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 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 vibrator assembly comprising a feed pipe that has a longitudinal axis as well as a first end and a second end. The vibrator assembly may further comprise a vibrator unit that is mechanically coupled to the feed pipe, and a filling assembly which extends into the feed pipe at the first end and is designed to pick up material and direct same into the feed pipe. The feed pipe may have at least two separate channels from the first end to the second end and parallel to the longitudinal axis.

A vibrator assembly comprising a feed pipe that has a longitudinal axis as well as a first end and a second end. The vibrator assembly may further comprise a vibrator unit that is mechanically coupled to the feed pipe, and a filling assembly which extends into the feed pipe at the first end and is designed to pick up material and direct same into the feed pipe. The feed pipe may have at least two separate channels from the first end to the second end and parallel to the longitudinal axis.

A drill assembly that includes one drill and a displacement unit, where the drill is releasably or permanently attached to said displacement unit, such that:the displacement unit includes a guide unit and a channel unit, where the channel unit includes a guide channel, and said guide unit includes one or more guides adapted to engage with said guide channel, such that said guide channel is a circumferential channel that follows a wave or wave like path;the drill includes a drill bit and/or a drill flight attached to a central shaft, wherein the drill bit and/or drill flight co-terminate at a first terminal end of the drill;said first terminal end is the terminal end of the drill that is configured to enter the ground first; andthe central shaft is a thin elongate member that extends between the longitudinally separated terminal ends of the drill.

A drill assembly that includes one drill and a displacement unit, where the drill is releasably or permanently attached to said displacement unit, such that:the displacement unit includes a guide unit and a channel unit, where the channel unit includes a guide channel, and said guide unit includes one or more guides adapted to engage with said guide channel, such that said guide channel is a circumferential channel that follows a wave or wave like path;the drill includes a drill bit and/or a drill flight attached to a central shaft, wherein the drill bit and/or drill flight co-terminate at a first terminal end of the drill;said first terminal end is the terminal end of the drill that is configured to enter the ground first; andthe central shaft is a thin elongate member that extends between the longitudinally separated terminal ends of the drill.

A method for detecting and controlling compaction when compacting a soil by a depth vibrator which has a rotationally drivable imbalance (3) and at least one sensor (6, 12, 13, 14, 19), comprising the steps of: inserting the depth vibrator (2) into the soil (17) up to a desired final depth (Tm); compaction of the soil (17) during which the forward angle () of the imbalance (3) as well as the oscillation amplitude (A) of the depth vibrator (2) are determined; detection of a soil stiffness profile from soil stiffness values (k) determined over time (t); determination of a first soil stiffness value (k1) and a second soil stiffness value (k2) from the soil stiffness profile (k), for which it applies that a rate of increase (k2) of the second soil stiffness value (k2) exceeds a rate of increase (k1) of the first soil stiffness value (k1) by a defined factor; calculation of a transition soil stiffness value (k12) which is between the first soil stiffness value (k1) and the second soil stiffness value (k2); and storing the transition soil stiffness value (k12) detected in the respective compaction step to the associated depth (T).

A method for detecting and controlling compaction when compacting a soil by a depth vibrator which has a rotationally drivable imbalance (3) and at least one sensor (6, 12, 13, 14, 19), comprising the steps of: inserting the depth vibrator (2) into the soil (17) up to a desired final depth (Tm); compaction of the soil (17) during which the forward angle () of the imbalance (3) as well as the oscillation amplitude (A) of the depth vibrator (2) are determined; detection of a soil stiffness profile from soil stiffness values (k) determined over time (t); determination of a first soil stiffness value (k1) and a second soil stiffness value (k2) from the soil stiffness profile (k), for which it applies that a rate of increase (k2) of the second soil stiffness value (k2) exceeds a rate of increase (k1) of the first soil stiffness value (k1) by a defined factor; calculation of a transition soil stiffness value (k12) which is between the first soil stiffness value (k1) and the second soil stiffness value (k2); and storing the transition soil stiffness value (k12) detected in the respective compaction step to the associated depth (T).

A method for detecting and controlling compaction when compacting a soil by a depth vibrator which has a rotationally drivable imbalance (3) and at least one sensor (6, 12, 13, 14, 19), comprising the steps of: inserting the depth vibrator (2) into the soil (17) up to a desired final depth (Tm); compaction of the the soil (17) during which the forward angle () of the imbalance (3) as well as the oscillation amplitude (A) of the depth vibrator (2) are determined; detection of a soil stiffness profile from soil stiffness values (k) determined over time (t); determination of a first soil stiffness value (k1) and a second soil stiffness value (k2) from the soil stiffness profile (k), for which it applies that a rate of increase (k2) of the second soil stiffness value (k2) exceeds a rate of increase (k1) of the first soil stiffness value (k1) by a defined factor; calculation of a transition soil stiffness value (k12) which is between the first soil stiffness value (k1) and the second soil stiffness value (k2); and storing the transition soil stiffness value (k12) detected in the respective compaction step to the associated depth (T).

A method for detecting and controlling compaction when compacting a soil by a depth vibrator which has a rotationally drivable imbalance (3) and at least one sensor (6, 12, 13, 14, 19), comprising the steps of: inserting the depth vibrator (2) into the soil (17) up to a desired final depth (Tm); compaction of the the soil (17) during which the forward angle () of the imbalance (3) as well as the oscillation amplitude (A) of the depth vibrator (2) are determined; detection of a soil stiffness profile from soil stiffness values (k) determined over time (t); determination of a first soil stiffness value (k1) and a second soil stiffness value (k2) from the soil stiffness profile (k), for which it applies that a rate of increase (k2) of the second soil stiffness value (k2) exceeds a rate of increase (k1) of the first soil stiffness value (k1) by a defined factor; calculation of a transition soil stiffness value (k12) which is between the first soil stiffness value (k1) and the second soil stiffness value (k2); and storing the transition soil stiffness value (k12) detected in the respective compaction step to the associated depth (T).