The invention relates to a method for applying a sheet pile wall by successively driving sheet piles into the ground and causing the longitudinal edges of said sheet piles to interlock and guide each other.
US-A-2 400 694 already discloses (in particular in figure 11 and page 3 left-hand column, lines 20 to 58) a method for driving a sheet pile wall by successively driving sheet piles of concrete into the ground and causing the longitudinal edges of said sheet piles to engage and guide each other (see in particular lines 47 to 58 of the above cited column), wherein each time a (following) sheet pile is driven an auxiliary section made of several parts is "inserted", whereby a complementarily formed longitudinal edge of said section is caused to engage the free longitudinal edge of said sheet pile, said section functioning as a support for at least one nozzle through which an hydraulic liquid is injected adjacent the free longitudinal edge of said sheet pile and said auxiliary section being retracted from the ground prior to driving a following sheet pile (see page 3, left hand column, lines 41 to 43).
The invention aims at providing an improved method of driving original sheet piles of steel i.e. interlockingly formed sheet piles of steel by enlightening the driving of such sheet piles while providing for conditions for a better water-tightness of the sheet pile wall when formed of relatively long sheet piles (i.c. a length of 30 m).
Accordingly the invention provides a method for driving a sheet pile wall by successively driving sheet piles of steel into the ground and causing the longitudinal edges of said sheet piles to interlock and guide each other, whereby each time a (following) sheet pile is driven an auxiliary section is inserted and a complementarily formed longitudinal edge of said section is caused to engage the free longitudinal edge of said sheet pile, said section functioning as a support for at least one nozzle, through which an hydraulic liquid, such as water, is injected adjacent the free longitudinal edge of said sheet pile, and said auxiliary section being retracted from the ground prior to driving a following sheet pile.
In a practical embodiment of the method of the invention the insertion and retraction of the auxiliary section is carried out in an intermediary phase between the insertion of two successive sheet piles or sheet pile pairs. The effect of the auxiliary section is to be seen in that the soil in the area around the free longitudinal edge of the last driven sheet pile is loosened up and pressed away, so that a next sheet pile (pair) may "smoothly" run into the key-way of the last driven sheet pile. The advantage of the effect of the auxiliary section may be taken even in an earlier stage by driving it each time simultaneously with a sheet pile (pair) into the ground.
A particular performance of the method of the invention is achieved by filling the hollow space which is created around the free longitudinal edge of the last driven sheet pile as a result of the retraction of the section, by a sealing substance, such as bentonite, which is injected under pressure through said nozzle.
This means that upon driving of a next sheet pile a high degree of water-tightness of the connection between the two sheet piles or sheet pile pairs is obtained, because the interconnected edges will become embedded in a column of the said sealing substance.
This manner of performing the method according to the invention is particularly suitable for applications such as those, whereby polluted soil areas have to be isolated. In this case the method according to the invention offers substantial advantages over the method which been used until sofar and according to which at first "bentonit piles" are formed into the ground at locations where - in a later stage - the joints between the individual sheet piles of the future sheet pile wall are expected to be located. With such a method there is a great chance that in the process of drilling said bentonite piles an undesired deviation will take place which may not be simply controllable, while with the subsequent driving of the sheet pile wall horizontal deviations relative to the location of the previously inserted bentonite piles may also easily occur.
The invention will be hereinafter explaned by way of example with reference to the accompanying drawing.
The sheet pile wall according to fig. 1 is composed of sheet piles 1 having a trapezoidal cross-section, the longitudinal edges of said piles engaging one another. The sheet piles are e.g. in sets of two previously interconnected sheet piles driven into the ground in a manner known per se, i.e. by hammering or vibrating. In Fig. 1 the sheet piles 1c and 1d constitute a set which is the latest one driven into the ground, while the sheet pile 1b has been driven in in an earlier stage. The key-way connection 2 between the sheet piles 1c and 1d may be easily rendered watertight by applying, beforehand, to the key-way of both of said sheet piles a substance adapted to form a sealing mass when it gets into contact with water. The drawing shows the right hand edge (key-way) 3 of the sheet pile set 1c, 1d in engagement with the auxiliary section 4 according to the invention. In the example shown use is made of an existing section, a so-called "delta" section, which is normally used to connect two sheet piles which are positioned perpendicularly to the other when seen in a horizontal plane. The web 5 of this well-known section constitutes a strip shaped carrier for a tube 6 which is connected thereto e.g. by welding and which extends substantially along the entire length (= length of the sheet pile) of the section. Said tube 6 is positioned at a slight distance opposite to the opening of the key-way 7 of the profile which has been formed complementarily to the key-way 3 at the longitudinal edge of the sheet pile 1d. A second tube 8 is connected to the side of the key-way wall 7a turned away from said tube 6. The tubes 6 and 8 have a rectangular cross-section. As a result of this the wall of the tube 6 facing to the opening of the key-way 7 may also function as a guide for the key-way wall 3a (vide fig. 2). To the upper ends of the tubes 6 and 8 conduits (not shown) may be connected, by means of which a liquid under pressure may be supplied. For example water may be supplied when driving section 4. The water which discharges from the tubes 6 and 8 at the lower ends of the latter will remove the soil from the area of the key-way 3 of the sheet pile 1d, as a result of which a next sheet pile may run easier into the key-way 3 of sheet pile 1d.
The tubes 6 and 8 may be further untilized to inject a sealing substance, such as bentonite, into the space left around the key-way 3 when retracting the section.