Vane Tester Research Articles

An inexpensive and lightweight dynamic cone penetrometer for the characterization of shallow submerged sediments

Abstract Sediment compaction is an indicator of the health of benthic communities. At the same time, many of the extractive or cultivation activities on the coast take place in areas of special environmental interest and remove or compact the sediment by their own activity or simply by access on foot. Measurements of compaction or penetration resistance of marine or river sediments are not common, especially in submerged environments. Although there are devices, such as vane testers, that can be used in non‐submerged sediments, lightweight and inexpensive devices for measuring compaction in submerged sediments are rare. An apparatus for measuring sediment penetration resistance based on the dynamic cone penetrometers used in terrestrial environments is described and tested. The device is lightweight and inexpensive, and although it is intended for use in submerged sediments, it can also be used manually in sediments accessible by foot. In the process of testing the apparatus, the penetration resistance values of surfaced sediments have been compared with those obtained with a vane tester to estimate compaction. This new lightweight penetrometer provides inexpensive penetration resistance values as a measure of compaction in the sediment layer of greatest interest for the management of habitats and communities and makes it possible to establish criteria for action and to measure its effectiveness.

Affordable inline structuration measurements of printable mortar with a pocket shear vane

The control of mortar rheology is of paramount importance in 3D printing concrete by extrusion. This is particularly sensitive for two-component (2K) processes that use an accelerator to switch the printed mortar very quickly from a liquid behavior to a sufficiently solid behavior to be able to be printed (i.e. structuration). After some main key points about measuring the structuration of printed mortars, we propose an original and simple inline test using a pocket shear vane tester. The test is able to measure over several decades of yield stress range, mobilizes small quantities of mortar and enables in-situ measurements on freshly printed layers. The results highlight the difference of structuration between a benchtop-prepared printable material and a truly printed material, fostering the importance of inline measurements, and demonstrating the quality of the method. This pocket shear vane test appears as good contender for a light and affordable rheometer for 2K printable mortars.

Effects of Herbaceous Plant Roots on the Soil Shear Strength of the Collapsing Walls of Benggang in Southeast China

Failure of collapsing walls is an important process affecting the development of Benggang and is closely related to the soil shear strength. Plant roots can increase the soil shear strength. However, the effects and mechanisms of root reinforcement on the soil shear strength of collapsing walls remain unclear. To explore the shear strength characteristics of collapsing walls and their influencing factors under different vegetation conditions, Pennisetum sinese, Dicranopteris dichotoma, Odontosoria chinensis, and Neyraudia reynaudiana were adopted as experimental objects in the Benggang district of Anxi County, Southeast China. We measured the root characteristics and in situ shear strength of root–soil complexes by dividing soil with the four vegetation conditions into five soil layers: 0–5 cm, 5–10 cm, 10–15 cm, 15–20 cm, and 20–25 cm. The average shear strength of the root–soil complexes of the various plants ranked as follows: Pennisetum sinese (30.95 kPa) > Odontosoria chinensis (28.08 kPa) > Dicranopteris dichotoma (21.24 kPa) > Neyraudia reynaudiana (14.99 kPa) > bare soil (11.93 kPa). The enhancement effect of the root system on the soil shear strength was mainly manifested in the 0–5 cm soil surface layer. The soil shear strength attained an extremely significant positive correlation with the root length density, root surface area density, root volume density, root biomass density, for root diameters (L) less than or equal to 0.5 mm and between 0.5 and 1 mm, the soil shear strength could be simulated by using root volume density. The shear strength of undisturbed root–soil complexes measured with a 14.10 pocket vane tester was higher than the value obtained with the Wu–Waldron model (WWM). The correction coefficient k′ varied between 0.20 and 20.25, mostly exceeding 1, and the average correction coefficient k′ value was 4.94. The average correction coefficient determined in this test can be considered to modify the WWM model when conducting experiments under similar conditions.

Friction and Shear Properties of Pine Biomass and Pellets.

Knowledge on the mechanical properties of granular biomass is important for the design and efficient operation of equipment used for handling, storage, and processing. Their mechanical properties are used as a measure of material quality. In this study, the mechanical properties of granular biomass obtained from pines (sawdust, shavings, long shavings, and pellets) were determined under a moisture content range of 10–50%. The coefficient of sliding friction µ of four construction materials was determined using a 210-mm-diameter direct shear tester (Jenike’s shear box). To measure the shear resistance of the biomass materials (represented as torque T), a prototype vane tester was constructed. The characteristics of shear resistance with respect to time T(t) were determined for material samples under normal pressure p ranging from 5 to 30 kPa and a vane rotation rate of 3 rpm. Measurements were performed for five geometries of the rotor, reflecting typical deformation conditions encountered in the processing of granular biomass. The coefficient of sliding friction was found to be affected by the type of material, moisture content, and normal compressive pressure. Depending on the biomass material, the highest µ, which ranged from 0.50 to 0.62, was obtained for black steel, whereas the lowest µ, which ranged from 0.27 to 0.52, was obtained for aluminum. The lowest coefficient of sliding friction was observed for dry materials and high normal pressure. The torque T was observed to be affected by the rotor shape, material, normal pressure, and moisture content. The parameters presented provide information useful for the design of transport equipment and processing of granular wood biomass.

Mechanical characteristics of pine biomass of different sizes and shapes

In the present study, the mechanical properties of granular biomass of pine origin (sawdust, shavings, long shavings and pellets) were determined. The bulk and tapped densities were determined in a cylindrical chamber. The compacted density was measured, and the influence of the moisture content on this quantity was examined in a vane tester. The flowability and strength properties were determined using a direct shear tester (Jenike box) 210 mm in diameter and standard Schulze ring shear tester. The tests in the Jenike tester complied with the Eurocode 1 procedure for normal pressure (σn) of 15 and 30 kPa and speed of shearing of 0.17 mm s−1. Ring shear testing was conducted using a Schulze annular shear cell of 195 mm outer diameter. Tests were performed for 10 and 20 kPa pre-shear σn. A prototype vane tester was constructed for determining the torque, shear strength, and relaxation of a consolidated sample of granular biomass. σn was exerted by a pneumatic system with a rubber air spring and yoke. The torque and density were measured for moisture content in the range of 10–50% and for σn in the range of 5–30 kPa. The torque was observed to be affected by σn and the moisture content, whereas no relationship between the torque and the rotational speed was observed.

Development of models for the interpretation of the dynamic cone penetrometer data

This study deals essentially with the development of models that describe the relations between the strength properties of soils (undrained shear strength obtained with a vane tester) on one hand, and the resilient properties (back-calculated modulus obtained with deflection tests) on the other hand, and the penetration index values obtained with the dynamic cone penetrometer. Laboratory tests were performed on five coarse-grained reconstituted soils. Also, field tests were performed on 10 fine-grained soils and on each of the four subgrade soils of the Laval University Experimental Test Road Site. The results obtained in the laboratory and in the field were compared and analysed in order to develop the relations between the strength and the resilience for different types of soils. Using a statistical analysis with three different sophistication levels, reliable correlations that include explanatory variables were developed.

In situ measurements of surficial mud strength: A new vane tester suitable for soft intertidal muds

A vane fitted to a standard shear vane tester is described, the purpose of which is to obtain better measurements of the rheological properties of soft, surficial, intertidal muds (and consequently, variations in their erodability). Specifications and geometry of this vane are presented. The computation procedure is detailed, so that the methodology can be applied to any vane tester. The main improvement is a greater vertical resolution, typically less than 1 cm. Sets of direct measurements with this equipment and correlation with dry densities for three intertidal mudflats (estuaries and bay) are presented. Direct easy and quick shear strength measurements with such a vane can constitute basic data to characterise the erodability of a mudflat.

Soil strength and soil pore characteristics for direct drilled and ploughed soils

Direct drilling has often been reported to increase density and strength and to affect pore continuity and tortuosity of the upper soil layers. In this study these aspects were studied for three texturally differing soils 4–6 years after initiation of continuous trials with direct drilling and mouldboard ploughing. The soils studied were a coarse sandy soil (Korntved, 5% clay), a sandy loam (Ballum, 8% clay) and a silty loam (Højer, 19% clay). The crop rotation at Korntved was spring barley and winter rye while at Ballum and Højer it was spring barley and winter wheat. Both crops were grown every year. All fields had been mouldboard ploughed for decades prior to the trial period. The ploughed treatment (PL) was imposed in the autumn and the seedbed preparation and drilling were performed with an S-tined seedbed harrow and a traditional drill. The direct drilled (DD) treatment received no tillage other than the drilling which was performed by a triple-disc drill. Straw and stubble were burned. In the 4th, 5th and 6th years of the trial period, minimally disturbed soil cores were taken from the 4 to 8, 14 to 18 and 24 to 28 cm depths, i.e. two horizons above the ploughing depth of 20 cm, and one horizon below this depth. Longer cores were sampled in the 18–27 cm depth in order to include this transition layer. Furthermore, in the 4th year of the trial period shear strength was measured in the field at 2-week intervals in the spring with a vane shear tester in the two upper layers mentioned. All samplings and measurements took place in the field grown with spring barley. In the laboratory air diffusivity and air permeability were measured at field-sampled water content and again when the soil cores were drained to a matric potential of −100 hPa. Cone penetration resistance was measured with a 2 mm diameter penetrometer. Separate core samples from the 14 to 18 cm depth of the Korntved and Højer soils were used for estimating soil cohesion and soil internal friction by a shear annulus method at field-sampled water content. For all soils, DD increased soil bulk density in the two upper soil layers. The shear vane tester also generally estimated higher shear strength for the DD compared to the PL treatment. The shear annulus measurements in the laboratory revealed no differences between tillage treatments for the Korntved soil, while a tendency of higher cohesion and internal soil friction was found for the DD treatment on the Højer soil. The cone penetration measurements indicated a stronger top-soil and fewer high-strength soil elements in the 24–28 cm horizon for the DD than for the PL treatment. Generally the DD treatment had lower volume of macropores (i.e. pores>30 μm ) in the 4–8 and 14–18 cm depths than the PL treatment. This was reflected in reduced air diffusivities and air permeabilities for these horizons. An exception was the 14–18 cm depth of the Ballum soil, where increased air diffusivity and air permeability was measured at field-sampled water content. Continuity indices calculated from air diffusivity and air permeability measurements showed that the DD soil from the 4 to 8 and 14 to 18 cm depths had less continuous and more tortuous macropores than the ploughed soil.

Two-Dimensional Random Field of Mechanical Soil Properties

In situ tests were performed and samples were taken from a uniform layer of clay used as a material for the production of bricks. The shear resistance was measured, using Geonor Inspection Vane Tester H-60, in a quadratic mesh of 961 test points in the horizontal plane, spaced at 15 cm. Vane resistance tests were also performed in the laboratory on 76 undisturbed samples, on which the constrained modulus in consolidometers was determined. The aim of the research was to find the parameters of the 2D random field of shear strength and the correlation of this field with that of constrained modulus. The strong correlation obtained eventually enabled estimating the autocorrelation function of the constrained modulus describing the elastic behavior of the soil. A simple estimation procedure is proposed, enabling curve fitting of different isotropic and anisotropic correlation functions. Additionally, some statistical analyses of data were performed, including regression and time series analysis. The problem of the local and global variabilities of soil properties and their ramifications is also considered.

Field investigations of different techniques for measuring surface soil shear strength

Field measurements of surface soil shear strength were made in three different Sicilian soils (a sandy loam, a silty loam and a clay soil) using four devices (two torvanes, one hand vane tester and one pocket penetrometer). The pocket penetrometer always gave the highest strength values while in most cases the two torvanes gave the lowest. This result was expected because a torvane applies a torsional shear to a soil layer which is much thinner than in the case of the hand vane tester, while the pocket penetrometer generates a compressive and shear type failure at the same time. Some slight differences can also occur between very similar devices as was the case for the two tested torvanes. Spatial variability at field scale can make it difficult to determine a single representative value of soil surface shear strength. As expected, soil surface moisture content played a major role in the performance of shear strength devices. Generally, a decrease of shear strength with increasing moisture content was observed and exponential regressions showed the best fit to the data. The values of cohesion at saturation obtained with a torvane for a highly compacted sandy loam top-soil and for uncompacted silty loam and clay loam soils were similar to those proposed as guide values for use as input data to the EUROpean Soil Erosion Model (EUROSEM). Correction factors, which vary with soil type, would be needed to values obtained with other instruments before the data could be used in EUROSEM. Since, in EUROSEM, soil cohesion is used to represent the resistance of the soil to detachment by runoff, the torvane and the hand vane tester are the most appropriate instruments to obtain input data. This is because they express the kind of shear involved in the detachment of soil particles by flow.

Vane Method to Evaluate the Yield Stress of Frozen Ice Cream

The ability of ice cream to be dipped or scooped is a direct consequence of yield stress; however, yield stresses of frozen ice cream have not been quantified because of the lack of suitable testing equipment. This work presents the experimental equipment and methodology to solve this problem. A vane tester was designed, constructed, and then used to measure the yield stress of ice cream at typical scooping temperatures of –16 to –14°C. The moisture and fat contents of each brand varied significantly. Yield stresses ranged from 2.5 to 8.0 kPa. In general, the yield stress of chocolate was higher than the yield stress of vanilla ice cream. Also, yield stresses decreased as temperature increased. Yield stress and temperature were highly correlated in the higher fat ice cream; the lower fat brand did not show a strong correlation.

An examination of the relationship between erodibility parameters and soil strength

Erosion rate of soil by the impact of raindrops and overland flow of water is often considered to be affected by the shear strength of surface soil. Physically based erosion models indicate a link between defined erodibility parameters and soil strength. The objectives of this paper are to determine erodibility parameters with the process-based erosion model GUEST for a. krasnozem soil of two contrasting strengths, and to examine the influence of soil strength on erodibility parameters. Soil beds of width 1 m and length 5.8 m, with and without compaction, were exposed to simulated, constant rate rainfall. A range of slopes was used. Detachment trays of width 300 mm and downslope length 200 mm containing soils of identical strength were placed at the same slope and exposed to the same rain in order to determine the effects of rainfall-driven processes alone on erosion. Soil strength was measured with a hand vane tester and a pocket penetrometer to determine whether compaction was effective in modifying soil strength. Temporal variation in sediment concentrations (c) for the large soil beds and detachment trays was measured for each slope and soil strength. The settling velocity characteristic of soil, with and without exposure to rain, was determined with the modified bottom withdrawal tube technique. Values of c decreased with increase in soil strength. The relationship between c and slope was influenced by soil strength in a manner consistent with the theoretical expectation of the role of soil strength in controlling erosion. Rilling during erosion was absent only when the soil was compacted. The average settling velocity of the soil exposed to rain (i.e. its depositability) was significantly lower than for the same soil not subjected to rain, indicating a breakdown of soil aggregates as a result of raindrop impact. Rainfall detachability parameters (estimated with GUEST) Were lower when soil strength was high. Runoff-driven erodibility parameters, namely the specific energy of entrainment (J), increased and the approximate erodibility parameter (�) decreased with increase in soil strength. The Variation in these erodibility parameters with soil strength was consistent with the theory implemented in GUEST. Detailed analysis of the relative contribution of rainfall- and runoff-driven processes to c at varying stream powers and soil strengths indicated that, at high soil strength, uncertainty in the values of J and � is high because of the higher contribution to c of rainfall-driven rather than runoff-driven processes. The adequacy of in situ measurement of soil strength as an indicator of soil erodibility is discussed in relation to the results presented.

Soil shear strength: Its measurement and soil detachability

Recent research on soil erosion mechanics has pointed out that the condition at which rill flow becomes erosive is controlled by soil surface shear strength ( TORRI et al. 1987a, RAUWS & GOVERS 1988). Also splash detachment processes are strictly linked to soil shear strength as shown by NEARING & BRADFORD (1985), TORRI et al. (1987b). A comparison of the proposed threshold conditions for incipient rilling immediately shows that they differ in the two quoted papers. The same situation characterizes the relations proposed between splash detachment and soil shear strength. Those differences may depend on the different instruments used for measuring soil shear strength: a Geonor model g-200 laboratory cone penetration apparatus, a laboratory vane tester and a pocket vane tester. Those instruments differ in shape (pocket and laboratory vane testers) or in the physics involved in their functioning (vane tester and drop-cone penetrometer). The experimental results show that the drop-cone penetrometer is characterized by a low repeatability. Moreover, it is sensitive to small variations in soil texture. The laboratory vane apparatus seems to determine a surface of shear close to that of a sphere circumscribed to the vane. The pocket vane apparatus, instead, is characterized by a cylindrical surface of shear. Those results seem to explain the main differences in soil detachment. In particular, incipient rilling conditions are clearly reduced to a single relation between critical shear velocity and soil shear strength. It can consequently be concluded that soil detachability is strictly linked to soil shear strength.

Some measurements of strength anisotropy in soft clays using diamond-shaped shear vanes

Soil strength anisotropy arises from two interacting anisotropies: geometrical anisotropy, i.e. preferred particle packing, and stress anisotropy. The authors explain that the in-situ diamond shaped vane was introduced for such measurements by Aas (1965) who carried out shear tests using a diamond vane making an angle of 45 degrees to the axis of rotation. By extending this concept and using diamond shaped vanes of different angles the variation of shear strength with direction may be measured. The diamond vanes used in the measurements presented in this note are described as being symmetrical and cruciform in cross section. They were used in conjunction with a Geonor H60 field inspection vane tester torque head, and were all designed to give the same torque as the conventional 2/1 rectangular head, assuming strength isotropy. The techniques adopted for carrying out the vane tests are described, and shear-stress relationships presented and discussed. Polar diagrams are used to illustrate typical results, and to compare these results with strength measurements obtained by the conventional rectangular shaped shear vane. /TRRL/