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Natural gas hydrate has gained significant attention in recent years. To safely and sustainably exploit the natural gas from gas hydrate-bearing sediments, it is crucial to understand the long-term mechanical characteristics of the hydrate reservoir. In this study, the influence of hydrate and fine particles on the strain rate dependence of hydrate-bearing sediments under plane strain conditions has been studied. The experimental results show that the strain rate dependency of the mechanical properties of hydrate-bearing sediments is positively correlated with hydrate saturation instead of the morphology of hydrate in sediments. The residual strength of hydrate-bearing sediments is primarily controlled by the hydrate saturation and is independent of the strain rate. Changes in hydrate saturation, and fines content, can affect the relationship between the strain rate and shear band angle. Finally, the local volumetric expansion effect of hydrate-bearing sediments without fines content is more significant and shows a strong strain rate dependence characteristic. Overall, this study provides valuable insights into the long-term mechanical characteristics of hydrate reservoirs. These insights can contribute to the development of a constitutive model of hydrate-bearing sediments with time-dependence in the future, and which is meaningful to the exploitation of natural gas hydrate.

The utilization of substance stabilizer in soil improvement can diminish the obstructive ecological effect in the development business, and respond as the soil stabilizers to the kaolin clay soils. In any case, the improvement of kaolin clay stays a test because of the significant expense and non-eco-accommodating materials like concrete and lime. This examination exhibits the capacity of SF in the mix with ESA in stabilizing the delicate kaolin clay soils, by means of particle size distribution (PSD), specific gravity, Atterberg limits, compaction parameters and undrained shear strength (USS) parameters. Its impact on the undrained shear strength upgrade was concentrated through the concrete substitution material in kaolin clay soil at the replacement degree of 2%, 4% and 6% (by dry weight of kaolin clay soil) of SF and ESA replacements of 3%, 6% and 9% (by dry weight of kaolin clay and SF content). The consideration of SF with ESA shows a lower specific gravity (4.9% decrease), lower plasticity index (PI) (48.4% decrease), diminished maximum dry density (MDD) (5.5% decrease), expanded in optimum moisture content (OMC) (8.7% increase), and higher USS (68.8%) when contrasted with the untreated kaolin clay soils and those treated with SF. The blends of SF and ESA as soil adjustment specialists effectively upgrade the undrained shear strength of the kaolin clay soils up to 68.8% strength improvement with the best percentage of 6% SF and 6% ESA for optimum enhancement of the expansive soil, which minimizing the expenses and as an eco-accommodating materials in soil improvement.

Depressurization is an effective method to produce methane gas from methane hydrate reservoirs. However, during gas production, sediments consolidate due to increasing effective stress. Revealing the compressive characteristics of methane hydrate-bearing sands during consolidation is essential for an accurate understanding of sediment properties and for the development of a constitutive model. Therefore, a series of isotropic consolidation tests was performed on sand in which methane hydrate was artificially generated, and its compressibility characteristics were evaluated. Furthermore, to assess prolonged production, creep compressive behavior was investigated. The experimental results showed volumetric strain due to increasing confining stress decreased with increasing initial methane hydrate saturation. Particle crushing during consolidation was inhibited by the presence of methane hydrate. It was confirmed that the increase in the effects of methane hydrate on soil compressibility followed a power function with the increase in methane hydrate saturation. Creep deformation was observed during the stress holding period regardless of the presence of methane hydrate. Creep behavior during the stress holding period was related to the extent to which the creep component had dissipated before the stress holding period in the past. A theoretical concept for creep strain was proposed based on the experimental results.

Water ice and gas hydrates can coexist in the permafrost and polar regions on Earth and in the universe. However, the role of ice in the mechanical response of ice-contained methane hydrates is still unclear. Here, we conduct direct million-atom molecular simulations of ice-contained polycrystalline methane hydrates and identify a crossover in the tensile strength and average compressive flow stress due to the presence of ice. The average mechanical shear strengths of hydrate-hydrate bicrystals are about three times as large as those of hydrate-ice bicrystals. The ice content, especially below 70%, shows a significant effect on the mechanical strengths of the polycrystals, which is mainly governed by the proportions of the hydrate-hydrate grain boundaries (HHGBs), the hydrate-ice grain boundaries (HIGBs), and the ice-ice grain boundaries (IIGBs). Quantitative analysis of the microstructure of the water cages in the polycrystals reveals the dissociation and reformation of various water cages due to mechanical deformation. These findings provide molecular insights into the mechanical behavior and microscopic deformation mechanisms of ice-contained methane hydrate systems on Earth and in the universe.

Dating the arrival of the first hominins in Java The World Heritage archaeological site at Sangiran on the island of Java in Indonesia has major importance for the understanding of human arrival and evolution in Asia. However, the timing of the first appearance of Homo erectus at the site has been controversial. Using a combination of dating techniques for hominin-bearing sediments, Matsu'ura et al. resolved the arrival of H. erectus at ∼1.3 million years ago (see the Perspective by Brasseur). This dating suggests that the earliest hominins in Sangiran are at least 200,000 years younger than has been thought and may represent an important step to the resolution of the controversy. Science , this issue p. 210 ; see also p. 147

Exploitation of gas from deep-sea methane hydrate-bearing layers might lead to some geological disasters, including marine landslides and excessive settlement of marine ground. The first offshore gas production tests for methane hydrate-bearing sediments were carried out in eastern Nankai Trough. However, knowledge on mechanical behavior of gas hydrate reservoirs with similar gradation and minerology component to the marine sediment is still insufficient. Consequently, proper modeling of geomechanical properties of methane hydrate-bearing sediments is crucial for reservoir simulation and deep ocean ground stability analysis for long-term gas production in the future. This study conducted a series of triaxial shear tests to examine the shear response of methane hydrate-bearing sediments with a similar grading curve and minerology components to the hydrate-rich sediments in Nankai Trough. The test results demonstrated that the presence of hydrate mass between sand grains altered the stress-strain pattern from strain-hardening to postpeak strain-softening. A simple constitutive model based on several empirical relationships of granular materials is proposed to describe the stress-strain relationship of methane hydrate-bearing sediments under triaxial stress condition. This model can reproduce the enhancement of shear strength, initial stiffness, and dilation behavior of methane hydrate-bearing sediments containing different amounts of fines content with a rise in the methane hydrate saturation at a wide range of effective confining pressures. The numerical results indicate that the parameter A associated with initial stiffness of stress-strain curve and the parameter α related with dilation properties are jointly governed by the confining pressure, fines content, and hydrate saturation.

The Vertesszőlős quarry, the Palaeolithic site where the “Samu” hominin fossil remains ( Homo heidelbergensis ) were found, is located in North West Hungary. The site is dated between the Early and Middle Pleistocene (ca. 310 ka). A short distance from where the Samu remains were found is an exposed surface of calcareous mudstone, preserving numerous fossil tracks made by a range of mammals and birds. Of particular interest are three elongate impressions - two potentially successive and one isolated. These tracks have previously been referred to either hominin or ursine trackmakers. Since bear pes tracks can superficially resemble human tracks, we attempted to discern the 3D morphology of the traces using digital photogrammetry. Our analysis suggests the isolated impression is likely the product of two superimposed tracks of a cloven hoofed ungulate. However, the two potentially successive tracks are more problematic. The highly weathered surface (first exposed in the 1960’s) has made interpretation difficult. Both impressions seem to possess a narrow, rounded end similar to the posterior heel margin of a human track. At the anterior end the impressions are broader, and bounded by smaller impressions that could be interpreted as toe marks. However, these two tracks differ considerably in their length/width ratios and are too widely spaced to be part of a single bipedal trackway. It is conceivable that one or both of these impressions may be highly weathered hominin tracks. However, given the highly weathered nature of the exposed surface, and the lack of morphological detail in the tracks, we cannot at this time confidently attribute the tracks to any specific trackmaker, despite our digital models of the tracks which provide a relatively objective means of analysis independent of prior assumptions.

Terrestrial records of the last geomagnetic reversal often have few age constraints. Chronostratigraphy using suborbital-scale paleoceanic events during marine isotope stage 19 may contribute to solving this problem. We applied the method to an 8 m long, high-resolution paleomagnetic record from a loess sequence in China and revealed millennial-to-sub-centennial scale features of the Matuyama–Brunhes (MB) transition. All samples were subjected to progressive thermal demagnetization with 14–15 steps up to 650–680 °C. As a result, 96% of the samples yielded a high-quality remanent magnetization. The MB transition terminated with a 75 cm thick zone with nine polarity flips. The polarity flip zone, dated at about 779–777 ka, began between the warm events “I” and “J” and terminated at the end of the cooling event coincident with the lowest axial-dipole strength interval. Most polarity flips occurred within 70 years. The virtual geomagnetic poles (VGPs) in the upper polarity flip zone clustered in the SW Pacific region, where the MB transitional VGPs from lavas of the Hawaiian and Canary Islands and lacustrine deposits of Java also clustered. These sites were probably dominated by dipolar fields. The absence of transitional fields across polarity flips implies a short time span for averaging fields due to a thin loess-magnetization lock-in zone. The reverse-to-normal polarity reversal dated at about 778 ka in Lingtai occurred at the end of the SW Pacific VGP zone, an important key bed for MB transition stratigraphy. The reversal is a good candidate for the main MB boundary. We found an excursion at about 766 ka spanning about 1 ka.

Magnetic enhancement of Chinese loess‐paleosol sequences has been used extensively as a proxy for East Asian summer monsoon variations. However, the pedogenic magnetic particles contributing to this magnetic enhancement are difficult to extract, so it is not clear how they formed. In this study, we reveal pedogenic magnetite and hematite using electron microscopy, synchrotron radiation X‐ray diffraction, and rock magnetic methods. First‐order reversal curves indicate that superparamagnetic/single domain/vortex state magnetic properties dominated both loess and paleosol samples. Samples of muscovite and chlorite, which are paramagnetic, have weak spontaneous magnetization. The 1‐ to 10‐μm‐sized fraction of host silicatesis responsible for most of the magnetic enhancement of paleosols. In the paleosol fraction, we found weathered phyllosilicates (muscovite/chlorite), including many elongated submicron to a few microns authigenic magnetite and hematite particles between layers; however, few such interlayer particles were found in phyllosilicates of the loess fraction. The concentration of magnetite/hematite particles within paleosol muscovite/chlorite grains and in aggregates of phyllosilicate fragments is much higher than that of the submicron iron oxides found on silicate surfaces. Interlayer magnetite particles are dominantly prism‐shaped with aspect ratios >~4. The authigenic magnetite must be mainly responsible for the spontaneous magnetization of the muscovites and chlorites and the paleosol magnetic properties. The protective silicates account for the low extraction efficiency and also the near absence of surface oxidation of pedogenic magnetite. Based on our results, we suggest that magnetite/hematite in weathered phyllosilicates contribute significantly to the magnetic enhancement of mature paleosols.

The effects of pedogenic magnetic grains on the magnetic fabric of paleosols were investigated using samples from the Paks loess profile, Hungary. Rock magnetic experiments, electron probe microanalysis, and scanning electron microscopy revealed characteristic signatures of (post-)pedogenic influences on the original sedimentary fabric. No differences were observed between low- and high-frequency fabric, suggesting that the particle orientation distribution of superparamagnetic particles was isotropic or nearly isotropic. In some samples with low frequency dependence, the presence of superparamagnetic contributors was negligible compared to the coarser magnetic contributors. No inverse fabric was identified, indicating that stable single-domain magnetite had a negligible contribution to the fabric. Despite differences in the magnetic mineral content, the relative contributions of coarse and ultrafine grains appeared to be constant. Various methods of altering or preserving the sedimentary fabric during (post-)pedogenic processes were described. Some processes, such as the hydromorphic effect, weakened the anisotropy of the original fabric and strengthened the orientation of the grains. Meanwhile, other processes, such as post-burial, compaction of materials, and fragmentation, strengthened the foliation with increasing anisotropy. Processes that can fix the fabric and magnetic fabric of paleosols will allow us to use the fabric to determine the paleowind direction in the Pleistocene interglacial periods in future studies.

Poor understanding of the differential evolution of interglacial climate over various regions in Eurasia greatly limits our ability to predict the specific local impacts of future climate change. Here we demonstrate starkly opposing trends in interglacial intensities in Asia and Europe over the early Middle Pleistocene and Mid-Brunhes Transitions based on the study of various climate proxies in the Paks loess record (Hungary), a key profile in the European Loess Belt. These contrasting climate trends imply major but unexplained differences in the regional response of Quaternary climate to shifts in forcing mechanisms during two major reorganizations of Earth's climate across Eurasia. Using new rock magnetic datasets from the Paks record we suggest that the changing dominance of Mediterranean, Atlantic (Westerlies) and continental air masses under the influence of the quasi permanent high pressure centres over the Fennoscandian ice sheet played a key role in the observed differences in the evolution of early Middle Pleistocene climate. We also propose that the intensification of the early Middle Pleistocene glaciation of Central Asian mountains may have strengthened and shifted the Siberian High westward on multi-millennial/orbital timescales, which in turn forced geographically contrasting expressions of the MIS 19 to 11 interglacials in Eurasia. This is the first coherent explanation for the geographically diverse response of regional climate to the early Middle Pleistocene climate transitions and points to the clear role of global cooling and expanded mid-latitude glaciers in driving these events.

Clinker ash is regarded as a granular waste of coal combustion but potentially employed as a recycled and light-weight backfill material for retaining wall and embankment in recent years. The physical, particle, compaction and mechanical properties of six selected types of clinker ash were thoroughly examined in this experimental investigation. Clinker ash owns very complex and angular shapes and it gives rise to the larger difference between the maximum and minimum void ratios. The single particle crushing strength of clinker ash is around 1/5–1/10 lower than natural sands and it indicates high crushability in nature. With similarity to natural sands, the mean crushing strength of clinker ash displays a decreasing tendency with the increase in grain diameter. A series of triaxial compression tests were performed on different types of clinker ash to examine the influences of particle characteristics, degree of compaction and effective confining pressure on their shear behaviour and deformation characteristics. Test results demonstrate that clinker ash possesses a higher peak friction angle at low effective confining pressures and gradually loses its shear strength with the rise in effective confining pressure. The great shear strength dependence on the stress level for clinker ash is confirmed. The stress-dilatancy behaviour of a given type of clinker ash is minimally affected by the degree of compaction and level of effective confining pressure. The stress ratios at the critical state of clinker ash are well correlated with the mean crushing strengths. A larger N value for clinker ash determined using Nova's rule indicates its higher crushability. The downward shift of critical state line of clinker ash due to grain crushing is identified on the void ratio and logarithm of effective mean stress plane. Additionally, grain crushing was confirmed by the comparison of the variation in grain size distribution curves and the observation of colored particles previously seeded in the tested samples before and after shearing.

Methane hydrate-bearing sediments with different amounts of fines content and at three densities were artificially prepared under controlled temperature and pressure conditions. The void ratios of specimens after isotropic consolidation tend to decrease with a rise in fines content. The fines particles enter into the pore space between sand grains and densify the specimens. A series of triaxial compression tests were performed to systematically investigate the influences of fines content and density on the shear properties of hydrate-free sediments and methane hydrate-bearing sediments. The test results demonstrate that a rise in fines content within methane hydrate-bearing sediments significantly enhances peak shear strength and promotes dilation behavior. These influences are particularly prominent for specimens at loose packing state. A decrease in void ratio increases the shear strength and stiffness of hydrate-free sediments and methane hydrate-bearing sediments containing fines content of 0% and 8.9%. It is noted that the formation of methane hydrate in samples with varying amounts of fines content increases the stress ratios at the critical state. The addition of fines particles into coarse-grained sand grains alters the internal microstructure of sand matrix and the hydrate formation pattern in the pore space between sand grains and fines particles.

We conducted diatom analyses of a core from the Pleistocene marine sequence drilled at the Chiba Section, central Japan, to reveal detailed paleoceanographic variations across the Early–Middle Pleistocene boundary. Diatom valves are most abundant at 4.5 m below the Matuyama–Brunhes magnetic polarity boundary, followed by the second highest abundance at 18.6 m above the boundary, which is consistent with the sea-level changes inferred from planktonic δ 18 O data. The highest abundance is correlated with the Marine Isotope Stage (MIS) 19.3 sea-level highstand, and the second-highest with the MIS 19.1 highstand. The abundance of the extinct species Actinocyclus ingens is quite low around these sea-level highstands, whereas it is greatest at the core depth with the minimum diatom total valves, which is correlated to the MIS 19.2 lowstand. Cold-water diatom species that are characteristic of the Oyashio Current are dominant but coexist with warm-water species of the Kuroshio Current below a core depth just postdating MIS 19.2. Above this depth, warm diatom species of the Kuroshio Current become dominant. The change in dominant diatoms suggests that the Kuroshio Front shifted northward just after MIS 19.2 and remained in the northern area until at least early MIS 18. This shift caused a rapid increase in sea-surface temperature by 4–5 °C within a sediment thickness of 1.3 m (representing ∼300 years).

Relative sea-level (RSL) observations for Marine Isotope Stage (MIS) 7 were obtained from three sites (Higashinada, Kakogawa and Mitsu) of the eastern Seto Inland Sea area, western Japan. We evaluated the magnitude of sea-level highstands during MIS 7 and the local tectonics based on RSL records of this coastal area. For this purpose, we analyzed diatom assemblages and sedimentary sulfur, and carried out tephra analysis. We also constructed a linear age model to determine the depositional ages of the sediments using altitudes of astronomical age control points obtained mainly from the present diatom data. At the Mitsu site, RSLs were estimated to be −22.87 ± 0.50 m at the MIS 7.5 highstand peak (234.6 ka), below −20.17 m at 211.2 ka, and below −20.00 m at 209.9 ka. With a tectonic subsidence rate of 0.11 ± 0.02 m/ka since the Last Interglacial Maximum at the Mitsu site, the elevation of the tectonically corrected MIS 7.5 highstand peak may have been +2.94 ± 5.19 m. The tectonically corrected sea-level elevations during MIS 7.3 are inferred to have been below +3.06 ± 4.72 m at 211.2 ka and below +3.09 ± 4.70 m at 209.9 ka. Comparisons between the diatom-inferred RSLs and the isotopically derived sea-level curve indicate that the MIS 7.3 highstand peak was above −18 m and may have been lower than the MIS 7.5 and 7.1 highstands. Based on the isotopically derived sea-level curve and the RSL data from Higashinada and Kakogawa, a tectonic subsidence rate of 0.26–0.32 m/ka was derived for Higashinada and a tectonic uplift rate of >0.17 m/ka and 0.43 m/ka and 0.26 m/ka and

A series of triaxial compression tests were performed on the methane hydrate-bearing sands formed with rounded glass beads and natural sands to examine their mechanical properties. The effect of particle characteristics on the mechanical response of methane hydrate-bearing sands with regard to the exertion of bonding force and de-bond mechanism between grains is explained from the grain-scale viewpoint. In comparison with the natural sand, methane hydrate-bearing glass beads owns a similar initial stiffness and rapidly attains the peak shear strength at a smaller axial strain. The obvious post-peak strain-softening behaviour of methane hydrate-bearing glass beads which differs from the tender post-peak strain-softening tendency of methane hydrate-bearing natural sand is observed. It is attributed to almost simultaneous exfoliation of hydrate mass from the glass beads with smooth surface within the straightly sheared layers. The substantial resource of shear strength enhancement for methane hydrate-bearing glass beads is the cohesion but the shear strength of methane hydrate-bearing natural sand was jointly governed by the cohesion and angle of internal friction. In contrast to the increasing tendency of difference of shear strength with the level of effective confining pressure for methane hydrate-bearing natural sand, the methane hydrate-bearing glass beads exerts a stronger effect of bonding force on the difference of shear strength at relatively lower pressures but this effect decreases at higher pressures.

Low field anisotropy of magnetic susceptibility (AMS) and rock magnetic measurements were applied to sediments deposited by the 2011 Tohoku-oki tsunami to reveal the dynamic of the tsunami run-up and the character of the sedimentation along the Misawa coast, Aomori Prefecture, northern Japan. In the tsunami deposits studied, elongated, coarse-grained, multi-domain titanomagnetite and magnetite minerals were the carriers of the AMS signal. Two main types of sedimentary environment are described: a higher energy, tangential stress-dominated environment with imbrication and traction/rolling transportation and a calmer, post-peak wave environment ruled by gravitational stress. Rapid characteristic changes in the tsunami dynamics are also described. The tsunami began with erosion of the pre-tsunami surface caused by rapidly increasing energy. Bedload features such as ripple stratification were developed by the repeated accelerations and decelerations of the tsunami wave during run-up. The arrival of the peak wave was indicated by high-density flow, “slurry-like” sediments. Following the peak wave, the decreasing energy was marked by a change in magnetic fabric (MF). The study showed that quite similar tendencies in the character of tsunami dynamics can be identified in tsunami deposits, despite their materials being deposited in currents with quite different energy levels.

It is recognized that methane hydrate (hereafter referred to as MH) is trapped in the sand sediments of alternating sand and mud layers in the turbidite of the Nankai Trough, Japan. The existence of fines within the marine sediment significantly affects its mechanical and physical properties. A series of plane strain compression tests at high pressures were performed in order to investigate the effect of the particle characteristics and fines content of the host sands on the shear behaviour of MH bearing sands. MH bearing sands were artificially produced using rounded glass beads and three other silica sands with different fines contents. A high-pressure low-temperature testing apparatus was equipped with a camera to observe deformation of the specimens during shearing and particle image velocimetry analysis was conducted on pictures taken during the experiments. The experimental results show that strength enhancement due to the bonding effect in MH bearing sand increases with the level of fines content. Values for both the cohesion and friction angle of MH bearing sand composed of Toyoura sand increased along with increasing MH saturation. However, in the case of MH bearing glass beads, only the value for cohesion increased when MH was formed. The maximum shear strain of MH bearing glass beads was mostly concentrated near the shear band. While the maximum shear strains of the three other MH bearing sands were concentrated within the shear band, some was widely distributed in the region outside of the shear band. A rise in the degree of MH saturation increased the angle and narrowed the width of the shear band, regardless of the fines content.

Stone column can be used as a ground improvement technique where a portion of soft soil is replaced with granular material such as stone or sand. The benefit of using stone columns in low strength soil has been proven as an efficient method to improve the bearing capacity and reduce settlement of soft soils. This study aims to investigate the improvement in shear strength of soft clay by embedded with a single crushed coconut shell (CCS) column. The cost of soil improvement can be reduced because of CCS is a waste material. This paper was done by determining the physical and mechanical properties of kaolin and CCS as well as the effect of height penetration ratio of a single CCS column on shear strength characteristics. Unconfined Compression Test (UCT) was conducted for 4 batch kaolin samples including a control sample in order to determine the shear strength. Each batch involved four samples to find the accurate value. The research variables are the height of crushed coconut shell column which is 60 mm, 80 mm and 100 mm where the column penetration ratio is 0.60, 0.80 and 1.00 respectively. A total of 16 unconfined compression tests had been conducted on kaolin sample with dimensions of 50mm in diameter and 100 mm in height. The increment of shear strength by embedded with crushed coconut shell columns is 19.02 %, 34.76 % and 24.34 % for with 4 % area displacement ratio at column penetration ratio of 0.60, 0.80 and 1.00 respectively. From the results obtained, the relationship between shear strength increases is influenced by the height of the column. The maximum column height (full penetration) does not generate the highest strength and it proves that "critical column length" theory is true in this study.

Soft clay soils are problematic soil that causes bearing capacity failure and excessive settlement, leading to severe damage to buildings and foundation. In this study, bottom ash is used to replace the natural aggregate while quicklime is used to increase the bonding between bottomash particles. This research is aimed to investigate the role of single encased lime bottom ash column (ELBAC) in improving the shear strength by using laboratory scale model. Kaolin is being used as soil sample while lime bottom ash as the reinforced column and the column is encased with non-woven geotextile. Laboratory tests are conducted to determine the physical properties of bottom ash, kaolin clay, and quicklime sample. Unconfined Compression Test (UCT) also used to test the shear strength of the reinforced kaolin samples. There are 21 kaolin samples being tested in this study and the dimension of the specimen used is 50mm in diameter and 100mm in height. However, there are two different types of the diameter of single lime bottom ash column being used which are 10mm and 16mm. The heights of the column are 60mm, 80mm and 100mm. The improvement of shear strength of single encapsulated lime bottom ash column with area replacement ratio of 4.00% (10mm column diameter) and 10.24% (16mm column diameter) are 43.58%, 50.00%, 49.17% and 38.08%, 42.67%, 32.75% at sample penetration ratio, Hc/Hs of 0.6, 0.8 and 1.0 respectively. It can be concluded that the shear strength of soft clay could be improved by the installation of the single encapsulated lime bottom ash column.

A series of undrained monotonic and cyclic triaxial tests were performed on silica sand at two initial densities and different confining pressures from 0.1 to 5 MPa to investigate their shear response and crushing behaviour. The influence of particle crushing on the undrained shear strength and pore-water pressure was examined. To clarify the evolution of particle crushing, undrained monotonic and cyclic tests were terminated at several distinctive stages and sieving analysis tests were subsequently performed on the tested specimens. In the undrained monotonic test, specimens exhibited remarkable dilation behaviour and experienced no apparent particle crushing at low confining pressures. An increase in the mean stress suppressed the dilatancy due to a faster increase of the pore-water pressure, giving rise to the occurrence of particle crushing. In the undrained cyclic test, a higher confining pressure and cyclic stress ratio resulted in a much higher relative breakage. At a specific cyclic stress ratio, the relative breakage increased as the cyclic loading progressed. The confining pressure and shear strain amplitude played a significant role in controlling the evolution of particle breakage. The correlation between the relative breakage and plastic work for specimens under isotropic consolidation, undrained monotonic, and cyclic loadings has been validated experimentally.

A series of high-pressure isotropic compression tests were performed on four types of poorly graded silica sand that were artificially prepared based on representative grading curves and similar mineralogy composition of seabed sediment containing different fines contents existing in the Nankai Trough. The addition of fines steepens the initial compression path and increases the decrement of the void ratio after loading. The transitional behaviour of the poorly graded sand with a larger amount of fines content was identified. The slope of the normal compression line shows a slight decreasing tendency with the level of fines content. The bulk modulus of silica sand with fines was lower when compared with the published results of silica sand without fines. A small amount of particle crushing of the four types of poorly graded sand with variable fines content levels was noticed, and the results indicated that the degree of particle crushing tended to decrease as the fines content increased.

Detailed sea-level variation was investigated for Marine Isotope Stage (MIS) 19, based on diatom and grain size analyses of a marine sequence in a core of the Osaka Group. Diatom sea-level proxies represent precession-related signals correlated with highstands MIS 19.3 and 19.1, and lowstand MIS 19.2. Astronomical tuning shows the marine sequence has a uniform accumulation rate of about 60 cm ka−1. A rapid sea-level fall event was found in the earliest MIS 19, demonstrated by several independent sea-level proxies of diatom and grain size. This event began with a rapid sea-level drop, followed by a gradual recovery, at about 783–782 ka. A maximum abundance of pelagic diatom taxa at a core depth of 402.20 m evidently shows the highest sea-level peak in MIS 19, supported by many other proxies. Based on the diatom data, sea-level change across MIS 19.1 is characterized by centennial to millennial fluctuations. The sea-level fall event began just after the onset of a cooling event previously reported from the same core. Observations of a comparable sea-level fall signal in many deep-sea core records suggest the event is global.

For methane hydrate production, it is essential to understand the mechanical behaviour related to safety and efficiency. Plane strain compression tests were carried out to investigate the macro and micro behaviour of both the MH-bearing sand and the host sand. It was found that whilst there were no clear peak stress ratios in the TC results, the PSC results showed a marked increase in the peak stress ratios, regardless of whether or not MH was included. The peak strength increased due to MH, and the dilative behaviour of the MH-bearing sand occurred more markedly than that of the host sand. As the confining pressure increased, the peak strength decreased and the volume change became contractive. Deformation in the shear band was suppressed as the confining pressure increased for the host sand, whereas contractive and dilative behaviour occurred in the shear band for the MH-bearing sand regardless of the level of confining pressure. The thickness of the shear band for the MH-bearing sand appeared to be thinner than that for the host sand and there was no dependence on the confining pressure. As the confining pressure increased, the occurrence of particle crushing also increased. Coefficient of uniformity Uc, inside the shear band, was 1.7 times larger than the original Uc of the host sand when σ 3 ′ = 5 M P a .

We present a detailed stratigraphy of the lithology, sedimentary facies, magnetic susceptibility, and chemical composition of a 54-m thick core sequence drilled adjacent to the Chiba section, a candidate for the Global Boundary Stratotype Section and Point of the early–middle Pleistocene boundary. Siltstones rich in trace fossils are dominant throughout the core, except for the lowermost sand beds. The Byakubi tephra is divided into three units, of which the uppermost (39.54–39.49 m core depth) is identified as a primary bed showing evidence of fallout. The preliminary Matuyama–Brunhes magnetic polarity boundary lies 1 m above the top of the fallout unit. Maximum and minimum susceptibility axes for anisotropy of magnetic susceptibility have shallow ( 73°) inclinations, respectively, throughout the core. The results suggest that sedimentary structures formed in calm environments remain undisturbed in the sediment. Clustered maximum axis directions indicate the influence of a persistent NW–SE contour current. The homogeneous depositional environment for the siltstone interval is supported by relatively smooth variations in magnetic susceptibility and chemical composition. Stratigraphic correlation with published oxygen isotope data indicates that the depositional age of the core may extend from the end of marine oxygen isotope stage (MIS) 20 to just after mid-MIS 19, from which an average sedimentation rate of 2–2.5 m/ky is estimated. These results suggest that the Chiba section has a high potential to provide an excellent stratotype for the early–middle Pleistocene boundary.

A summary of approximately three decades and greater than thirty loess magnetic fabric studies is presented here. The revised studies cover various loess regions from the Chinese Loess Plateau across the European Loess Belt to Alaska. Although there is still an ongoing argument about the feasibility of the magnetic fabric of loess in paleowind reconstructions, the determination of prevailing wind direction during various periods of the Pleistocene is the main goal of magnetic anisotropy analysis of the revised loess successions. The magnetic fabric analysis of loess from Chinese Loess Plateau provided significant information about the characteristics of paleomonsoon in East Asia, and the results from other loess regions, such as Alaska, the European Loess Belt, and Siberia, are also promising. As it is shown in this review, the synthesis of the paleowind direction results from the studied profiles may already provide a significant foundation for future climate models by the reconstruction of key climate centres and main continental level wind tracks. Besides the reconstruction of prevailing paleowind directions, there are numerous loess magnetic fabric studies using magnetic anisotropy parameters in the reconstruction of the characteristics of long-term climate trends, climate transitions and glacial- interglacial cycles. There are some lesser known aspects contributing to magnetic fabric of loess, such as the influence of various types of magnetic contributors on the overall fabric (i.e. the study of sub-fabrics) and their role in environment reconstruction. Besides the identification of aeolian magnetic fabric, not so many studies focus on the magnetic anisotropy characteristics of materials, possibly developed by water-lain sedimentation, pedogenesis, mass movements and permafrost activity. Novel results from Hungarian loess, especially from Paks, connected to some of the latter topics are also presented. Such topics includes the analysis of the nanofabric in paleosols, developed by pedogenesis, the comparison of magnetic fabric, formed during high energy transportation by aeolian or aquatic agents, and the periodicity analysis of magnetic parameters during the early Middle Pleistocene. New research lines, introduced in this review, may inspire new researches, and provide new perspectives for the next generation of magnetic anisotropy studies of loess successions., Project BU235P18 (Junta de Castilla y Leon, Spain) and the European Regional Development Fund (ERD), project PID2019-108753GB-C21/AECI/10.13039/501100011033 of the Agencia Estatal de Investigación and project PID2019-105796GB-100/AECI/10.13039/501100011033 of the Agencia Estatal de Investigación. A fellowship was awarded to B. Bradák at Kobe University, Japan, by the Japan Society for the Promotion of Science (JSPS; P15328) during the period of 2015.10–2017.10.

Reasonable prediction of marine ground stability is vital for the safe exploitation of methane gas from the seabed and development of relevant technologies for gas production. Constitutive models based on a critical state soil mechanics framework for methane hydrate-bearing sediments have been proposed in recent decades. They required careful calibration of laboratory results to obtain accurate information on model parameters. This study presents a comprehensive analysis of triaxial shear test data to examine the effects of hydrate saturation on the geomechanical characteristics of methane hydrate-bearing sediments, particularly at the critical state. Multiple critical state lines are identified for methane hydrate-bearing sediments with different levels of hydrate saturation on the specific volume and logarithm of mean stress plane. A rise in hydrate saturation shifts the critical state line of methane hydrate-bearing sediments upward and slightly increases the gradient of critical state line in the v − ln p ′ plane. Non-unique critical state lines are observed for methane hydrate-bearing sediments under plane-strain loading conditions. Considering methane hydrate saturation as an extra dimension of critical states, the critical state line in the plane of specific volume and logarithm of mean stress, becomes a three-dimensional critical state surface.

Methane hydrate (MH) becomes a promising new energy in some countries including China and Japan due to its huge reservation. The key mission is to find the safe and efficient exploitation method. The exploitation processes will cause stress changes, which may induce submarine landslides and failures of engineering projects. This chapter described some state-of-art exploitation methods reproduced in laboratory and in numerical modelling to understand the responses of soils during exploitation process. These studies could provide valuable guidance for real life projects.

The chronology of the World Heritage Site of Sangiran in Indonesia is crucial for the understanding of human dispersals and settlement in Asia in the Early Pleistocene (before 780,000 years ago). It has been controversial, however, especially regarding the timing of the earliest hominin migration into the Sangiran region. We use a method of combining fission-track and uranium-lead dating and present key ages to calibrate the lower (older) Sangiran hominin-bearing horizons. We conclude that the first appearance datum for the Sangiran hominins is most likely ~1.3 million years ago and less than 1.5 million years ago, which is markedly later than the dates that have been widely accepted for the past two decades.

This research was aimed to investigate the role of group encapsulated lime bottom ash columns in improving the shear strength by using laboratory scale model. Kaolin was being used as soil sample and lime bottom ash as the reinforced columns. The reinforc ed kaolin samples were tested by using Unconfined Compression Test (UCT). A total 7 batches of kaolin sample had been tested and each batch consist of 3 specimens represent sample without lime bottom ash column, partially penetration and fully penetration for group lime bottom ash columns. The specimen used was 50 mm i n diameter and 100 mm in height . The height of the group columns was 60 mm, 80 mm and 100 mm with 10 mm and 16 mm column diameter . The group encapsulated lime bottom ash columns was installed in the triangular pattern, as it was much easier to maintain the location of installed columns and the spacing in between the columns. The improvement of shear strength of group encapsulated lime bottom ash columns with area replacement ratio of 12.00 % (1 0 mm column diameter) and 30.72 % (16 mm column diameter) was 29.00 %, 44.17 %, 29.75 % and 1.00 %, 3.92 %, 7.33 % at sample penetration ratio, H c /H s of 0.6, 0.8 and 1.0 respectively. It can be concluded that the shear strength of soft clay could be improv ed by the installation of group encapsulated lime bottom ash columns. However, the improvement of shear strength of 10 mm group encapsulated lime bottom ash columns was increased more significant compared to 16 mm group encapsulated lime bottom ash columns .

Granulated coal ash (GCA), a mixture of the by-product from milling processes with a small amount of cement added, has recently come to be used as a new form of geomaterial. The shear strength and deformation behaviours of GCA are greatly determined by its relative density or void ratio. A series of drained triaxial compression tests were performed on cylindrical specimens of GCA at confining pressures of between 50 kPa and 400 kPa at initial relative densities of 50%, 70% and 80%. Experimental results show that a rise in relative density increases the peak shear strength and intensifies the dilation behaviour. The initial tangent modulus and secant modulus of the stress-strain curve increase with increasing initial relative density, whereas the axial and volumetric strains at failure decrease with level of initial relative density. The stress-dilatancy relationships of GCA at different relative densities and confining pressures display similar tendency. The dilatancy behaviour of GCA is modelled by the Nova rule and the material property N in Nova rule of GCA is much larger than that of natural sand.

Recent high-resolution magnetic and microfossil data from a long core penetrating the Osaka Group, Japan are astronomically tuned and reassessed to reveal detailed stratigraphic features across the Matuyama–Brunhes (MB) polarity transition during Marine Isotope Stage (MIS) 19. The sediments have a uniform and high average accumulation rate of 63 cm/ky. Astronomical tuning based on six calibration points, including a clear MIS 19.2 sea-level lowstand, dates the main MB boundary (MBB) to 777.6 ka, the sea-level peak of the MIS 19.3 highstand to 780.7 ka, and the climatic thermal maximum (TM) to 776.4 ka. The MB transition began with a short-lived normal polarity episode that occurred before the highstand at MIS 19.3, and terminated with multiple rapid reversals that occurred between highstand MIS 19.3 and lowstand 19.2. The TM just postdates the termination of the MB transition, and occurs about 4000 years after the sea-level peak. The delayed TM is also observed at Gesher Benot Ya'aqov, Israel and on the Mediterranean coast, and possibly at Lake Baikal. In high-resolution records from Chinese loess–paleosols and deep-sea sediments, the rapid reversal zone of the MBB has a very similar climatostratigraphic character. These magneto-climatostratigraphic features in MIS 19 are useful for correlating between terrestrial and marine sediments. The delay in warming relative to the sea-level highstand seems to have been due to a cloud-albedo effect induced by an increase in galactic cosmic ray flux during an extremely low magnetic field intensity interval.

We describe magnetic fabric and depositional environments of aeolian (loess) deposits from Paks, Hungary, and develop a novel, complex conceptual sedimentation model based on grain size and low-field magnetic susceptibility anisotropy data. A plot of shape factor (magnetic fabric parameter) and dry deposition velocity estimated from grain-size reveals primary and secondary depositional processes during the sedimentation of loess. Primary ones are driven by gravity, with poorly oriented MF for fine grain materials, and by tangential stress, with flow-aligned or flow-transverse fabric for coarser grain sediments. The fabric developed by a primary process is called depositional magnetic fabric. Secondary processes develop in unconsolidated sediments, beginning right after deposition and terminating before the start of diagenesis. Under slow sedimentation conditions, deposited materials are likely to be exposed near the surface for longer periods. Therefore, relatively strong winds with a stable direction can alter the fabric of non-buried surficial sediments. As a result, grain orientations may change from scattered, non-flow oriented fabric to flow-oriented fabric. This type of fabric, developed by a secondary process, is called transformed magnetic fabric, and is characterized by relatively well-defined grain orientation, which allows us to estimate a dominant wind direction.

An active sequence of earthquakes (foreshock, main-shock, and aftershocks) hit the Kumamoto area (Japan) in April 2016, resulting in 69 deaths and considerable economic loss. The earthquakes induced numerous ground failures and cascading geo-hazards, causing major damage to important infrastructures. The main damage patterns include: (a) surface rupture with widespread subsidence of the surface ground, resulting in damage and disruption to transport infrastructure; (b) landslide and slope failure of mountains causing severe damage, collapse and near-collapse of bridges; and (c) liquefaction in some areas of Kumamoto City. Following the earthquakes, field surveys were conducted to study the damages and to understand the main cause of the observed failures. This technical note provides a summary of the geotechnical and infrastructural damage in Kumamoto and the lessons learnt and future research needs are also highlighted.