The present invention relates to the placement of concrete via tremie pipe in deep foundations, e.g. bored piles and diaphragm walls. Particularly the invention aims at improving the first charging of tremie pipe by avoiding the impact caused erosion at the base of drilled shafts for better construction quality of deep foundations.

The use of bentonite/polymer suspension as supporting fluid for excavations with small areas has made the construction of deep foundations, such as bored piles and diaphragm walls, in poor ground conditions possible. The excavation of the drilled shaft for bored piles and of the trenches for diaphragm walls with supporting fluid and the subsequent placement of concrete by the use of tremie method has become the state of the art in foundation engineering (see Fig. 1). The principle of the tremie method is to place the concrete through the tremie pipe, which is immersed into the interior of the freshly poured concrete to avoid segregation and contamination (mixing) of concrete by the supporting fluid (see Fig. 1).

The tremie pipe is assembled of robust steel pipes of short sections with screw joints with a hopper at the top end. The joints are sealed by gaskets to form a water-tight pipe. The pipe diameter is about 20-30 cm, large enough to avoid jamming of concrete during placement. The lower pipe end should remain about one meter under the concrete surface during pouring. The length of the tremie pipe can be adjusted by retrieving the pipe sections without lifting the pipe end out of the concrete surface. The concrete exiting the tremie pipe pushes the upper part of the concrete upwards and displaces the supporting fluid. The concrete, except an upper layer, has no contact with the supporting fluid. In this way, any mixing of concrete with the supporting fluid can be avoided. Usually ready -mix concrete is continuously fed into the hopper until the pouring of an entire pile is completed. The tremie method is also used for augured piles in the dry because simply pouring concrete in the shaft may cause segregation of concrete.

While the tremie method is well developed and standardized, the initiation of pouring, i.e. the first shot of concrete into the empty tremie pipe still presents a challenge for contractors. There are evidences that the improper initiation of pouring is responsible for some often- observed damages such as debris at pile end and bleeding along piles and diaphragm walls. Often the initiation of pouring is not specified in the design documents and therefore at the discretion of the contractors. The construction practices range from simply dropping concrete into the empty tremie pipe, to the use of some go-devils, e.g. to stuff the tremie pipe with a ball of wrapped paper, or a textile bag filled with straw, or with a soft ball of foam with size of about the pipe diameter. After sufficient concrete is charged into the tremie pipe, the concrete together with the go-devil will descend to the end of the tremie pipe under the weight of the concrete column above the go-devil. The increasing weight of concrete gives rise to an accelerated downward motion through the pile shaft like the piston motion in a cylinder. The piston motion and the enormous impact upon touchdown of the concrete at the pile base give rise to strong turbulence in the supporting fluid and may cause serious erosion and local failure at the pile base and the shaft near the pile end. The impact increases with the depth of deep foundation. Sometimes a wood plate is held at the pipe end to de-water the tremie and control the outflow of the concrete. Once the go-devil reaches the pipe end at pile base, the tremie pipe is lifted to allow the concrete to flow out. Upon exiting the end of the tremie pipe, the go-devil either float up the surface of the supporting fluid or remains trapped between the reinforcement, which adds further uncertainty to the quality of deep foundations. Often the damages caused by improper initiation of pouring remains hidden, e.g. debris at pile base and bleeding along piles and diaphragm walls.

CN 209082489 relates to an anchoring device in the technical field of rock and soil anchoring in slope support under the condition that a cavity exists in a slope body. The anchoring device comprises an umbrella-shaped anchoring head, an anchor cable and a chain. A waterproof umbrella cover in the umbrella-shaped anchoring head is used for injecting mortar after being opened by an umbrella framework in the cavity, so that a mortar expansion head is formed in the wrapping range of the waterproof umbrella cover. The problem solved by this device is to avoid breaking of the anchor cable due to non-uniform stress, while providing enough anchoring force for the anchor cable in a working state. The umbrella-shaped anchoring head remains in the cavity.

CN 203729302 U relates to a pouring pile construction, in particular to an umbrella horizontal support. Cast-in-situ piles are widely used in the foundation of buildings and bridges. In the construction of cast-in-situ piles, usually the uppermost part of the concrete, the so-called pile head, is removed due to its poor strength. This removal can be done by breaking the concrete manually or with the aid of machine tools. In order to facilitate removal of the pile head and avoiding damaging of the pile in the course of removing the pile head an umbrella-like horizontal support is suggested that serves as a separation layer between the pile and the pile head. The umbrella-like horizontal support remains in the concrete during setting.

DE 3246387 Al describes a method for increasing erosion resistance of fresh filter concrete to be placed under water. For introducing fresh filter concrete in a water-filled borehole with the help of a contractor pipe, a ball is placed in the contractor pipe, the bottom end of said contractor pipe being placed on the bottom of the borehole. Filter concrete is introduced in the contractor pipe above the ball. The weight of the concrete pushes down the ball and the water in the pipe underneath it. As soon as the ball is pushed out of the pipe, the water below the pipe flows through the pores of the fresh filter concrete, until the water level inside and outside the pipe is equal.

The objective of the present invention is to provide a device for the initial charging of a tremie pipe in a well-controlled manner so that disturbances caused by the charging can be avoided.

The present invention solves the problem by providing a device for charging concrete in tremie pipe, comprising a shank, ribs hingedly connected to the shank, the ribs extending radially from the shank, a canopy attached to the ribs, wherein the angular range of motion of the ribs about their connection to the shank in respect of the longitudinal extension of the shank is greater than 120°, preferably greater than 150°.

The diameters of tremie pipes are not standardized and therefore may vary. To make the inventive device applicable to a great range of different tremie pipes it is preferred that the ribs are angularly movable about their connection to the shank in a rotational angle from less than 30° to more than 150°, preferably from 0° to 180°, in respect of the longitudinal extension of the shank. A rotational angle of 0° means that the ribs are directed to a second end of the shank that defines a hanging point and are parallel to the longitudinal extension of the shank.

In a preferred embodiment the ribs are hingedly connected to the shank via a rib holder attached to the shank, preferably to a first end of the shank.

For securely moving down and up the device for charging concrete in tremie pipe through the tremie pipe by means of a rope or chain mounting means for attaching a rope or chain may be provided at a second end of the shank, wherein preferably the mounting means are designed as an eye. In another preferred embodiment of the invention spreaders are provided that are linked to the ribs and to a stopper, which stopper is slidably mounted on the shank. The spreaders support the ribs and hold them in a position defined by the stopper. It is preferred to design the stopper with fixation means for firmly holding the stopper in place on the shank in a predefined or adjustable position. Further, when the spreaders or parts of the spreaders are releasably linked to the stopper they allow the rips to rotate downwards about their connection to the shank when the device moves out from the bottom end of the tremie pipe, such that the device for charging concrete can be pulled up through the tremie pipe without the ribs hindering pulling up. In an easy to assemble yet very reliable embodiment of the invention the releasable links between the spreaders or parts of the spreaders and the stopper are configured as socket-plug-connections.

It is preferred that the canopy is made of a sturdy, flexible textile that is robust to survive the harsh site conditions but is still flexible enough to being unfolded and collapsed during use.

The invention also provides a method for charging concrete in tremie pipe, comprising the steps of providing a device according to any of the preceding claims, mounting the shank of the device to a rope, cable, or chain, unfolding the device into a state where its spreaders have a rotational angle of less than 90° in respect of the longitudinal extension of the shank and the canopy covers at least a part of the cross-sectional area of the tremie pipe, inserting the device into the top end of the tremie pipe, charging concrete in the tremie pipe, letting the device slide down with controlled descent speed under control of the rope, cable, or chain, when the device moves out from the bottom end of the tremie pipe it is collapsed such that the spreaders are directed downwards, pulling up the device through the tremie pipe.

The invention will now be explained in detail by way of exemplary embodiments and with reference to the attached drawings.

Fig. 1 schematically shows steps of construction of a bored pile as part of a deep foundation applying the tremie pipe method. Fig. 2 schematically shows an embodiment of the device for charging concrete in tremie pipe in accordance with the present invention.

Fig. 3 and Fig. 4 show use of the present device.

Fig. 5 is an elevational view of an embodiment of the device for charging concrete in tremie pipe in accordance with the present invention.

Fig. 6 is a view depicting details of the device of Fig. 5.

Fig. 7 is a view showing the state of the device for charging concrete in tremie pipe of Fig. 5 in use after it has been pulled up through the tremie pipe.

Fig. 1 schematically shows the construction of a bored pile as part of a deep foundation. First, an excavation is made in the ground 20. Here, the excavation takes the shape of a drilled shaft 21 for a bored pile. The drilled shaft 21 is filled with a bentonite/polymer suspension 22 as supporting fluid. Subsequently, a hollow tremie pipe 23 is placed into the drilled shaft 21, such that its bottom end 23a terminates slightly above the bottom of the drilled shaft 21. A hopper is placed upon the top end 23b of the tremie pipe 23. Concrete 25 is poured into the hopper. The concrete sinks down into the drilled shaft 21 through the tremie pile 23 and displaces the bentonite/polymer suspension 22. Pouring concrete 25 into the tremie pipe 23 is continued until the drilled shaft 21 is filled with concrete. The excavation of the drilled shaft for bored piles and of the trenches for diaphragm walls with supporting fluid and the subsequent placement of concrete by the use of tremie pipes has become the state of the art in foundation engineering. Pouring the concrete 25 through the tremie pipe 23, which tremie pipe 23 is immersed into the interior of the freshly poured concrete 25 in the drilled shaft 21 avoids segregation and contamination (mixing) of the concrete 25 by the bentonite/polymer suspension 22.

While the tremie method is well developed and standardized, the initiation of pouring concrete 25, i.e. the first shot of concrete 25 into the empty tremie pipe 23 still presents a challenge for contractors. As has been discussed in the introduction of this documents, there is evidence that the improper initiation of pouring is responsible for some often-observed damages such as debris at pile end and bleeding along piles and diaphragm walls.

The present invention solves or at least mitigates this problem.

The device 10 for charging concrete in tremie pipe in accordance with the invention is depicted in Figs. 2, 5, 6 and 7. The device 10 comprises a shank 1, ribs 2 hingedly connected to the shank 1, the ribs 2 extending radially from the shank 1. The ribs are hingedly connected to the shank 1 via a rib holder 3 that is attached on the shank 1 at or close to a first end la of the shank 1. A canopy 6 made of a sturdy, flexible textile is attached to the ribs 2. The angular range of motion P of the ribs 2 about their connection to the shank in respect of the longitudinal extension of the shank is greater than 120°, preferably greater than 150°. The ribs 2 are angularly movable about their connection to the shank 1 in a rotational angle a from less than 30° to more than 150°, preferably from 0° to 180°, in respect of the longitudinal extension of the shank 1. Mounting means 9 for attaching a rope, cable or chain are provided at a second end lb of the shank 1. In the present embodiment the mounting means 9 are designed as an eye.

Spreaders 4 are provided that are linked to the ribs 2 and to a stopper 5. The stopper 5 is slidably mounted on the shank 1. The stopper 5 comprises fixation means 7, such as a screw, for firmly holding the stopper 5 in place on the shank 1 in a pre-defined or adjustable position. The spreaders 4 are releasably linked to the stopper 5. The releasable links between the spreaders 4 and the stopper 5 are configured as socket-plug-connections 8.

The use of the device 10 according to the invention is now described with reference to Figs. 3 and 4. The device 10 for charging concrete in tremie pipe basically looks like an inversed umbrella (Fig. 2), which is adapted for being placed upside down into the tremie pipe 23 near the top end 23b of the tremie pipe 23 prior the first pouring (Fig. 3). The device 10 has an eyed shank 1 (Fig. 2), which is connected to a rope 26 and to a tripod 28 via with a double head-mounted pulley 27 (Fig. 3). Alternatively, the device 10 can also be hanged to a drilling rig, which is available at construction sites. The device 10 slides down the tremie pipe 23 under the weight of concrete 25 upon pouring. The downward motion of the device 10 with the concrete column above it can be controlled with the pulley 27. With controlled descending speed, the supporting fluid, i.e., the bentonite suspension 22, is displaced by concrete without inducing turbulence (Fig. 4). Once the device 10 reaches the bottom end 23 a of the tremie pipe 23 and leaves the tremie pipe 23 through the bottom end 23 a. Then, the ribs 2 rotate downwardly and the canopy 6 turns down (collapses) under the weight of the concrete 25. This is like the upturning of an umbrella in strong wind. The device 10 with the downtumed (collapsed) canopy 6 and ribs 2 can be easily pulled up through the tremie pipe 23 with the help of the pulley 27, until the device 10 slides out at the top end 23 a of the tremie pipe. The device 10 can be retrieved, washed and is ready to be used for the next pour of concrete 25.

It should be noted that the stopper 5 can slide along the shank 1 and the position of the stopper 5 can be adjusted with the help of the fixation means 7 (see Fig. 6). By changing the stopper position the span of the canopy 6 can be adjusted to the diameter of the tremie pipe 23.

Unlike a rain umbrella, where spreaders are connected to the ribs by means of hinges (not detachable), the spreaders 4 in the present device 10 are detachable by putting them into the sockets of socket-plug-connections 8 that are connected to the ribs 2 via hinges 11. The spreaders 4 remain connected with the sockets of socket-plug-connections 8 when compression forces are exerted onto the spreaders 4. This is the case while the device 10 is charged with concrete 25 and slides down the tremie pipe 23 under the weight of concrete 25. However, the spreaders 4 are detached from the sockets of socket-plug-connections 8 when stretched. This is the case when the device 10 slides out of the bottom end 23a of the tremie pipe 23. The sockets of socket-plug-connections 8 can be easily aligned to accommodate the spreaders 4 to adjust to the diameter of the tremie pipe 23. The canopy 6 and the ribs 2 can be easily downtumed with the detachable spreaders 4 when the device 10 leaves the tremie pipe. Fig. 7 shows the device 10 when it is downtumed (collapsed). The downturned canopy 6 of the device 10 is folded and the device 10 can be easily pulled up through the tremie pipe 23. The retrieved device can be cleaned and is ready for the use.

The device 10 can also be used to re-initiate pouring when the concrete process is interrupted inadvertently by lifting the tremie pipe 23 above the concrete surface. In this case, the device 10 can be put into the tremie pipe 23, charged with concrete 25 and lowered until the device 10 is immersed in the concrete. Once the concrete 25 starts flowing out of the bottom end 23a of the tremie pipe 23, the device 10 is downturned and folded. Afterwards, it can be pulled up and retrieved.