Increase Of Mud Content Research Articles

Sedimentary diversity of the 2011 Tohoku-oki tsunami deposits on the Sendai coastal plain and the northern coast of Fukushima Prefecture, Japan

This paper documents the sedimentary characteristics of the widespread deposits associated with the 2011 Tohoku-oki tsunami on the lowlands along the Pacific coast of the Sendai and Fukushima regions, northern Japan, and observed tsunami inundation depths. In eight areas of the region, field observation was carried out at a total of 123 locations and sampling at a total of 49 locations. Grain-size analysis and soft X-ray imaging reveal that the tsunami deposits are usually composed of sheetlike sandy beds and generally show landward-thinning and landward-fining trends and a landward increase in mud content, although site-specific distributional patterns are apparent along each transect. These thickness and grain-size patterns indicate a landward decrease in flow capacity. This information on the sedimentology of tsunami deposits and observed inundation depths will assist with the identification of paleo-tsunami deposits in the geological record and provide valuable constraints for mathematical analyses of tsunami hydraulic conditions related to sedimentary characteristics.

Research and Development of Intelligent Cleaning and Mud Content Detection Technology for Machine-Made Sand

In this paper, an improved method of sand and mud content detection for concrete is proposed, and a set of sand and mud content detection device for concrete is designed. In this paper, a concrete gas content meter and a bubble parameter analysis system were used to study the effect of sand clay content on the gas content of commercial concrete, the loss rate of gas content in warp time, the bubble spacing coefficient and the distribution of hardened appearance pores. The pore structure test shows that the increase of mud content will appropriately reduce the proportion of harmless pores in machine-made sand concrete, and play a role in refining the pore structure in machine-made sand concrete. By using PLC controller and automatic detection device of liquid level and turbidity, the problems of complicated operation, inconvenient carrying and poor repeatability of test data are solved. It reduces the influence of human operation error and improves the accuracy of test data.

The late Holocene Erin deflected and asymmetric wave-dominated delta – Puerto Grande Bay, Trinidad

The Erin modern marginal-marine depositional system sits along the Trinidad southwestern coastline. It is among the many unstudied and undocumented modern, dynamic coastal depositional systems around Trinidad. Our study defines the Erin system as being a deflected and asymmetric wave-dominated delta, and in so doing, elucidates the dynamics of the Erin system. This was done using a compendium of satellite images, temporal cross-shore elevation profiles, modern shallow sediment cores, and sediment samples.Geomorphologically, the Erin system comprises a vegetated delta plain and the unvegetated modern deposits. The delta plain has four amalgamated sand bars with intercalated lagoonal deposits. The unvegetated modern deposits is defined as the fifth bar of the system. These five bars were loosely correlated to the five 6th order eustatic cycles of the Holocene highstand. The modern, unvegetated deposit of the fifth bar is divided into an updrift segment and a downdrift segment relative to the inlet mouth. The updrift segment comprises a spit and beach depositional elements, while the downdrift segment comprises a barrier spit, back-barrier lagoon, rip-channels, and sometimes a bayhead delta at the Erin River mouth. The dynamic, annual evolution of the spit reflects a seasonally controlled, possibly cyclical evolution wherein the delta transitions from being asymmetric to deflected-asymmetric. This phenomenon is postulated to be brought on by seasonal changes in the wave regime, and not, as one might expect, seasonally controlled river discharge. That is, during the summer wave season, when net-deposition occurs, the system morphology is deflected as a consequence of increase sedimentation in the nearshore. During the winter wave season, when net-erosion is expected, the system morphology reflects that of a typical asymmetric delta, as a consequence of reduced sedimentation in the nearshore. This cyclical movement of sediment is also observed in cross-shore elevation profiles.Sedimentologically, six depositional elements were sampled using sediment cores: foreshore, updrift spit, channel bars, mouth bar, barrier spit (downdrift), and back-barrier lagoon. Physical sedimentary structures reflected wave energy dominance across the system with an increase in tidal signatures within the lagoon deposits and lower foreshores. Biogenic sedimentary structures were limited across much of the system, but the traces recorded were mostly isolated in the downdrift back-barrier lagoon deposits, and few in the upper barrier spit. Grainsize distributions showed an average grainsize of fine sand across the system with coarse-grained, poorly sorted, bio-clastic sands present as channel lag deposits. An increase in mud content was recorded in the downdrift segment of the delta. The geomorphological, sedimentological, and ichnological data described above provided sufficient evidence to define the Erin system as an asymmetric wave-dominated delta with seasonally controlled deflected morphology.

Experimental Study on Critical Shear Stress of Cohesive Soils and Soil Mixtures

HighlightsErosion tests were performed to study the critical shear stress of cohesive soils and soil mixtures.Linear relationships were observed between critical shear stress and cohesion of cohesive soils.Mixture critical shear stress relates to noncohesive particle size and cohesive soil erodibility.A formula for calculating the critical shear stress of soil mixtures is proposed and verified.Abstract. The incipient motion of soil is an important engineering property that impacts reservoir sedimentation, stable channel design, river bed degradation, and dam breach. Due to numerous factors influencing the erodibility parameters, the study of critical shear stress (tc) of cohesive soils and soil mixtures is still far from mature. In this study, erosion experiments were conducted to investigate the influence of soil properties on the tc of remolded cohesive soils and cohesive and noncohesive soil mixtures with mud contents varying from 0% to 100% using an erosion function apparatus (EFA). For cohesive soils, direct linear relationships were observed between tc and cohesion (c). The critical shear stress for soil mixture (tcm) erosion increased monotonically with an increase in mud content (pm). The median diameter of noncohesive soil (Ds), the void ratio (e), and the organic content of cohesive soil also influenced tcm. A formula for calculating tcm considering the effect of pm and the tc of noncohesive soil and pure mud was developed. The proposed formula was validated using experimental data from the present and previous research, and it can reproduce the variation of tcm for reconstituted soil mixtures. To use the proposed formula to predict the tcm for artificial engineering problems, experimental erosion tests should be performed. Future research should further test the proposed formula based on additional experimental data. Keywords: Cohesive and noncohesive soil mixture, Critical shear stress, Erodibility, Mud content, Soil property.

Study on Aeolian Sand Bearing Capacity Based on California Bearing Ratio in the Northwest of China

California Bearing Ratio is a kind of method for testing the bearing capacity of the material. Aeolian sand is wildly distributed in north-west of China, such as Qinghai, Ningxia, Shaanxi and Inner Mongolia. Different sedimentary history and condition makes the sand have different characteristics. This paper aim to testing different moisture content, mud content and gradation affect the Aeolian sand strength and bearing capacity through California Bearing Ratio method. The result of this experience shows that moisture content and mud content have a significant influence of the Aeolian sand strength and bearing capacity. Before the optimal moisture content, the CBR is increased, after the optimal moisture content, the CBR is decreased. Before the optimal mud content, the CBR is increased, after the optimal mud content, the CBR is also decreased. With the increase of compaction, the result of CBR is increasing. Under the same gradation condition, the CBR becomes smaller and smaller with the increase of mud content. Increasing compaction work, the CBR value also increased.

Clinoform growth and sediment flux into late Cenozoic Qiongdongnan shelf margin, South China Sea

AbstractThe South China Sea continental margin in the Qiongdongnan Basin (QDNB) area has incrementally prograded since 10.5 Ma generating a margin sediment prism more than 4km‐thick and 150–200 km wide above the well‐dated T40 stratigraphic surface. Core and well log data, as well as clinoform morphology and growth patterns along 28 2D seismic reflection lines, illustrate the evolving architecture and margin morphology; through five main seismic‐stratigraphic surfaces (T40, T30, T27, T20 and T0) frame 15 clinothems in the southwest that reduce over some 200 km to 8 clinoforms in the northeast. The overall margin geometry shows a remarkable change from sigmoidal, strongly progradational and aggradational in the west to weakly progradational in the east. Vertical sediment accumulation rate increased significantly across the entire margin after 2.4 Ma, with a marked increase in mud content in the succession. Furthermore, an estimate of sediment flux across successive clinoforms on each of the three selected seismic cross sections indicate an overall decrease in sediment discharge west to east, away from the Red River depocenter, as well as a decrease in the percentage of total discharge crossing the shelf break in this same direction. The QDNB Late Cenozoic continental margin growth, with its overall increased sediment flux, responded to the climate‐induced, gradual cooling and falling global sea level during this icehouse period.

Geocronologia com 210Pb na avaliação das taxas de sedimentação e da dinâmica deposicional na Lagoa Itapeva, sul do Brasil

Lagoas costeiras são ambientes potencialmente ameaçados pelo aumento recente das taxas de sedimentação e elevação relativa do nível do mar. Neste trabalho foram analisadas as condições de preenchimento sedimentar da Lagoa Itapeva utilizando o método geocronológico 210Pb, a partir dos valores da atividade do 210Pb e 226Ra obtidos de três testemunhos geológicos. As taxas de sedimentação medidas no testemunho C3 indicam forte influência da drenagem do Rio Três Forquilhas, com valores na ordem de 3,2 mm.a-1. Os pontos de coleta no centro C2 e norte C1 apresentaram valores sensivelmente menores, 2,4 e 2,9 mm.a-1, respectivamente. Tais valores mostram-se inferiores as taxas de elevação relativa do nível do mar, indicando um cenário transicional entre a estabilização e o déficit sedimentar no processo de preenchimento lacustre. A análise granulométrica nos testemunhos indica a presença de significativa energia hidrodinâmica no processo de sedimentação. A fração silte é a classe dominante, com variação entre o tamanho médio a grosso em todas as amostras, seguida pela ocorrência da fração areia em relação à argila que apresentou baixa concentração, não ultrapassando 9%. Entretanto, foi verificado no testemunho C3 um aumento do teor de lamas nas últimas décadas, o que sugere modificações na bacia de drenagem do Rio Três Forquilhas pelo aumento na produção de sedimentos. A urbanização e a introdução da agricultura no último século são as principais variáveis que explicam este comportamento.

The limiting role of oxygen penetration in sediment nitrification.

Oxygen penetration is a key determinant of sediment nitrification rates. In this study, we analyzed the effect of oxygen penetration on the sediment nitrification rate based on sediment oxygen profiles. Six sediments were designed to produce different oxygen profiles by adding different amounts of silica gel to the collected river mud. The oxygen profiles in the sediment were detected using a voltammetric microelectrode. With increased mud content, the sediment oxygen penetration depth decreased from 8.3 to 2.6 mm, and the oxygen concentration in the overlying water and at the sediment-water interface also showed a decreasing trend. The measured nitrification rate displayed a quadratic pattern that changed with the increase in mud content. Based on the detected oxygen profiles, the nitrification rate at each depth was calculated and summed to obtain the bulk sediment nitrification rate. The bulk sediment nitrification rate showed a consistently changing pattern with the measured rate. Oxygen profiles used to calculate nitrification rates could be approximated by the penetration depth (δ). The resulting nitrification model based on δ could explain the limiting role of oxygen penetration in sediment nitrification.

Seasonal Controls On the Development And Character of Inclined Heterolithic Stratification In A Tide-Influenced, Fluvially Dominated Channel: Fraser River, Canada

Abstract Inclined heterolithic stratification (interbedded sand and mud with depositional dip; IHS) is developed on an in-channel bar in the tide-influenced, fluvially dominated (brackish water) reach of the Fraser River, British Columbia, Canada. The vertical bar succession is characterized by a fining-upward profile with an increase in mud content and mud-bed thickness from the shallow subtidal zone to the upper intertidal zone. There is also an increase in the number and lateral continuity of mud beds from the upstream side to the downstream side of the bar. Sand beds are dominated by current ripples in the intertidal zone, and by current ripples and trough cross-beds in the shallow subtidal zone. The channel base is mantled by downstream (ebb)-oriented dune-scale bedforms. Mud beds are dominantly parallel laminated, although current ripples may develop in silt-rich and sand-rich mud beds. Current-generated bedforms are predominantly ebb-oriented. Sediment deposition is seasonally controlled. Sand deposition occurs during periods of high discharge (snowmelt-induced freshet), and mud is deposited during waning freshet flow and low discharge (base flow). In mud-dominated deposits, current ripples may develop in sand-rich mud beds deposited during the freshet. Seasonal cyclicity in sediment deposition is also recorded in the ichnological characteristics of the IHS. Bioturbation is significantly more common in base-flow deposits (mud beds) than freshet deposits (sand beds). Burrows in sand beds typically subtend from overlying mud beds. Diminutive, vertical burrows dominate the trace suite, reflecting a very low diversity of infauna. Bioturbation is more common on the downstream side of the bar, associated with the thicker and more laterally contiguous mud beds. Based on these observations, seasonal cyclicity in channel-bar deposits, formed in tide-influenced, fluvially dominated channels, can be identified using a combination of sedimentological and ichnological characteristics, particularly in mud-dominated successions and in IHS. In mud-dominated deposits, seasonal controls are best-expressed ichnologically through the interbedding of bioturbated and unbioturbated intervals. The dominance of a low-diversity suite of mainly vertical traces can also be considered indicative of brackish-water conditions in the channel. In IHS successions, interbedded sand and mud beds are the best indicators of seasonal cyclicity: sand beds are typically unburrowed, and mud beds are burrowed. In sand-dominated successions that lack mud interbeds, it is difficult to recognize seasonal cyclicity.

Temporal variability in the Abra alba community determined by global and local events

Macrobenthic communities in temperate, shallow coastal waters are characterised by strong seasonal and year-to-year variations in community characteristics. These temporal variations were investigated in the Abra alba community on the Belgian Continental Shelf over a period of nine years (1995 – 2003). During this period, the community did not show a cyclic pattern, but a shift between the years 1995 – 1997 and 1999 – 2003 that was possibly triggered by changes in the hydroclimatic state of the North Sea and was reflected by a small shift of the dominant species in the A. alba community. In the years 1995 – 1997, the temporal pattern was dominated by strong year-to-year differences, coinciding with different successive events (strong recruitment, sedimentological changes, cold winters). Therefore, these years were characterised as the unstable period. Such events may affect the macrobenthic density, diversity and species composition. The mass recruitment of S. subtruncata may have been responsible for an initial decrease in the density and diversity of the macrobenthos, whereas the increase of mud content was responsible for a crash of the species richness and macrobenthic density in the winter of 1996. After those events, the A. alba community needed time to recover (1996 – 1998). The recovery was possibly retarded by a slow amelioration of the habitat conditions, unsuccessful recruitment and the occurrence of a cold winter. This period was followed by some years in which the seasonal dynamics in the community exceeded the lower year-to-year variability and therefore these years were characterised as the stable period. The seasonal dynamics in the study were characterised by high macrobenthic densities and diversity in spring and summer, followed by declines in the autumn-winter period. The conclusion is that mainly local factors were responsible for the short-term variations within the community, whereas global events (hydroclimatic, cold and mild conditions) caused the long-term changes.

Biological influences on morphology and bed composition of an intertidal flat

Biological activity is known to influence sediment strength at bed–water interfaces. However, its precise effect on geomorphology and on bed composition is not known. This paper proposes a parameterization of sediment destabilizing and stabilizing organisms on three parameters that describe the erosion and mixing processes of the sediment bed, namely the critical bed shear stress, the erosion coefficient and the bioturbation coefficient. This parameterization is included in a 3D sand–mud morphodynamic model to form the sand–mud–bio model. The performance of the sand–mud–bio model is demonstrated by testing it on the Paulinapolder intertidal flat in the Western Scheldt estuary of The Netherlands. Model results show that biological influences on sediment strength result in significant morphological change and bed composition variations. Destabilizing organisms always cause a significant decrease in mud content in the bed and an increase of erosion. On the other hand, stabilizing organisms can, but do not necessarily, cause an increase of mud content and additional sedimentation.

Sedimentary Layer Properties of Graded-Shelf Deposits, Colorado Group (Cretaceous), Saskatchewan: ABSTRACT

Middle Albian to Santonian detrital sediments were deposited in a shallow sea east of the Rocky Mountain geosyncline. Two transgressive phases of dominant mud deposition were separated by a major regressive phase, represented by a north-eastward-thinning wedge incorporating conglomerate and sandstone. The transgressive Joli Fou Formation is represented on the east by the Spinney Hill Sandstone, comprising cosets of planar sandy foresets and subordinate mudstone intercalations (proximal fluviomarine deposits). These grade westward into a succession of vertically repeated, sandy, fining-upward sequences (distal fluviomarine deposits) overlain by and passing laterally into mudstone. The fining-upward sequences comprise, in ascending order, planar sandy foresets, bioturbated sandstone, alternating sandstone and mudstone, and mudstone. The sequence probably reflects lateral migration of the tidal channels of an estuarine delta. The regressive Viking Formation gave rise to deposits in which size fractionation through increase in the proportion of admixed mud northeastward is accompanied by progressive change in assemblages of sedimentary structures. A thick sequence of planar sandy foresets and subordinate mudstone intercalations (nearshore deposits) is replaced by clinobeds composed of coarsening-upward sequences (proximal shelf deposits), which northeastward grade to bioturbated, muddy sandstone (distal shelf deposits) and mudstone (shelf muds). The Flatten Lake sand displaying southwestward diminution of grain size along the erosional edge of the Colorado succession is referable to the regressive phase. The pre-Cenomanian (Big River Formation) of the late transgressive phase is predominantly mudstone, replaced northeastward by fine-grained, horizontally laminated and micro-crosslaminated sandstone and bioturbated sandstone, with abundant discontinuous mudstone intercalations (St. Walburg Sandstone). These beds are succeeded by a thick mudstone incorporating northeastward-thinning units rich in bioclastic debris: a basal unit rich in fish remains (fish-scale marker) and 2 main calcareous units containing coccolith aggregates and pelecypod debris (Greenhorn and Niobrara equivalents). The bioclastic debris commonly is in thin, graded layers passing upward into mudstone. Lateral size fractionation within the units occurs by progressive decrease in proportion of sand and silt and concomit nt increase in mud content. The principal agents of sediment transportation recognized are tidal currents occasionally augmented by storm-surge waves giving rise to both laterally migrating channels and large-scale sand ridges. Mass movement of sand downslope apparently was confined to local salt-solution sinks. End_of_Article - Last_Page 961------------