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.

“Cut-and-cover” method involves the construction of open cut at the first place, followed by the construction of tunnels under open excavation. Upon completion of the structure, backfilling and reinstatement would be subsequently carried out.

“Cover-and-cut” method involves firstly the construction of cover followed by the second stage in which construction activities are carried out under the cover. As such, the disturbance to the public owing to constructional activities could be reduced to a minimum.

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.

The concept of ground freezing involves the lowering of temperature of ground near the excavation area. Drillholes with designed spacing are installed so that a chilled brine or liquid nitrogen is introduced into the holes. Brine requires continuous circulation while liquid nitrogen is for rapid freezing and it is unrecoverable. With the addition of a chilled brine or liquid nitrogen, the groundwater is frozen into ice. Upon frozen, soils exhibit higher shear strength and the frozen zone acts as an impermeable barrier so that water could not enter the excavation zone.

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.