Common methods of Soil Investigation in the EUA
Soil investigation is imperative for various geological reasons. In most cases, subsurface investigation programs are carried to examine the underlying characteristics suggested by field reconnaissance and office research so as to modify, deny or confirm the assumed properties and conditions below the ground surface. Soil investigation and exploration program present a reasonable idea about the underlying soil condition and characteristics. The main aim of soil investigation and subsurface exploration is to determine the geomorphic and geological structures of the site’s subsurface (Ameratunga, Sivakugan & Das, 2016). There are two major methods of soil investigation employed across the UAE.
The Standard Penetration Test (SPT) and Cone Penetrometer Test (CPT) are widely used across the country owing to their widespread benefits. The tow methods have transformed the geological industry ever since their inception. The Standard Penetration Test and Cone Penetrometer Test have transformed to be the industry standards for subsurface geological investigation through the use of small diameter soundings and borings (Jha & Suzuki, 2009). The techniques for solid research have evolved over the years to perfect the subsurface exploration technique.
Standard Penetration Test (SPT)
Standard Penetration Test has attained its widespread application due to its low cost as well as its simplicity. The method is used to provide significant information in very explicit types of soil conditions. This kind of soil investigation technique employs the use of a sample tube. The sample tube is positioned at the bottom of a borehole. It is designed with thick walls so as to withstand the test environment (Ameratunga, Sivakugan & Das, 2016). After the tube has been positioned at the bottom of the borehole, a heavy slide hammer is dropped continuously 30 inches above the sample tube. Dropping the hammer on top of the sample tube ensures that it is driven deeper into the soil under test. The Standard Penetration Test involves the technician counting the number of strikes it takes to drill the sample tube six inches at a go. The sample tube is withdrawn so as to examine the properties of the sample soil collected. The depth of the borehole is increased while repeating the same procedure. The Standard Penetration Test has poor soil recovery technique. Also, it is exposed to counting errors per interval (Ameratunga, Sivakugan & Das, 2016).
Standard penetration resistance is the number of hammer strikes used before the sample tube fully penetrates both the second and the third depth of 6 inches each. It is referred to as the N value. The N value is utilized to determine the resistance of the underlying subsurface soil property. It is also used to examine the density of the soil (Ameratunga, Sivakugan & Das, 2016). The standard penetration resistance offers specific information about soil density which is rather daunting to investigate using simple borehole techniques. In most cases, it is imperative to couple the borehole drilling and sampling with the standard penetration test so as to comprehend various soil types in the subsurface.
Cone Penetrometer Test (CPT)
Cone Penetrometer Test presents some advantages over the Standard Penetration Test. It used, and application is widespread owing to the benefits it offers above other soil investigation techniques. It is widely applied in the examination of geotechnical engineering attributes of soil. As compared to the Standard Penetration Test, Cone Penetrometer Test is widely accepted owing to its simplicity and efficiency. Soil investigations using this technique can be performed from the ground surface with the help of a borehole. The cone is forced into the ground while maintaining the sleeve stability. The force check located in the cone is used to examine and tabulate the resistance of the cone for different depths. Both the cone and the sleeves are moved and penetrated at the same time so as to determine the combined sleeve and cone resistance. The tension load cells in the sleeves are used to record the penetration resistance.
Cone Penetrometer Test attains its efficiency for constant repetition and measurement of the procedure. The measurement is repeatedly done at habitual intervals in the course of penetration (Ameratunga, Sivakugan & Das, 2016). Cone penetrometer technique is effective in other types of soil investigation since it is used to collect the sleeve friction, the stress on the tip of the sleeve and pore-water pressure. There is some test proves with the ability to measure temperature and shear wave velocity (Robertson, 2009). The proposed empirical curves are used to correlate the shear strength parameter with the cone penetration resistance values.
Dewatering techniques
The dewatering technique is the control of water through pumping with the aim of locally lowering groundwater levels in the vicinity of the mine. The easiest method of achieving dewatering is through the use of sump pumping. Sump pumping allows water to enter the mine which allows it to collect in a sump. The collected water is then pumped away through the use of tough, solid handling pumps (Jha & Suzuki, 2009). Even though the technique is beneficial in numerous situations, it exhibits a limitation with instability. Water can sip into the excavation thus resulting in the risk of unsteadiness and other construction crisis (Jha & Suzuki, 2009). Therefore, it is imperative to reduce the level of groundwater in advance so as to avoid significant seepage of groundwater (Ye et al., 2012).
Concrete issues
Concrete has different issues which should be looked into before construction so as to avoid a real life concrete crisis.
Review of cover letter
The owner of the site is Amir Mohamed. The Plot number is 5627889, Nadd Al Shiba 4th, Dubai UAE. The job reference number for this report is Ref. XSD/13-6654 dated 21/03/2016. It was performed by the confirmation dated 11th Feb 2016. This repost was awarded to contractor Muhairi Al Abdulla in Dubai Municipality.
Project scope, boreholes and drilling methods
The purpose of the research is to examine the subsurface and surface conditions at the proposed site. Additionally, the study determines the mechanical, chemical and physical attributes of the foundation ground so as to present the structural engineer with enough data for the design.
The scope of the project includes; gathering maps and information relevant to the building site, performing necessary laboratory and field tests, analyzing the findings from both field and laboratory tests, drilling two boreholes of depth 6 and 8mm respectively with the aim of sampling both disturbed and undisturbed samples.
Drilling
Drills of two boreholes were made at the site. While one borehole was drilled to a depth of 6 meters, the other was drilled to a depth of 8 meters below the surface of the ground.
Sampling
The project collected both split spoon and disturbed samples from the borehole. There was no undisturbed sample collected as a result of the non-cohesive nature of the materials experienced until the drilled depth. The collected sampled were placed under examination, description and classification of the team geotechnical engineers. They were neatly arranged in wooden boxes and transported to the laboratories for further testing.
Field testing in boreholes
The relative densities of the ground material were assessed using the Standard Penetration Test at different depths in the borehole. The tests were conducted according to the standards of BS1377:1190 Part 9 AMD8264-95 (Kitazume & Terashi, 2013). The field testing was performed using a standard 50 mm thin wall sampler. The sampler was driven into the soil at the bed of the borehole through the application of 63.5 kg falling through 760mm. The standard penetration test N value for this report is the amount of blows needed to attain a penetration of 300 mm after an original seating drive of 150 mm.
Subsurface soil condition
Boring log and SPT test
Standard Penetration Test was performed to a depth range of 2.5 to 2.82. This reported the following outcome; The N value was reported to be 54. This was determined by adding the value of the second and the third column. The N value obtained is higher than the reported field value of 50. Additionally, the following observations were made; highly gravelly, dense pale yellow, sand, silty and gravel composed of sandstone pieces (Pujades et al., 2014).
Conclusion
All in all, soil investigation and subsurface examination play an imperative role in any construction project. It is used in determining the bearing capability, chemical and physical attribute of soil. These attributes vary depending on the place and the proposed structure.
References
Ameratunga, J., Sivakugan, N., & Das, B. M. (2016). Cone Penetrometer Test. InCorrelations of Soil and Rock Properties in Geotechnical Engineering (pp. 115-157). Springer India.
Ameratunga, J., Sivakugan, N., & Das, B. M. (2016). Standard Penetration Test. In Correlations of Soil and Rock Properties in Geotechnical Engineering (pp. 87-113). Springer India.
Jha, S. K., & Suzuki, K. (2009). Reliability analysis of soil liquefaction based on standard penetration test. Computers and Geotechnics, 36(4), 589-596.
Kitazume, M., & Terashi, M. (2013). The deep mixing method. CRC Press.
Pujades, E., Vàzquez-Suñé, E., Carrera, J., & Jurado, A. (2014). Dewatering of a deep excavation undertaken in a layered soil. Engineering Geology, 178, 15-27.
Robertson, P. K. (2009). Interpretation of cone penetration tests-a unified approach. Canadian Geotechnical Journal, 46(11), 1337-1355.
Ye, X. W., Ran, L., Yi, T. H., & Dong, X. B. (2012). Intelligent risk assessment for dewatering of metro-tunnel deep excavations. Mathematical Problems in Engineering, 2012.
