25/10/2020 9:53 صباحا
This study investigates the reduction of vibration effect between two footings by placing a trench between them . The first footing (designated as the source footing ), on electric-rotary motor is fitted , it has dimension of (100x100) mm. Beside the source footing a second footing is placed and on this footing the reduction in vibration effects are to be investigated . Both the source footing , nearby footing and trench are placed over compacted gypseous soil in a steel tank having gypsum contents with (50%) . Single type of footing is investigated, a square footing with dimensions (80x80) mm. Tests are performed under dry and soaking conditions. The footing is loaded with static weight, while the source footing is with its self-weight. The experimental work is carried out taking the following parameters into observance: types of materials that it is used to fill the trench (PPR pipe with SBR rubber, SBR rubber, low density polyethylene and styropor) as for dimensions of the trench two depths for the trench are used (B and 2B when B is width of footing equal 80mm), and operating frequency of the mechanical oscillator.
Forty-eight tests are carried out for square shape foundation, under three operating frequencies namely, 8, 14, and 20 Hz. The spacing (S) between the footing and trench is ( S=2B) and the spacing(S) between the source of vibration and trench is(S=3B), as for dimensions of trench as follows (length=3B, width= 0.5B and depth=B, 2B). Displacement amplitude, velocity, acceleration and settlement of footing are measured during tests.
The reduction in displacement amplitude for footing when the depth of trench (depth=B) at frequency of 8 Hz is (91 % and 67 %) at dry state in each techniques (PPR with SBR and XPS) gradually, and (100 % and 70 %) at soaking state ,as for frequency of 20 Hz at same depth is (68 % and 60 %) at dry state in (PPR with SBR and XPS) gradually and (47 % and 30%) at soaking state. But at same frequency for depth of trench (depth=2B) is (84 % and 53 %) at dry state and (70 % and 1%) at soaking state.
The reduction in settlement value for footing when the depth of trench (depth=B) at frequency of 8 Hz is (85 % and 15%) at dry state in each techniques (PPR with SBR and XPS) respectively, and (70 % and 25%) at soaking state. As for frequency of 20 Hz at same depth is (58% and 45 %) at dry state and (60 and 5%) at soaking state in all from (PPR with SBR and XPS ) respectively. But at same frequency for depth of trench ( depth=2B) is (65 %) at dry state and (67%) at soaking state in (PPR with SBR). As for Styropor, it is give negative results.