Anchored mechanical fastener system for lateral assembly of concrete elements

Abstract

A fastening system for a concrete segment, the fastening system comprising at least mating approaching and receiving fasteners. Each of the at least approaching and receiving fasteners comprises a fastener body section, for being at least partially embedded with a respective concrete segment, and a prong section. A 90° bend is located at a transition between the fastener body section and the prong section. A receiving body hole is located adjacent the bend and the receiving body hole is sized and shaped to receive and retain the prong section of one of the approaching and the receiving fastener. A central axis of the receiving body hole is parallel to a central axis of the prong section.

Description

ANCHORED MECHANICAL FASTENER SYSTEM FOR LATERAL ASSEMBLY OF CONCRETE ELEMENTSFIELD OFTHE DISCLOSURE

[0001] This invention pertains generally to construction couplings and, in particular, to the assembly of precast concrete segments or elements to form a ring, a primary example of such being precast concrete tunnel liner segments for fabrication of a tunnel.BACKGROUND OFTHE INVENTION

[0002] Various structures such as tunnels, walls, floor plates, roads, etc., can be manufactured and assembled using precast building materials. Tunnels, specifically, can be built by assembling and securing a plurality of precast rings adjacent to one another along a longitudinal axis of the tunnel to be formed from the inlet to the end point er outletof the tunnel. Depending on the size of the tunnel being constructed, each such precast ring typically includes a plurality of precast arcuateshaped ring segments, e.g., typically between 5 and 10 or so segments, which are coupled together to form a ring. Each ring segment includes opposite radial end surfaces that engage with corresponding radial end surfaces of adjoining ring segments to define radial joints.

[0003] According to the prior art, the ring segments must be coupled together at the radial joints with bolts or other means in order to prevent relative movement between the ring segments. The process of bolting the ring segments together is relatively labor intensive and the bolts may be susceptible to corrosion over the course of time.

[0004] As is conventional in the art, tunnels are typically excavated by means of a tunnel boring machine. The tunnel boring equipment also includes apparatuses for handling and placing concrete segments in order to assemble complete rings. Successive rings are assembled sequentially, one afterthe other, as the tunnel boring equipment gradually bores through the earth at a desired site from an inlet to an outlet or end point. As is conventional in the art, the diameter of the excavation beingachieved by the tunnel boring equipment is marginally larger that the concrete ring outside diameter. As is also conventional in the art, the resulting annular space, located between the exterior surface of the completed ring (formed from the installed precast concrete elements) and the earth, is typically filled with grout.

[0005] The joints between segments in a ring are typically referred to as “longitudinal joints” or “radial joints”. The joints between rings are typically referred to as “circumferential joints”. The individual segment shapes are designed to allow assembly into a complete ring with all of the radial and circumferential joints fitting tightly together with one another. There are various possible segment shape combinations in a ring, however, the final segment installed to complete a ring must be generally trapezoidal. This final segment is commonly referred to as the “keystone”.

[0006] As a precast concrete (arcuate) segment is moved into its place to form the ring, it typically travels in the direction of and parallel to a central axis of the ring. Thus, the trailing circumferential face of the segment being installed travels in a direction generally normal to the previously installed rings leading circumferential face. The radialjointfaces of the segment being installed travel in a direction parallel to the previously installed radial joint faces.

[0007] Once the segment is in its final position, it typically must be fastened in place. The circumferential joints are typically fastened by means of a one-way lock-up dowel system, or by spear bolts inserted through holes in one ring and screwing into threaded sockets embedded in the other ring. The radial joints are typically fastened by spear bolts. Dowel systems are not used for the radial joints because the dowels must be inserted into the dowel sockets in the direction of the dowel axis.

[0008] Accordingly, it would be beneficialto have a system of accurately and securely joining adjacent precast concrete segments to one another merely by lateral or axial movement of the precast concrete segment to be installed relative to another previously installed precast concrete segment, without requiring any additional hardware or components to facilitate an interlocking connection between the twoprecast concrete segments to one another, and, once all of the necessary precast concrete segments are assembled with one another, thereby form a completed ring for the tunnel.SUMMARY

[0009] Wherefore, it is an object of the present disclosure to overcome the above- mentioned shortcomings and drawbacks associated with the prior art connection techniques forformation of tunnel rings and simplify the construction orformation of a completed ring.

[0010] An object of the present disclosure is to provide a fastening system for securely joining two adjacent precast concrete segments to one another merely by lateral or axial movement of the precast concrete segment, to be installed, relative to another previously installed precast concrete segment, without requiring any additional hardware or additional components in order to connect the two precast concrete segments to one another.

[0011] Further, the present invention relates to a fastening system for a concrete segment, the fastening system comprising: at least matingapproachingand receiving fasteners, and each of the at least approaching and receiving fasteners comprising: a fastener body section, for being at least partially embedded within a respective concrete segment, and a prong section, and a 90° bend being located at a transition between the fastener body section and the prong section; a receiving body hole being located adjacentthe bend, the receiving body hole being sized and shaped to receive and retain the prong section of one of the approaching and the receiving fasteners, and a central axis of the receiving body hole being spaced from and extending parallel to a central axis of the prong section.

[0012] The present invention also relates to a fastening system for precast concrete segments, the fastening system comprising at least mating receiving and approaching fasteners; the receiving fastener comprising: a fastener body section,for being at least partially embedded within a first concrete segment, and a prong section, and a 90° bend being located at a transition between the fastener body section and the prongsection of the receiving fastener; a proximal end ofthe fastener body section having features which facilitate retaining the fastener body section of the receiving fastener within the first concrete segment and a receiving body hole being located adjacent the bend, the receiving body hole being sized and shaped to receive and retain a prong section of the approaching fastener, and a central axis of the receiving body hole of the receiving fastener extending parallel to and spaced from a central axis of the prong section of the receiving fastener; the approaching fastener comprising: a fastener body section, for being at least partially embedded within a second concrete segment, and a prong section, and a 90° bend being located at a transition between the fastener body section and the prong section of the approaching fastener; a proximal end of the fastener body section having features which facilitate retainingthefastener body section of the approachingfastenerwithin the second concrete segment and a receiving body hole being located adjacent the bend, the receiving body hole being sized and shaped to receive and retain the prong section of the receiving fastener, and a central axis of the receiving body hole of the approaching fastener being parallel to and spaced from a central axis of the prong section of the approaching fastener; and engagement between the receiving and the approaching fasteners occurs by receiving the prong section of the receiving fastener within the receiving body hole of the approaching fastener and simultaneously receivingthe prong section of the approachingfastenerwithin the receiving body hole of the receiving fastener to thereby interconnect the first and the second concrete segments with one another.

[0013] Lastly, the present invention relates to a method of providing a fastening system for precast concrete segments, forming the fastening system from at least mating receiving and approaching fasteners; forming the receiving fastener to have a fastener body section and a prong section; forming a 90° bend at a transition between the fastener body section and the prong section of the receiving fastener; at leastpartially embedding the fastener body section, of the receiving fastener, within a first concrete segment; forming features, which facilitate retaining the fastener body section of the receiving fastener within the first concrete segment, in a proximal end of the fastener body section; locating a receiving body hole adjacent the bend, and sizing the receiving body hole to receive and retain a prong section of the approaching fastener, and aligning a central axis of the receiving body hole of the receiving fastener parallel to and spaced from a central axis of the prong section of the receiving fastener; forming the approaching fastener to have a fastener body section and a prong section; forming a 90° bend at a transition between the fastener body section and the prong section of the approaching fastener; at least partially embedding the fastener body section, of the approaching fastener, within a second concrete segment; forming features, which facilitate retaining the fastener body section of the approaching fastener within the second concrete segment, in a proximal end of the fastener body section; locating a receiving body hole adjacent the bend, and sizing the receiving body to receive and retain the prong section of the receiving fastener, and aligning a central axis of the receiving body hole of the approaching fastener parallel to and spaced from a central axis of the prong section of the approaching fastener; and engagingthe receiving and the approachingfasteners with one another by receiving the prong section of the receiving fastener within the receiving body hole of the approaching fastener and simultaneously receiving the prong section of the approaching fastener within the receiving body hole of the receiving fastener to thereby interconnect the first and the second concrete segments with one another.BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate various embodiments of the invention and together with the general description of the invention given above and the detailed description of the drawings given below, serve to explain the principles of the invention. It is to be appreciated that the accompanying drawings are not necessarily to scale since theemphasis is instead placed on illustrating the principles of the invention. The invention will now be described, by way of example, with reference to the accompanying drawings in which:

[0015] Figure lA shows two fasteners in opposing, readyto be assembled positions.

[0016] Figure 1 B shows two fasteners in an assembled position.

[0017] Figure 2 is a simplified, fully assembled PCTL ring.

[0018] Figures 3A - 3F illustrate a typical sequence of assembly of a PCTL ring.

[0019] Figures 4A - 4D are section views illustrating the positional relationship between two segments with the fastening system as a segment is being installed.

[0020] Figure 4E is an enlarged section view showing the assembled fasteners within the receiving pockets.

[0021] Figure 5 is an isometric view of a simplified “keystone” segment with the disclosed fastening system.

[0022] Figure 6 is a view of same segment, normal to a radial joint face.

[0023] Figure 7A is a section view through the longitudinal centerline of a cast-in fastener.

[0024] Figure 7B is an isometric view of section 7A.

[0025] Figure 8A is a diagrammatic view showing assembly of a first segment to a previously assembled ring.

[0026] Figure 8B is a diagrammatic view showing assembly of a second segment to a previously assembled ring.

[0027] Figure 8C is a diagrammatic view showing assembly of a third segment to a previously assembled ring.

[0028] Figure 8D is a diagrammatic view showing assembly of a fourth segment to a previously assembled ring.

[0029] Figure 8E is a diagrammatic view showing assembly of a fifth segment to a previously assembled ring.

[0030] Figure 8F is a diagrammatic view showing assembly of a “keyring” (“key” or “keystone”) segment to a previously assembled ring to complete fabrication of the new ring.

[0031] Figure 9 is a front perspective view showing assembly of a first segment to a previously assembled ring.

[0032] Figure 9A is an enlarged front perspective view showing the sealing gasket and insertion of a dowel prior to assembly of a first segment to a previously assembled ring.

[0033] Figure 10 is a front perspective view showing assembly of a second segment to a previously assembled ring.

[0034] Figure 10A is an enlarged front perspective view showing the sealing gasket and insertion of a dowel prior to assembly of a second segment to a previously assembled ring.

[0035] Figure 11 is a front perspective view showing assembly of a third segment to a previously assembled ring.

[0036] Figure 11 A is an enlarged front perspective view showing the sealing gasket and insertion of a dowel prior to assembly of a third segment to a previously assembled ring.

[0037] Figure 12 is a front perspective view showing assembly of a fourth segment to a previously assembled ring.

[0038] Figure 13 is a front perspective view showing assembly of a fifth segment to a previously assembled ring.

[0039] Figure 14 is a front perspective view showing assembly of a keystone sixth segment to a previously assembled ring to complete fabrication of the new ring.

[0040] Figure 15 is a diagrammatic cross-sectional view showing initial alignment of the two mating fasteners and the associated gaskets immediately prior to interlocking engagement of the mating fasteners.

[0041] Figure 15A is a diagrammatic view along sectional line 15A-15A of Figure 15.

[0042] Figure 16 is a diagrammatic cross-sectional view just prior to engagement of the two aligned mating fasteners with one another.

[0043] Figure 16A is a diagrammatic view along sectional line 16A-16A of Figure 16.

[0044] Figure 17 is a diagrammatic cross-sectional view showing initial engagement of the two mating fasteners with one another.

[0045] Figure 17A is a diagrammatic view along sectional line 17A-17A of Figure 17.

[0046] Figure 18 is a diagrammatic cross-sectional view showing completed engagement of the two mating fasteners with one another as well as compression of the associated gaskets.

[0047] Figure 18A is a diagrammatic view along sectional line 18A-18A of Figure 18.

[0048] Figure 18B is a diagrammatic perspective view of the interlocking arrangement of the two mating fasteners with one another and the compressed gaskets, with concrete material removed to show those components.

[0049] Figure 19 is a diagrammatic plan view showing a fastener embedded within a pocket of a concrete segment.

[0050] Figure 19A is a diagrammatic view along sectional line 19A-19A of Figure 19.

[0051] Figure 19B is a diagrammatic view along sectional line 19B-19B of Figure 19.

[0052] Figure 20 is a diagrammatic perspective view showing a fastener embedded within a pocket of a concrete segment.DETAILED DESCRIPTION

[0053] Although the following text discloses a detailed description of example methods, apparatus and / or articles of manufacture, it should be understood that the legal scope of the property right is defined by the words of the claims set forth at the end of this patent. Accordingly, the following detailed description is to be construed as examples only and does not describe every possible example, as describing every possible example would be impractical, if not impossible. Numerous alternative examples could be implemented, using either current technology or technology developed after the filing date of this patent. It is envisioned that such alternative examples would still fall within the scope of the claims.

[0054] The examples disclosed herein relate to couplings or fasteners for joining segments together with one another. It is to be appreciated that the segments can be ring concrete segments, tunnel segments, building segments, interlocking barrier segments, interlocking concrete components, etc. As a result, the segments can be assembled in less time and generally with less effort and manpower as compared to conventional installation techniques and methods. Additionally, the fastening system provides a relatively high pull-out resistance and a relatively high shear resistance without requiring any extra or supplemental attachment components. It is to be noted that having a higher pull-out resistance and / or a higher shear resistance can be advantageous when the fastening system is utilized in environments in which the internal pressure of the structure (e.g., the tunnel) formed by the concrete segments is higher than the external pressure of the structure and / or when the environment poses seismic-event risks.

[0055] With reference to the following description, the accompanying drawings and claims, the term “leading end” refers to a direction facing toward the direction that the tunnel boring equipment is boring toward, while the term “trailing end” refers to the direction facing toward an inlet in which the tunnel boring equipment commenced its boring activity. The term “receiving fastener means a fastener 11 which, following installation, has a leading end of its prong(s) facing in the direction that the tunnel boring equipment is boring toward while the term “approaching fastener” means a fastener 11 ’ which, following installation, has a leading end of its prong(s) facing in the direction toward the inlet of the tunnel.

[0056] The invention disclosed herein is a fastening system for the radial joints described above or other applications where the mating surfaces of two adjacent elements are assembled in a generally lateral motion relative to each other. The primary component is a piece of hardware, i.e., the fastening system, that is cast into the end or radial surfaces of a concrete element or segment. An identical mating piece of hardware, i.e., the fastening system, is also cast into the mating end or radial surface of another (mating) concrete element or segment, to which the concreteelement is to be fastened, but facing in the opposite direction. The fastening system comprises a fastener comprising a prong 1 that is bent at an angle, e.g., 90° angle, relative to the fastener body 2, a receiving body hole 3 is formed in the fastener body 2, adjacent the bend, through which the prong 1 of the mating fastener is inserted, a stem 4 protrudes into and is embedded within the concrete. A flared shape, or pair of ears, 5 are provided at the embedded end of the stem 4 for securely anchoring the fastener in the concrete segment and a securing hole 6, formed in the end of the stem 4, is provided for the insertion of optional piece of rebar, or other hardware, for the purpose of providing additional pull out resistance of the fastening system from the concrete system. A first chamfered surface 7 is provided along a surface of the prong 1 , and pair of opposed second chamfered surfaces 8 are provided along both side surfaces of the prong 1. The first and second chamfered surfaces 7, 8 facilitate guidance and insertion of the tip end 20 of the prong 1 , of a mating approaching fastener 11 ’, into the receiving body hole 3 of a receiving fastener 11 , as shown in Fig. 1 B and will be discussed below in further detail.

[0057] The fastening system further includes a pocket 9 that is formed into the radial joint or side wall 10 of each one of the concrete segments in conjunction with the cast in fastener 11 (see Figs. 7A and 7B for example). Each pocket 9 is shaped in such a way that helps to guide the tip end 20 of the prong 1 of the mating approaching fastener 11 ’ into the receiving body hole 3 of the receiving fastener 11 (see Figs. 7A- 4E for example). The pocket 9 also provides a space, or clearance, beyond the receiving body hole 3 for the leading end of the inserted prong 1 to extend into and occupy and provides a backing surface to resist deformation of the prong 1 under load.

[0058] The preferred embodiment of the fastening hardware or system is made from a corrosion resistant material, such as galvanized steel or stainless steel. It is to be appreciated that composites or combinations of such materials, that meet the specific application requirements, may also be used.

[0059] A fastening system for precast concrete elements, especially precast concrete tunnel liner (PCTL) segments, consisting of an interlocking piece of hardware that is cast into the radial (or lateral) sides of each precast concrete element to be joined and allows for the assembly of the precast concrete elements with one another via a predominantly lateral motion relative to one another. Accordingly, the resulting connection does not require any additional hardware, fasteners or other components in order to join securely one precast concrete (arcuate) segment to another adjacent precast concrete (arcuate) segment. The resulting connection constrains movement of the segments, relative to one another, in all directions except the axial vector along which the segments were assembled. This remaining axial freedom of motion is constrained by the circumferential connections of the previously installed ring and subsequently by the next ring segments installed against them.

[0060] Turning now to Figs. 1 A and 1 B, a further description concerning the various components of the present disclosure will now be discussed. As can be seen in those Figures, each one of the mating receiving and approaching fasteners 11 , 11 ’ is substantially identical to one another. That is, each fastener 11 , 11 ’ generally comprises both a fastener body section 14 and a prong section 16 with a 90° bend 18 being located at the transition between the fastener body section 14 and the prong section 16. The fastener body section 14 comprises the stem 4which has a generally rectangularly shaped cross-section and includes a generally rectangularly shaped receiving body hole 3. The prong section 16 has a central prong axis PA and the receiving body hole 3 has a central hole axis HA which extends parallel to but is spaced from the central prong axis PA of the prong section 16, as generally shown in Fig. 1A. The receiving body hole 3 is sized and shaped so as to closely receive and accommodate, with minimal play, a mid-section of the prong 1 of a mating fastener 11 ’, following engagement of the two mating fasteners 11, 11 ’ with one another, as generally shown in Fig. 1 B and discussed below in further detail.

[0061] The proximal end of the stem 4 also has a securing hole 6 and either a flared exterior shape or a pair of opposed ears or some other retention feature 5. It is to be appreciated that the shape of the securing hole 6 may be cylindrical (as shown) or the securing hole may have virtually any other desired configuration or shape such as conical, oval, oblong, rectangular, triangular, etc. The securing hole 6 and the flared exterior shape or pair of opposed ears 5 are all designed to interact with the surrounding concrete and thereby facilitate securely embedding and permanently attaching the proximal end of the fastener body section 14 of the fastener 11 into the precast concrete, during the manufacturing process, as is well known and conventional in the art. It is to be appreciated that the securing hole typically receives a conventional rebar, or another system, that connects to the fastener at the opposite radial end. Assembled rings with this system would have a continuous 360° steel connection or construction. This continuous connection or construction possibility is a primary advantage of this system, that is, to provide superior resistance to internal pressure.

[0062] As also shown, the stem 4 includes the receiving hole 3 which is generally rectangular in shape, although other shapes and configurations forthe receiving hole 3 are possible. The important aspect is that the shape of the receiving hole 3 mirrors and is marginally slightly larger in size than the midsection of the prong 1 so as to achieve a relatively tight mating engagement, with minimal play, between the mating prong 1 and the receiving hole 3.

[0063] The prong section 16 also typically has a rectangularly shaped cross-section, along its midsection. As noted above, the leading tip end 20 of the fastener 11 comprises the first chamfered surface 7 and the pair of opposed second chamfered (side) surfaces 8 which together all gradually taper toward the leading tip end 20. As generally shown in Figs. 1A and 1 B, a length of the first chamfered surface 7 is longer than a length of the second pair of opposed chamfered surfaces 8. The three chamfered surfaces 7, 8 facilitate guidance and insertion of the tip end 20 of the prong section 1 , of an approaching fastener 11 ’, into and through a mating receivingbody hole 3 of the mating receiving fastener 1 1 while, at the same time, the three chamfered surfaces 7, 8 facilitate guidance and insertion of the tip end 20 of the prong section 1 , of the receiving fastener 1 1 , into and through a mating receiving body hole 3 of the mating approaching fastener 1 1 ’ as generally shown in Figs. 1 A and 1 B. It is to be appreciated thatthe size and shape of each of the stem 4, the flared exterior shape or pair of opposed ears or other external features 5 and the securing hole 6 can vary from application to application but are all designed to create a secure and permanent attachment of the proximal end of the fastener body section 1 of the fastener 1 1 , 1 1 ’ to the respective precast concrete segment.

[0064] It is to be noted that each one of the fasteners 1 1 , 1 1 ’ is substantially identical in size, shape and function to one another, but the fasteners 11 , 11 ’ are arranged opposite to and face one another such that the chamfered surfaces 7 and 8, of the respective prong sections 1 , assist with receiving the tip ends 20 of the prong sections 16 within the respective receiving body holes 3 of each one of the mating fasteners 11 , 1 1 ’ (as shown in Fig. 1 B) as the two concrete segments move axially relative to and engage with one another, as generally shown in Figs. 3A-3F, 4A-4E, 8B-8F and9-18 and described further below.

[0065] The fastener body section 14 of each fastener 11 typically has an overall length of between 4.5 inches and 10 inches or so, more preferably has an overall length of about 7.5 inches, typically has a height of between 5.0 inches and 1.5 inches or so, more preferably has a height of about 3.75 inches, and typically has a thickness of between 1.0 inches and 0.5 inches or so, more preferably has a thickness of about 0.75 inches. In addition, the prong section of each fastener 11 typically has an overall length of between 5.0 inches and 2.0 inches or so, more preferably has an overall length of about 3.0 inches, typically has a width of between 1.75 inches and 0.75 inches or so, more preferably has a width of about 1 .25 inches, and typically has a thickness of between 0.5 inches and 1 .0 inches or so, more preferably has a thickness of about 0.75 inches.

[0066] The receiving body hole 3 of the fastener body section 14 typically has a height of between 1 .75 inches and 0.75 inches or so, more preferably has a height of about 1 .37 inches, and typically has a width of between 0.6 inches and 1 .25 inches or so, more preferably has a thickness of about 0.875 inches or so.

[0067] With reference now to Figs. 2, 3A-3F, and 9-15, a detailed discussion concerning one embodiment of the plurality of precast (arcuate) concrete segments which can be utilized to fabricate a completed ring 100, will now be discussed. As shown in these figures, the completed ring 100 is fabricated from 5 precast concrete segments S1 , S2, S3, S4, S5 plus the precast keystone concrete segment S6, for a total of six concrete segments S1 , S2, S3, S4, S5, S6. When all six of the precast concrete segments are sequentially interconnected with one another, as generally shown in Fig. 2 and described below, fabrication of the completed ring 100 is achieved. It is to be noted that the combined accurate length of the plurality of precast concrete segments S1 , S2, S3, S4, S5 and S6 will form a completed ring 100 which spans an angle equal to 360°.

[0068] As generally shown in Fig. 3A, the precast reverse key and the key concrete segments S1 and S6 both generally, but not precisely, have a trapezoidal shape, e.g., a quadrilateral with at least one pair of almost parallel leading and trailing arcuate faces, while each of the remaining precast concrete segments S2, S3, S4 and S5 are each generally, but not precisely, parallelograms, e.g., a quadrilateral with a first pair of parallel sides and a second pair of almost parallel leading and trailing arcuate faces, as generally shown in Figs2, 3A-3F, and 9-15.

[0069] It is to be appreciated than when boring a tunnel, via the tunnel boring equipment, as is conventional in the art, each ring 100 is designed to have a desired amount of taper, e.g., the width of the ring 100 along a first section has a maximum width while the width of the ring 100, along a second section located 180° from the maximum width section, has a minimum width (e.g., typically 1 - 3 inches or so less than the maximum width - depending upon the maximum bend required for the tunnel). As a result of the taper of each ring 100, 100’, the circumferential accurateend walls of each segment are not precisely parallel to one another. It is to be appreciated, as well known in the art, that the taper of the rings 100, 100’ allows a plurality of rings 100, 100’ to be assembled with one another and form a tunnel having curved sections. That is, as a result of the gradual taper of the rings 100, 100’, the rings 100, 100’ can be assembled with one another to form a tunnel curvature which can gradually curve upwardly, downwardly, toward the left or toward the right, and anywhere therebetween, depending upon the tunnel requirements. In addition, for straight sections of the tunnel, the maximum and minimum widths of the rings 100 can be rotated 180°, with respect to one another, in an alternatingfashion, to thereby form straight sections of the tunnel, as is conventional and well known in the art. It is to be appreciated that other build patterns are common as well to achieve a straight alignment of sequential rings 100, 100’.

[0070] The precast first (reverse key) concrete segment S1 has a curved arcuate length, along a trailing arcuate face 22 of the first concrete segment S1 , which is slightly longer than the arcuate length along the second opposed leading arcuate face 24 of the first concrete segment S1 . In addition, a first end of each of the first and second radial faces 26, 28 of the first concrete segment S1 are generally linear and each forms an acute angle, e.g., an angle of about 81 .5°, with the trailing arcuate face 22 of the first precast concrete segment S1 while, a second end of each of the first and second radial faces 26, 28 of the first concrete segment S1 forms an obtuse angle, e.g., an angle of about 98.5°, with the leading arcuate face 24 of the first precast concrete segment S1 (see Figs. 8A and 8B for example). The first concrete segment S1 has 4 spaced apart fasteners 11 embedded with the first and second radial faces 26, 28 of the first precast concrete segment S1 , e.g., two spaced apart fasteners along each of the first and the second radial faces 26, 28, and each fastener 11 is arranged in a similar orientation. That is, each one of the embedded fasteners 11 has the tip end 20 of the fastener 11 oriented and projecting toward the leading arcuate face 24 of the first concrete segment S1. Each embedded fastener 11 is embedded within the first or the second radial faces 26 or 28 of the first concretesegment S1 close to but spaced from the leading and trailing arcuate faces 24, 22, e.g., spaced for the respective leading and trailing arcuate face by approximately % the overall width of the first concrete segment S1 .

[0071] The precast keystone concrete segment S6 is similar, but generally oppositely configured to the first concrete segment S1 . That is, the keystone concrete segment S6 has a curved arcuate length, along a leading arcuate face 24 of the keystone concrete segment S6, which is slightly longer than the arcuate length along the opposed trailing arcuate face 22 of the keystone concrete segment S6 (see Figs. 3F, 8F and 14 for example). In addition, each of the first and the second radial faces 26, 28 of the keystone concrete segment S6 are generally linear and form an obtuse angle, e.g., an angle of about 98.5°, with the trailing arcuate face 22 of the keystone concrete segment S6, while each of the first and the second radial faces 26, 28 of the keystone concrete segment S6 forms an acute angle, e.g., an angle of about 81.5°, with the leading arcuate face 24 of the keystone concrete segment S6. The keystone concrete segment S6 has 4 spaced apart fasteners 1 1 ’ embedded within the first and the second radial faces 26, 28 of the keystone concrete segment S6, e.g., two spaced apart fasteners along each of the first and the second radial faces 26, 28, and each fastener 11 ’ is arranged in a similar orientation. That is, each one of the embedded fasteners 1 1 ’ has the tip end 20 of the fastener 1 1 ’ oriented and projecting toward the trailing arcuate face 22 of the keystone concrete segment S6.

[0072] The precast second, the third, the fourth and the fifth concrete segments S2, S3, S4 and S5, on the other hand, are each generally parallelograms so that they each have a curved accurate length along a leading arcuate face 24 of the respective concrete segmentwhich is generally the same length as the accurate length along an opposed trailing arcuate face 22 of each of those concrete segments S2, S3, S4 and S5 (see Figs. 3B-3E, 8B-8E, 10, 11 , 12 and 13 for example). As noted above, due to the taper of the ring 100, the leading arcuate face 24 is not precisely parallel to the trailing arcuate face 22.

[0073] A second radial face 28 of each of the second and the fourth concrete segments S2, S4 is generally arcuate and one end of the second radial face 28 forms an acute angle, e.g., an angle of about 81 .5°, with the trailing arcuate face 22 of the respective second or fourth concrete segment S2 or S4, while an opposed second end of the second radial face 28 forms an obtuse angle, e.g., an angle of about 98.5°, with the leading arcuate edge of the respective second or fourth concrete segment S2 or S4. The first radial face 26 of the second and the fourth concrete segments S2 or S4 is also generally linear and parallel to the second radial face 28. A first end of the first radial face 26 forms an obtuse angle, e.g., an angle of about 98.5°, with the trailing arcuate face 22 of the respective second or fourth concrete segment S2 or S4 while an opposed second end of the first radial face 26 forms an acute angle, e.g., an angle of about 81.5°, with the leading arcuate face 20 of the respective second or fourth concrete segment S2 or S4. Each of the second and the fourth concrete segments S2, S4 has a total of 4 spaced apart fasteners 11 , 11 ’ embedded therein and two of the fasteners 11 arranged along the first radial face 26 are arranged opposite to the two fasteners 11 ’ arranged along the second radial face 28. That is, two of the fasteners 11 embedded and arranged along the second radial face 28 of the respective second and fourth concrete segment S2 or S4 has the tip end 20 of each of the fasteners 11 oriented and projecting toward the leading arcuate face 24 of the second and the fourth precast concrete segments S2, S4 while the two fasteners 11 ’ embedded and arranged along the first radial face 26 of the respective precast concrete segment S2 or S4 has the tip end 20 of each of the fasteners 11 ’ oriented and projecting toward the trailing arcuate face 22 of the second and the fourth concrete segments S2, S4.

[0074] A second radial face 28 of each of the third and the fifth precast concrete segments S3, S5 is generally linear and one end of the second radial face 28 forms an obtuse angle, e.g., an angle of about 98.5°, with the trailing arcuate face 22 of the respective third or fifth concrete segment S3 or S5 while an opposed second end of the second radialface 28 forms an acute angle, e.g., an angle of about 81.5°, with theLeading arcuate face 24 of the respective third orfifth concrete segment S3 or S5. The first radial face 26 of the precast concrete segment S3, S5 is generally linear and also parallel to the second radial face 28. A first end of the first radial face 26 forms an acute angle, e.g., an angle of about 81.5°, with the trailing arcuate face 22 of the respective third or fifth concrete segment S3 or S5 while an opposed second end of the first radial face 26 forms an obtuse angle, e.g., an angle of about 98.5°, with the leading arcuate face 24 of the respective third or fifth concrete segment S3 or S5. Each of the third and the fifth concrete segments S3, S5 has 4 spaced apart fasteners 11 , 11 ’ embedded therein with the two spaced apart fasteners 11 arranged along the first radial face 26 being arranged opposite to the two fasteners 11 ’ arranged along the second radial face 28. That is, two of the fasteners 11 ’ embedded along second radial face 28 of the respective third and the fifth concrete segments S3, S5 has the tip end 20 of each of the fasteners 11 ’ oriented and projecting toward the trailing arcuate face 22 of the third and the fifth concrete segments S3, S5 while the two fasteners 11 embedded along the first radial face 26 of the respective third and the fifth precast concrete segments S3, S5 has the tip end 20 of each of the fasteners 11 oriented and projecting toward the leading arcuate face 24 of the third and the fifth concrete segments S3, S5.

[0075] As is conventional in the art, each one of the concrete segments S1 , S2, S3, S4, S5, S6..., has at least one perimeter gasket(s) 40 which extends around the entire periphery of the respective concrete segment S1 , S2, S3, S4, S5, S6 so as to form a water-tight seal following installation of the respective concrete segment S1 , S2, S3, S4, S5, S6 (see Figs. 9-18B). The at least one perimeter gasket(s) 40 is located within a continuous channel or groove 42 which is formed in and extends around the entire perimeter of respective concrete segment S1 , S2, S3, S4, S5, S6. For some applications, a pair of space apart perimeter gaskets 40 and channels or grooves 42 are formed along the leading and the trailing arcuate faces 24, 22 and the first and the second radial faces 26, 28 of the respective precast concrete segments. In addition, as is also conventional in the art, the leading and the trailing arcuate faces 24, 22 ofeach of the concrete segments S1 , S2, S3, S4, S5, S6..., has a plurality of spaced apart dowel hole(s) 38, for receiving a respective dowel (see Figs. 10B, 1 1 B and 14 for example), and preventing relative movement of the ring 100 being fabricated relative to the concrete segment(s) of another ring 100’ which was previously fabricated.

[0076] During engagement of the two fasteners 1 1 of one of the concrete segments51 , S2, S3, S4, S5, S6..., with the two mating fasteners 11 ’ of another concrete segment S1 , S2, S3, S4, S5, S6..., the mating gaskets are brought into alignment with one another and are sufficiently compressed, as two of the concrete segments S1 ,52, S3, S4, S5, S6 gradually engage with one another, as shown by the engagement sequent depicted in Figs. 15-18B, so that the mating gaskets achieve a fluid tight seal along the joined radial side walls. The dowel(s) 36 also assist with aligning the gasket(s) 40, along circumferential end walls with one another so that the mating gasket(s) 40 achieve a fluid tight seal along the joined circumferential end walls, as generally shown in Figs 18B and 18C.

[0077] It is to be appreciated that the total number of precast concrete segments, which are to be interconnected with one another, in order to form a completed ring 100 as shown in Fig. 2, typically ranges from 5 to 10 precast concrete segments but may vary from one application to another. It is also to be appreciated that, depending upon the application and the size of the tunnel to be bored, either more or less precast concrete segments may be utilized to form a completed ring 100. In addition, the acute and the obtuse angles, indicated above for the precast concrete segments S1 , S2, S3, S4, S5, S6 are by way of example only and can vary from one application to another application. That is, the acute angles typically vary between 77.5° and 90° while the obtuse angles typically vary between 90° and 102.5°, for example.

[0078] As shown in Figs. 4A-7, 15, 16, 17 and 18, each of the first and the second radial faces 26, 28 of the plurality of precast concrete segments S1 , S2, S3, S4, S5 and S6 has at least one, and more preferably, two spaced apart pockets 9 formed therein. Each pocket 9 is sized and shaped so as to accommodate a respective fastener 1 1 or 11 ’ therein such that a significant portion of the fastener body section14 of the fastener 11 , 11 ’ is embedded within the respective precast concrete segment while a remaining portion of the fastener body section 14 and a first portion of the prong section 16 is accommodated within the pocket 9. As shown in Figs. 7A and 7B, a remainingsecond portion of the prong section 16 projects out of the pocket 9 and is located so as to facilitate mating engagement with the receiving body hole 3, of a mating fastener 11 or 11 which is similarly accommodated within the pocket 9 of another precast concrete section to be engaged with, as discussed below in further detail.

[0079] A base surface 30, of each respective pocket 9, is planar and designed to assist with receiving and guiding the leading tip end 20, of the mating prong section 16, into mating engagement with the receiving body hole 3 of the fastener 11 or 11 ’ supported by the respective pocket 9, as generally shown by the engagement sequence depicted in Figs. 4A-4E and 15-18, and thereby facilitate an interlocking relationship of the two mating fasteners 11 , 11 ’, and associated precast concrete segments, with one another. The base surface 30 of the pocket 9 extends parallel to one of the surfaces defining the receiving body hole 3, as shown in Figs. 19A-19C, for example. Preferably, the base surface 30 of the pocket 9 is coplanar with one of the surfaces definingthe receiving body hole 3.

[0080] The base surface of the pocket 9 typically has a length of between 6.5 inches and 15 inches or so, more preferably has a length of about 10.0 inches, typically has a width of between 1 .0 inches and 2.5 inches or so, more preferably has a width of about 1 .5 inches or so. An end surface 32 of the pocket 9 extends generally at an obtuse angle, relative to the base surface 30 and typically has a height of between 2.25 inches and 5.0 inches or so, more preferably has a height of about 2.5 inches or so, and typically has a width of between 1.0 inches and 2.5 inches or so, more preferably has a width of about 1.5 inches or so. Each of the side surfaces 34 of the pocket 9 typically has the shape of an obtuse triangle. In some applications, the opposed side surfaces 34 of the pocket 9 may converge slightly toward one another, in the vicinity of the receiving body hole 3 (as generally shown in Fig. 19), so as toassist with guiding or directing the leading tip end 20 of the approaching fastener 11 ’ into the receiving body hole 3 of the receiving fastener, and vice versa.

[0081] As shown in Fig. 7A, the fastener body section 14 of the fastener 11 , 11 ’ extends generally normal to the base surface 30 of the pocket 9, with the receiving body hole 3 of the fastener body section being only spaced slightly from the base surface 30 of the pocket 9 (see Fig. 7B) so as to facilitate engagement with the prong 1 of another mating fastener 11 or 11 ’. The central hole axis HA of the receiving body hole 3 extends parallel to the base surface 30 of the pocket 9. It is to be appreciated that the base surface 30 of each of the pockets 9 extends generally normal to both the leading and the trailing arcuate faces 24, 22 of the respective precast concrete segments.

[0082] During manufacture of each respective precast concrete segment S1 , S2, S3, S4, S5 and S6, each pocket 9 is designed to accommodate typically about 1 / 2 of the proximal end of the fastener 11 while approximately 1 / 2 of the distal portion of the fastener 11 is either accommodated within the pocket 9 or projects out of the pocket 9 and is thereby located for engagement with another mating fastener 11 , 11 ’ (see Figs.5, 7A and 7B for example).

[0083] With reference now to Figs, 3A-3F, 8A-14, a description concerning assembly of a ring 100 will now be described. Duringthe tunnel boring process, once the tunnel boring equipment has bored a desired length, e.g., created an additional 3 to 8 feet of tunnel, the tunnel boring equipment will then commence assembly of another sequential assembled ring 100. As is conventional in the art, a segment erector (not shown in detail), of the tunnel boring equipment (not shown in detail), will pick up a first concrete segment S1 , fed by the tunnel boring equipment, to commence assembly of the next sequential ring 100. The segment erector will position, in a conventional manner, the trailing arcuate face 22 of that first concrete segment S1 adjacent to but slightly spaced from the leading arcuate face 24 of the previously assembled ring 100’. Typically, one or more dowel(s) 36 will be installed in the appropriate dowel hole(s) 38 of the first concrete segment S1 prior to the segmenterector retrieving or installing the same. The segment erector will install that first concrete segment S1 , with respect to a desired concrete segment, e.g., the first concrete segment S1 , of the previous ring 100’, so that the first and the second radial faces 26, 28 are offset with respect to the first and second radial faces 26, 28 of the previously assembled ring 100’, as generally shown in Fig. 8A.

[0084] Next the associated hydraulic rams (not shown), of the tunnel boring equipment, will force or bias the trailing arcuate face 22 of the positioned first concrete segment S1 into abutting engagement with the leading arcuate face 24 of one of the concrete segments of the previously assembled ring 100’ such that the dowel(s) 36 will be received within the associated dowel hole(s) 38 of the previously assembled ring 100’ and suitably compress the associated gasket(s) of the first concrete segment S1 against the associated gasket(s) of the previously assembled ring 100’ to create a water-tight seal therebetween. Following installation of the first concrete segment S1 , each one of the prongs 1 of the fasteners 11 , provided along both the first and second radial faces 26, 28 of the first concrete segment S1 , are facing toward the leading arcuate face 24 of the first concrete segment S1 as well as toward the leading end of the tunnel being bored by the tunnel boring equipment.

[0085] Thereafter, the segment erector will pick up either the fed second precast concrete segment S2 or the fed third concrete segment S3. In the event that the second precast concrete segment S2 is picked up, the segment erector will then position the trailing end of the second concrete segment S2 adjacent to but slightly spaced from the leading end of the previously assembled ring 100’ and also closely adjacent the second radial face 28 of the recently installed first concrete segment S1 , as generally shown in Figs. 3B and 8B. Typically, one or more dowel(s) 36 will be installed in the appropriate dowel hole(s) 38 of the second concrete segmentS2 prior to the segment erector retrieving or installing the same. Due to the orientation of the second radial face 28 of the first concrete segment S1 and the orientation of the first radial face 26 of the second concrete segment S2 as well as the orientation of the respective fasteners 11 , 11 ’ supported along those respective first and second radialfaces 26, 28, when the associated hydraulic rams (not shown in detail), of the tunnel boring equipment, thereafter forces or biases the trailing arcuate face 22 of the second concrete segment S2 into abutting engagement with the leading arcuate face 24 of the previously assembled ring 100’ (as indicated by the arrows in Figs. 3B and 8B), such relative motion forces the one or more dowel(s) 36 into the associated dowel hole(s) 38 of the previously assembled ring 100’ and suitably compresses the associated gasket(s) of the second concrete segment S2 against the associated gasket(s) of the previously assembled ring 100’ to create a water-tight seal therebetween. Such motion also simultaneously causes interlocking engagement of the prongs 1 of the two fasteners 11 ’, located along the first radial face 26 of the second concrete segment S2, facing in the direction of the trailing end of the tunnel, with the prongs 1 of the two adjacent fasteners 11 of the first concrete segment S1 , facing in the direction of the leading end of the tunnel, thereby connecting and interlocking the first and the second concrete segments S1 , S2 with one another. In addition, the interlocking engagement of the prongs 1 of the fasteners 11 , 11 ’ also aligns and suitably compresses the associated gasket(s) 40 of the first and the second concrete segments S1 , S2 to create a water-tight seal therebetween.

[0086] In the event that the third precast concrete segment S3 is picked up, the segment erector will then position the trailing end of the third concrete segment S3 adjacent to but slightly spaced from the leading end of the previously assembled ring 100’ and also closely adjacent the first radial face 26 of the recently installed first concrete segment S1 , as generally shown in Fig. 3C and 8C. Typically, one or more dowel(s) 36 will be installed in the appropriate dowel hole(s) 38 of the third concrete segment S3 prior to the segment erector retrieving or installing the same. Due to the orientation of the first radial face 26 of the first concrete segment S1 and the orientation of the second radial face 28 of the third concrete segment S3 as well as the orientation of the respective fasteners 11 , 11 ’ supported along those first and second radialfaces 26, 28, when the associated hydraulic rams (not shown in detail), of the tunnel boring equipment, thereafter forces or biases the trailing arcuate face22 of the second concrete segment S3 into abutting engagement with the leading arcuate face 24 of the previously assembled ring 100’ (as indicated by the arrow in Fig. 3C and 8C), such relative motion forces the one or more dowel(s) 36 into the associated dowel hole(s) 38 of the previously assembled ring 100’ and suitably compresses the associated gasket(s) 40 of the third concrete segment S3 and the previously assembled ring 100’ to create a water-tight seal therebetween. Such motion also simultaneously causes interlocking engagement of the prongs 1 of the two fasteners 11 ’, located along the second radial face 28 of the third concrete segment S3, facing in the direction of the trailing end of the tunnel, with the prongs 1 of the two adjacent fasteners 11 of the first concrete segment S1 , facing in the direction of the leading end of the tunnel, thereby connecting and interlocking the first and the third concrete segments S1 , S3 with one another. In addition, the interlocking engagement of the prongs 1 of the fasteners 11 , 11 ’ also aligns and suitably compresses the associated gasket(s) 40 of the first and the third concrete segments S1 , S3 to create a water-tight seal therebetween.

[0087] Next, the segment erector will pick up either the fed fourth precast concrete segment S4 or the fed fifth concrete segment S5. In the event that the fourth precast concrete segment S4 is picked up, the segment erector will then position the trailing end of the fourth concrete segment S4 adjacent to but slightly spaced from the leading end of the previously assembled ring 100’ and also closely adjacent the second radial face 28 of the recently installed second concrete segment S2, as generally shown in Figs. 3D and 8D. Typically, one or more dowel(s) 36 will be installed in the appropriate dowel hole(s) 38 of the fourth concrete segment S4 prior to the segment erector retrieving or installing the same. Due to the orientation of the second radial face 28 of the second concrete segment S2 and the orientation of the first radial face 26 of the fourth concrete segment S4 as well as the orientation of the respective fasteners 11 , 11 ’ supported along the first and second radial faces 26, 28 of those concrete segments S2, S4, when the associated hydraulic rams (not shown in detail), of the tunnel boring equipment, thereafter forces or biases the trailingarcuate face 22 of the fourth concrete segment S4 into abutting engagement with the leading arcuate face 24 of the previously assembled ring 100’ (as indicated by the arrow in Fig. 3D and 8D), such relative motion forces the one or more dowel(s) 36 into the associated dowel hole(s) 38 of the previously assembled ring 100’ and suitably compresses the associated gasket(s) 40 of the fourth concrete segment S4 and the previously assembled ring 100’ to create a water-tight seal therebetween. Such motion also simultaneously causes interlocking engagement of the prongs 1 of the two fasteners 11 ’, located along the first radial face 26 of the fourth concrete segment S4, facing in the direction of the trailing end of the tunnel, with the prongs 1 of the two adjacent fasteners 11 , located along the second radial face 28 of the second concrete segment S2, facing in the direction of the leading end of the tunnel, thereby connecting and interlocking the second and the fourth concrete segments S2, S4with one another. In addition, the interlocking engagement of the prongs 1 of the fasteners 11 , 11 ’ also aligns and suitably compresses the associated gasket(s) 40 of the second and the fourth concrete segments S2, S4 to create a water-tight seal therebetween.

[0088] In the event that the fifth precast concrete segment S5 is picked up, the segment erector will then position the trailing end of the fifth concrete segment S5 adjacent to but slightly spaced from the leading end of the previously assembled ring 100’ and also closely adjacent the first radial face 26 of the recently installed third concrete segment S3, as generally shown in Figs. 3E and 8E. Typically, one or more dowel(s) 36 will be installed in the appropriate dowel hole(s) 38 of the fifth concrete segment S5 prior to the segment erector retrieving or installing the same. Due to the orientation of the first radial face 26 of the third concrete segment S3 and the orientation of the second radial face 28 of the fifth concrete segment S5 as well as the orientation of the respective fasteners 11 , 11 ’ supported along the first and the second radial faces 26, 28 of both of those concrete segments, when the associated hydraulic rams (not shown in detail), of the tunnel boring equipment, thereafter forces or biases the trailing arcuate face 22 of the fifth concrete segment S5 into abutting engagement with the leading arcuate face 24 of the previously assembledring 100’ (as indicated by the arrow in Fig. 3E), such relative motion forces the one or more dowel(s) 36 into the associated dowel hole(s) 38 of the previously assembled ring 100’ and suitably compresses the associated gasket(s) 40 of the fifth concrete segment S5 and the previously assembled ring 100’ to create a water-tight seal therebetween. Such motion also simultaneously causes interlocking engagement of the prongs 1 of the two fasteners 11 , located along the first radial face 26 of the third concrete segment S3, facing in the direction of the leading end of the tunnel, with the prongs 1 of the two adjacent fasteners 11 ’, located along the second radial face 28 of the fifth concrete segment S5, facing in the direction of the trailing end of the tunnel, thereby connecting and interlocking the third and the fifth concrete segments S3, S5 with one another.

[0089] In order to complete fabrication of the ring 100, the segment erector, of the tunnel boring equipment, will then pick up the precast keystone concrete segment S6, fed by the tunnel boring equipment. Typically, one or more dowel(s) 36 will be installed in the appropriate dowel hole(s) 38 of the keystone concrete segment S6 prior to the segment erector retrieving or installing the same. The segment erector will position, in a conventional manner, a trailing end of that keystone concrete segment S6 adjacent to but slightly spaced from the leading end of the previously assembled ring 100’ at a location generally centered between the first radial face 26 of the fifth concrete segment S5 and the second radial face 28 of the fourth concrete segment S4. As noted above, each one of the prongs 1 of the fasteners 11 ’, provided along both the first and second radial faces 26, 28 of the keystone concrete segment S6, are facing toward the trailing end of the tunnel while each one of the prongs 1 of the fasteners 1 1 , provided along the second radial face 28 of the fourth concrete segment S4 and provided along the first radial face 26 of the fifth concrete segment S5, are facing toward the leading end of the tunnel.

[0090] Next, the associated hydraulic rams (not shown), of the tunnel boring equipment, will force or bias the trailing arcuate face 22 of the keystone concrete segment S6 between the first radial face 26 of the fifth concrete segment S5 andsecond radial face 28 of the fourth concrete segment S4 and into abutting engagement with the leading arcuate face 24 of the previously assembled ring 100’ (as indicated by the arrow in Fig. 3F). Such relative motion forces the one or more dowel(s) 36 into the associated dowel hole(s) 38 of the previously assembled ring 100’ and suitably compresses the associated gasket(s) 40 of the keystone concrete segment S6 and the previously assembled ring 100’ to create a water-tight seal therebetween.

[0091] Such motion also simultaneously causes interlocking engagement of the prongs 1 of the two fasteners 11 , located alongthe second radial face 28 of the fourth concrete segment S4, facing in the direction of the leading end of the tunnel, with the prongs 1 of the two adjacent fasteners 1 1 ’ located along the first radial face 26 of the keystone concrete segment S6, facing in the direction of the trailing end of the tunnel, thereby connecting and interlocking the fourth concrete segment S4 with the keystone concrete segment S6. Further, the interlocking engagement of the prongs 1 of the fasteners 11 , 11 ’ also aligns and suitably compresses the associated gasket(s) 40 of the fourth and the sixth concrete segments S4, S6 to create a water-tight seal therebetween.

[0092] At the same time, such relative motion also causes interlocking engagement of the prongs 1 of the two fasteners 11 , located along the first radial face 26 of the fifth concrete segment S5, facing in the direction of the leading end of the tunnel, with the prongs 1 of the two adjacent fasteners 1 1 ’ located along the second radial face 28 of the keystone concrete segment S6, facing in the direction of the trailing end of the tunnel, thereby connecting and interlocking the fifth concrete segment S5 with the keystone concrete segment S6 and completing fabrication of the ring 100. Further, the interlocking engagement of the prongs 1 of the fasteners 1 1 , 11 ’ also aligns and suitably compresses the associated gasket(s) 40 of the fifth and the sixth concrete segments S5, S6 to create a water-tight seal therebetween.

[0093] Each one of the formed rings 100, 100’ typically has a diameter of between 8 feet and about 100 feet or so, more preferably has a diameter between 10 feet and 40feet or so. In addition, each formed ring 100, 100’ typically has an axial width of between 2 feet to 8 feet, more preferably a width of between about 3 feet and about 6 1 / 2 feet or so. In addition, each accurate segment, for forming a ring 100, 100’, typically has a curved accurate length which spans an angle of between 20° and 90°, more preferably each accurate segment has an accurate length which spans an angle of between 35° and 67.5° or so. Each precast concrete segment typically has a thickness of between 6 inches and 24 inches or so, and more preferably has a thickness of between 12 inches and 18 inches or so. In addition, each precast concrete segment typically weighs between 1 / 2 of a ton and 20 tons, and more preferably each precast concrete segment weighs between 1 and 10 tons or so.

[0094] While the fasteners of the present disclosure have thus far been described as couplings used in connection with coupling mating radial surfaces of ring segments for use in tunnel building applications, it is to be appreciated that the same fasteners could be used to couple other prefabricated or pre-cast building materials. For example, the couplings could be used to couple adjacently positioned side faces of vertically arranged pre-cast concrete wall sections for retaining walls or building foundations, or side faces of horizontally arranged pre-cast concrete slabs for floor or road construction, for example. That is, a variety of other applications are possible and would be readily apparent to those skilled in the art.BENEFITS AND ADVANTAGES

[0095] A spear bolt connection requires the bolt to transverse the joint between the concrete elements at a non-perpendicular angle to the joint plane. In the case of PCTL segments a recess or bolt pocket must be formed in the inside surface of a segment. The pocket includes an end surface with a hole allowing for the bolt to be inserted through the hole and into a threaded socket embedded in the second segment. This arrangement is a necessary compromise that does not provide positive alignment of the joint and tends to pull the joint out of alignment when tightened. Because of this, a separate system for maintaining alignment is oftenrequired, typically a “guide rod” and half-round groove formed into each of the segments.

[0096] Advantages of the invention disclosed herein include:1. This system provides positive tensile resistance and positive alignment of the longitudinal joints.2. This system eliminates bolt pockets, holes and embedded threaded inserts.3. This system eliminates the need for any additional alignment system.4. This system eliminates loose bolts and washers and the labor and time to handle and install them.5. The connection of the concrete elements is complete once they are put into position, improving assembly efficiency.6. This system allows for a continuous circumferential connection, greatly increasing the ability of a tunnel to resist internal pressures.7. This system is simple, with only one, universal piece of hardware.

[0097] Further, while several examples have been disclosed herein, any features from any examples may be combined with or replaced by other features from other examples. Moreover, while several examples have been disclosed herein, changes may be made to the disclosed examples without departing from the scope of the claims.

Claims

1. I Claim:

1. A fastening system for a concrete segment, the fastening system comprising: at least mating approaching and receiving fasteners, and each of the at least approaching and receiving fasteners comprising: a fastener body section, for being at least partially embedded within a respective concrete segment, and a prong section, and a 90° bend being located at a transition between the fastener body section and the prong section; a receiving body hole being located adjacentthe bend, the receiving body hole being sized and shaped to receive and retain the prong section of one of the approaching and the receiving fasteners; and a central axis of the receiving body hole being spaced from and extending parallel to a central axis of the prong section.

2. A fastening system for precast concrete segments, the fastening system comprising at least mating receiving and approachingfasteners; the receiving fastener comprising: a fastener body section, for being at least partially embedded within a first concrete segment, and a prong section, and a 90° bend being located at a transition between the fastener body section and the prong section of the receiving fastener; a proximal end of the fastener body section having features which facilitate retaining the fastener body section of the receiving fastener within the first concrete segment and a receiving body hole being located adjacent the bend, the receiving body hole being sized and shaped to receive and retain a prong section of the approaching fastener, and a central axis of the receiving body hole of the receiving fastener extending parallel to and spaced from a central axis of the prong section of the receiving fastener; the approachingfastener comprising: a fastener body section, for being at least partially embedded within a second concrete segment, and a prong section, and a 90° bend being located at a transitionbetween the fastener body section and the prong section of the approaching fastener; a proximal end of the fastener body section having features which facilitate retaining the fastener body section of the approaching fastener within the second concrete segment and a receiving body hole being located adjacent the bend, the receiving body hole being sized and shaped to receive and retain the prong section of the receiving fastener, and a central axis of the receiving body hole of the approaching fastener being parallel to and spaced from a central axis of the prong section of the approaching fastener; and engagement between the receiving and the approaching fasteners occurs by receiving the prong section of the receiving fastener within the receiving body hole of the approaching fastener and simultaneously receiving the prong section of the approaching fastener within the receiving body hole of the receiving fastener to thereby interconnect the first and the second concrete segments with one another.

3. The fastening system for precast concrete segments according to claim 2, wherein the features which facilitate retaining the fastener body section, of each of the at least approaching and the receivingfasteners, comprise at least one of a flared shape, a pair of ears, and a securing hole which provide pull out resistance for the approaching and the receiving fasteners.

4. The fastening system for precast concrete segments according to claim 2, wherein the prong section, of each of the at least approaching and the receiving fasteners, comprise a first chamfered surface along a first surface of the prong section and a pair of opposed second chamfered surfaces along side surfaces of the prong section, and the first and second chamfered surfaces facilitate guiding and insertion of a tip end of the prong section within the receiving body hole of respective approaching fastener or receiving fastener.

5. The fastening system for precast concrete segments according to claim 2, wherein the precast concrete segments comprise a plurality of arcuate concrete segments which, when assembled together with one another via thefastening system, form a ring, and each of the arcuate concrete segments has a leading arcuate face, a trailing arcuate face and first and second radial faces, and each of the first and the second radial faces support either two spaced apart receiving fasteners ortwo spaced apart approaching fasteners.

6. The fastening system for precast concrete segments according to claim 5, wherein the first concrete segment has two spaced apart receiving fasteners along both the first radial face and the second radial face, while a keystone concrete segment has two spaced apart approaching fasteners along both the first radial face and the second radial face.

7. The fastening system for precast concrete segments according to claim 6, wherein the second concrete segment, required for formation of the ring, has two spaced apart receiving fasteners along the first radial face thereof and two spaced apart approaching fasteners along the second radial face thereof.

8. The fastening system for precast concrete segments according to claim 7, wherein each remaining concrete segment, required for formation of the ring, has two spaced apart receiving fasteners along one of the first radial face and the second radial face and two spaced apart approaching fasteners along another of the second radial face and the first radial face.

9. The fastening system for precast concrete segments according to claim 8, wherein each of the precast concrete segments, forformation of the ring, has at least one perimeter gasket which extends around an entire periphery of the respective concrete segment for forming a water-tight seal, following assembly, with each adjacent concrete segment.

10. The fastening system for precast concrete segments according to claim 9, wherein the leading arcuate face and the trailing arcuate face, of each one of the concrete segments forformation of the ring, has a plurality of spaced apart dowel holes, formed therein, for receiving a dowel and preventing relative movement of the respective concrete segment, of the ring being assembled, relative to a concrete segment of a previously assembled ring.1 1. The fastening system for precast concrete segments according to claim 5, wherein the first radial face, of each of the precast concrete segments for assembling the ring, forms one of an acute angle of between 77.5° and 90° or an obtuse angle of between 90° and 102.5° with the leading arcuate face, and the second radial face, of each of the precast concrete segments for assembling the ring, forms one of an obtuse angle of between 90° and 102.5° or an acute angles of between 77.5° and 90° with the leading arcuate face; and the first radial face, of each of the precast concrete segments for assembling the ring, forms one of an obtuse angle of between 90° and 102.5° or an acute angle of between 77.5° and 90° with the trailing arcuate face, and the second radial face, of each of the precast concrete segments for assembling the ring, forms one of an acute angle of between 77.5° and 90° or an obtuse angle of between 90° and 102.5° with the trailing arcuate face.

12. The fastening system for precast concrete segments according to claim 5, wherein the first radial face and the second radial face, of each of the plurality of arcuate concrete segments for forming the ring, has a pair of spaced apart pockets therein, and each pair of spaced apart pockets supports either the receiving fastener or the approachingfastener.

13. The fastening system for precast concrete segments according to claim 5, wherein each pocket is sized and shaped so as to accommodate a respective receiving fastener or the approaching fastener therein such that a significant portion of the fastener body section, of the respective receiving fastener or the approaching fastener, is embedded within the respective concrete segment while a remaining portion of the fastener body section and a first portion of the prong section is accommodated within the pocket, and a second portion of the prong section projects out of the pocket and is located so as to facilitate mating engagement with the receiving body hole of one of the receiving fastener or the approaching fastener.

14. The fastening system for precast concrete segments according to claim 13, wherein a base surface, of each respective pocket, is planar and designedto assist with receiving and guiding a leading tip end, of the prong section of one of the receiving fastener or the approaching fastener, into mating engagement with the receiving body hole, of the other of the approaching fastener or the receiving fastener.

15. The fastening system for precast concrete segments according to claim 14, wherein the fastener body section, of the receiving fastener, extends normal to the base surface of the respective pocket, and a surface of the receiving body hole, of the fastener body section, extends generally parallel to the base surface of the pocket so as to facilitate engagement with the prong section of the approaching fastener; the fastener body section, of the approaching fastener, extends normal to the base surface of the respective pocket, and the receiving body hole, of the fastener body section, extends generally parallel to the base surface of the pocket so as to facilitate engagement with the prong section of the receiving fastener; and the base surfaces of each of the pockets extend generally parallel to one another and normal to both the leading arcuate face and the trailing arcuate faces of the respective precast concrete segments.

16. The fastening system for precast concrete segments according to claim 5, wherein each segment, for formation of the ring, has a curved accurate length which spans an angle of between 20° and 90°, each precast concrete segment has a thickness of between 6 inches and 24 inches or so; and each precast concrete segment weighs between 1 of a ton and 20 tons.

17. The fastening system for precast concrete segments according to claim 16 wherein each segment, for formation of the ring, has a curved accurate length which spans an angle of between 35° and 67.5°; each precast concrete segment has a thickness of between 12 inches and 18 inches; and each precast concrete segment weighs between 1 and 10 tons.

18. The fastening system for precast concrete segments according to claim 5, wherein each ring, which is assembled from a plurality of the precast concrete segments has a desired taper such that a first portion of the ring, formed by the plurality of the precast concrete segments, has a maximum width while a second portion of the ring, located 180° from the first portion of the formed ring, has a minimum width, and, as a result of the taper of the formed ring, leading and trailing accurate end walls of each concrete segments are not parallel to one another.

19. A method of providing a fastening system for precast concrete segments, forming the fastening system from at least mating receiving and approaching fasteners; forming the receiving fastener to have a fastener body section and a prong section; forming a 90° bend at a transition between the fastener body section and the prong section of the receiving fastener; at least partially embedding the fastener body section, of the receiving fastener, within a first concrete segment; forming features, which facilitate retaining the fastener body section of the receiving fastenerwithin the first concrete segment, in a proximal end of the fastener body section; locating a receiving body hole adjacent the bend, and sizing the receiving body hole to receive and retain a prong section of the approaching fastener, and aligning a central axis of the receiving body hole of the receiving fastener parallel to and spaced from a central axis of the prong section of the receiving fastener; forming the approaching fastener to have a fastener body section and a prong section; forming a 90° bend at a transition between the fastener body section and the prong section of the approaching fastener; at least partially embedding the fastener body section, of the approaching fastener, within a second concrete segment;forming features, which facilitate retaining the fastener body section of the approaching fastener within the second concrete segment, in a proximal end of the fastener body section; locating a receiving body hole adjacent the bend, and sizing the receiving body to receive and retain the prong section of the receivingfastener, and aligning a central axis of the receiving body hole of the approaching fastener parallel to and spaced from a central axis of the prong section of the approaching fastener; and engaging the receiving and the approaching fasteners with one another by receiving the prong section of the receiving fastener within the receiving body hole of the approaching fastener and simultaneously receiving the prong section of the approaching fastener within the receiving body hole of the receiving fastener to thereby interconnect the first and the second concrete segments with one another.

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