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An evaluation of repair mortars installed by worm-pump spraying
Published in E.Stefan Bernard, Shotcrete: Engineering Developments, 2020
C.I. Goodier, S.A. Austin, P.J. Robins
The workability was measured by the slump test (BS1881: Part102: 1983) and by a modified form of the shear vane test for soils (BS 1377: Part 9: 1990). The shear vane consisted of a torque measuring device at the head of the instrument together with a set of vanes to provide sufficient shear resistance to register on the torque scale. The shear strength for the mortar (in kPa) was then calculated from the maximum torque. The pressure bleed apparatus (Browne & Bamforth 1977) consisted of a 125 mm diameter steel cylinder lined with a 75 μm mesh on the inside of the base and a bleed hole with a stop tap located beneath the mesh. The apparatus was filled with approximately 1700 cm3 of mortar and subjected to a load of 12.2 kN, equivalent to 10 bar (1000 kPa), which was the highest pumping pressure recorded with the TS3EVR worm pump. The valve was opened after 10 seconds and the liquid emitted collected on a digital balance and the change in weight was data-logged for 30 minutes. Sprayability was assessed both qualitatively (did the material pass through the nozzle) and quantitatively (in terms of the amount of material that could be built up on a vertical grit-blasted concrete substrate).
Quaternary alluvial and swamp deposits
Published in W. A. Peck, J.L. Neilson, R.J. Olds, K.D. Seddon, Engineering Geology of Melbourne, 2018
As successive stages of the project were developed progressively further west, poorer soils were encountered. The area between the Wells Road sand ridge and the current line of coastal dunes is described on the 1:25,000 Chelsea and Keysborough geology sheet as a “mixed restricted marine lagoonal and fluviatile environment” with an age of less than 6000 years. At the retirement village site south of McLeod Road and east of Canberra Street soft black clays were encountered to depths of up to 4m. The clays were characterised by their shelly nature which supports the marine lagoonal depositional conditions referred to above. Undrained shear strengths measured by shear vane were in the range 8–27 kPa. A consolidation test on one sample yielded the following results:- natural moisture content, w 122%liquid limit, wL 116plasticity index, Ip 86compression index, Cc 1.44existing overburden stress, p′o 20 kPamaximum past effective stress, pc′ 40 kPa approx.
Vane Shear Test for Cohesive Soils
Published in Bashir Ahmed Mir, Manual of Geotechnical Laboratory Soil Testing, 2021
Shear strength of sensitive or soft clay deposits is difficult to obtain accurately in the laboratory by conventional “UCS” or triaxial tests as getting undisturbed samples is very difficult because of sampling disturbance. Therefore, the vane shear test is an alternative test in which undrained shear strength of too sensitive or soft clays can be determined. This test is suitable for characterization of saturated clays of soft to medium consistency, highly sensitive or very soft clays without the sample being disturbed by sample preparation or soils which are fissured or highly susceptible to sampling disturbance. The schematic diagram of the VST apparatus is shown in Figure 13.1a. The laboratory vane shear is 10 mm in diameter, 10 mm in height, and 1 mm thick, while the field vanes have diameters ranging from 50 mm to 150 mm. In the laboratory vane shear test, a properly trimmed and undisturbed soft clayey soil sample is placed in a cup and the shear vane is inserted into the specimen up to the desired depth and rotated in the sample by applying torque. It may be noted that the torque is gradually applied to the upper end of the torque rod until the soil fails in shear due to the rotation of the vanes. It is assumed that the undrained shear strength (cu) is constant throughout the sheared soil sample. The applied torque is measured by a torsion spring of specified stiffness by recording the angle of twist (θ). When soil is stressed to its shear strength, the vanes will rotate (@ 0.1o/sec or 1° per minute or with a rate of 1 revolution per second) in the soil. The resistance to applied torque in the soil sample is mobilized throughout the vertical and horizontal faces of the soil sample of diameter “D” and the diameter of vane. Since the soil fails along a cylindrical surface, the shearing resistance can be calculated from the vane dimensions and the applied torque. It may be noted that the undrained strength varies as zero at the center and maximum value at the outer surface (e.g. R = D/2), as shown in Figure 13.1. Also, there could various types of variation of mobilization of shear strength from the center of the torque to the outer end as shown in Figure 13.1(b). Assuming that distribution of shear resistance is linearly increasing with increasing radius of the soil sample, then the shear stress can be expressed as: τ=[cu2RD](R→0atcentreR→D/2atoutersurface)
Stabilisation of clay soil with polymers through electrokinetic technique
Published in European Journal of Environmental and Civil Engineering, 2022
A. R. Estabragh, M. Moghadas, A. A. Javadi, J. Abdollahi
After placing the sample of soil in the main cell the anode and cathode were filled with desired fluid and then a surcharge pressure of 1.0 kPa was applied to the soil via the loading plate. The level of fluid was kept constant at both reservoirs and consolidation was recorded using a dial gauge. The consolidation settlement stopped after about five days. This consolidation stage under the surcharge pressure will be referred to as preloading consolidation stage. Osmosis consolidation was carried out after the preloading consolidation stage by keeping the fluid levels constant in the anode and cathode reservoirs. Therefore, the hydraulic gradient between the two reservoirs was set to zero. The osmosis consolidation was enforced by applying a DC current through the soil. During the test the changes in vertical deformation were measured using a dial gauge and the changes in volume of the sample were determined by measuring the volume of discharge fluid that flowed out from the cathode reservoir. In addition, the values of pH and EC of the fluid in both reservoirs were measured during the test. The total time for the consolidation stage was about 10 days for different voltages. The tests were conducted in a temperature control room at 20–22 °C. The temperatures of both reservoirs during the test were measured from time to time and were nearly the same. It was not realised that during the injection of polymer materials to the soil they were decomposed and changed to toxic gas. When the test was completed the surcharge load and the geomembrane were removed. After that the undrained shear strength of soil was measured by using shear vane apparatus. This was performed at the distances of 4, 11, 18 and 26 cm from the anode. A number of samples were also taken from these points after the strength tests for determination of water content and Atterberg limits.
Sticky stuff: biological cohesion for scour and erosion prevention
Published in Environmental Technology, 2022
Rob Schindler, Richard Whitehouse, John Harris
Initial surface shear strength was measured using a 20 mm diameter shear vane in the uppermost 25 mm of sediment at ten locations towards the margins of each substrate prior to each experiment and averaged to yield a representative mean shear strength value, τ.