A TUBULAR PILE ENCASED IN CONCRETE AND A PILE-DRIVING METHOD

Abstract: The invention relates to tubular piles encased in concrete, which comprise a metal pile tube (2) to be driven into soil, and in the upper end of the said tube an aperture for feeding liquid concrete mass into the pile tube interior (12). The lower end of the pile tube is provided with a pile shoe (1) comprising a longitudinal tip section (3) with uniform broadness and a ferrule (6), the maximum diameter (D1) of which is bigger than the outer diameter (D2) of the pile tube, and flow apertures (7), which are arranged above the lowermost upwards free base (24) of the ferrule and pass through the circumferential surface (23) of the said pile tube extension for the out-flow of concrete mass. The distance (L1) of the pile shoe from the tool tip (10) is at least five times the outer diameter (D2) of the pile tube.

Description: A tubular pile encased in concrete and a pile-driving method The present invention relates to a tubular pile to be encased in concrete, the pile comprising a metal pile tube to be driven into soil; an aperture/apertures in the upper end for feeding liquid concrete to the interior of the pile tube; and in the lower end a downwards tapering pile shoe, the diameter of the upper end of which is bigger than the diameter of the pile pipe, and to the area of which the lower end of the pipe tube opens for making it possible for the said concrete to come out. The invention also relates to a method for driving the tubular pile into soil and encasing it in concrete, the tubular pile comprising a metal pile tube having an aperture/apertures in the upper end and in the lower end a tapering pile shoe the diameter of which is bigger than the diameter of the pile tube, and to the area of which the lower end of the pile tube opens. The bearing capacity of building foundations is known to be improved by using piles driven into soil; in new construction, the piles usually consist of relatively long steel concrete piles and their parts. In conservation, i.e. supporting foundations of previously built houses or constructions, short and sectional piles are used, due to lack of space, because pile-driving may have to be conducted in small and low spaces inside a building. In situations like this, light impacts or even vibrations are used for driving the piles into soil in order to avoid excessive trembling and to prevent the building around and above from being damaged. For driving the pile into said soil, an impact piece may be moved up and down inside the pile tube or, alter- natively, impacts or vibrations may be directed to the upper end of the pile. The internal volume of a tubular steel pipe is usually filled with concrete after driving the pile into soil. A tubular steel pipe as such is preferable for this purpose, as it is easy to extend, for example, by welding or by using a suitable sleeve joint and, when driven into soil, the pile resistance is smaller than, for example, of a concrete pile, due to the smooth surface of the steel pile. If the pile tip cannot be driven into rock or some other similar well bearing structure, the pile has to act as a friction pile supporting itself to soil layers along the length of the pile. In a situation like this, the bearing capacity of the steel pipe is poor, due to its smooth surface, while the bearing capacity of a concrete pile is substantially better. This is true, for example, in clayey soil, in which the clay layer may be very thick. NO-121440 discloses the injection of stabilizing mass in connection of a foundation pile driven into soil, consisting of otherwise completely conventional steel concrete pile with a concrete surface and a conventional rock tip [cf. for example Swedish standard SIS 911196: 1972-11-20], and of a channel extending through the steel concrete of the pile, through which channel the stabilizing mass is driven into soil near the pile tip. This pile has to be driven into soil in the same way as conventional steel rock piles, and it has no small resistance due to the surface. Usually lime is used for stabilising the soil but, in this case, concrete is used, which probably refers to cement, as in the publication EP-0539 630. The pile shoe in accordance with the Norwegian publication has an end with a diameter substantially similar to that of the pile tube end and a projecting narrower tip section and, in this thin tip section, chan- nels for injecting the stabilising substance into soil. The object is to stabilise the soil near the tip of the pile and especially below it. A formula is given to the tip length, according to which linear measure L is (R + r)V3, i.e. in the picture, about three times the diameter of the tip section and approximately equal to the pile diameter. It is difficult to place the effectively bearing area at the point of the tip, as the area which is to be made bearing has a very limited surface area. Especially if the poorly bearing soil continues below the area containing cement and set at the tip, the meaning of such a set area may be non-existent or even harmful. EP-0 539 630 Al discloses a manufacturing method for a foundation pile screwed into soil, in which method, upon driving the pile into soil, first a mixture of water and bentonite is fed from the screw tip of the pile at a point in front and, as the screw tip of the pile reaches the bearing soil layer, a mixture of cement and water is fed under high pressure which is higher than hydrostatic pressure, whereafter the screw-like tip of the pile strongly mixes cement and soil. The driving pressure for the cement mixture is very high, even 500 bar - 1000 bar. As a result, a bearing zone of a large diameter is formed between the lower part of the pile and the bearing soil. First of all, the method is complicated, as it first requires as drilling liquid a mixture of water and bentonite and thus equipment for changing the mass to be driven out of the tip. In addition, the method requires large and expensive equipment both for screwing the pile into soil and for generating the said high pressure. In conservation, machines of this type usually are too large to be used, because they simply cannot fit into room or cellar spaces. Both the solution of NO- 121440 and of EP- 0 539 630 require the mass to be fed under very high pressure, because the mass is fed into soil below the frontal surface of the tip where the counter pressure of soil is at the highest and the counter pressure has to be exceeded with pumping pressure. The publication US-4 909 673 relates to an injection method according to which the pile tube is provided with a large number of injection apertures, injection valves being attached into there apertures from the inside of the pile so that friction between the pile and soil can be increased by injecting mortar setting to the outer surface of the steel pile. Like the EP publication referred to above, also this method requires that high pressures and large machines be used. Further, the structure is much too complicated and expensive to be used in small working projects, such as for increasing the bearing capacity of a single house, etc. A method completely different from the ones described above is disclosed in the publication FI-30911 relating to a manufacturing method of a ram pile encased in concrete. According to this method, a tubular pile shank provided with a pile shoe with an open upper end and with a larger cross-section in the upper end than the cross-section of the pile shank, is rammed down into soil, and cement gruel or thin concrete is pressed along the hollow pile shank through the pile shoe into a cavity created between soil and the pile shank by action of the pile shoe. In this method, liquid cement or concrete is thus pressed from above simultaneously and continuously with ramming into the created soil cavity under low pressure in order to continuously fill the cavity. At the end of ramming, the filled cavity space is sealed from above, and the feeding of concrete is carried on under higher pressure. It is true this method provides a tubular steel pile with a bearing concrete casing by very simple means. However, this arrangement includes considerable problems. When trying to use a construction of the type described it is found that most often the pile does not advance in soil along a direct path but clearly tends to curve so that so high bending forces may be directed to the pile tube that the progress of the pile into soil stops, or the pile may even break. Although the publication mentions feeding ce- ment or concrete mass merely under low pressure, achieving this requires machines too large and/or expensive for several sites. Publication GB-2 234 774 A describes a method of forming a pile and a method for supporting a building structure. The pile disclosed includes a tubular casing and an enlargement or protrusion near its leading end as well as a plurality of apertures passing through the casing on the side of said protrusion, which apertures are at first closed or sealed off by a rupturable material. Nothing about the dimensions or about ratios of dimensions are defined in the publication. According to the teaching of this publication a passage is at first formed through the wall and the footing of the building by a separate drilling work, whereafter the pile disclosed is guided through the preformed passage and driven further into the soil until a sufficient depth is reached. The apertures in the casing are closed e.g. by an adhesive tape during said guiding and driving. Finally the space between the casing and the passage is sealed by fluent cementitious mix or grout, which is passed under pressure into the casing at which stage the closures or coverings of the apertures are ruptured allowing the grout to pass up the hole formed by the protrusion, thereby bonding the casing to the building structure. This suggested method and pile has several drawbacks. At first the force required for driving the pile into the soil is very high, which means need for large, heavy and expensive machinery. Secondly the walls of the hole formed by the protrusion in the soil easily collapses, which makes the filling of the gap between the casing and the soil with cementitious mix impossible. Finally the disclosed pressurized feeding of the cementitious mix also requires heavy, expensive and power consuming machinery. The object of the invention thus is to provide a metal, typically a steel pile, for example, a tubular pile, the outer surface of which, when driven into soil, could be encased in settable mass, such as concrete, without complicated, expensive, and/or large machines so that the bearing capacity of a finished pile with a concrete surface would be at least equal to the bearing capacity of prefabricated concrete piles. Another object of the invention is to provide a metal pile, for example a tubular pile, which requires minimum power when driving it into soil, corresponding at most to the power a straight tubular steel tube requires in soil. The third object of the inven- tion is a metal pile, for example a tubular pile which, when driven into soil, would not tend to progress in a direction which is not in direct line with the intended direction, at least not to a harmful extent. At least in general outline, the pile should remain straight. The fourth object of the invention is a pile of the type described with a simple structure and advantageous manufacturing and operating costs. The fifth object of the invention relates to a method for driving such a metal pile into soil and encasing it in concrete, which can be carried out even in tight places and in different types of soil. Still another object of the invention is to provide such a method which provides, for example, a tubular pile with good bearing capacity in different types of soil. Thus, the object of the invention is to provide a pile-driving method and pile combining the easy installability of a tubular steel pile and the good adhesion of a concrete pile in soil. The disadvantages described above can be eliminated and the objects determined may be carried out by a tubular pile in accordance with the invention, characterized in what is defined in the characterizing part of claim 1, and by a method of the invention characterized by what is defined in the characterizing part of claim 12. Surprisingly, it has now been noticed that by providing the lower end of the pile, which is first driven into soil, with such a pile shoe having a ferrule, the diameter of which is larger than the diameter of the pile tube, and with a relatively long tip section projecting from the ferrule to the push direction of the pile, i.e. downwards; and by arranging the outlet for the settable mass from the interior of the pile tube through apertures on the circumference above the contacting point of the ferrule and the pile tube, the pile is by impacts and/or vibrations made to sink sufficiently straight into soil, irrespective of quality or variations in quality. Further, it has surprisingly been noted that the settable mass travels efficiently and fast through the apertures on the circumference from the interior of the metal pile tube to the cavity created around the pile tube by the ferrule merely by action of the sinking impacts and/or sinking vibrations of the pile so that it is not necessary to use pressure for feeding the hardening mass at the upper end of the pile tube above the ground surface, but the mass may simply be poured inside the pile tube. The force required by the tubular pile for driving it into soil is small, and the bearing capacity of the finished tubular pile encased in and filled with concrete is excellent when it acts as friction pile either over its entire length or over a predetermined part of its length. Further, an advantage of the invention is that it is not necessary to arrange complicated means to the upper end of the pile tube for making it possible to simultane- ously feed the settable mass and make the sinking impacts or vibrations as, in accordance with the invention, the stages are carried out separately. The improved pile structure and installation method of the invention are excellently suited for the repair of building foundations, but the invention is not limited to this application. The invention may be used in piles that are driven into soil both by driving and vibration. The invention is next described in more detail referring to the enclosed drawings in which: Figs 1A - 1H are schematic elevation views perpendicular to the ground level of the various stages of the method of the invention when using a tubular pile and a pile shoe provided with its long tip section; Fig. 2 is similar to Figs 1A - 1H, showing a first embodiment of the finished pile structure made by the pile and method of the invention in soil; Fig. 3 shows a second embodiment of the finished pile structure made by the pile and method of the invention in soil, similarly to Fig. 2; Fig. 4A is a longitudinal section along the line II - II of Fig. 4B of the first embodiment of the pile shoe of the invention attached to the pile tube; Fig. 4B is a cross-section along the line II - II of Fig. 4A of the first embodiment of the pile shoe of the invention attached to the pile tube; Fig. 5 A is a longitudinal section along the line III - III of Fig. 5B of the second embodiment of the pile shoe of the invention attached to the pile tube; Fig. 5B is a cross-section along the line IN - IN of Fig. 5A of the second embodiment of the pile shoe of the invention attached to the pile tube; Fig. 6 A is a longitudinal section along the line N - N of Fig. 6B of the third embodiment of the pile shoe of the invention attached to the pile tube; Fig. 6B is a cross-section along the line VI - VI of Fig. 6A of the third embodiment of the pile shoe of the invention attached to the pile tube; Fig. 7 is a longitudinal section similar to Figs. 4 A - 6 A of the fourth embodiment of the pile shoe of the invention attached to the pile tube; and Figs 8A - 8C show three different joints of the invention for extending the pile tube sections as longitudinal sections of the pile tube, similar to Figs 4A - 6A and 7. The invention relates to a tubular pile 40 to be encased in concrete, the shank com- prising a pile tube generally referred to with the reference number 2. Only when it is necessary to separate the various parts or sections of the pile tube from each other, more individual reference numbers 2a, 2b, 2c, etc. are used. The general reference number 2 refers to these all. Thus, the tubular pile 40 comprises a metal pile tube 2, usually of tubular steel material, to be driven or pushed into soil which may, in a way described below, consist of one or several pile sections 2a, 2b, 2c, etc. In this description, the concepts "lower end", "downwards", "down", etc., refer to the direction to which the pile sinks, or to the position in the direction to which the end is driven; and, correspondingly, the concepts "upper end", "upwards", "up", etc., refer to the position of the pile end remaining above the ground or pointing outwards from the ground surface. Usually, piles 40 are driven into soil in a vertical or close to a vertical position, as is shown in Figs 1A - 3, so that the directions and sides explained above are self-evident, but they have to be understood in the way defined even if the centre line 31 of the pile formed an angle deviating considerably from the right angle to the horizontal level or to the level describing the ground surface 20; the deviation may be dozens of degrees of angle. The cross-section of the pile tube 2 typically consists of conventional circular steel tube but, naturally, also a tube with a different cross-section, such as square, diamond-shaped, or rectangular, may be used. The outer diameter D2 of the pile tube may be, irrespective of the cross-sectional shape, for example, 25 mm - 1500 mm, preferably between at least 40 mm and at most 300 mm, and typically between at least 50 mm and at most 200 mm. The wall thickness of the pile tube 2 may be 1 mm - 20 mm, depending on the outer diameter of the pile tube, preferably at least 3 mm and at most 15 mm, and typically at least 5 mm and at most 12 mm. The inner diameter of the pile tube naturally is smaller than the outer diameter by a measure corresponding to the wall thickness, and it forms the interior 12 of the pile tube, along which the concrete mass B passes from the upper end 29 to flow apertures 7. The lengths of pile sections 2a, 2b, 2c, etc., of the pile tube 2 to be connected to each other are smaller than the height of the space, inside which the tubular pile 40 is driven into soil so that the lengths L2 of the pipe sections 2a, 2b, 2c, etc., often are at least 0.5 m and at most 3 m, typically 1 m - 2.5 m. If there is enough space, it naturally is possible to use also longer pile sections, e.g. 6 m or even longer. When necessary, the outer surface of the pile tube 2 is provided with adhesions 30, such as tack- welded pieces of steel strip or otherwise manufactures shapes, in order to improve the reciprocal adhesion between the settable concrete B and the pile tube. Although the typical and preferable embodiment of the invention relates to conservation and to resupporting already existing structures, such as foundations of houses, bridges, roads and other fixed structures, the pile according to the invention may also be used in other connections, such as new construction, and as soil anchors and soil nails. The upper end of the pile tube 2 of the tubular pipe 40 remaining above the ground surface 32 or at last near the ground surface 32 and thus pointing towards external space includes an aperture or apertures 29 for feeding liquid concrete mass into the interior 12 of the pile tube. In its simplest form, the aperture 29 of the pile tube 2 is only an open tube end, into which the liquid concrete mass is poured, as is shown in Figs IB, ID and 1G. Alternatively, the upper end of the pile tube may be provided with an aperture or apertures 29 either on the circumference of the tube and/or on a driving base which is possibly used at the upper end of the tube and used for transmitting force F driving the pile into soil, and which is not shown in the figures. Such a driving base may consist, for example, of connection pieces 21 for the tube sections or of some other kind of pieces attachable to and releasable from the pile tube end, protecting the pile tube end from damage and deformation and distributing the force F directed to it in a desired way to the pile tube, with which force the tubular pile 40 is driven into soil. A downwards tapering pile shoe 1 according to the invention and with a large outer diameter Dl is provided at the lower end of the tubular pile 40; the pile tube and especially its interior 12 open to the area of the pile shoe 1 in order to make it possible for the concrete mass B to come out. The pile shoe 1 of the invention comprises a longitudinal tip section 3 having a substantially uniform broadness, i.e. outer trans- o verse dimensions along the length thereof, a tool tip 10 at the lower end, and a ferrule 6 at the upper end, the maximum diameter Dl of which is substantially larger than the outer diameter D2 of the pile tube. The maximum diameter Dl of the ferrule forms a soil cavity M or a space T around the pile tube for the concrete B. It is usually attempted to put a layer of concrete of a predetermined thickness around the pile tube, the thickness of the layer being about half of the difference between the maximum diameter Dl of the pile shoe and the outer diameter D2 of the pile tube. Thus, the desired layer thickness W B for the concrete is achieved by the thickness W extending in the direction of the radius of the cavity T surrounding the pile tube, the thickness W being achieved by predetermining the maximum diameter Dl of the pile shoe in relation to the outer diameter of the pile tube, i.e. W = [Dl - D2]/2. A desired layer thickness on the pile tube surface typically is at least 5 mm and at most 200 mm, generally at least 15 mm and at most 100 mm, preferably 30 mm - 50 mm. The difference W between the maximum diameter Dl of the pile shoe and the outer diameter D2 of the pile tube is, as determined above, at least 10 mm - 400 mm, etc. It has to be noted that with the tubular pile of the invention, when using a pile shoe of the invention and following the method of the invention, the difference between the diameters of the pile shoe and the pile tube, etc., i.e. the thickness W in direction of the radius and the nominal thickness W B of the concrete layer are not exactly equal in real soil M, due to various reasons. The nominal thickness W B of this concrete layer surrounding the steel pile tube, and thus the maximum diameter Dl creating the ferrule, may also be proportioned to the outer diameter D2 of the pile tube by arranging the maximum diameter Dl about 1 - 4 times or preferably 1.5 - 2.5 times the outer diameter D2 of the pile tube. It has to be understood that if the cross- sectional shapes of the pile tube 2 and the ferrule 6 are different from each other, as is the case in the embodiment of Figs 5A and 5B and in the embodiment of Figs 6A and 6B, the derived thickness W and the nominal thickness W B of the concrete vary on different sides of the pile. Likewise it has to be noted that, depending on the quality of and quality variations in soil M, such as sheeting or non-homogeneity, the real thickness W B of the concrete layer varies in the longitudinal direction of the pile, i.e. in the direction of the centre line 31, as is shown in Figs 1A - 3. The ferrule of the invention may be substantially cylindrical in the direction of the centre line of the pile, as in Fig. 6A. However, the ferrule 6 of the invention has an outer surface 8 which at least in part narrows or tapers towards the tool tip 10, as is clearly shown in Figs 4A, 5 A and 7. This outer surface may thus be in form of a truncated cone or a pyramid, or have otherwise tapering shape so that the side line in longitudinal sections through the pile centre line 31 corresponding to Figs 4A, 5 A, 6A and 7 may be a straight line, a convex or concave curve, a step line with acute or rounded angles, or some other kind of line. However, the truncated cone or pyramid, either with straight or curved side lines, or a combination of these, is preferable in accordance with the invention, as with it the soil layer limited to the space or cavity T created around the pile tube 2 of the tubular pile 40 becomes compact in a more efficient way and, supposedly, with a lower force F driving the pile into soil, than if the side line did not form a substantially tapering form in the ferrule towards the tool tip. Thus it is believed that the embodiments in Figs 4 A, 5 A and 7 are more preferable than the embodiment in Fig. 6. The cross-sectional shape of the ferrule against the centre line 31 of the pile may vary within extensive limits in the longitudinal section. The cross-section may be oval or round, as in Fig. 4B; a rectangle or square, as in Fig. 5B; provided with projecting arms, as in Fig. 6B; or it may be of some other symmetrical shape in relation to one or several longitudinal planes generally passing through the central line 31. Thus, the cross-sectional shape of the pile shoe 1 does not necessarily have to be identical with the cross-sectional shape of the pile tube 2. However, the maximum diameter Dl of the pile shoe has to fulfil the conditions determined above at every place on the circumference of the pile shoe. For example, in Fig. 6B, both the maximum diameters Dl differing from each other have to be substantially larger than the outer diameter of the pile tube. It is especially noted that this tapering shape of the ferrule 6 is a separate feature independent of the tapering end shape of the pile shoe 1. According to a special feature of the invention, the distance LI at the point R corresponding to the maximum diameter Dl of the ferrule 6 from said tool tip 10 is at least five times the outer diameter D2 of the pile so that a tip section 3 with principally uniform or linear outer dimensions over its length is arranged between the ferrule and the tool tip 10. According to present views, the tip section 3 between the tool tip and the ferrule and extending downwards from the ferrule 6, which tip section is not encased in concrete during driving of the tubular pile 40 into soil, guides the entire tubular pile to go straight as it supports itself e.g. during the pile impacts and vibrations to soil M tightly surrounding the pile shoe 1 and, especially, the tip section 3. A still more efficient guidance for the pile tube 2 and its tube sections 2a, 2b, etc., is achieved by arranging the distance LI between the point R corresponding to the maximum diameter of the ferrule and the tool tip, i.e. the length of the tip section and a portion of the ferrule, so long that it is at least seven, and preferably ten times the outer diameter D2 of the pile tube. The length L3 of the narrowing or tapering outer surface 8 of the ferrule 6 is at most 40% and typically under 30% of the length LI between the point R of the maximum diameter of the ferrule and the tool tip 10. The exemplary distance LI is between 30 cm - 1 m, generally 0.5 m, or more. The cross-sectional shape of the tip section 3 may vary within extensive limits, so it can be round, oval, angular, star shaped, a shape equipped with web, etc., but preferably it is a shape which is symmetrical in relation to one or several longitudinal planes passing through the centre line 31. The tip section 3 may comprise a metal bar and metal tube made of solid material. The said tip section 3 consists of, for example, section 2' of the pile tube 2, as in Fig. 7; or of a tube piece 11 fastened to the ferrule 6, as in Fig. 6A; or of a portion 17 of a connection part 4 explained in more detail later; or of a bar piece 18 attached to a recess in the ferrule 6. In the embodiment of Fig. 7, the actual pile tube 2 thus passes through the aperture 16 in the ferrule, the part 2' extending below the ferrule forming the tip section. In this case, the ferrule is attached to the pile tube, and thus to the tip section, by welds forming the connection elements 15a. The ferrule may naturally be attached also by rivets, screws or bolts passing through the ferrule and pile tube, or by other fastening means. In the embodiment of Fig. 6A, the tube section 11 has been pushed downwards of the ferrule 6 onto a projecting pin 33 and, when necessary, welded to the ferrule by using welds forming the connection elements 15a. In the embodiment in Fig. 5 A, the bar piece 18 has been pushed into the cavity 34 in the ferrule and, when necessary, welded to the ferrule by using welds forming the connection elements 15a. If the tube piece sits tightly enough on the pin 33, or if the bar piece fits tightly enough into the cavity 34, welding is not needed. The outer diameter D3 of the tip section preferably is at most equal to the outer diameter D2 of the pile tube, but in some cases, a broader tip section 3 may be used, the outer diameter D3 of which however being substantially smaller than the maximum diameter Dl of the ferrule. Normally the outer diameter D3 of the tip section thus is smaller than the diameter of the pile tube, and the principal outer diameter of the tip section 3 varies in its length at most 30% of the difference between the diameters [Dl - D3] of the tip section and the ferrule, but usually at most 10% of the said difference. The principal diameter is derived from a shape, which is given by a combination of those tip section portions forming over half of the cross-sectional circumference of the tip section. The tip section has to be seen as having a substantially uniform broadness, although it contained support flanges 35 extending in the direction of the centre line 31, as is shown in broken lines in Fig. 6A, or other similar parts which cover typically only a fraction of the circumfrence of the tip section, and/or the tip section 9 contained a slightly extended part 36, as in Fig. 6A. -, -, According to the invention, the pile shoe 1 further includes flow apertures 7 above the lowermost upwards free base 24 of the ferrule 6 surrounding the pile tube or its extension and passing through the circumferential surface 13, 22, 23 of the said pile shoe 1 and/or pile tube 2 and/or pile tube extension for the outflow of the concrete mass B. The upwards free base refers to a surface transverse to the centre line of the pile, which is outside the outer diameter D2 of the pile tube 2 and the area of which is not limited by the cross-sectional area of the pile tube. The flow apertures 7 are permanently open from the interior 12 of the pile tube to the exterior of the pile tube in radial directions. The ferrule may comprise a principally flat upwards free base 24, as in Fig. 6A, but preferably, the ferrule 6 includes an upwards lifted outer edge 25, forming an upwards open recess 5 surrounding the pile tube 2 or its extension, such as the connection part 4. In this case, the upwards open free base 24 consists of the base of the recess 5, as in Figs 4A, 5A and 7, the base 24 then joining the said circumferential surface 13, 22, 23 and the ferrule or its upwards lifted outer edge 25 outside the flow apertures 7. In the embodiment of the figures, the base 24 is planar, but is may also be of some other shape. Radial flow apertures may be round or elongated, as can be seen in the figures, and they are generally equally spaced on the said circumferential surface. The number of flow apertures is at least two, but most often there are three - five apertures approximately in the same height. If flow aper- tures 7 are arranged in several heights for extending the neck between the apertures, as in Figs 5A and 7, the total number of the apertures may be bigger. The added cross-sectional area of the flow apertures is smaller than the cross-sectional area of the interior 12 of the pile tube, so that it may be under 90%, under 70%, under 50%, or even about 30% of the cross-sectional area of the pile tube interior 12. A diameter of the apertures may be, for example, 10 mm - 100 mm. The internal outer diameter D5 of the ferrule recess 5 is substantially bigger than the upper diameter D4 of the next connection part, or the outer diameter D2 of the pile tube so that the thickness of the upwards lifted ferrule edge 25 would be small. Preferably, the flow apertures 7 are at least partly arranged on the plane of the outer edge 25 of the ferrule, or on the measure of the height HI for the recess 5. The recess height HI here refers to the distance between the base 24 and the upwards lifted edge 25. This design, with which either only a relatively small change of direction or a change of direction with a flat curve is achieved for the concrete flow N, is believed to make the flow of the liquid concrete mass B from the pile tube interior 12 to the cavity T in soil M made by the ferrule more effective during the drive or vibration of the pile into soil The concrete mass, i.e. cement mortar, is thus transmitted at least at the place of the flow apertures 7 and, to the best of belief, also outside them to the cavity T principally from the centre upwards. The tip section 3, the possible tip piece 9, and the outer surface 8 of the ferrule 6 from the lower part to the outer edge 25, or a similar other outer surface, are solid, i.e. they do not contain apertures for the concrete mass, but the mortar B flows only above the ferrule. Said extension of the pile tube is a connection part 4, extending from above the ferrule to below, with which the ferrule 6 is joined to the pile tube 2, as is shown in Fig. 4A. For this purpose, the outer upper diameter D4 of the upper part of the connection part is bigger than the outer lower diameter D3. The difference between the diameters form a downwards pointing stop face to the connection part. The ferrule, again, is provided with a straight-through aperture 16 for the passing through of the connection element. In this case, the stop face 14 of the connection element, the upper diameter D4 of which is bigger than the diameter D6 of the ferrule aperture 16, supports itself to the base 15 of the ferrule. In this case, the connection part 4 comprises in its upper part an internal depression 26a for receiving the lower end of the pile tube 2 and a channel 27 which extends from the pile tube interior 12 at least to the flow apertures 7, the flow cross-section of the channel 27 preferably corresponding to the flow cross-section of the interior 12. The connection part 4 consists either of the same piece as the tip section 3, as is shown in Fig. 4A or, alternatively, of a tip section and a stopping piece attached to each other. The connection part may al- tematively be provided with an outer recess or projection for the fastening of the pile tube in a similar way as has been done in Fig. 5A using the ferrule 6. From its lower end, the pile tube 2 may be attached either to the ferrule 6 and the tip section 3 by using the connection part 4, as described above, or directly to the fer- rule. For fastening with the pile tube, in the embodiment of Fig. 7, the ferrule comprises a thorough hole 16, the diameter D6 of which corresponds to the outer diameter D3 of the tip section, which in this case is equal to the outer diameter D2 of the pile tube, for passing through of the pile tube. In the embodiment of Fig. 5A, the ferrule 6 comprises an upwards pointing projection 19, the outer diameter D8 of which has been adapted to receive the end of the pile tube 2. Further, a circumferential depression 26b may be formed to the transition point of the said projection 19 and the base 24 of the recess 5 for ensuring that the pile tube end remains stable, for example, against bending forces in a similar way that has been described in the applicant's previous patent FI-81415. In the embodiment of Fig. 6, the ferrule is provided with an upwards pointing projection 19 with a circumferential depression 26a, the inner diameter D7 of which is adapted to receive the end of the pile tube 2. Also in this case, the ferrule 6 includes a channel 27, extending from the interior 12 of the pile tube at least to the flow apertures 7. The ferrule 6 or connection part 4 described above further comprise either first connection elements 15 a, such as welds between the ferrule or the connection part and the pile tube; or second connection elements 15b, such as screws, rivets or bolts passing through the ferrule or connection part and the pile tube; or third connection elements 15c, such as the crimp connection described in the previous patent FI- 81415 or some other kind of crimp connection, or a transverse grooving for adhesion between the pile tube 2 and the ferrule 6 or connection part 4. The crimp connection of the said patent may be applied by using a male counterpart for the pile tube, as in the said publication, or a reversed structure in which there is provided a female counterpart for the end of the pile tube 2. Naturally, also the threaded connection of Fig. 8 A may be used for attaching the end of the pile tube 2 to the ferrule 6 or connection part 4 by applying it at this point between the ferrule or connection part and the pile tube. As mentioned above, the pile tube 2 consists of several tube sections 2a, 2b, 2c, etc. The tube sections are connected to each other, for example, by connection pieces 21 or connections 20. The connection pieces may comprise sleeves in accordance with Figs 8A and 8B, into which the tube sections of the pile tube project. When neces- sary, such a connection may be secured by screws or rivets 38 between the connection piece and the tube section, as in Fig. 8A, or by a weld between the sleeve-like connection piece and tube sections, or by a corresponding crimp connection as in the applicant's patent FI-81415, except that a female counterpart i.e. a sleeve-like connection is used, as in Fig. 8B, or by some other kind of a crimp connection or trans- verse groovings in the tube sections and the connection piece. The alternatively used connection 21 again consists of a weld between the ends of the tube sections 2a and 2b, 2b and 2c, etc., as in Fig. 8C. It is in itself possible to also use a male counterpart which projects inside the tube sections, but it has the slight disadvantage that the cross-sectional area of the pile tube interior 12 becomes smaller at their point. The method of the invention for driving the tubular pile into soil M and encasing it in concrete is next described. First, a pile shoe of the invention is assembled of its possible elements using necessary measures on the pile-driving site or alternatively at the manufacturing factory, and next the pile shoe 1 is attached to the lower end of the pile tube 2, which is to be driven into soil, so that a usable tubular pile 40 is achieved, in which the flow apertures 7 for the concrete mass B are initially open, i.e. they are not closed so that an undisturbed flow is made possible for the concrete mass from the beginning of the pile driving without it being necessary to feed the concrete under pressure. After this step the tubular pile is placed to the desired point and position in relation to soil M and its surface 32, and then the tubular pile is driven into soil M in accordance with Fig. 1 using a pulsating force or some other corresponding force F having a frequence. The device, with which force F is gener- ated either as impacts or vibrations has not been shown in the figures, because it may be of any appropriate type. As the tubular pile has sunk into soil by a predetermined distance, the pile tube interior 12 is filled with liquid mortar, i.e. concrete mass B consisting of hydraulically settable binding agent, stone material as filler, as well as water and possible additives or the like. The hydraulically settable binding agent most often used is cement, but also furnace slag, other corresponding binding agent or a combination of these may be used. In this case, it is enough to fill the interior 12 of the pile tube 2 without pressure, for example, simply by pouring, as is shown in Figs IB, ID and 1G, and there is no need to attempt to drive the concrete mass B out of the flow apertures 7. Next the pile tube is driven deeper into soil M by the said pulsating force F in accordance with Fig. 1C so that the concrete mass flows in the direction of the flows marked in the figure as the fluidity of the concrete mass increases from the initially open flow apertures 7 in the interior of the pile tube 2 around it and perhaps to some extent upwards to a cavity T made in the soil by the pile shoe 1. It is believed that the pulsating force F increases the fluidity or consis- tency of the concrete mass, i.e. the concrete mass reacts to such a handling in the same manner as thixotropic materials. This flow from the interior 12 to the cavity T is apparently made more effective by an underpressure generated by a downwards advancing movement in the cavity T as well as that the flow V of the concrete mass B from the pile tube interior to the cavity T requires totally or partly a change of di- rection of only about 90°, as in Figs 5 A, 6 A and 7, and/or a change of direction in a flat radius of about [Dl - D2]/2, as in Figs 4A, 5 A and 7. In the next stage, said mortar or concrete mass B is added into the pile tube interior 12, and the tubular pile is further driven into soil M by a pulsating force F alternately with the adding of concrete mass B into the interior 12 of the pile tube in accordance with Figs ID and IE. The number of these alternate stages may naturally vary. After the first tube section 2a has been driven into soil at least in part, i.e. generally in most part, the first tube section 2a is extended with the second tube section 2b by using the above described connections 20 or connection pieces 21 for creating an extension in accordance with Fig. IF. The pile tube 2 is then further extended with new tube sections 2c, 2d, 2e, etc., and the said concrete mass B is alternately added at least in part into the pile tube interior 12, and the pile tube is driven deeper into soil by the pulsating force F, as is shown in Figs 1G and 1H, respectively. These stages are carried on until the tip section 2 of the tubular pile reaches the intended depth SI in soil M. According to the first embodiment of the method, the liquid concrete mass B is added continuously as the tubular pile 40 is driven into soil and, when necessary, the final filling of the pile tube is carried out; after this the concrete mass B is let to set both around the pile tube and in the interior 12 of the pile tube 2. The result is a finished tubular concrete pile in accordance with Fig. 2. According to the second embodiment of the method, the tubular pile 40 is first driven into soil M by the pulsating force F without the concrete mass B being fed into the pile tube interior until the tubular pile 40 has reached a certain depth S2, whereafter a part, such as one part of concrete is fed into the pile tube interior 12, and the short driving of the pile tube is carried out by the force F. This short driving into soil corresponds, for example, to the cavity length T the amount of concrete mass in the pile tube is able to fill. When necessary, also two or more fillings of the tubular pile and two or more driving stages with force F may be conducted, which also means said short driving of the tubular pile into ground, although respectively a longer length of cavity T. Then the part between the ground surface and the upper side of a block thus created from the concrete mass to the cavity is filled around the tubular pile with stone material G, such as sand, gravel, or some other similar material. Next the pile tube interior 12 is further filled with concrete B and the tubular pile is alternately driven further into soil M by force F, as is described above. These stages are continued until the tip section 3 of the tubular pile reaches the intended depth SI in soil M. Last the rest of the pile tube interior 12 is filled with concrete. Finally, concrete mass B is let to set both around the pile tube and in the pile tube interior 12 so that a finished tubular concrete pile according to Fig. 3 is provided. Concrete mass is thus fed into the pile tube interior without substantial overpressure, and the said pulsating or similar force F is generated by impacts and/or vibrations, and its maximum is such that a pressure impulse occurs in the pile tube interior which, according to present views, is at least 10 bar and preferably at least 15 bar, and the duration of which is at most 50 ms, generally 0.1 ms - 15 ms, typically 0.1 - 10 ms, and preferably as short as possible, such as under 5 ms. The pulsating force thus generates a pressure impulse of short duration injecting mortar or concrete mass, the size of which in a test installation has been measured to be 20 - 50 bar or close to that value. According to observations made, it appears that the level of the concrete mass B in the cavity T does not substantially rise during pile-driving, but remains principally on the same level within the variation limits caused by the alternation of the adding of mortar or concrete mass and the driving of the tubular pile into soil. In addition to the procedure disclosed above with alternate feeding of the cemetitious mass B and driving of the pile tube with aforce into the soil, the adding of cemetitious mass B and the driving of the pile tube into the soil may be performed simultaneously, but this practice requires special arrangements for the aperture/apertures 29 at the upper end of the pile tube. In the alternating mode of the method the time difference between adding/feeding the concrete mass B and subjecting the driving force F to the pile can be greatly varied from practically zero to consirebly longer time.

Claims: Claims 1. Tubular pile to be encased in concrete, comprising a metal pile tube (2) for driving into soil; an aperture/apertures (29) at the upper end of the pile tube for feeding concrete mass into the pile tube interior (12); and at the lower end a pile shoe (1) comprising a longitudinal tip section (3) with a substantially uniform broadness and a ferrule (6) at the upper end, the diameter (Dl) of which is bigger than the diameter (D2) of the pile tube, and the area of the pile shoe being provided with flow apertures (7) for enabling the concrete mass (B) to come out; characterized in that further in the pile shoe (1): - the maximum diameter (Dl) of the ferrule (6) is substantially bigger than the outer diameter (D2) of said pile tube, and the distance (LI) of the point (R) corresponding to said maximum diameter of the ferrule from the tool tip (10) of the tip section (3) is at least seven times the outer diameter (D2) of the pile tube; the ferrule (6) comprises an outer surface (8) tapering at least partly towards said tool tip; and the ferrule (6) comprises an upwards extending outer edge (25) forming an upwards open recess (5) surrounding the pile tube (2) or its extension. 2. Tubular pile to be encased in concrete according to claim 1 , characterized in that the flow apertures (7) are arranged above the lowermost upwards open base (24) of the ferrule (6) surrounding the pile tube or its extension, and that they pass through the circumferential surface (13, 22, 23) of said pile shoe and/or said pile tube and/or a pile tube extension for the outflow of the concrete mass (B) upon driving the pile into soil; and that the flow apertures (7) are open outside the pile tube (2) in radial directions. 3. Tubular pile to be encased in concrete according to claim 1 or 2, characterized in that the said pile tube extension is a connection part (4), extending from above the ferrule to below said ferrule, said connection part having an upper diameter (D4) bigger than the lower diameter (D3) thereof. 4. Tubular pile to be encased in concrete according to claim 1 or 3, character- ized in that the outer diameter (D5) of said ferrule recess (5) is substantially bigger than the upper diameter (D4) of the said connection part or the outer diameter (D2) of the pile tube; and that the flow apertures (7) are at least partly placed on the level of the ferrule outer edge (25) or on the measure of the height (HI) of the recess (5). 5. Tubular pile to be encased in concrete according to claim 1, characterized in that the outer diameter (D3) of the tip section is at maximum equal to the outer di- l o ameter (D2) of the pile tube; that the tip section (3) consists of a metal bar or a metal tube; and that the said distance (LI) between the tool tip and the point (R) corresponding to the maximum diameter of the ferrule is ten times the outer diameter (D2) of the pile tube. 6. Tubular pile to be encased in concrete according to claim 1, said tip section being of a metal tube, characterized in that the tip section (3) is at the point of the tool tip closed by a tip piece (9); and that the tip section (3) comprises either a part ( ) of the pile tube (2) or a tube piece (11) attached to the ferrule (6) or a portion (17) of the connection part (4). 7. Tubular pile to be encased in concrete according to claim 1, said tip section being of a metal bar; characterized in that the said tip section (3) comprises either a bar piece (18) attached to a cavity (34) in the ferrule (6), or the section of the connection part (4). 8. Tubular pile to be encased in concrete according to claim 1 or 6, character- ized in that the ferrule further comprises either: a thorough hole (16), the diameter (D6) of which corresponds to the outer diameter (D3) of the tip part for passing through of the pile tube or the connection part; or an upwards pointing projection (19), the inner diameter (D7) or outer diameter (D8) thereof being adapted to receive the end of the pile tube (2). 9. Tubular pile to be encased in concrete according to claim 3 or 8, characterized in that the connection part (4) or the ferrule (6), respectively, comprises in its upper part an internal or external depression (26a, 26b) for receiving the lower end of the pile tube (2), and a channel (27) extending from the pile tube interior (12) at least to the flow apertures (7); and that the connection part (4) comprises a stop face (14), the upper diameter (D4) of which is bigger than the diameter (D6) of the ferrule hole (16) for supporting against the ferrule bottom (15), and the connection part (4) consists of a piece which is integral with the tip section. 10. Tubular pile to be encased in concrete according to claim 8 or 9, character- ized in that the ferrule (6) or the connection part (4) further comprises connection elements (15a or 15b or 15c) for attachment between the pile tube (2) and the ferrule (6) or the connection part (4). 11. Tubular pile to be encased in concrete according to claim 1, characterized in that the pile tube (2) consists of several tube sections (2a, 2b, 2c, etc.) and of con- nection pieces (21) or connections (20) connecting these; and that the outer surface of the pile tube (2) is provided with adhesions (30) for the concrete. 12. Method for driving a pile tube into soil (M) and for encasing it in concrete, the tubular pile comprising a metal pile tube (2), the upper end of which is provided with an aperture/apertures (29) and the lower end being provided with a tapering pile shoe (1), the diameter (Dl) of which is bigger than the diameter (D2) of the pile tube, and to the area of which the lower end of the pile tube opens; characterized in that the method comprises the steps: {A} a pile shoe (1) is fastened to the lower end of the pile tube (2) to be driven into soil for providing a tubular pile, the pile shoe comprising: a longitudinal tip section (3) with a mainly uniform broadness and provided with a ferrule (6) within a distance (LI) from the tool tip (10), said distance being at least five times the outer diameter (D2) of the pile tube, and the maximum diameter (Dl) of which is substantially bigger than the outer diame- ter of the pile tube, and radial flow apertures (7) opening above the ferrule; {B } the pile tube is driven into soil (M) by pulsating force; {D} the interior (12) of the pile tube is filled with concrete mass (B) consisting of hydraulically settable binding agent, stone material as filler, and water; {E} the pile tube is driven deeper into soil (M) by using pulsating force so that concrete mass travels through the flow apertures (7) around the pile tube (2) and upwards into the cavity (T) made by the pile shoe (1) in soil; {F} said concrete mass B is added into the interior (12) of the pile tube; and {G} the tubular pile is driven further into soil (M) by pulsating force alternately with the adding of concrete mass (B) into the interior (12) of the pile tube. 13. Method according to claim 12, characterized in that the method further comprises the steps: {H} the first tube section (2a) driven at least partly into soil is extended by a second tube section (2b) by using connections (20) or connection pieces (21); {1} the pile tube is further extended by additional tube sections (2c, 2d, 2e, etc.) according to an intended piling depth (SI), and the tubular pile is further driven into soil by pulsating force alternately with at least a partial adding of said concrete mass (B) into the interior (12) of the pile tube, until the tip section (3) of the tubular pile reaches the intended depth (SI) in soil (M); and {J} concrete mass (B) is let to set both around the pile tube and in the interior (12) of the pile tube (2) for providing a finished tubular concrete pile. 14. Method according to claim 12, characterized in that concrete mass is fed into the pile tube interior without substantial overpressure; and that the said pulsating force (F) is generated by impacts and/or vibrations, and its maximum is such that pressure impulses occur in the pile tube interior, said impulse being at least 10 bar and preferably at least 15 bar, and the duration being at maximum 50 ms, typically 0.1 ms - 15 ms, and preferably as short as possible. 15. Method according to claim 12, characterized in that the method further comprises the steps, when necessary: {Cl }the tubular pile (40) is further driven into soil by pulsating force into a certain depth (S2); {C2} an amount of concrete mass (B) is added into the interior (12) of the pile tube, and the tubular pile is driven into soil until the intended depth (SI) is reached; {C3 } a portion between the upper surface of the concrete mass layer and the ground surface around the tubular pile is filled with stone material (G) or similar material; and {C4}the pile tube (2) is further filled with concrete mass (B) and alternately driven further into soil (M) by pulsating force (F), until the tip section (3) of the tubular pile reaches the intended depth (SI) in soil (M); and {C5 }the rest of the pile tube interior (12) is filled with concrete (B).

Inventors: LEHTONEN JOUKO, LEHTONEN, JOUKO
Applicants: LEHTONEN JOUKO, RAUTARUUKKI OYJ, LEHTONEN, JOUKO
Application year: 1999
Main classification: E02D5
IPC codes: E02D5, E02D7