Performance of Mortar and Chemical Grout Injection into Surrounding Soil When Slurry Pipe-jacking Method is Used

Small-diameter shallow tunnels are often being built by using the slurry pipe-jacking method. This system involves the pushing or thrusting of a drivage machine and concrete pipes into the ground. Chemical grout injection into the surrounding soil around the tunnel is carried out after the drivage and pushing processes are finished. The purpose of the chemical grout injection is to maintain permanent stability of the surrounding soil. However, the behavior of the chemical grouting material in the surrounding soil around the tunnel and the amount of optimum injection is not clearly understood. From these points of view, this paper discusses the performance of the chemical grouting material, when it is injected into the surrounding soil around the tunnel, by means of 2-D Eulerian–Lagrangian seepage analysis. Moreover, the effectiveness of the chemical grout injection was evaluated by using the non-linear finite element method. This investigation show when the range of the grouted zone is designed; it is necessary that the relationship between Young’s modulus of the soil/grouted zone and the confining stress be taken into consideration in order to establish effective, economical and safe chemical grout injection system. Understanding the performance of the seepage/dispersion behavior of the chemical grout and the characteristics of soil/ grouted zone is also important.     

Seasonal variations in the nitrogen isotopic composition of settling particles at station K2 in the western subarctic North Pacific

Intensive observations using hydrographical cruises and moored sediment trap deployments during 2010 and 2012 at station K2 in the North Pacific Western Subarctic Gyre (WSG) revealed seasonal changes in δ ¹⁵N of both suspended and settling particles. Suspended particles (SUS) were collected from depths between the surface and 200 m; settling particles by drifting sediment traps (DST; 100–200 m) and moored sediment traps (MST; 200 and 500 m). All particles showed higher δ ¹⁵N values in winter and lower in summer, contrary to the expected by isotopic fractionation during phytoplankton nitrate consumption. We suggest that these observed isotopic patterns are due to ammonium consumption via light-controlled nitrification, which could induce variations in δ ¹⁵N(SUS) of 0.4–3.1 ‰ in the euphotic zone (EZ). The δ ¹⁵N(SUS) signature was reflected by δ ¹⁵N(DST) despite modifications during biogenic transformation from suspended particles in the EZ. δ ¹⁵N enrichment (average: 3.6 ‰) and the increase in C:N ratio (by 1.6) in settling particles suggests year-round contributions of metabolites from herbivorous zooplankton as well as TEPs produced by diatoms. Accordingly, seasonal δ ¹⁵N(DST) variations of 2.4–7.0 ‰ showed a significant correlation with primary productivity (PP) at K2. By applying the observed δ ¹⁵N(DST) vs. PP regression to δ ¹⁵N(MST) of 1.9–8.0 ‰, we constructed the first annual time-series of PP changes in the WSG. This new approach to estimate productivity can be a powerful tool for further understanding of the biological pump in the WSG, even though its validity needs to be examined carefully.     

Chlorophyll-specific absorption coefficients and pigments of phytoplankton off Sanriku, northwestern North Pacific

The variety in shape and magnitude of thein vivo chlorophyll-specific absorption spectra of phytoplankton was investigated in relation to differences in pigment composition off Sanriku, northwestern North Pacific. Site-to-site variations of the absorption coefficients,a _ph ^* (λ), and pigment composition were clearly observed. At warm-streamer stations, higher values ofa _ph ^* (440) anda _ph ^* (650) were found with relatively high concentrations of chlorophyllb (a green algae marker). At stations located in the Oyashio water (cold streamer),a _ph ^* (440) values were lower and fucoxanthin (a diatom marker) concentrations were higher, compared to the other stations. The peak in the absorption spectra at the Oyashio stations was shifted toward shorter wavelengths, which was probably due to the presence of phaeopigments. In a Kuroshio warm-core ring, the magnitude ofa _ph ^* (440) was in between those at the warm-streamer and Oyashio stations, and the diagnostic pigment was peridinin (a dinoflagellate marker). These findings indicated that major differences in phytoplankton absorption spectra of each water mass were a result of differences in the phytoplankton pigment composition of each water mass, which was probably related to the phytoplankton community.     

Effects of deforestation and weather on diurnal frost heave processes on the steep mountain slopes in south central Japan

Freezing and thawing processes play an important role for the gravitational transport of surface materials on steep mountain slopes in Japan. The effects of deforestation on frost heave activity were observed through the 2012/2013 winter season in Ikawa University Forest, a southern mountainous area in central Japan (1180–1310 m above sea level). During periods without snow cover, needle ice development prevailed at a clear‐cut site, and the downslope sediment movement of upper soil was 10 to 15 cm through the winter season. At a non‐cut site, rise and fall in the ground surface level prevailed on a weekly scale, with no evident downslope movements at the surface; ice lens formation in the soil layer is assumed. Abrupt changes in the radiation budget, such as the strengthening of nighttime radiative cooling and increases in daytime direct insolation, induced frequent development/deformation of needle ice at the clear‐cut site. In snow‐free periods, the day‐to‐day variability in needle ice growth length and in nighttime averaged net radiation showed significant correlations; cloudy weather with warmer and moist air intrusion associated with synoptic disturbances prevented the occurrence of needle ice. Namely, day‐to‐day weather changes directly affected the mass movement of the upper soil after deforestation. Shallow snow cover occurred discontinuously through the winter and is likely an important factor in keeping the soil moisture sufficiently high in the upper soil layer for initiating needle ice during snow‐free periods. We also discuss contributions of coastal extratropical cyclone activities providing both snow cover and cloudy weather in the southern mountain areas of central Japan to the intra‐seasonal variability in frost heave and its indirect effect on soil creep and landslides on the deforested steep slopes. Copyright © 2015 John Wiley & Sons, Ltd.     

Satellite and ship observations of Kuroshio warm-core ring 93A off Sanriku, northwestern North Pacific, in spring 1997

Synoptic ship and satellite observations were performed of the Kuroshio warm-core ring (KWCR) 93A and its adjacent waters, off Sanriku, northwestern North Pacific, between early April and late June 1997. The temporal and spatial distribution of chlorophylla (Chl-a) and sea surface temperature in the study area were analyzed using data from ADEOS Ocean Color and Temperature Scanner (OCTS) and NOAA Advanced Very High Resolution Radiometer (AVHRR). The objective of this study was to describe the temporal and spatial variability of the spring bloom and understand its relationship with the changes in the hydrographic structure of these waters in and around KWCR 93A. The maximum value of Chl-a concentration in the ring was less than 1 mg/m³ during April. The spring bloom in the ring occurred early in May and the relatively high maximum (>1.0 mg/m³) continued from early in May to mid-June. In late June, a ship-observed surface Chl-a concentration of less than 0.4 mg/m³ suggests that the spring bloom had already declined in and around KWCR 93A. Double spiral structures of warm and cold streamers appeared from late April to mid-May, which may have an influence on the occurrence of the spring bloom in and around the ring. In this episodic event, the warm streamer can maintain the available potential energy of the ring and the strength of upwelling around the ring. The cold streamer provided water with a high Chl-a concentration to the surface layer of the ring. In order to understand the temporal and spatial variability of Chl-a distribution in the ring, the behavior of the warm and cold streamers needs to be taken into consideration.     

The role of crabs (Macrophthalmus japonicus) burrows on organic carbon cycle in estuarine tidal flat,Japan

The objective of this study is to elucidate the burrow structure and to clarify the role of burrows in material cycle in the tidal flat. In our work, we focused on the dominant species in muddy tidal flat, crab Macrophthalmus japonicus.Burrow structure of Macrophthalmus japonicus was investigated on a Katsuura river tidal flat in Tokushima prefecture, Japan, using in situ resin casting. Sampling was conducted in August 2006, and a total of 48 burrow casts were obtained. Burrows consisted mainly of J-shaped structures (98%) while the rest belonged to U-shaped structures (2%). The maximum measured burrow volume was 120 cm³ and wall surface area was 224 cm², while maximum burrow length and depth were 23.2 cm and 16.5 cm, respectively. Burrow volume and surface area were strongly correlated with carapace width of M. japonicus. Investigation of the individual number of M. japonicus in 13 quadrats (50 × 50 × 20 cm) was conducted using 2 mm sieve. The number of M. japonicus was 15–31 ind./m². Using cohort analysis we estimated that surface area of burrows was 0.07–0.15 m²/m².CO₂ emission rate was measured at the surface sediment during the period from June to December 2008. Results varied from 13.8 ± 2.2 to 49.4 ± 3.2 mg CO₂/m²/h, and organic carbon decomposition was 3.8 ± 0.6–13.5 ± 0.9 mg C/m²/h. This leads the increase of organic carbon decomposition by 1.1 times, because of the expansion of the tidal flat surface area by burrowing activity. Organic carbon decomposition in burrow walls therefore contributed to organic matter decomposition in the tidal flat. These results indicated that in situ activities of Macrophthalmus japonicus significantly influence the material cycle and it is important to consider the existence of burrow in order to understand the fluxes of materials and to evaluate the purification function of the tidal flat.     

Evolution and effect of the stress concentration and rock failure in the deep multi-seam coal mining

Supports crushing accident occasionally occurs in the protected seam exploitation of deep multi-seam coal mining structure and results in adverse effect to the production. To prevent its recurrence in a newly developed working field, a 3D numerical extraction model was built based on the geologic and mining conditions of Jining coal mine to evolve the changes, state and characteristics of the reconstructed vertical and lateral stress in rock interlayer after protective seam exploitation. Stress release and increase zones of this mining structure were separated. Mining-induced localized stress concentration and the interlayer rock failure behavior were explored. The action of concentrated stress on the hydraulic supports in protected seam was discussed upon the major stress redistribution. Using the infinitesimal strain method, a mechanical model was created to further explore, from the vertical and lateral directions, the cause and mechanism of localized stress concentration and rock failure behavior in rock interlayer. The field investigation was finally performed to verify the numerical and mechanical results, and the essential control measures were proposed to prevent this accident. Key findings of this study bring some new insights into the deep multi-seam coal extraction and help to promote a more reliable underground mining.     

Seasonal changes in the mesozooplankton biomass and community structure in subarctic and subtropical time-series stations in the western North Pacific

Seasonal changes in mesozooplankton biomass and their community structures were observed at time-series stations K2 (subarctic) and S1 (subtropical) in the western North Pacific Ocean. At K2, the maximum biomass was observed during the spring when primary productivity was still low. The annual mean biomasses in the euphotic and 200- to 1000-m layers were 1.39 (day) and 2.49 (night) g C m^?2 and 4.00 (day) and 3.63 (night) g C m^?2, respectively. Mesozooplankton vertical distribution was bimodal and mesopelagic peak was observed in a 200- to 300-m layer; it mainly comprised dormant copepods. Copepods predominated in most sampling layers, but euphausiids were dominant at the surface during the night. At S1, the maximum biomass was observed during the spring and the peak timing of biomass followed those of chlorophyll a and primary productivity. The annual mean biomasses in the euphotic and 200- to 1000-m layers were 0.10 (day) and 0.21 (night) g C m^?2 and 0.47 (day) and 0.26 (night) g C m^?2, respectively. Copepods were dominant in most sampling layers, but their mean proportion was lower than that in K2. Mesozooplankton community characteristics at both sites were compared with those at other time-series stations in the North Pacific and with each other. The annual mean primary productivities and sinking POC fluxes were equivalent at both sites; however, mesozooplankton biomasses were higher at K2 than at S1. The difference of biomasses was probably caused by differences of individual carbon losses, population turnover rates, and trophic structures of communities between the two sites.