Fundamentals of Geotechnical Engineering (MindTap Course List)
5th Edition
ISBN: 9781305635180
Author: Braja M. Das, Nagaratnam Sivakugan
Publisher: Cengage Learning
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Chapter 12, Problem 12.15P
To determine
Find the pressure meter modulus
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Example 4.3
The following compression readings were taken during an oedometer test on a saturated clay
specimen (G,=D2.73) when the applied pressure was increased from 214 to 429 kPa:
TABLE G
1
Time (min)
1
4
9.
16
25
4
Gauge (mm)
Time (min)
5.00
4.67
4.62
4.53
4.41
4.28
4.01
3.75
3.49
36
49
64
81
100
200
400
1440
Gauge (mm)
3.28
3.15
3.06
3.00
2.96
2.84
2.76
2.61
After 1440nmin, the thickness of the specimen was 13.60mm and the water content was 35.9%.
Determine the coefficient of consolidation from both the log time and the root time methods and the
values of the three compression ratios. Determine also the value of the coefficient of permeability.
Q3) You are in charge of drilling operations in a sedimentary basin. The figure bellow
gives the setting. Prior to drilling you have performed a numerical analysis. The table
below states the necessary information at the bottom of the shale layer and at the top
of the sandstone layer. Assume hydrostatic pore pressure throughout the reservoir.
Stress results from your numerical models at 2250m:
To [MPa]
Rock layer Sy [MPa] S [MPa] S, [MPa] [deg] So [MPa]
Shale
Sandstone 55.2
55.2
65
40
30
20
10
0.25
30
25
30
10
5
0.25
planned wellpath
Shale thickness- 2250m
Sandstone: thidkness 250m
A. Your drilling crew on the rig wants to drill with a setting P-Po through the
shale. Will you approve this and give permission? Prove your decision by
calculating the necessary stresses and show a Mohr Circle construction so that
the driller can understand your reason. If unsafe, which borehole failure
mechanism do we expect? ;
B. Should they increase, decrease P, or stay with P=Po? Why?
C. Determine the…
Q: I an oedometer test on a specimen of saturated clay (Gs = 2.72), the applied pressure was increased from 107 1o 214 kPa and the following compression readings recorded: TaBLE| Tmen 0 025 05 1 225 4 &5 9 16 Guugelmm) 78 742 732 721 6% 678 &6 643 637 Teme(mi) 25 % 4 s om0 X0 a0 Guge(nm) 629 626 621 618 616 615 610 602 After 1440 min, the thickness of the specimen was 15.30 mm and the water content was 23.2%. Determine the values of the coefficient of consolidation and the compression atios from (a) the root time plot and (b) the log time plot. Determine also the values of the coefTicient of volume compressibility and the coefficient of permeability.
Chapter 12 Solutions
Fundamentals of Geotechnical Engineering (MindTap Course List)
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- Problem Ex. Consider the upward flow of water through a layer of sand in a tank as shown in Figure. 1.5 m 0.7 m I m 2 m Valve (open) Inflow O Sand For the sand, the following are given: void ratio (e) = 0.52 and specific gravity of solids (G.) = 2.67. Calculate the total stress, pore water pressure, and effective stress at points A and B. What is the upward seepage force per unit volume of soil? Total stress, porewater pressure, effective stress. Point A t B Total stress (kN/m?) Porewater pressure Effective stress Upward seepage force.arrow_forwardA line load of q=60kn/m with alpha =300 is placed on a ground surface as shown in figure p4.1.Calculate the increase of pore water pressure at M immediately after application of the load for the cases given below. (a) z=10m ,X=0m ,v=0.5 ,A=0.45 (b) z=10m, X=2m,v=0.45, A=0.6arrow_forward(b) An oedometer test on a specimen of fully saturated stiff clay gave the following results in Table 1 for the pressure increment from 100 kN/m2 to 200 kN/m?. The initial thickness of the specimen under no pressure was 19 mm. Determine my, cy and k using Taylor's Method.arrow_forward
- (e) A soil profile consists of a clay layer between layers of sand, the water table being in theupper sand layer. Before the construction of a raft foundation for a large reservoir, piezometers were placed in the saturated clay layer. The whole process of filling the reservoir may be approximated to applying rapidly a single pressure increment of 200 kPa uniformly throughout the clay layer. One year after filling the reservoir, the piezometers indicated a distribution of excess porewater pressure as indicated in Figure Q-e. Estimate the average degree of consolidation at this time.arrow_forwardThe following readings were obtained from an oedometer test on a specimen of saturated clay, see Table 1. The load being held constant for 24 hour before the addition of the next increment. Applied stress 25 50 100 200 400 800 (kN/m2) Thickness 19.60 19.25 18.98 18.61 18.14 17.68 17.24 (mm) Table 1 At the end of the last load period the load was removed and the sample allowed to expand for 24 hour, at the end of which time its thickness was 17.92 mm and its water content found to be 31.8%. The specific gravity of the soil was 2.66. i. Plot the e/o' curve and determine the coefficient of volume compressibility (m,) for an effective stress range of 220-360 kN/m? ii. Plot the e/log ơ' curve and from it determine the compressibility index (Cc) and the pre-consolidation pressure (Oʻpe) ii. Use the data obtained in (i), (ii) and (ii) to obtain and Plot a mlo' curve for the soil iv. compare the values for consolidation settlement for 4 m thick layer of the clay when the average effective…arrow_forwardshown in the figure. The coefficient of permeability of the Water is flowing through the permeability apparatus as coil is k m/s and the porosity of the soil sample is 0.50. 0.4 m Soll 0.8 m 0.4 m The total head, elevation head and pressure head in metres of water at the point R shown in the figure arearrow_forward
- For a falling head permeability test, the following values are given: Length of specimen: 200 mm Area of specimen:1000 sq. mm Area of standpipe: 40 sq. mm Head difference at t= 0: 500 mm Head difference at t= 180 sec : 300 mm Determine the hydraulic conductivity (cm/sec)arrow_forward4.1 A line load of q = 60kN/m with a = 0 is placed on a ground surface as shown in Figure P4.1. Calculate the increase of pore water pressure at M immediately after application of the load for the cases given below. (a) z = 10m, x = 0m, v=0.5, A=0.45. (b) == 10m, x= 2m, v= 0.45, A=0.6. 2 m 4. G.W.T. Clay XI 1arrow_forwardA thin cylindrical vessel contains a fluid at an internal pressure of 2 N/mm?. If the internal diameter of the vessel is 1.25 meters, determine the maximum thickness of the cylinder. Suppose that the longitudinal stress and the circumferential stress is not to exceed 30 N/mm? and 45 N/mm?, respectively.arrow_forward
- 1. (30 pts) The soil profile shown below consists of 10 meters of sandy silt overlying gravel. The pore water pressure at the top surface of the silty sand is zero and can be assumed to remain zero. a) Calculate the level to which water would rise in a piezometer tube inserted into the top of the gravel if the silty sand is just stable? Use submerged unit weights and seepage forces to arrive at your answer (do not calculate total stresses and pore water pressures). Express your answer as an elevation, e.g. "Elev. 130". (Note: Elevations are in meters) (10 pts) b) Using the piezometric elevation calculated in part (a), calculate the pore water pressure at the bottom of the silty sand if the silty sand is just stable (10 pts). c) Calculate the total stress at the base of the silty sand and show that it is equal to the pore water pressure calculated in part (b) (10 pts) Elev. 120 m. Elev. 110 m. Sandy Silt (saturated) Void ratio, e = 0.68 G = 2.65 Gravelarrow_forwardProblem 3) Shown below is a cross-section through a soil layer. A Shelby tube sample was taken from a depth of 25 ft. The sample was extruded in a laboratory, thus subjected to zero total stress. Assume Ko = 0.5 and Ā = -0.1, determine the effective stress on the sample after extrusion. Use the basic Skempton (1954) and Ladd and Lambe (1963) approach to determine the change in pore pressure.arrow_forwardThe results of a constant-head permeability test for a sand sample having a sectional area of 10000mm2 and a length of 200 mm are as follows: (1) Constant head difference 400mm (2) Time of collection of water = 30 seconds (3) Volume of water collected = 600 cm3. The hydraulic conductivity is: Oa. 1.0 mm/sec Ob. 1,7mm/sec c. 2.9 mm/sec O d. 0.5mm/secarrow_forward
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