Effective length and Allowable pile load. From the structural design it is identified that the load on pile is around XXX kN in clay of average cohesion XXX kN/m’. There are three metres of soft peat above the clay. It is recommended to be a friction bearing pile, in the clay with some form of plastic sleeve over the top three metres to prevent negative skin friction. In line with the data student should: i. Determine allowable pile load, Using Skempton’s formula. (10 marks) Where, a = Adhesion factor (assume 0.48 for clay) and Factor of safety as 2.5 ii. Determine the diameter of the pile (200mm – 400mm), actual length (8m — 30m) and effective length (5m — 27m) of a pile to cover the applied load. (5 marks)
Consider a 200 kN loading on a pile in clay of average cohesion 80 kN/m2. There are two metres of soft peat above the clay. Firstly, we recognised that the pile is predominantly a friction bearing pile, bearing in the clay with some form of plastic sleeve over the top two metres to prevent negative skin friction. If we try a pile ten metres long and diameter 350 mm, then the effective length is eight metres. Using Skempton’s formula:
Where
aP1C + 9AhC Qa — Factor of safety
Qa = Allowable pile load a = Adhesion factor (usually 0.45 for London clay) P = Perimeter of pile shaft 1 = Effective length of pile shaft for design C = Average cohesion value for pile shaft Ab = Area of pile base C = Cohesion value at pile base Factor of safety is usually 2.5
Foundation Construction and Design
0.45x 2 xnx0.175 x 8 x 80+ 9 x xx0.1752 x80 Qa — 2.5 Qa — 217 + 9.3_ 154.4 kN 2.5
This is not enough and so we must extend the pile to say 12 m long Effective length is 10 tn.
Qa —0.45 x(2xnx0.175)x 10 x 80 + 9 x(xx0.1752)x 80
2.5 Qa = 395.8 + 69.3 — 186 kN 2.5
This is not enough and so we must extend the pile to say 14 m long Effective length is 12 m.
0.45 x(2 xxx 0.175)x 12 x 80 + 9 x(nx 0.1752)x 80 Qa — 2.5 Qa =475 + 69.3 — 217 7 kN 2.5
143
This is sufficient to cover the applied load and we would call up 14 in long piles of 350 mm diameter on the drawings. This is a simplified design because. it is usual for the cohesion value to increase with depth and we would therefore need to find the average value of cohesion along the effective length of the pile for the above calculations.
Report Sections:
- Introduction (maximum 100 words]
Student shall start with a brief overview and introduction to the report. Student must provide significance of earthwork, ground water control and capabilities and limitations of construction plant.
Distribution of marks for below sections are provided at assignment tasks in detail - Ground water control methods [maximum 200 words)
- Output of construction plant team [variable, Maximum 300 words] 4. Capacity calculation of a compaction plant [variable, Maximum 150 words] 5. Effective length and Allowable pile load [variable, Maximum 150 words]
- Conclusion [maximum 50 words] Student shalliiinendations through the knowledge pursued through this coursework. Student must discuss outcomes of this coursework through the knowledge gained from various tasks of this study.
- References – CU Harvard style referencing format
Student must provide respective citations and references as per CU Harvard referencing style. Minimum S references 2 e-library and 3 general references
The post Effective length and Allowable pile load appeared first on My Assignment Online.