14-Review 2022s

10/27/2022 1 Professor Hadi Khabbaz Email: hadi.khabbaz@uts.edu.au CB11.11.244 Geotechnical Engineering (Part 14) Revision of Main Topics Question 1 (10 Marks) (i) Brick veneer walls were used for a residential building. The settlements of the all around strip footing at north and south sides of the building were 18 mm and 9 mm, respectively. The horizontal distance between these two points of the footing was 10 m. Are these settlements values acceptable? Comment according to AS 2870 (Residential Slab and Footings) - settlement limits. (ii) Classify a site in Sydney, includes active clay with an average soil movement of 50 mm. The site is highly contaminated with gasoline constituents and the water table is just 2m below the ground level. (iii) For an infinite slope failure mechanism, “the stable slope in coarse grained soils is approximately between the friction angle and one-half the friction angle of soil depending on the location of water level, which is usually parallel to the slope.” Is this statement correct? Provide a clear numerical example to elaborate this point.

10/27/2022 2 (i) Use AS 2870 (Residential Slab and Footings) Type of Building Maximum Settlement Differential Settlement Ratio Brick Veneer 20 mm 1/600 = 1.7x10 -3 𝛿 𝐿 = 18 − 9 10 × 1000 = 9 × 10 −4 < 1 600 North Side Settlement = 18 mm < 20 mm  South Side Settlement = 9 mm < 20 mm   Question 1 (10 Marks) (i) Brick veneer walls were used for a residential building. The settlements of the all around strip footing at north and south sides of the building were 18 mm and 9 mm, respectively. The horizontal distance between these two points of the footing was 10 m. Are these settlements values acceptable? Comment according to AS 2870 (Residential Slab and Footings) - settlement limits. (ii) Classify a site in Sydney, includes active clay with an average soil movement of 50 mm. The site is highly contaminated with gasoline constituents and the water table is just 2m below the ground level. (iii) For an infinite slope failure mechanism, “the stable slope in coarse grained soils is approximately between the friction angle and one-half the friction angle of soil depending on the location of water level, which is usually parallel to the slope.” Is this statement correct? Provide a clear numerical example to elaborate this point.

10/27/2022 4 (iii) Yes it is an acceptable statement. Question 2 (20 marks) A 2.5m×2.5m square footing is constructed at a depth of 1.2 m below the ground level and carries an eccentric inclined load shown in the figure below. The soil is medium dense sand with the following properties: Total unit weight  t = 20 kN/m 3 Effective friction angle  = 36 o Effective cohesion c  = 0 kPa The water table is at the ground level. (a) Use the Hansen’s theory of bearing capacity and determine the ultimate bearing capacity of the foundation, q u in kPa. (b) Use a factor of safety of 3 and determine the net allowable inclined load that can be applied on the foundation, P in kN. 2.5m 1.2m P 1m Section Not to Scale    2.5m P 1m Plan 2.5m

10/27/2022 5 m

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10/27/2022 8 Question 4 (15 marks) A square group of 4 circular solid concrete piles is arranged with 2 rows and 2 columns and a centre to centre spacing of 0.7 m. The piles have a diameter 0.50 m and are to be cast-in-situ to a depth of 10 m in a deep layer of stiff clay. The clay has an undrained cohesion of c u = 150 kPa and a Young’s modulus of 40 MPa. The water table is 2.5 m below the ground level. (a) Calculate the allowable bearing capacity of the each individual pile assuming a factor of safety of 3. (b) Calculate the ultimate bearing capacity of the pile group, taking into account the block failure of the entire group as well as the capacity of individual piles. Asume the pile group efficiency is 95%. F Q4. Clay, only Undrained Condition 𝐿 ? = 10 0.5 = 20 ≥ 4 ∴ 𝑁 ? ′ = 9 ? 𝑢? = 150𝑘𝑃𝑎,

10/27/2022 10 Question 5 (20 marks) A concrete cantilever wall is shown in the following figure. Determine the global factors of safety for sliding and overturning stability of the wall. Groundwater table is 6m below the base of the wall. The effect of passive force due to soil should be included in your calculations. 1 Section Not to Scale 2.3m 0.6m 6.5m  c = 25 kN/m 3 25 5 m In situ backfill: sand  t = 18.5 kN/m 3  = 34  Base soil: clayey sand  t = 19 kN/m 3 c  = 0 kPa,  =  = 30  ; In situ backfill: sand q = 30 kPa 1m 1 Section Not to Scale 2.3m 0.6m 6.5m  c = 25 kN/m 3 25 5 m In situ backfill: sand  t = 18.5 kN/m 3  = 34  Base soil: clayey sand  t = 19 kN/m 3 c  = 0 kPa,  =  = 30  ; In situ backfill: sand q = 30 kPa 1m W B W D W C W A

10/27/2022 11 Note: All forces are per metre run (pmr). pmr 39.8 1.8 69 69 tan30  = 39.8 kN pmr

10/27/2022 13 C u = 40 kPa, Question 6 1.3

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10/27/2022 16 Q7 (a): )

10/27/2022 17 o o o o 2 . 28 2 / 63 . 33 45 2 / * 45        Minimum Length:  m 6 . 2 tan ) 2 . 1 4 2 ( L min       pmr kN 51 T  The grout length should be added. 2 / * 45 o     Q7 (b) Assume x = 2m and find the anchor force and its length Check 3.6 m < 4 m  ok Q7 (c) Find the Position of the Maximum Moment

10/27/2022 19 Point tan (  ) tan (  )  (°)  (°)  (Rad)  z (kPa) A 0 1 0 45 0.785 81.81 * B 0 2 0 63.43 1.11 48.01 C 1 0.5* 45 26.57 0.464 3.36 Solution: 2m P = 100 kPa C 2m 2m 2m     0 2m P = 100 kPa 2m 2m B  2m P = 100 kPa 2m 2m A    0   ) 2 cos( sin p z           10 1 0.1 0.01 0.00 0.05 0.10 0.15 0.20 0.25 I r m 0.2 0.4 0.6 0.8 1.0 2.0 0.1 0.5 0.3 1.4  n mz z Fadum’s Chart  z = q I r                                   1 n m n m 1 n m mn 2 tan 1 n m 2 n m 1 n m n m 1 n m mn 2 4 1 I 2 2 2 2 2 2 1 2 2 2 2 2 2 2 2 2 2 r m = B/z n = L/z Note: m and n are inter- changeable Rectangular Loading

10/27/2022 20 10 m 10 m 40 m 40 m 20 m q 2 = 150 kPa q 1 = 100 kPa A Depth z = 5 m Find the change in vertical stress at a level 5 m below point A. Example: Vertical Stress Increase due to Rectangular Loading 10 m 10 m 40 m 40 m 20 m 1 2 3 4 q 2 q 1 Solution: