Excitation device and method for downhole seismic testing using the same

Abstract

An excitation device for downhole seismic testing, includes an excitation hammer, a holding arm connected at one end thereof to the excitation hammer to allow the excitation hammer to rotate about the other end thereof, a support post having the other end of the holding arm rotatably coupled to an upper end thereof to support the excitation hammer and the holding arm at a certain height, and an excitation source configured to allow the support post to stand upright on the upper side thereof and which generates a seismic wave when struck by the rotated excitation hammer. The support post is formed at a lower end thereof with a securing section detachably inserted into a groove for the support post formed on the upper side of the excitation source such that the support post, the holding arm, the excitation hammer and the excitation source can be separated from each other.

1 - 8 . (canceled) 
     
     
         9 . A seismic test method includes:
 removing an upper soil and a protective layer from a target ground to secure an installation space placing an excitation device inside the installation space, the excitation device comprising;
 an excitation hammer; 
 a holding arm connected at one end thereof to the excitation hammer to allow the excitation hammer to rotate about the other end thereof; 
 a support post having the other end of the holding arm rotatably coupled to an upper end thereof to support the excitation hammer and the holding arm at a certain height, the support post being formed at a lower end thereof with a securing section detachably inserted into a groove for the support post formed on an upper side of an excitation source such that the support post, the holding arm, the excitation hammer and the excitation source can be separated from each other; and 
 an excitation source which is configured to allow the support post to stand upright on the upper side thereof and generates a seismic wave when struck by the rotated excitation hammer; 
   placing a detection receiver in an observation hole for observing an underground water level, and obtaining a seismic wave signal generated from the excitation device to perform downhole seismic testing; and   removing the excitation device and inserting a cover block into the installation space, after finishing testing.   
     
     
         10 . The method of  claim 9 , wherein the protective layer comprises a ground pavement material. 
     
     
         11 . The method of  claim 9 , wherein the installation space is formed orthogonal to the observation hole. 
     
     
         12 . The method of  claim 9 , wherein a boundary block made of a stretchable material is disposed on a vertical plane of the installation space. 
     
     
         13 . The method of  claim 9 , wherein the cover block comprises a gripper on an upper surface thereof 
     
     
         14 . The method of  claim 9 , wherein the target ground in the installation space is formed with a wedge reference socket. 
     
     
         15 . The method of  claim 14 , wherein the wedge reference socket is made of wood. 
     
     
         16 . The method of  claim 9 , wherein the excitation source is formed at a lower side thereof with an indentation frame into which a transfer wedge is removably inserted, and the transfer wedge comprises a head inserted into the indentation frame and a tip directly inserted into the target ground or into a wedge reference socket in the target ground. 
     
     
         17 . The method of  claim 9 , wherein the support post has an “L” shape to secure a rotation space for allowing the excitation hammer to strike a side surface of the excitation source. 
     
     
         18 . The method of  claim 9 , wherein the excitation source is made of wood. 
     
     
         19 . The method of  claim 9 , wherein the excitation source has a parallelepiped shape having a width of 30 to 50 cm, a height of 20 to 40 cm, and a length of 50 to 80 cm. 
     
     
         20 . The method of  claim 9 , wherein the groove for the support post has a depth of one third the height of the excitation source. 
     
     
         21 . The method of  claim 16 , wherein the indentation frame and the transfer wedge are made of an iron-based material. 
     
     
         22 . The method of  claim 16 , wherein the indentation frame is formed at a place a quarter of the length of the excitation source from a distal end of the excitation source and has a depth of one third the height of the excitation source.