Direct Shear and Vane Shear Testing Equipment for Soil

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Direct Shear and Vane Shear Testing Equipment for Soil
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Shear strength is the parameter that stability and bearing calculations rest on, and soil laboratories measure it in two main ways. Direct shear fails a specimen along a single plane in a box while a normal load is held, and it remains the most common strength test in a soil laboratory. It follows ASTM D3080 for consolidated drained conditions, with BS 1377-7 and AASHTO T 236 as related references. The laboratory vane takes a different route: a cruciform vane rotates in the specimen until the soil fails around it, which gives a quick undrained strength figure for soft, saturated fine-grained soil under ASTM D4648.

Bench machines run the test under microprocessor control with closed loop speed control up to 11 mm/min, and they record force and displacement throughout. Some apply the normal load with dead weights on a lever, and others use a pneumatic closed loop so that consolidation steps and shearing run as one unattended sequence. A large floor-standing machine takes coarse material and geosynthetic interfaces on samples up to 300 mm square. The vane apparatus is portable and suits site work as well as the main laboratory. Machines are installed and calibrated by NextGen engineers, operators are trained, and support continues for the life of the equipment.

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What Direct Shear and Vane Tests Measure

In a direct shear test one specimen is consolidated under a chosen normal stress and then sheared slowly enough to keep drained conditions. A single test gives the shear resistance at that normal stress, so a drained strength envelope is built from several tests at different stresses. The apparatus forces failure onto one plane of fixed area, which is why the method gives strength but is not intended to produce a full stress and strain curve for deriving a shear modulus.

The vane test works the other way round. A small four-bladed vane is rotated in the specimen and the torque needed to reach failure is converted into an undrained shear strength. It suits saturated, cohesive, fine-grained soil and is intended for strengths below about 100 kPa. It is not meant for sandy soils or non-plastic silts that may drain during shearing.

Standards for Soil Shear Strength Testing

ASTM D3080 covers consolidated drained direct shear, AASHTO T 236 is the AASHTO equivalent and BS 1377-7 covers shear strength tests in terms of total stress, including the shear box and the laboratory vane. Interface strength between soil and a geosynthetic, or between two geosynthetics, is covered by ASTM D5321, and EN ISO 12957 gives the European series for friction characteristics, with direct shear as its first part. ASTM D4648 describes the miniature vane shear test.

What Affects Shear Test Results

Box size comes first. Strength from a shear box is an average over the shear plane, so the box has to be large relative to the largest particle, otherwise a few stones bridging the plane decide the result. Normal stress is the second point: a dense soil dilates as it shears, and a stiff passive loading system lets the vertical stress climb. A straight load path matters too, because a slack or offset path shows up as a softer response than the soil actually has. The Shearmatic 300 article covers sample size and the straight load path for coarse fill.

Shear Testing Equipment from NextGen

The Shearmatic loads pneumatically, with up to 50 consolidation steps and a 5 kN horizontal force, and the NG-Shear DGEN runs the same test with dead weights on a lever. The Shearmatic 300 takes samples up to 300 mm square and 100 kN, for shale, industrial slag, brick rubble, colliery spoil and geosynthetics. The laboratory vane apparatus is supplied with a standard 12.7 mm vane and four calibrated springs, in manual or motorized form.

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Soil testing rarely stops at one machine. NextGen equips the whole geotechnical laboratory, from consolidation and shear testing to triaxial systems, vane apparatus and moisture determination, and stays responsible for it after delivery.

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Products

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Shearmatic - Automatic Shear Testing Machine 5 kN Direct shear testing Shearmatic - Automatic Shear Testing Machine Shearmatic is an automatic shear testing machine for soil laboratories performing direct and residual shear tests. View product Get quote Most requested Automatic Shear Testing Machine 5000 N Direct shear testing Automatic Shear Testing Machine The Automatic Shear Testing Machine, also known as NG-Shear DGEN, is built for direct shear testing of soil under… View product Get quote Most requested Shearmatic 300 - Large Shear Testing Machine 100 kN Direct shear testing Shearmatic 300 - Large Shear Testing Machine Shearmatic 300 is a large automatic shear testing machine for soils, geosynthetics, industrial slag, shale, brick… View product Get quote Most requested Laboratory Vane Apparatus Vane shear testing Laboratory Vane Apparatus The Laboratory Vane Apparatus measures undrained shear strength of soft cohesive soils directly in a sample or… View product Get quote

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FAQs

Start with the specimen. The two bench machines cover 60 and 100 mm laboratory specimens, while the Shearmatic 300 takes samples up to 300 mm square, reducible to 150 mm, for coarse or non-uniform material. Between the bench machines, the Shearmatic removes dead weights and runs consolidation steps automatically, and the NG-Shear DGEN uses dead weights on a lever. Tell us the material, the largest particle and the standard, and we will confirm the box and inserts.

The Shearmatic 300 is the machine for it. Its page lists ASTM D5321 and EN ISO 12957 for interfaces between soil and geosynthetics; its product page also lists ASTM D6243, the method for geosynthetic clay liners. The 300 mm sample size gives a more representative result on non-uniform material and is the practical way to measure the friction angle between two materials.

The vane apparatus measures the shear strength of soft soil by rotating a cruciform vane until the soil fails. It comes with a standard 12.7 mm square vane and four calibrated springs, and other vane sizes are available. Testing can be done directly on the sample or inside the sampling tube using an attachment. It weighs about 11 kg, runs manually or motorized, and follows ASTM D4648 and BS 1377-7.

The Shearmatic does: its pneumatic closed loop applies the axial pressure, and it needs a supply of up to 10 bar, with a working pressure of up to 8 bar. The NG-Shear DGEN applies vertical load with dead weights on a lever, and the Shearmatic 300 applies its consolidation steps hydraulically. Check which loading system suits the services your laboratory already has before choosing between them.

Yes. The NG-Shear DGEN and the Shearmatic 300 can be set to different speeds and travel, forward and reverse, for residual shear, and the Shearmatic runs direct and residual shear tests with up to 10 forward and reverse cycles. Data is downloaded over the RS 232 port into the direct and residual shear Geo-Analysis templates, so both results are reported from the same machine. Ask for the Shearmatic details if you report both.