A drill unit for forming a column in ground which includes an outer drill and a concentric inner drill, where attached to the outer drill there is at least one drill tooth which includes a first face, a second face and a base face wherein: the first face and the second face are immediately adjacent one another and are coterminous at a first edge and a second edge; the base face is the face closest to, or coterminous with, the first terminal end; all faces, except the base face, are independently coterminous with the base face; and extend away from the base face in the same direction; at least part of the at least one drill tooth extends away from the first terminal end to terminate at the second edge; the second edge is the edge of the at least one tooth that is most longitudinally distant from the first terminal end; the first face further includes a first alpha edge, where the first alpha edge is an edge of the first face opposite the first edge; a line joining the first edge and the first alpha edge, where the first face and the base face are coterminous, a first face alignment line, is at an angle of to a perpendicular extending from the first outside surface; the second face further includes a second alpha edge which is an edge of the second face opposite the first edge; and a line joining the first edge and the second alpha edge, where the second face and the base face are coterminous, a second face alignment line, is at an angle of to a tangent on the first outside surface; such that, when in use forming the column, the first edge is configured to be a leading edge.

A drill unit for forming a column in ground which includes an outer drill and a concentric inner drill, where attached to the outer drill there is at least one drill tooth which includes a first face, a second face and a base face wherein: the first face and the second face are immediately adjacent one another and are coterminous at a first edge and a second edge; the base face is the face closest to, or coterminous with, the first terminal end; all faces, except the base face, are independently coterminous with the base face; and extend away from the base face in the same direction; at least part of the at least one drill tooth extends away from the first terminal end to terminate at the second edge; the second edge is the edge of the at least one tooth that is most longitudinally distant from the first terminal end; the first face further includes a first alpha edge, where the first alpha edge is an edge of the first face opposite the first edge; a line joining the first edge and the first alpha edge, where the first face and the base face are coterminous, a first face alignment line, is at an angle of to a perpendicular extending from the first outside surface; the second face further includes a second alpha edge which is an edge of the second face opposite the first edge; and a line joining the first edge and the second alpha edge, where the second face and the base face are coterminous, a second face alignment line, is at an angle of to a tangent on the first outside surface; such that, when in use forming the column, the first edge is configured to be a leading edge.

A jet grouting method is capable of reducing an unnecessary portion (redundant portion) exceeding an effective wall thickness without narrowing a construction pitch, and capable of allowing easy mechanical control. A ground improvement structure including a plurality of ground improvement bodies is constructed through use of the jet grouting method. Each of the ground improvement bodies is constructed so as to have a sectional shape formed by a combination of different kinds of fan shapes having different radiuses. The sectional shape of the ground improvement body is a combination of at least two kinds of fan shapes. One of the kinds of the fan shapes corresponds to a fan shape with a smaller radius, and the other corresponds to a fan shape with a larger radius. The sectional shape of the improvement body has a minimum diameter portion formed of the fan shapes with the smallest radius and a maximum diameter portion formed of the fan shapes with the largest radius. When designing the ground improvement body, a central angle is determined from a fan shape having the smallest radius with respect to the effective wall thickness. When constructing the ground improvement body, a diameter thereof is controlled by stepwisely changing a rotation speed of the injection rod. At that time, a soil breaking achieved by an improving material injected at high pressure is monitored so as to check the diameter of the ground improvement body and the effective thickness thereof.

A concrete forming tube formed from a thermoplastic material and having a first end, a second end, and a substantially uniform circumference from the first end to the second end.

A tubing device is operatively connectable to an excavation machine. The tubing device comprises a base frame, at least one guiding tower operatively connected to the base frame, and a tube operating unit, operatively connected to the guiding tower. The tube operating unit is slidable along the guiding tower and is provided with engaging means capable of both selectively holding a tube segment, and of transmitting a rotary motion and an axial sliding movement to such a tube segment so as to allow the progressive driving in the ground and subsequent extraction from the ground.

A tubing device is operatively connectable to an excavation machine. The tubing device comprises a base frame, at least one guiding tower operatively connected to the base frame, and a tube operating unit, operatively connected to the guiding tower. The tube operating unit is slidable along the guiding tower and is provided with engaging means capable of both selectively holding a tube segment, and of transmitting a rotary motion and an axial sliding movement to such a tube segment so as to allow the progressive driving in the ground and subsequent extraction from the ground.

A method for improving ground is capable of preventing a clod whose representative size is large from remaining in the ground. The method for improving ground includes cutting a ground by injecting a cutting fluid (e.g. high-pressure water or high-pressure air: including a case where a solidification material is injected) from jet devices, feeding a solidification material, mixing the cut ground, the cutting fluid and the solidification material, and agitating a mixture thereof to form an underground consolidated body. A plurality of nozzles are located at an interval in a vertical direction in the jet devices, and when the cutting fluid is injected, a cutting fluid is injected from an upward nozzle in a downward skewed direction, and a cutting fluid is injected from a downward nozzle in an upward skewed direction.

A drill unit for forming a column in ground which includes an outer drill and a concentric inner drill, where attached to the outer drill there is at least one drill tooth which includes a first face, a second face and a base face wherein:the first face and the second face are immediately adjacent one another and are coterminous at a first edge and a second edge;the base face is the face closest to, or coterminous with, the first terminal end;all faces, except the base face, are independently coterminous with the base face; and extend away from the base face in the same direction;at least part of the at least one drill tooth extends away from the first terminal end to terminate at the second edge;the second edge is the edge of the at least one tooth that is most longitudinally distant from the first terminal end;the first face further includes a first alpha edge, where the first alpha edge is an edge of the first face opposite the first edge;a line joining the first edge and the first alpha edge, where the first face and the base face are coterminous, a first face alignment line, is at an angle of to a perpendicular extending from the first outside surface;the second face further includes a second alpha edge which is an edge of the second face opposite the first edge; anda line joining the first edge and the second alpha edge, where the second face and the base face are coterminous, a second face alignment line, is at an angle of to a tangent on the first outside surface; such that, when in use forming the column, the first edge is configured to be a leading edge.

A sheath for constructing a reinforced concrete pile, characterized in that the sheath is formed by at least one circular knit having a series of meshes helically positioned so as to form a pipe. A method for constructing a reinforced concrete pile includes excavating to form a well, inserting one end of a reinforcing rod in a sheath, positioning the sheath on an area of the rod and introducing the rod into the well, installing a tremie pipe inside the rod, and filling the well with concrete using the tremie pipe.

A concrete forming tube formed from a thermoplastic material and having a first end, a second end, and a substantially uniform circumference from the first end to the second end.