Field Identification In-Situ Test

          This type of soil testing is necessary for getting knowledge of soil property information, measuring groundwater pressure, gathering moisture content data and other important data points, and which can be safety-critical in a number of different instances. In this post, we are going to take a deep dive into a few different types of soil tests that can be performed in-situ.

               In-situ soil testing can be achieved in a variety of different ways. Every soil has its own property so every soil test also has its own place and benefit.  The most accurate and comprehensive in-situ soil testing for determining a wide variety of technical attributes can be taken as Cone Penetration Testing (CPT).     

1)Standard Penetration test

         This test is conducted by driving a split spoon into the soil for a distance of 450 mm by a standard hammer of 65 kg weight falling through a height of 750 mm.

          The spoon which is attached to a drill rod is lowered into the bottom of the hole. The monkey hammer is allowed to fall on the top of the drill rut until the sampler gets penetrated into the soil through a distance of 150 mm. This penetration is not recorded. After this actual test is started and blows required for the next two successive penetration of 150 mm are recorded and added. This value is called N-value or SPT value. This test is conducted for each 1.5 m interval of depth.

2)Plate load Test

             The plate load test is used to determine the ultimate bearing capacity of the soil. This type of test is most suited for sands and clay.

Procedure:-

           A pit 5 times the size of the plate is excavated at the proposed depth of foundation. The pit is leveled and the test plate is placed at the center of the pit.

a)A seating load of 70 gm/cm^2 is applied and released after some time.

b)The plate is loaded either through a kentledge or by the reaction through a truss or a beam.

c)The load is applied in the increment of 1/5th of the design load or 1/10th of failure load.

d)For each increment of load four dial gauges are on the plate to measure the settlement.

e)The next higher load is applied when the rate of settlement of plate becomes 0.25 mm per hour.

                 The test is simultaneously carried out until failure or the load reaches 5/2of design load whichever is earlier.

                    From the test result, a load settlement curve is drawn.

3)Cone penetration test

     This test collects important and accurate sub-surface information from standard tests and can be determined by important factors to your business or project, enabling you to design foundations for structures. This type of testing is not only accurate,  it also can collect data at a speedy rate and from there will interpret the data on the site, enabling you to gain a competitive advantage as an engineer.

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