especially likely to occur consist of organic-rich (≥ 2%) thick clay (≥ 15 m) deposits in a topographically narrow depression with deep Litorina water (≥ 30 m), or where there is a moderate depth clay (3–5 m) in a local depression with shallow Litorina water (10–20 m). The best individual predictor for sulphide clay occurrence in the study area was found to be the sediment organic content, and, together with sediment water content, these variables very accurately predicted the occurrence of sulphide clay. In addition, clay depth is a very good predictor and, together with the topographic class narrow depression and the Litorina water depth or current elevation, can be used to predict sulphide occurrence.

The Tiller-Flotten research site: Geotechnical characterization of a very sensitive clay deposit

The Tiller-Flotten research site was developed through the Norwegian GeoTest site (NGTS) project. The site consists of a more than 50 m thick marine clay deposit. The top 7.5 m of the deposit shows a low to medium sensitivity, while sensitivity increases up to approximately 200 from 7.5 to 20 m below the ground surface. A wide variety of in situ and laboratory data have been acquired to investigate the geotechnical, geological and geophysical properties of the material. The sensitive clay shows low to medium plasticity and a liquidity index (IL) above 1.6. It shows some overconsolidation (OCR ≈ 1.5-3.0) linked to the glacial history of the area. Its strength and stiffness properties show good agreement with some well-known correlations for sensitive clays. Anisotropy in undrained shear strength is also similar to other sensitive clays of Norway. It is hoped that the next years will see an increased use of this benchmark test site at Tiller-Flotten. The site can be used as a research tool, as training and teaching facilities and as ground for development of new soil models, testing of new investigation methods and further advance the state-of-the-art in sensitive clay material.

An observational method for consolidation analysis of the PVD-improved subsoil

Surcharge preloading together with prefabricated vertical drains (PVDs) have been widely used to improve properties of thick clay deposits. To assess the performance of soil improvement works, the average degree of consolidation needs to be estimated. A curve fitting formula is proposed in this paper to simulate the degree of consolidation versus a non-dimensional time factor relationship. The proposed formula fits the theoretical consolidation solutions well with a regression coefficient R2 larger than 0.9996 and an error of less than 1.2%. Based on the formula, a modified Asaoka's observational method is proposed to predict the ultimate settlement and calculate the coefficient of consolidation using field settlement monitoring data. The effectiveness of the proposed observational method has been verified using some well-documented case histories. Comparisons between the proposed method and the Asaoka's method indicate that the proposed method will give a less than 1.0% higher ultimate settlement than that by the Asaoka's method and the proposed method is able to predict the ch value with the consideration of both vertical and horizontal flow through the ratio of time factor in horizontal and vertical direction νhv.

Back-analysis of geotechnical parameters on PVD-improved ground in the Mekong Delta

This study presents a back-analysis of geotechnical parameters on prefabricated vertical drain improved ground at a site in the Mekong Delta. Various time−settlement behaviors that reflected different clay thicknesses and loading patterns were observed. The total surface settlement behavior at several monitoring locations was simulated using an updated exponential method that considered staged construction. The analyzed results were validated by substituting the values into a theoretical solution for radial consolidation. The estimated theoretical behaviors were comparable with the monitored behaviors. The geotechnical parameters were back-analyzed by applying the previously analyzed results to various theoretical and empirical formulas. However, the use of extensometer data that were installed at large intervals produced different values of the geotechnical properties. Furthermore, finite element analysis supported the back-analyzed total settlement behaviors and nearly disregarded the application of the geotechnical properties that were obtained using either surface or subsurface settlement data. However, settlements and excess pore pressures in the sublayers were not successfully predicted even when the geotechnical properties were adjusted. Thus, subsurface instruments that can be installed closely in thick clay deposits are required to reliably reevaluate the variations in geotechnical properties along a certain depth.

Geomorphic evolution of a non-glaciated river catchment in Lesser Himalaya: Response to tectonics

The study discusses detail valley formation and sedimentation processes in the monsoon dominated non-glaciated catchment of the Ramganga river in the Lesser Himalaya. The geomorphic and sedimentological studies in this basin indicates phases of massive aggradation that was controlled mainly by channel bound processes and debris flows/landslides. The luminescence chronology of the fill sequences suggests that the valley filling occurred mainly in response to the enhanced monsoon after the Last Glacial Maxima (LGM), during Medieval Warm Period (MWP) and Little Ice Age (LIA). This phase is common in both glaciated and the non-glaciated catchments of Himalaya.The Ramganga River that flows through various tectonic structures of the Lesser Himalaya shows development of wide valleys with thick fill deposits in the fault zones. Chaukhutiya Fault (CF) and Binau-Bhikiyasain-Naurar Fault (BBNF) are the two main transverse faults where the evolved geomorphology pertains to their tectonic activity. The computed morphometric variables such as Ratio of valley floor width to valley height (Vf) and Stream Gradient Index (SL) show higher values in the transverse fault zones. Basin asymmetry vectors along the South Almora Thrust and BBNF are characterized by preferred stream migration in NE and SW direction suggesting BBNF with dip slip movement. Thick clay deposits at different sites along the Ramganga River resulting from blocking of the river, particularly along the BBNF, also point towards tectonically induced landslide and channel blockage. Later phase of tectonic activity, bracketed between 27 and 24 ka, is evident from deformed fluvial deposits in the form of folds and faults. Evidences of tectonic activity in the form of soft sediment deformation structures (SSDS) generic to seismic activity in layers comprising alternation of clay and sand are observed in the Himalayan Frontal Thrust (HFT) zone. The diagnostic features such as dykes, faults and folds suggests that the shaking event took place between 38 ka and 30 ka.

피압에 따른 연약지반의 압밀 거동

Vertical drain has usually been used to accelerate the consolidation of soft clay deposits with high moisture content. Busan thick clay deposits are subjected to artesian pressure from an aquifer in sand and gravel layers. However, effect of artesian pressure existing in drainage-installed soft ground on consolidation behaviors is not well known. This paper investigates the consolidation behavior of drainage-installed soft ground at the Nakdong river estuary with artesian pressure and without artesian pressure. A series of one-dimensional large size column test was carried out to find out the consolidation characteristics of clay. Test results indicated that total settlement of clay with artesian pressure was higher than that without artesian pressure because effective stress decreased due to upward flow. Dissipation rate of excess pore water pressure delayed and excess pore water pressure did not fully dissipate in clay layer with artesian pressure. Undrained shear strength of clay ground with artesian pressure was lower than that without artesian pressure.

Settlement of Thick Clay Deposits under Piled-Raft Foundation and Design Considerations (Pile Dimensions)

Characteristics and histories of the deltaic deposits in geotechnical perspective are studied. Geotechnical issues of clay deposits under floating foundation systems also analyzed. Theoretical expressions and parameters were examined by an experimental study and numerical analysis on the laboratory scales and field measurement in this study. Also, piled raft foundation on thick clay deposits is designated to optimize pile configuration. The predictions of settlements of piled rafts foundation are proposed based on pile dimensions by utilizing a normalized Ap/nL and Bg/Br. Practical design of piled raft foundations is made for the light bridges and five story buildings on thick clay deposits to discuss the long-term settlement, and it is found that the piled raft is well applicable and effective on thick clay deposits, and that differential settlements of the foundation should be managed by designing the configuration of pile lengths and spacing.

Assessment of concrete maturity and overturning mechanism of primary diaphragm walls in very soft clay during cold winter

Many underground excavation failures are caused by severe water inflow due to the piping through the opening in the diaphragm wall. The opening can be created by slurry pocket or air pocket during concrete placement by tremie method. This type of defect in diaphragm wall can be detected by sonic logging to show the condition of trench wall and by measuring actual concrete dosage during placing. The same detecting method can be used in two very rare case histories where just-completed primary panels in very soft and thick clay deposit were overturned from the adjacent tremie concreting secondary panel during cold winter. The abnormal increasing concrete dosage and the smooth trench wall profile of secondary panel from sonic logging identify the occurrence of this incident. The causes to trigger this incident include (1) panel size, (2) weather condition, (3) tremie concreting speed of secondary panel, (4) initial and final setting times of concrete in trench, (5) roughness of trench wall, etc. Since the temperature for the two case histories is very low during tremie concreting, the initial setting time of concrete in secondary panel, given by equivalent age maturity function, is much longer than the time to place the concrete in secondary panel. To clarify the failure mechanism, the force-equilibrium analysis of inclined primary panel is conducted taking into account the driving force induced by the concrete pressure in the unset secondary panel and the resistant force given by the adhesion between inclined primary panel and soft clayey soil. It can be concluded from this investigation that the concrete in the secondary panel due to lower concrete curing temperature still remains unset or in plastic form and this will generate much larger driving force to push the adjacent just-completed primary panel to tilt. The measures to prevent similar incidents from happening are also suggested in this paper.

Long-term settlement analysis of partially improved thick clay deposit

Prefabricated vertical drains (PVDs) were partially or fully penetrated into thick clay deposits at a reclamation project in Busan City, Korea. Elasto-viscoplastic finite element analysis is conducted to predict the long-term behaviors using a macro-element technique. Settlements predicted using laboratory-based and back-analyzed soil parameters are in good agreement with monitored data. The relationships of time versus volumetric strain and excess pore pressure at each element are effective in investigating the overall behaviors; that is, the settlements in the improved zone degrade from steep to gentle slopes, whereas those in the unimproved zone change with a relatively gentle slope. The effect of partially penetrated PVD on ue dissipation appears to be in relatively good agreement with results obtained by Ong et al.'s (2012) method.

Origin and chemical nature of the thermal fluids at Caldeiras da Ribeira Grande (Fogo Volcano, S. Miguel Island, Azores)

The Caldeiras da Ribeira Grande (CRG) site is characterised by low-temperature fumaroles, boiling mud-pools and gas ground-emissions, some of them artificially confined to a tank. Cooling and oxidation of deep hydrothermal fluids under boiling control the formation of acid condensates and strong hydrothermal alteration of the hosting volcanic rocks. The latter feature is locally reinforced at shallow levels through flow of mixtures of acid condensates with surface and shallow groundwater triggering the development of thick clay deposits used in mud-therapy purposes at an old Thermal Bath facility. The emerging aqueous fluids are acidic (pH 3; and (3) rain, runoff, and subsurface water contributions must be balanced to confine the pH of thermal fluids between 3 and 5. Any change in conditions of geothermal fluid boiling at depth or in environmental and hydrological characteristics of the site can cause significant changes in leaching processes and sediment formation.

Case study of a full-scale load test of a piled raft with an interposed layer for a nuclear storage facility

The ICEDA nuclear waste storage facility is being constructed near Lyon, France. It is founded on a thick clay deposit using settlement-reducing piles as soil improvement, making it the first nuclear installation in France employing this technique. The high safety requirements of the project, combined with the use of an innovative system based on piles disconnected from the foundation, have necessitated detailed studies of the soil–structure behaviour. In addition to an extensive ground investigation, a full-scale in situ test was carried out over a period of 6 months. This paper presents some of the experience gained from the project, focusing on the findings from the full-scale test compared with a class A prediction. It illustrates the difficulty in choosing soil parameters that are representative of the soil formation as a whole, and the value that the full-scale test had in the design for ICEDA.

Calcium Leaching Mechanism of Lime Treated Soil Immersed in Seawater

The lime and the cement treated soil have been regarded as stable for a long time due to hydrate generated by pozzolanic reaction. As the treated soil is exposed to natural conditions, its strength would decrease by calcium leaching. In lowland having the thick alluvial clay deposit, the chemical soil treated method is often applied to improve the strength of soft clay ground. The lime treated soil applied to the base of a tidal river dike is deteriorating. It had been constructed in about twenty years ago and now appears to be muddy and leakage of river water. The treated soil is exposed to seawater in this area. This study considered mechanism of calcium leaching from the lime treated soil when it was immersed in seawater. Leaching tests were carried out to clear influences of the component of seawater on calcium leaching. Artificial seawater, NaCl, MgCl2, MgSO4 solutions were used in the test. Influence of NaCl on calcium leaching was very small. Magnesium containing in seawater reduced pH value of the solution-treated soil mixture. Calcium leaching was accelerated when magnesium concentration was higher. Magnesium was founded to be a main component to cause calcium leaching.

과압밀 및 정규압밀영역의 응력상태에 따른 부산점토 장기압밀특성

Numerouslong-term consolidation and secondary compression settlements may occur in Busan clay, which is astructured soft clay and consists of a thick clay deposit. As a surcharge load is applied to soils, soils experience different stress paths with depth. Therefore, it is necessary to study the long-term consolidation behavior of Busan clay considering stress conditions such as OC or NC states. In this study, a series of long-term consolidation tests were performed to investigate the consolidation characteristics of Busan clay for 20 days. The undisturbed clay samples were taken from 3 sites located in the Nakdong River estuary. The results showed that the creep rate of the Busan clay gradually decreased with time, which indicated that the secondary compression settlement decreased with time. In addition, the experimental results for 3 samples showed that the ratios were about 0.0363 and 0.051, respectively.

Investigation on Static Stability of Sheet Pile Quay Wall Improved by Cement Treated Sea-Side Ground from Centrifuge Model Tests

The static stability of sheet pile quay walls on a thick clay deposit against horizontal loads was studied through a series of centrifuge model tests. In the tests, an overconsolidated Kaolin clay layer was prepared over a layer of dense Toyoura sand in a rectangular container. The model quay wall was set to the bottom of the sand layer. The sea-side area adjacent to the quay wall was improved with cement-treated Kawasaki clay. Under 50 g centrifugal acceleration, the clay deposit was consolidated and horizontal line loads of about 0 to 70 kN/m were applied to the quay wall. The width and the depth of the improved area were varied and its performance was compared with that of a quay wall embedded in unimproved ground. Results of the study indicated that the improved ground provided significant resistance against horizontal loading. In addition, a numerical model to estimate the mechanical behavior of the sheet pile quay wall is presented. The outcomes of the numerical model show good agreement with the centrifuge test results.

Till Stratigraphy and Late Wisconsinan Deglaciation of Southern Maine: A Review

At least two glaciations are recorded by the till stratigraphy of southern Maine. A more deeply weathered lower till is tentatively correlated with the early Wisconsinan (or older) Nash Stream Till in New Hampshire and its inferred equivalents in southern New England and Québec. The Laurentide Ice Sheet flowed south-southeastward across southern Maine in late Wisconsinan time and deposited the upper till. By about 14,000 years ago the ice sheet started to recede from the Maine coast, and the high peaks of the Mahoosuc Range emerged as nunataks in western Maine. Marine transgression accompanied déglaciation of lowland areas of southern Maine, with deposition of end moraines, deltas, and subaqueous outwash along the active ice margin, while thick clay deposits of the Presumpscot Formation accumulated on the ocean floor. The ice margin retreated quickly, reaching the marine limit in central Maine by 13,000 yr BP. The Pineo Ridge moraine system in eastern Maine, formerly thought to represent a major readvance, is reinterpreted as a glacial stillstand near the marine limit. Deglaciation inland from the marine limit in eastern and southwestern Maine occurred by recession of an active ice margin in some areas, and elsewhere by stagnation and downwasting of ice that was separated from the active ice sheet. Southern Maine was ice-free by 12,000 yr BP. but marine submergence persisted until about 11,000 years ago in the southwestern coastal lowland.

Centrifuge model tests on behavior of double sheet pile wall cofferdam on clay

The behavior of double sheet pile wall cofferdam on a thick clay deposit subjected to a flash flood was studied through a series of centrifuge model tests. In a rectangular container a thick layer of kaolin clay was placed on a layer of fine silica sand. The clay layer was prepared with a defined stress history. The model cofferdam consisted of two aluminum sheet pile walls, with tie rods at the top and ground level. After driving the sheet pile walls to the sand layer, the inside of the sheet pile walls was excavated and filled with the same silica sand as used in preparing the bottom sand layer. Under 70 g centrifugal acceleration, the clay deposit was consolidated under the load from the fill to a certain degree and then water was fed upstream of the cofferdam to simulate high floodwater until the water level reached nearly to the top of the cofferdam or large deflection of the cofferdam was observed. Various factors affecting stability of the cofferdam and mechanism of failure were examined. Stability of the double sheet pile wall cofferdam on a thick clay deposit was also compared with a cofferdam on the sand deposit. Test results implied that: (i) shear deformation of the fill dominates the failure mechanism of the cofferdam, (ii) as the width of the cofferdam increases, the water height at failure increases, (iii) the resistance against high water does not always increase with increasing the embedment depth, (iv) the degree of consolidation of the clay foundation affects the stability of the cofferdam, though degree of consolidation was simulated after construction of the cofferdam, (v) performance with respect to the mechanical behavior of a cofferdam in a sand deposit is better than that in a clay deposit, and (vi) both the upstream and downstream sheet pile walls in a clay foundation are subjected to almost the same flexural stress compared to the larger flexural stress in the downstream sheet pile wall in a sand foundation.

Woodlands of the past — The excavation of wetland woods at Zwolle-Stadshagen (the Netherlands): Reconstruction of the wetland wood in its environmental context

AbstractInformation on the vegetation and landscape history of a region is often limited, and available data are hard to interprete. A concept is presented here on how a more comprehensive picture of the structure and development of landscapes and vegetations of the past can be gained by integrating the information of several disciplines. Archaeological field methods have been combined with methods used in landscape studies (geology, soil science, micromorphology) and vegetation studies (ecology, palynology and dendrochronology).This concept has been applied and tested during an integrated study of a buried woodland at Zwolle-Stadshagen (Province of Overijssel, the Netherlands). Many large wood remnants were found in a peat layer preserved below a thick clay deposit. The wood remnants were dated by using dendrochronology to the period between ca. 150 BC and AD 580 (ca. 2200 - 1400 cal. BP). Two phases could be distinguished in the development of the peat. The woodland consisted of a closed stand with ash, alder and oak as main species, in the first phase mostly resembling an alder carr, and in the second one the near-extinctFilipendulo-AlnetumPassage et Hofmann 1968. No evidence of exploitation of the woodland by man nor of animal foraging was found.The followed integrated procedure has led to a more substantiated reconstruction of the palaeo-environment with its wetland wood, but also of the influence of human activities on the palaeo-landscape and its woodlands, that could not have been obtained otherwise.

Design and performance of Fibredrain in soil improvement projects

The effective coefficient of consolidation Ch, and hence the effective discharge capacity, of prefabricated vertical drains (PVDs) is a function of the hydraulic conductivity and compressibility of the clay as well as of the field performance of the PVD. The field performance is influenced by the deformation of the core and the filter, clogging of the filter, and kinking of the PVD during the consolidation process. The design of soil improvement projects using PVDs is a function of the effective Ch, the final settlement, the drain spacing, and the lateral pressure on the drain. Prefabricated vertical drains should possess sufficient tensile strength to withstand the installation stresses associated with thick clay deposits, as well as the densification of granular soil layers at the surface by heavy tamping. Fibredrain is a PVD that is biodegradable and ecologically harmonious. Several selected projects in East and South East Asia are discussed to illustrate the field performance of Fibredrain. Le coefficient de consolidation effective Ch et, de là, la capacité de décharge effective des drains verticaux préfabriqués (PVD) est fonction de la conductivité et compressibilité hydrauliques de l'argile ainsi que de la performance de terrain des PVD. La performance de terrain est influencée par la déformation du cur et du filtre, l'occlusion du filtre et la déformation des PVD pendant le processus de consolidation. La conception des projets de consolidation des sols utilisant les PVD dépend du Ch effectif, du tassement final, de l'espacement des drains et de la pression latérale sur le drain. Les drains verticaux préfabriqués devront posséder une résistance à la traction suffisante pour supporter les contraintes d'installation dans des dépôts d'argile épais ainsi que la densification en surface des couches de sol granulaires, densification causée par un compactage lourd. Le Fibredrain est un PVD biodégradable et sans danger pour l'environnement. Nous avons choisi pour notre étude plusieurs projets en Asie orientale et Asie du sud-est afin d'illustrer la performance sur le terrain du Fibredrain.

Données complémentaires sur les variations du niveau marin relatif, à l’holocène, à l’Anse de Bellechasse, sur la côte sud du moyen estuaire du Saint-Laurent

À l'embouchure du ruisseau de Bellechasse, trois petits glissements de terrain dans la berge escarpée de la terrasse de 10 m, survenus au printemps de 1998, ont permis de découvrir une couche organique (tourbe) et des troncs d'arbres, à la surface d'un dépôt argileux, marin (rythmites datées à environ 10 ka), recouvert de 2 à 3 m de sédiments fins intertidaux. L'âge de la tourbe et des troncs d'arbres semblable (6 à 7 ka) à celui des coupes de Montmagny et de Cap-Saint-Ignace permet d'affirmer que les événements mis en évidence dans ces deux localités (bas niveau suivi d'une transgression) ont une extension géographique plus grande, sur la rive sud de l'estuaire du Saint-Laurent, qu'on le croyait jadis.

An Overview of Some Significant Eastern Canadian Earthquakes and Their Impacts on the Geological Environment, Buildings and the Public

Numerous moderate to large earthquakes have occurred in eastern Canada. Some ofthese events had significant geological effects such as surface faulting, liquefaction,submarine slumping, rock avalanches, rock falls, landslides, railroad embankmentslides, and one tsunami. Some of these earthquakes caused considerable damage tobuildings with unreinforced masonry elements that were located on thick clay deposits. These events also had strong psychological and social impacts, mainly due to the unpreparedness of the population. To minimize these impacts, programs should be designed to map the land and offshore areas most susceptible to mass movements (Earth Sciences), to define buildings most at risk (Engineering) and to educate the public about mitigation actions (Education, science popularization).