Civil Engineering Tests

In sampling clays or silts, Piston sampler is lowered into boreholes and the piston is locked at the bottom of the sampler. This prevents debris from entering the tube prior to sampling. After reaching the sampling depth, the piston is unlocked so that the piston stays on top of the sample going into the tube. Prior to the withdrawal of the sampler, the piston is locked to prevent the downward movement and the vacuum generated during the movement of the piston from the sampler’s end aids in retaining the samples recovered. As such, sample recovery is increased by using Piston samplers.

This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.

Core barrel samplers are originally designed to sample rock. In single tube sampler, the core barrel of the sampler rotates and this poses the possibility of disturbing the sample by shearing the sample along certain weak planes. Moreover, the cored samples are subjected to erosion and disturbance by the drilling fluid.

For double tube samplers, the tube samplers do not rotate with the core barrels and the samplers are not protected against the drilling fluid. The logging of samples presents difficulty for highly fractured rock. The triple core barrel basically consists of a double core barrel sampler including an addition of a stationary liner which is intended to protect the cored samples during extraction. Therefore the quality sample obtained from triple core barrel is the best among the three types of barrels mentioned above.

This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.

In slopes, trial pits are transformed into another method called slope surface stripping. It involves the removal of slope surface protection and vegetation to reveal the soil conditions below slope surface for inspection purpose. The strip is about 0.3m to 0.5m wide and 150mm to 300mm deep and it usually extends from the crest to the toe of slopes. Slope surface stripping is commonly used in Hong Kong.

This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.

A trial pit is used for obtaining information on the subsurface soil conditions. It allows logging of the various soils types and soil sampling. Typical size of trial pits has minimum base plan area of 1.5m². Trial trench serves the same purpose of trial pit except that they differ in size and dimension. For instance, the length of a trial trench is normally larger than its width by a certain factor (e.g. 5) to cater for its “trench” shape.

An inspection pit is a pit used for identifying and positioning of underground utilities and structure.

This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.

Continuous piezocone penetration test basically consists of standard cone penetration test and a measurement of pore water pressure. Three main parameters, namely sleeve friction, tip resistance and pore water pressure measurement are measured under this test.

Pore water pressure generated in the soils during penetration of the cone is measured. An electrical transducer located inside the piezocone behind saturated filter is used for the measurement. By analyzing the results of pore pressure with depth, the stratigraphy of fine-gained soils with different layers is obtained readily.

This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.

Cone Penetration Testing measures the pressure at the end of cone (end resistance), friction on sleeve and pore water pressure. Friction ratio is defined as the ratio of friction/end resistance.

For clay, typical CPT results exhibit low end resistance, high friction ratio and high pore water pressure.

For sand, typical CPT results exhibit high end resistance, low friction ratio and low pore water pressure.

This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.

(I) Standard Penetration Test is carried out in boreholes at 1.5-2m intervals. However, Cone Penetration Testing allows a continuous record of ground resistance profile.

(II) Disturbance to ground is less by Cone Penetration Testing when compared with Standard Penetration Test.

(III) The use of Cone Penetration Testing is faster and cheaper when compared with the combination of boring, sampling and Standard Penetration Test.

This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.

Standard Penetration Test (SPT) is an in-situ dynamic penetration test to provide information on the properties of soil. It may also collect a disturbed soil sample for grain-size analysis and soil classification. SPT involves the driving of a standard sampler through a distance of 450mm into the bottom of a borehole using the standard weight of 63.5kg falling through 760mm.

Dynamic Probing Test as per BS1377: Part 9: 1990 involves the driving of a metal cone into the ground through a series of 1-metre length steel rods. These rods are driven from the surface by the hammer system on the rig which drops 63.5 kg weight onto the rods through a fall of 760mm. The number of blows that is required to drive the cone down each 100mm increment is then recorded until a required depth is reached or a refusal is achieved. Dynamic Probing has many applications. For instance, it may be used to estimate the depths of at the interface between hard and soft strata and to trace the outline of objects buried underground.

SPT test is used to provide valuable information on soil properties. However, the main use of dynamic probing is to interpolate information between boreholes/trial pits swiftly and to supplement information found from boreholes and trial pits at a low cost. For instance, dynamic probing is carried out close to a borehole where the underground conditions are identified. As such, by using the dynamic probing, the result of borehole can be extended to other areas in between two boreholes.

This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.

By
Er. Kaushal Kishore ,
Materials Engineer, Roorkee

INTRODUCTION
Concrete can be converted into precast masonry units such as Hollow and Solid normal and light weight concrete blocks of suitable size to be used for load and non-load bearing units for wallings. Use of such concrete blocks are more appropriate in region where soil bricks are costly, poor in strength and are not available. Depending upon the structural requirements of masonry unit, concrete mixes can be designed using ingredients available locally or if not found suitable then with in the most economical distance. The concrete mix used for normal hollow and solid blocks shall not be richer than one part by volume of cement to 6 parts by volume of combined room dry aggregates before mixing. Hollow concrete blocks for normal work used in masonry when reinforced is used shall not be leaner than 1 part cement to 8 parts room dry sand by volume. The mixes are designed with the available materials to give overall economy and the required properties of the products. The hollow load bearing concrete blocks of the standard size 400 x 200 x 200 mm will weight between 17 and 26 kg (1063 to 1625 kg/m3) when made with normal weight aggregates. Normal weight blocks are made with cement, sand, gravel, crushed stone and air-cooled slag. The grading for sand used in Hollow concrete block shall be as given below:
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This procedure I came across in one of the site.Just for info to Beginners. This test is called WINSOR probe test.

When the concrete is done and its up and you want to know the strength of concrete with minimum damage,this is the one of the test.

Engineer will select the location.In this case its in column.
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