Fish Anchor Dived – Confirmation Through Field Tests in the Swan River

This paper reports the results from field tests on a 1/15th scale recently developed fish anchor. The tests were conducted at three locations in the Swan River, Perth. Two series of tests were performed from the Burswood and Maylands jetties with water depths between 1.1 and 1.9 m. The final series of tests were undertaken in deeper waters of 2.6 m from a barge. The riverbed at the Burswood Jetty and barge test location consisted of soft clay, and that at the Maylands Jetty comprised sandy silt. The tip embedment depths of the scaled fish anchor, with dry weight of 0.304 kN and impact velocity of 5.89∼9.55 m/s, in soft clay were 1.17∼2.40 times the anchor length. For similar impact velocities, the tip embedment depths in sandy silt were 30 ∼ 60% shallower than those in soft clay. By comparing the field test data in clay, the fish anchor achieved normalised embedment depths similar to those of the torpedo and OMNI-Max anchors under half or less impact velocity. Most importantly, the field tests confirmed the diving behaviour of the fish anchor under loading with mudline inclination of 20° and 25°, with the second peak dictated the capacity. The ultimate capacity was 5∼7 times the anchor submerged weight in water.

Confirmation of Homoeoneuria Eaton, Confirmation of Homoeoneuria Eaton, 1881 (Ephemeroptera: Oligoneuriidae) record in Colombia

Homoeoneuria Eaton, 1881 is a genus of the Oligoneuriidae family whose geographical distribution remains poorly documented, especially in the Northern region of South America. Here we confirm the record of Homoeoneuria inColombia, thus extending its distribution in South America beyond the records from Brazil, Peru, and Argentina. The confirmation was done on three nymphs from the department of Cesar found on sandy-silt sediments in the transition between the Andean and Caribbean regions.

The effect of tamping conditions and sample preparation on undrained shear strengths of a non-plastic sandy silt tailings

A series of direct simple shear (DSS) tests were carried out on a non-plastic sandy silt lead-zinc-silver tailings to develop a relationship between undrained shearing behaviour and density, where in situ testing had identified contractive behaviour. The critical state line was also obtained through triaxial compression tests to enable the DSS tests to be viewed in a critical state framework and allow comparison with in situ testing. It was found that the gravimetric water content (GWC) used to tamp the specimens had a significant effect on the resulting undrained strengths when attempting to achieve dense states - with higher GWC giving lower strength at a given density than a lower GWC. Intact and slurry deposited (SD) samples were also tested to access denser states without inducing tamping-related stresses. These showed a more consistent trend with the loose-tamped specimens, and with other data from the literature. Plausible explanations as to the causes of the increased strength of dense-tamped samples were obtained through estimating potential preconsolidation stresses and “locked in” horizontal stresses that may occur from dense tamping. The importance of these observations on the development of density - strength profiles in engineering practice was outlined.

Influence of Some Additives on the Properties of OPC Solidified Sandy Silt

The ordinary Portland cement (OPC)-based solidification process is used extensively to reinforce soils due to its available and good bonding properties. Alternative products are used in cementitious materials to enhance the strength and to reduce OPC consumption. In this study, the effect of additive type and mass fraction on the microstructure and mechanical properties of solidified sandy silt are investigated. There are four types of additives (gypsum, lime, clay particles, and fly ash) at mass fractions of 2, 3, and 4% that are considered in order to study their mechanical properties (unconfined compression, indirect tensile, flexural strength, and compressive resilient modulus) at 7, 14, 28, 60, and 90 days. The optimal contents of additive gypsum, clay particles, and fly ash are determined to be 2%, 4%, and 4%, respectively. Such improvement of additive-modified OPC solidified sandy silt is due to the formation of the crystalline compound or the gradation composition improvement via field emission scanning electron and X-ray diffraction analysis.

Impact-Induced Liquefaction Mechanism of Sandy Silt at Different Saturations

Landslide-induced liquefaction has received extensive attention from scholars in recent years. In the study of loess landslides in the southern Loess Plateau of Jingyang, some scholars have noted the liquefaction of the near-saturated sandy silt layer that is caused by the impact of loess landslides on the erodible terrace. The impact-induced liquefaction triggered by landslides is probably the reason for the long-runout landslides on the near-horizontal terrace. In order to reveal the mechanism of impact-induced liquefaction, this paper investigates the development of pore pressure and the impact-induced liquefaction of sandy silt under the influence of saturation through laboratory experiments, moisture content tests, and vane shear tests. It has been found that both the total pressure and pore water pressure undergo a transient increase and decrease at the moment of impact on the soil, which takes 40–60 ms to complete and only about 20 ms to arrive at the peak. Moreover, silty sand with a saturation of more than 80° was liquefied under the impact, and the liquefaction occurred in the shallow layer of the soil body. The shear strength of the liquefied part of the soil is reduced to 1.7∼2.8 kPa. Soils with lower saturation did not liquefy. The mechanism of the impact-induced liquefaction can be described as follows: under impact, the water in the soil gradually fills the pores of the soil body as the pore size decreases, and when the contact between the soil particles is completely replaced by pore water, the soil body loses its shear strength and reaches a liquefied state. Soils in the liquefied state have a very high permeability coefficient, and the water inside the soil body migrates upward as the particles settle, resulting in high-moisture content in the upper soil.

Analysis of the Development Characteristics and Influencing Factors of Freezing Temperature Field in the Cross Passage

Based on the analysis of the temperature measurement data of the Shanghai Metro Line 15 cross passage freezing project, it was found that the gray silt layer of cross passage No. 2 outperforms that of cross passage No. 1 on the freezing effect, which is mainly attributed to the large loss of cooling capacity in the latter passage. Within the same stratum, the soil temperature at the duct piece is higher than that of the deep soil. When the soil freezes for 45 days, the temperatures of the sandy silt and gray silt layers of the same cross passage drop to −8.25°C and −6.91°C, respectively, indicating that the freezing effect of the sandy silt layer is better than that of the gray silt layer. Moreover, simulations were performed for deviation freezing pipes, nondeviation freezing pipes, and different freezing pipe diameters in the cross passage No. 1, respectively. It was found that the maximum difference of the closure completion time between the deviation and nondeviation freezing pipes is 6 days. Furthermore, for deviation freezing pipes and nondeviation freezing pipes at the center of the cross passage, the minimum difference in the freezing wall thickness reduces from 0.45 mm after 20 days of freezing to 0.06 mm after 45 days of freezing, indicating that the difference in the freezing wall thickness gradually weakens as freezing develops gradually. The deviation freezing pipe increases the spacing of freezing pipes in the deep soil. As the pipe spacing increases, the influence of the pipe diameter on the closure completion time of the freezing wall decreases.

Key drivers of pyrogenic carbon redistribution during a simulated rainfall event

Pyrogenic carbon (PyC) is produced by the incomplete combustion of vegetation during wildfires and is a major and persistent pool of the global carbon (C) cycle. However, its redistribution in the landscape after fires remains largely unknown. Therefore, we conducted rainfall simulation experiments on 0.25 m2 plots with two distinct Swiss forest soils (Cambisol (clay loam) and Luvisol (sandy silt)). We applied PyC produced from wood (Picea abies) labeled under FACE conditions and C4 grass (Miscanthus sinensis) to the soil surface to study PyC redistribution by runoff and splash and the vertical mobility of PyC in a 10 cm unsaturated soil column based on the differences in δ13C of soils and PyC. We assessed the effect of soil texture, slope angle and PyC characteristics (feedstock and particle size) on the mobility of PyC during 30 min of intense rainfall (102 mm h−1). Our results highlight that PyC is highly mobile. Surface runoff transported between 0.2 % and 36.0 % of the total added PyC. Erosion by splash further redistributed 10.3 % to 25.3 % of the added PyC. Soil type had a substantial impact on the redistribution of PyC by both runoff and splash: on average, we recovered 10.5 % of the added PyC in runoff and splashed material for the clay-rich Cambisol and 61.3 % of the added PyC for the sandy silt Luvisol combined. PyC feedstock had a clear but contrasting effect on PyC redistribution: relocation in the runoff and splashed material was greater for wood PyC (43.4 % of total added PyC) than grass PyC (28.4 %). However, more wood PyC (11.5 %; fraction of organic C derived from the PyC) remained where it was initially applied compared to grass PyC (7.4 %). The results further suggest that the effect of PyC characteristics on its mobility can be highly variable and depend not only on the material from which it was derived, but also on other factors (e.g., particle size, porosity, density). In particular, the mobility of PyC was almost twice as large for fine-grained PyC (< 63 µm) than for coarse PyC (63 µm–2 mm). Vertical mobility of PyC up to 10 cm depth was greater in the clay-rich, well-aggregated Cambisol but limited in the physically instable Luvisol, likely due to quick aggregate breakdown and surface sealing. The addition of PyC to the surface of the studied soils further induced changes in the export of native soil organic carbon (nSOC) after the 30 min rainfall event. Our study shows that large quantities of PyC can be redistributed by water erosion over short timescales and that the mobility of PyC depends to a great extent on the response of soils to rainfall. Moreover, the addition and redistribution of PyC affects the export of nSOC and thus the C budget of fire-affected soils and catchments.