Underground space foundation vibration weakening device and method

Abstract

The invention relates to the technical field of foundation vibration weakening devices, and discloses an underground space foundation vibration weakening device and method.The underground space foundation vibration weakening device comprises a vertical damper, the top end and the bottom end of the vertical damper are connected with an underground space, and elastic materials are arranged at the joint of the inner walls of the underground space and comprise but not limited to rubber materials; a lateral buffering mechanism is connected to the outer side of the vertical damper and used for abutting against the wall of the underground space and buffering the horizontal vibration acting force. According to the device, transverse vibration force can be effectively converted and absorbed through the supporting pieces arranged at the vertical dampers in the circumferential direction, so that vibration destructive force of an underground space foundation is weakened, and when the device suffers from too large vertical vibration force, the balance weight pieces moving on the outer walls of the vertical dampers can be started, so that the vibration destructive force of the underground space foundation is reduced. And the vibration force in the vertical direction is weakened in cooperation with the two strong springs and the balance weight piece.

Description

Technical Field

[0001] The present invention relates to the technical field of foundation vibration attenuation devices, and particularly to an underground space foundation vibration attenuation device and method. Background Art

[0002] The external vibration sources of underground space foundation vibration are generally divided into: traffic vibration, engineering construction, mechanical equipment, and seismic waves. Among them, traffic vibration: the vibration generated when subways, high-speed rails, and highway vehicles pass through is transmitted to the underground structure through the soil. Engineering construction: the formation disturbance caused by adjacent construction (such as piling, blasting, tunnel excavation). Mechanical equipment: the vibration generated when heavy equipment (such as water pumps, generators) in the underground space operates. Seismic waves: the elastic waves (P waves, S waves) released by seismic activities or geological faults are transmitted through the foundation.

[0003] The vibration propagation mechanism is as follows: vibration energy propagates in the formation in the form of compression waves (P waves) and shear waves (S waves), which is affected by the density, stiffness, and damping characteristics of soil / rock; and when the vibration frequency approaches the natural frequency of the underground structure, resonance may be triggered, exacerbating the vibration amplitude.

[0004] In the Chinese invention patent with the publication number CN118653591A, a vertical vibration isolation damping device for buildings is disclosed, belonging to the technical field of damping and vibration resistance. It includes a first buffer pad, a damper baffle, a cover, a shear-resistant side wall, a support plate, and a damper body. The shear-resistant side wall is connected to the lower structure of the building through the support plate. The bottom end of the damper body is arranged inside the shear-resistant side wall and fixedly connected to the top side of the support plate. The damper body is pre-tensioned by prestressed cables. The shear-resistant side wall is filled with damping liquid. The damper baffle is fixedly connected to the top end of the damper body; the first buffer pad is connected to the upper structure of the building. The cover has an upward-facing cover opening, and the top of the cover is connected to the bottom side of the first buffer pad. A cavity is formed inside the cover. The damper body penetrates the bottom plate of the cover, and there is a gap between the side wall of the damper body and the opening of the bottom plate of the cover. The damper baffle is located inside the cavity. Compared with the prior art, the above-mentioned invention device realizes two-stage vertical buffering under earthquake conditions.

[0005] Regarding the above-mentioned related technologies, the inventor believes that there are the following defects: when the underground space foundation vibration wave diffuses, it is divided into vertical propagation and horizontal propagation. However, the above-mentioned invention device can only deal with the propagation force in the vertical direction and cannot cope with the force in the horizontal direction; the vibration wave in the horizontal direction diffuses in the horizontal direction through the shear action between soil particles or the flow of groundwater, which may generate lateral stress on the surrounding underground pipelines or the side walls of adjacent buildings, thereby affecting the stability of the underground space. Summary of the Invention

[0006] To solve the technical problems proposed in the background art, the present invention provides an underground space foundation vibration attenuation device and method.

[0007] The present invention is implemented by the following technical solutions: An underground space foundation vibration attenuation device includes a vertical damper. The top and bottom of the vertical damper are respectively connected to the underground space, and elastic materials are provided at the connection parts of the inner walls of the underground space. Specifically, the elastic materials include but are not limited to rubber materials. A lateral buffer mechanism is connected to the outside of the vertical damper for abutting against the wall of the underground space and buffering the horizontal vibration force.

[0008] The vertical damper is composed of an outer shell and an inner rod. The inner rod is vertically and slidably connected inside the outer shell, and a damping ring block is provided at the connection part between the inner rod and the inner wall of the outer shell. A first spring is provided at the middle connection part between the inner wall of the outer shell and the damping ring block. The top of the inner rod is fixedly connected with a convex plate outside the outer shell, and a second spring is connected between the top of the outer shell and the convex plate. The second spring is wound around the outer wall of the inner rod. Among them, the bottom of the outer shell is fixedly connected to the ground of the underground space, and the top of the convex plate is fixedly connected to the roof of the underground space.

[0009] As a further improvement of the above solution, a counterweight is also connected to the outer wall of the vertical damper. The counterweight includes communication grooves symmetrically opened on the outer wall of the outer shell. Two gears are symmetrically rotatably connected below the two communication grooves, and two rack plates two are meshed and connected to the outside of the two gears. Two counterweight ring blocks are fixedly connected to the outside of the two rack plates two.

[0010] As a further improvement of the above solution, the counterweight ring block moves vertically on the outer wall of the outer shell, and annular dampings are provided at the connection parts between the inner wall of the counterweight ring block and the outer wall of the outer shell below.

[0011] As a further improvement of the above solution, two side plates are symmetrically and fixedly connected to both sides of the bottom of the inner rod, and two rack plates one are connected to the outside of the two side plates. The outside of the two rack plates one is meshed and connected to the gear.

[0012] As a further improvement of the above solution, the lateral buffer mechanism includes a support member fixedly connected to the outer wall of the outer shell. The support member is at least one group. Each group of support members includes a ring groove body fixedly connected to the outer wall of the outer shell, and a convex-shaped notch is opened in the middle of the outside of the ring groove body. A rotating block is rotatably connected in the notch, and a damping is provided at the connection part between the rotating block and the ring groove body.

[0013] As a further improvement of the above solution, four rotating sleeve blocks one are circumferentially and fixedly connected to the outer wall of the rotating block. Among them, two rotating sleeve blocks one are a group. A first rotating rod is rotatably connected in each group of rotating sleeve blocks one. Two opposite arc-shaped articulated telescopic rods are fixedly connected to the outside of the two first rotating rods. The articulated telescopic rods are arranged in an S shape.

[0014] As a further improvement of the above solution, the articulated telescopic rod is provided in two sections, one section is the outer shell, and the other section is the inner plate. The inner plate slides relative to the outer shell, and the other end of the inner plate is fixedly connected to the outer wall of the middle part of the first rotating rod.

[0015] As a further improvement of the above solution, a second rotating rod is rotatably connected to the center connection of the two articulated telescopic rods, and a second rotating sleeve block is rotatably connected to the outermost ends of the two articulated telescopic rods. Moreover, a contact plate is relatively horizontally slidably connected to the outside of the two second rotating sleeve blocks.

[0016] As a further improvement of the above solution, two horizontal notches are symmetrically formed on the inner side of the contact plate. The horizontal notches are parallel to the plane of the moving direction of the articulated telescopic rod. The second rotating sleeve block is slidably connected in the horizontal notches, and the outer end of the contact plate abuts against the wall of the underground space.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0018] (1) The present invention utilizes the support member circumferentially arranged at the vertical damper to effectively convert and absorb the lateral vibration force, thereby weakening the vibration destructive force of the underground space foundation.

[0019] (2) When the present invention suffers from excessive vertical vibration force, the counterweight member movable on the outer wall of the vertical damper can be activated, and the two strong springs and the counterweight member are used to weaken the vertical vibration force. Description of the Drawings

[0020] Figure 1 It is a schematic diagram of the overall structure of a device and method for weakening the vibration of an underground space foundation provided in Embodiment 1 of the present invention;

[0021] Figure 2 For the present invention Figure 1 Schematic front view structure diagram;

[0022] Figure 3 For the present invention Figure 2 Schematic top view structure diagram;

[0023] Figure 4 For the present invention Figure 3 Schematic cross-sectional structure diagram in the A-A direction in the present invention;

[0024] Figure 5 Schematic three-dimensional cross-sectional structure diagram of the present invention;

[0025] Figure 6 For the present invention Figure 5 Schematic enlarged structure diagram at a in the present invention.

[0026] Main Symbol Description:

[0027] 1. Outer shell; 2. Inner rod; 3. Damping ring block; 4. First spring; 5. Second spring; 6. Side plate; 7. First rack plate; 8. Communication groove; 9. Gear; 10. Counterweight ring block; 11. Second rack plate; 12. Ring groove body; 13. Rotating block; 14. First rotating sleeve block; 15. First rotating rod; 16. Second rotating rod; 17. Second rotating sleeve block; 18. Abutting plate; 19. Hinged telescopic rod. Detailed implementation manner

[0028] Next, in combination with the accompanying drawings and the specific implementation manners, the present invention will be further described. It should be noted that, on the premise of no conflict, any combination of the following-described embodiments or technical features can form a new embodiment.

[0029] Embodiment 1: Please refer to Figures 1-6 , an underground space foundation vibration attenuation device in this embodiment includes a vertical damper. The top and bottom of the vertical damper are respectively connected to the underground space, and an elastic material is provided at the connection of the inner wall of the underground space. The specific elastic material includes but is not limited to rubber material. A lateral buffer mechanism is connected to the outside of the vertical damper for abutting against the wall of the underground space and buffering the horizontal vibration force.

[0030] The vertical damper is composed of an outer shell 1 and an inner rod 2. The inner rod 2 is vertically and slidably connected inside the outer shell 1, and a damping ring block 3 is provided at the connection of the inner rod 2 and the inner wall of the outer shell 1. A first spring 4 is provided at the middle connection of the inner wall of the outer shell 1 and the damping ring block 3. A convex plate is fixedly connected to the top of the inner rod 2 outside the outer shell 1, and a second spring 5 is connected between the top of the outer shell 1 and the convex plate. The second spring 5 is wound around the outer wall of the inner rod 2. Among them, the bottom of the outer shell 1 is fixedly connected to the ground of the underground space, and the top of the convex plate is fixedly connected to the top plate of the underground space.

[0031] A counterweight is also connected to the outer wall of the vertical damper at the outer shell 1. The counterweight includes communication grooves 8 symmetrically opened on the outer wall of the outer shell 1. Two gears 9 are symmetrically and rotatably connected below the two communication grooves 8. A second rack plate 11 is meshed and connected to the outside of each of the two gears 9. A counterweight ring block 10 is fixedly connected to the outside of each of the two second rack plates 11. The counterweight ring block 10 is vertically movable on the outer wall of the outer shell 1. Two side plates 6 are symmetrically and fixedly connected to both sides of the bottom of the inner rod 2. A first rack plate 7 is connected to the outside of each of the two side plates 6. The outside of the two first rack plates 7 is meshed and connected to the gear 9. When the vertical damper is subjected to a vertical vibration force, it can buffer the vibration wave under the cooperation of two strong springs. When the vertical force is too large, the inner rod 2 will vertically move downward and simultaneously compress the two strong springs. When the inner rod 2 vertically moves downward, it will drive the other second rack plate 11 to stretch and the counterweight ring block 10 to move upward through the transmission of the gear 9 by the first rack plate 7, so as to convert the vertical vibration force into kinetic energy and absorb and weaken the vibration force in cooperation with the gravity of the counterweight ring block 10, thereby further reducing the vibration intensity.

[0032] In the embodiment of the present application, the implementation principle of an underground space foundation vibration attenuation device is as follows:

[0033] After the device is installed, when facing the vibration force in the vertical direction, it can perform vertical support telescopic action under the action of two strong springs. And when the vertical vibration force is too large, when the outer shell 1 and the inner rod 2 approach each other, it will cause the inner rod 2 to drive the side plates 6 on both sides of the bottom to move downward relative to the gear 9, and use their relative displacement to drive the gear 9, and use the gear 9 to vertically stretch the outer counterweight ring block 10, further realizing the absorption and attenuation of vibration. And as the vibration frequency decreases, the counterweight ring block 10 will gradually return to its original position under the action of gravity.

[0034] Embodiment 2: Combining Figures 1-5 , on the basis of Embodiment 1, the further improvement of this embodiment lies in:

[0035] The lateral buffer mechanism includes a support member fixedly connected to the outer wall of the outer shell 1. The support member is at least one group. Each group of support members includes an annular groove body 12 fixedly connected to the outer wall of the outer shell 1. And a convex-shaped notch is provided in the middle of the outer side of the annular groove body 12. A rotating block 13 is rotatably connected in the notch. And a damping is provided at the connection between the rotating block 13 and the annular groove body 12. Four rotating sleeve blocks one 14 are fixedly connected to the outer wall of the rotating block 13 in the circumferential direction. Among them, two rotating sleeve blocks one 14 are a group. A rotating rod one 15 is rotatably connected in each group of rotating sleeve blocks one 14. Two ends of opposite arcs of the articulated telescopic rod 19 are fixedly connected to the outer sides of the two rotating rods one 15. Specifically, the articulated telescopic rod 19 is arranged in an S shape. And the articulated telescopic rod 19 is provided in two sections. One section is the outer shell, and the other section is the inner plate. The inner plate slides relative to the outer shell. The other end of the inner plate is fixedly connected to the outer wall of the middle part of the rotating rod one 15. And a rotating rod two 16 is rotatably connected to the center connection of the two articulated telescopic rods 19. The outermost ends of the two articulated telescopic rods 19 are rotatably connected to the rotating sleeve blocks two 17. And a contact plate 18 is relatively horizontally slidably connected to the outer sides of the two rotating sleeve blocks two 17. Two horizontal notches are symmetrically provided on the inner side of the contact plate 18. The horizontal notches are parallel to the plane of the movement direction of the articulated telescopic rod 19. And the outer end of the contact plate 18 abuts against the wall of the underground space. Further, when one side of the contact plate 18 is subjected to a lateral vibration force, it will push one side of the articulated telescopic rod 19 in the direction of the force point to drive the entire rotating block 13 to rotate. However, under the articulation of the other articulated telescopic rod 19 in the same group, it will further push the rotating sleeve block two 17 on the other side of the contact plate 18 to abut tightly against the wall of the underground space. While ensuring the stability of the equipment, it also further releases the lateral vibration force. And because the support member is arranged on the outer wall of the outer shell 1, when the equipment is subjected to a combined vibration force in the vertical and lateral directions, it can also play the role of reducing the vibration intensity.

[0036] In the embodiments of the present application, the implementation principle of an underground space foundation vibration attenuation device is as follows:

[0037] By fitting the surrounding with the underground space wall and installing the corresponding number and angle of support members according to the lateral vibration environment of the underground space, when subjected to horizontal vibration force, since the horizontal vibration force is relatively complex and not necessarily completely perpendicular to the abutting plate 18, when it is completely perpendicular, two symmetrically arranged abutting plates 18 are used, and the rotating sleeve block two 17 slidably connected to the abutting plate 18 and the telescopic hinge telescopic rod 19 are used to release the vibration force. When the vibration force is not completely perpendicular, the stressed abutting plate 18 will push the corresponding area of the hinge telescopic rod 19 and the rotating sleeve block two 17 to make corresponding changes, and push the rotating block 13 to rotate at the ring groove body 12. And as the rotating block 13 rotates, it will cause the hinge telescopic rod 19 rotatably connected to the current hinge telescopic rod 19 by the rotating rod two 16 to push the other side of the abutting plate 18, realizing the abutment with the wall and the conversion of the vibration force.

[0038] Example 3: Combining Figures 1-6 , the installation method of a vibration attenuation device in this embodiment is as follows:

[0039] S1. On-site inspection and requirement analysis

[0040] Measure the structural dimensions, vibration source position and frequency range of the underground space (such as mechanical vibration frequency, rail transit vibration spectrum); evaluate the environmental conditions (humidity, temperature, corrosive medium), and determine the weather resistance requirements of the materials (for example, ACF or polyurethane materials are preferably selected in high humidity environments); clarify the vibration reduction goal: reduce the vibration amplitude (dB) or isolate a specific frequency band (such as 20 - 200 Hz).

[0041] S2. Device design and selection

[0042] Select the device type according to the vibration characteristics. For low-frequency vibration, spring types (metal / hydraulic springs) or ACF artificial cartilage materials are mostly used; for high-frequency vibration, rubber pads, polyurethane elastomers or foam composite materials are mostly used; calculate the parameters of the vibration reduction device: stiffness coefficient, damping ratio, load capacity (such as rubber pads need to match the equipment weight). Design the installation layout: determine the number and distribution of support points (such as 4 - 6 shock absorbers are arranged per square meter of the equipment base).

[0043] S3. Foundation treatment and pre-installation

[0044] Clean the installation surface, remove the dust and oil stains on the underground space base surface, and polish it flat if necessary. Moisture-proof treatment, apply epoxy resin or lay a moisture-proof film (for rubber-like materials that are prone to aging). Embed anchor fittings: Drill holes in the concrete base surface and implant chemical anchor bolts (depth ≥ 50 mm).

[0045] S4. Installation of the main body of the shock absorber

[0046] Cut the rubber pad or ACF board to the designed size and fix it to the bottom of the equipment base with adhesive; when stacking multiple layers, stagger the joints (to reduce stress concentration).

[0047] Installation of vertical dampers: Use leveling shims to adjust the height of the spring group to ensure uniform force on each support point; fix the spring supports with bolts, and control the torque value according to the design specifications (for example, the torque of M12 bolts is 30 - 40 N·m).

[0048] S5. Sealing and sound insulation treatment

[0049] Fill polyurethane foam or silicone rubber sealing strips at the edge of the device to block the vibration transmission path; cover sound insulation felt (such as fiberglass felt with a mass density ≥ 5 kg / m2) to enhance the high-frequency sound insulation effect.

[0050] S6. Commissioning and testing after installation

[0051] No-load test: Start the equipment to run idly and measure the amplitude before and after shock absorption with a vibration tester (the target reduction rate ≥ 70%). Load test: Simulate the actual working conditions and adjust the spring pre-pressure or the thickness of the rubber pad. Resonance point detection: Avoid the critical frequency through sweep frequency testing (such as adjusting the position of the damper).

[0052] S7. Acceptance of concealed works

[0053] There is no visible deformation or looseness in the shock absorber; the vibration transmission loss (TL) ≥ 25 dB (refer to ISO 10846 standard).

[0054] S8. Operation and maintenance and monitoring

[0055] Regularly check the aging condition of elastic materials (check for cracks in rubber materials every 6 months, and detect the performance of ACF materials every 2 years); monitor vibration data and replace failed components in time when abnormal.

[0056] The above embodiments are only the preferred embodiments of the present invention and cannot be used to limit the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention fall within the scope of protection required by the present invention.

Claims

1. An underground space foundation vibration reduction device, comprising a vertical damper, wherein the top and bottom ends of the vertical damper are respectively connected to the underground space, and an elastic material is provided at the connection of the inner wall of the underground space, and a lateral buffer mechanism is connected to the outer side of the vertical damper for abutting against the wall of the underground space and buffering the horizontal vibration force; Features: The vertical damper is composed of an outer shell and an inner rod, the inner rod is vertically slidably connected to the inner rod in the outer shell, and a damping ring block is arranged at the connection between the inner rod and the inner wall of the outer shell, and a spring 1 is arranged at the middle connection between the inner wall of the outer shell and the damping ring block, the top end of the inner rod is located on the outside of the outer shell and is fixedly connected with a convex plate, and a spring 2 is connected between the top end of the outer shell and the middle of the convex plate, and the spring 2 is wound around the outer wall of the inner rod, wherein the bottom end of the outer shell is fixedly connected to the ground of the underground space, and the top end of the convex plate is fixedly connected to the top plate of the underground space.

2. The underground space foundation vibration reduction device according to claim 1, characterized in that: The vertical damper is located at the outer wall of the shell and is also connected to a counterweight. The counterweight includes connecting grooves symmetrically opened on the outer wall of the shell. Gears are symmetrically connected to the lower part of the two connecting grooves for rotation, and the outer sides of the two gears are meshed with rack plates 2, and the outer sides of the two rack plates 2 are fixedly connected with counterweight ring blocks.

3. The underground space foundation vibration reduction device according to claim 2, characterized in that: The counterweight ring block moves vertically on the outer wall of the shell, and an annular damper is arranged at the connection between the inner wall of the counterweight ring block and the lower part of the outer wall of the shell.

4. The underground space foundation vibration reduction device according to claim 1, characterized in that: Two side plates are symmetrically fixedly connected to the bottom end of the inner rod on both sides, and the outer sides of the two side plates are connected to rack plates 1, and the outer sides of the two rack plates 1 are meshed with gears.

5. The underground space foundation vibration reduction device according to claim 1, characterized in that: The lateral buffer mechanism includes a support member fixedly connected to the outer wall of the shell, and the support member is at least one group. Each group of support members includes an annular groove body fixedly connected to the outer wall of the shell, and a convex-shaped groove is opened in the middle of the outer side of the annular groove body. A rotating block is rotatably connected in the groove, and a damping is arranged at the connection between the rotating block and the annular groove body.

6. The underground space foundation vibration reduction device according to claim 5, characterized in that: The outer wall of the rotating block is circumferentially fixedly connected with four rotating sleeve blocks, wherein two rotating sleeve blocks form a group, each group of rotating sleeve blocks is rotatably connected with a rotating rod, and the outer sides of the two rotating rods are fixedly connected with articulated telescopic rods, and the articulated telescopic rods are arranged in an S shape.

7. The underground space foundation vibration reduction device according to claim 6, characterized in that: The hinged telescopic rod is arranged in two sections, one section is an outer shell, and the other section is an inner plate. The inner plate slides with the outer shell, and the other end of the inner plate is fixedly connected to the outer wall of the middle part of the rotating rod.

8. The underground space foundation vibration reduction device according to claim 7, characterized in that: The central connection points of the two articulated telescopic rods are both rotatably connected with a second rotating rod, the outermost ends of the two articulated telescopic rods are both rotatably connected with a second rotating sleeve block, and the outer sides of the two rotating sleeve blocks are both relatively horizontally slidably connected with abutment plates.

9. The underground space foundation vibration reduction device according to claim 8, characterized in that: Two horizontal slots are symmetrically arranged on the inner side of the abutment plate, and the horizontal slots are parallel to the plane of the movable direction of the hinged telescopic rod. The horizontal slots are slidably connected with the second rotating sleeve block, and the outer end of the abutment plate abuts against the wall of the underground space.

10. A method for installing a vibration reduction device, characterized in that: It is used in conjunction with an underground space foundation vibration reduction device as described in any one of claims 1 to 9, and the specific use steps are as follows: S1. Site survey and requirements: fully measure the structural dimensions, vibration source location and frequency range of the underground space; evaluate environmental conditions and determine the weather resistance requirements of materials; clarify vibration reduction goals: reduce vibration amplitude or isolate specific frequency bands; S2. Device design and selection: Select the device type according to the vibration characteristics. For low-frequency vibration, springs or ACF artificial cartilage materials are often used; for high-frequency vibration, rubber pads, polyurethane elastomers or foam composite materials are often used; Calculate the parameters of the vibration reduction device: stiffness coefficient, damping ratio, load capacity; Design installation layout: determine the number and distribution of support points; S3. Foundation treatment and pre-installation: clean the installation surface, remove dust and oil stains on the base of the underground space, and polish it to make it smooth if necessary; Moisture-proof treatment: Apply epoxy resin or lay moisture-proof membrane; Embedded anchors: Drill holes in the concrete base and embed chemical anchors; S4. Installation of the main body of the vibration reduction device: Cut the rubber pad or ACF sheet to the designed size and fix it to the bottom of the equipment base with adhesive; staggered laying is required when multiple layers are stacked; Installation of vertical damper and lateral buffer mechanism: Use leveling washers to adjust the height of the spring group to ensure that each support point is evenly stressed; bolts are used to fix the spring support, and the torque value is controlled according to the design specifications; S5. Sealing and sound insulation: Fill the edge of the device with polyurethane foam or silicone sealing strips to block the vibration transmission path; cover with sound insulation felt to enhance high-frequency sound insulation effect; S6. Debugging and testing after installation: No-load test: Start the equipment to run at idle speed, and use a vibration tester to measure the amplitude before and after vibration reduction; Load test: simulate actual working conditions and adjust spring preload or rubber pad thickness; Resonance point troubleshooting: avoid critical frequencies through frequency sweep testing; S7. Concealed project acceptance: The vibration reduction device has no visible deformation or looseness; the vibration transmission loss (TL) ≥ 25dB; S8. Operation and monitoring: Regularly check the aging of elastic materials; monitor vibration data and replace failed components in time when abnormalities occur.

Images