MEC316: Bài tập 02
- Đăng bởi: nguyenphuocbinh
- Sinh viên
1 A rubber balloon is ﬁlled with dry sand. The pressure in the pores is reduced by 5 kPa with the aid of a vacuum pump. Then what is the change of the total stress, and the change of the eﬀective stress?
2 An astronaut carries a packet of vacuum packed coﬀee into space. What is the rigidity of the pack (as determined by the eﬀective stresses) in a spaceship? And after landing on the moon, where gravity is about one sixth of gravity on earth?
3 A packet of vacuum coﬀee is dropped in water, and it sinks to a depth of 10 meter. Is it harder now?
4 A treasure hunter wants to remove a collection of antique Chinese plates from a sunken ship. Under water the divers must lift the plates very carefully, of course, to avoid damage to the plates. Is it important for this damage to know the depth below water of the ship?
5 The bottom of a lake consists of sand. The water level in the lake rises, so that the water pressure at the bottom is increased. Will the bottom of the lake subside by deformation of the sand?
6 A lake is being reclaimed. The soil consist of 10 meter of homogeneous caly, having a saturated volumetric weight of 18 kN/m3. Below the clay the soil is sand. After the reclamation the phreatic level is at 2 m below the ground surface, but the soil remains saturated. Make a graph of total stresses, eﬀective stresses and pore pressures before and after the reclamation.
7 A concrete caisson having a mass of 5000 ton, a foundation surface of 20 m× 20 m, and a height of 10 m, is being placed on dry sand. Calculate the average total stress and the average eﬀective stress just below the caissson.
8 A similar caisson is placed in open water, on a bottom layer of sand. The water level is 5 m above the top of the sand, so that the top of the caisson is at 5 m above water. Again calculate the average total stress and the average eﬀective stress just below the caissson.
9 Solve the same problem if the depth of the water is 15 m. And when it is 100 m.
10 A certain soil has a dry volumetric weight of 15.7 kN/m3 , and a saturated volumetric weight of 21.4 kN/m3. The phreatic level is at 2.5 m below the soil surface, and the capillary rise is 1.3 m. Calculate the vertical eﬀective stress at a depth of 6.0 m, in kPa.