Abstract:
A method for the waterproofing of joints and/or cracks in the upstream face of dams, other hydraulic works and concrete or masonry structures. A waterproofing membrane includes a strip of elastically yielding synthetic material that is fastened to the surface to be protected along the whole joint and/or crack. Prior to positioning the waterproofing membrane, sliding elements are positioned onto the surface to support the membrane. A protection and sliding substrate is properly fastened independently from the waterproofing membrane so that the waterproofing membrane is allowed to freely elongate and follow the movements of the joint and/or the crack while maintaining a water tightening condition.

Description:
FIELD OF THE INVENTION 
     This invention refers to the waterproofing of hydraulic structures such as roller compacted concrete dams (RCC dams), concrete gravity dams and masonry gravity dams, embankment dams with a concrete waterproofing upstream facing, canals, tunnels, reservoirs and similar, and of concrete and masonry structures in general. In particular, this invention concerns a method for the waterproofing of contraction and/or construction joints, deteriorated joints and/or cracks, here in after referred to also as “joints” or “cracks” in the concrete or masonry lining or body of hydraulic structures as well as in the concrete and/or masonry structures of the type previously referred to, having a surface in contact with water or a surface with joints and/or cracks through which water seepage can occur; the invention also relates to a layered waterproofing covering device for joints, cracks and the like, obtained by the waterproofing method mentioned above. 
     According to well known concepts, in the construction of hydraulic structures, for example of concrete dams or roller compacted concrete dams, or in the construction of embankment dams, both earthfill and rockfill, it is necessary to provide a proper waterproofing of the upstream face in order to prevent water seepage from the reservoir, which represents an economic loss and which can compromise the integrity and the stability of the dam body itself. 
     The constructive methodology of dams and hydraulic structures, or of concrete or masonry structures of any type, has therefore to take into account the shrinkage and thermal expansion phenomena, and the movements due to settlement or to other causes which the hydraulic structure or the concrete structure can undergo over time, for example at variation in hydraulic load on the upstream side of a dam, which can cause the opening or widening of the joints of the concrete waterproofing liner, or the formation of dangerous cracks through which seepage of water could occur. 
     In particular, in the design and construction of RCC dams it is necessary to consider the deformations induced by the hydration process of the concrete because, after reaching the maximum hydration heat, the decrease of the temperature of the dam body until it reaches a stable condition, is accompanied by contraction phenomena of the concrete volume, which can cause cracking. 
     Therefore, in these hydraulic structures it is necessary to provide proper contraction joints in order to avoid that uncontrolled cracking can occur. 
     The contraction joints generally create preferential lines for the formation of cracks in the upstream face of the dam, due to the contraction of the concrete, which develop vertically parallel to the slope. 
     The contraction joints also undergo some movements, generally to a lesser extent, even after the concrete has reached its equilibrium temperature. These movements can be caused by the variations of the water level in the reservoir, by seismic phenomena, or by other causes. 
     In general, joints and/or cracks represent a discontinuity in the concrete or masonry waterproofing liner of the upstream face of a dam or of any hydraulic structure or other structure. Therefore this discontinuity must be treated so as to avoid possible water seepage. 
     STATE OF THE ART 
     The traditional systems which are at present adopted for the waterproofing of joints and/or cracks usually foresee the use of synthetic or copper material, the so-called “waterstops”, arranged in single or double rows, embedded in the concrete as it is being cast during the construction of the hydraulic structure or other structure, and therefore they interfere with the constructive process. 
     In general, the employment of the known waterproofing systems, besides interfering with the constructive process, makes it quite difficult to intervene for any maintenance or repair operation, when joints deteriorate. As a matter of fact, these systems generally do not provide a proper waterproofing, durable over time and capable of compensating movements or settlements that should occur in the body of the hydraulic structure or of the concrete and/or masonry structure, without losing their fundamental waterproofing characteristics. 
     While the contraction joints in RCC dams or the construction joints in concrete dams or similar hydraulic works represent a discontinuity induced in the concrete waterproofing liner, and therefore waterproofed since the construction of the hydraulic work itself, other casual discontinuities can occur during operation, when, for any reason, the concrete or the masonry crack, or the waterstops waterproofing the joints deteriorate over time or for accidental causes. 
     Therefore, this cracks or deterioration, if not properly protected and checked, can cause water seepage, with damaging consequences. 
     OBJECTS OF THE INVENTION 
     The general object of this invention is to provide a method for the waterproofing of joints and/or deteriorated joints and/or of cracks in the concrete liners of hydraulic structures such as dams or similar, and in concrete and/or masonry structures, which can remedy the inconveniences of waterproofing systems previously in use. 
     More in particular, an object of this invention is to provide a waterproofing method as referred to above, which is quite independent from the constructive process of the hydraulic structure or structure and which can be applied subsequently. 
     Another object of the invention is to provide a method for the waterproofing of joints and/or cracks as mentioned above, which has such a high degree of elastic deformability and of independence of its components, that it can follow any movement which should occur in joints or cracks, subsequent to the movements of the dam body or the hydraulic structure to be protected and/or repaired, without losing the waterproofing and mechanical resistance characteristics. 
     A further object of the invention is to provide a waterproofing of joints, cracks and the like as previously defined, which is external to the hydraulic structure or other type of structure and which therefore allows control and repair interventions after its installation. 
     The invention is also aiming to employ a membrane in elastically yieldable synthetic material, for the waterproofing of contraction joints, construction joints, cracks and the like, in particular in the upstream faces or in existing surfaces which get in touch with water in hydraulic structures such as RCC dams, concrete dams, embankment dams having a concrete upstream face, tunnels, water conveyance structures, reservoirs and similar hydraulic structures. 
     BRIEF DESCRIPTION OF THE INVENTION 
     What has been previously mentioned can be provided by means of a method for the waterproofing of joints and/or cracks in the concrete and/or masonry linings or body of hydraulic structures, masonry structures and similar, as well as with a waterproofing covering device for joints, cracks and the like. 
     In particular, according to the invention, a method has been provided for the waterproofing covering of joints and/or cracks in hydraulic structures, masonry structures and similar, by means of a waterproofing membrane comprising a strip of elastically yieldable synthetic material, which is positioned along a joint or crack on an existing surface of the hydraulic and/or masonry structure to be protected, comprising the steps of: 
     positioning at least one support element of rigid material on the existing surface of the hydraulic and/or of the masonry structure, to cover the joint and/or crack, and to provide a support surface for the membrane, anchoring said support element across the joint and/or the crack to allow a sliding movement in respect to said existing surface; 
     positioning at least one protection substrate for the membrane, over the support element, between the latter and the membrane to allow a sliding movement of the same membrane in respect to the support element and the existing surface; 
     placing the waterproofing membrane over the protection substrate and the support element; and 
     watertightly fastening the peripheral edges of the membrane to the existing surface of the hydraulic and/or of the masonry structure, along the sides of the joint and/or the crack. 
     According to another aspect of this invention, over the waterproofing strip of the membrane it is possible to install a protection slab, preferably in steel or another proper material, to cover the waterproofing strip along its whole development or along only a portion of it, anchoring this protection slab in such a way as to allow it independently move in respect to the waterproofing membrane. Should the membrane be employed to waterproof a crack through which water can seep from the back side, the protection slab can be used for frontally supporting the same membrane and avoid its swelling. 
     According to another aspect of this invention, it is preferable to extend the waterproofing of the joint to waterproofing a concrete beam at the dam heel, extending and positioning the waterproofing covering membrane on a foundation beam, watertightly anchoring the membrane in correspondence of the area where the joints of the foundation beam, if any, are waterproofed. 
     According to another aspect of the invention a waterproofing covering device for joints and/or cracks on an existing surface of hydraulic or masonry structures has been provided, said covering device comprising: 
     at least a support element longitudinally extending for at least a portion of the joint or crack, said support element being fastened to the existing surface, so that it can slide in respect to said surface; 
     a waterproofing membrane comprising a strip of elastically yieldable material, longitudinally extending over the support element and tightly fastened to the existing surface on both sides of the joint or crack; 
     an intermediate protection substrate between the waterproofing membrane and the support element; and 
     fastening means for water tightly fastening the waterproofing membrane to the existing surface on both side of the elastically yieldable strip. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other characteristics of the method and the covering for the waterproofing of joints and/or cracks in the concrete waterproofing liners of dams and similar structures, will better result from the description and the examples of the attached drawings, in which: 
     FIG. 1 is a front view of an area of the upstream face of a RCC dam, provided with a waterproofing covering for a contraction joint according to the invention; 
     FIG. 2 is an enlarged cross-sectional view, made along line  2 — 2  of FIG. 1; 
     FIG. 3 is an enlarged detail of FIG. 2; 
     FIG. 4 is a front view of the waterproofing covering, in correspondence of a foundation beam; 
     FIG. 5 is a longitudinal sectional view along line  5 — 5  of FIG. 4; 
     FIG. 6 is a view made along line  6 — 6  of FIG. 4; 
     FIG. 7 shows the connection between the waterproofing membrane according to the invention and the original defective waterproofing of a pre-existing joint or crack; 
     FIG. 8 is a front view of FIG.  7 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     We will describe here below the general principles of the method for the waterproofing of joints and/or cracks according to the invention, by means of a waterproofing membrane, referring as an example to a roller compacted concrete dam, without intending this example in a restrictive way, since the waterproofing method described can be applied to any concrete and/or masonry structure; for the aims of this invention, “waterproofing membrane” means a strip of prefixed width, obtained from a synthetic, waterproofing and elastically yieldable material, such as PVC, PP, PE and similar synthetic material. 
     CONTRACTION JOINTS OF RCC DAMS 
     FIG. 1 shows a front view of the upstream face  10  of an RCC dam consisting of superimposed layers of roller compacted concrete; during the construction of the layers, contraction joints  11  are formed, which extend vertically, parallel to the slope of the upstream face, for the whole height of the dam body. 
     As shown in FIG. 2, the contraction joint  11  prolongs inside the concrete body of the single layers  10 , so as to constitute a preferential line for cracking. 
     DESCRIPTION OF THE METHOD 
     As shown in the two above-mentioned figures, the method for the waterproofing of joint  11  foresees the use of a strip of waterproofing membrane  13 , of suitable width, obtained from a sheet of flexible and elastically yieldable material, with a low permeability, which is installed on the whole vertical development of joint  11  so that it entirely covers it, if needed prolonging it in correspondence with the dam heel in order to allow the connection with the waterproofing system of a curb or a foundation beam, as it will be further explained. 
     Strip  13  of waterproofing material is installed external to the upstream face  10  in order not to interfere with the construction of the dam. 
     In order to adequately support the waterproofing membrane  13  and to avoid the membrane to be damaged by puncturing or intrusion in the crack, according to this invention it is foreseen to previously install a suitable support element for supporting the membrane  13  which prevents the intrusion of the same membrane  13  into the joint  11  under the thrust of the hydraulic load of the water impounded in the upstream reservoir, or due to any movement of the dam body. 
     The support element for supporting the waterproofing membrane must be executed in such a way as to be able to follow the maximum allowed opening movements of the contraction joint  11  under the maximum foreseen hydraulic load, and the subsequent closing movements, without interfering with the strip of the waterproofing membrane. 
     The support element can consist of one or more rigid plates in steel or another kind of material, connected to the concrete body of the upstream face, and placed across joint  11  so as to allow relevant movements. 
     More precisely, in the example shown in FIGS. 1 and 2, the support element consists of two plates  14  and  15 , partially overlapped; each plate is fastened at spaced apart points, along only one lateral edge, by means of anchoring rods, respectively  16  and  17 , so as to allow free sliding of the two plates one over the other during the opening and closing movements of joint  11 , while allowing support of membrane  13 . 
     The two supporting plates  14  and  15  consist of one or more shaped portions, axially aligned, which extend for the whole length of joint  11 . 
     In order to prevent the waterproofing membrane  13  from any failures or puncturing actions caused by the supporting plates  14  and  15 , and in order to grant the independence of movement between the support plates and the same membrane, one or more protection and sliding substrates are interposed, between the supporting plates and the waterproofing membrane  13 , said substrates being fastened to the concrete body of the upstream face  10 , on both side of the supporting plates  14 ,  15 . 
     More precisely, as shown in FIGS. 1 and 2, immediately over the supporting plates  14  and  15 , a transition substrate  13  of considerable thickness is provided, for examples having a weight from 0.5 to 3 Kg/m 2 , comprising a synthetic sheet material, preferably a geotextile with great mass per unit area; over the transition substrate  16  a second sliding substrate  19  is overlapped, in geosynthetic material, for example constituted by a strip of the same material used for the membrane  13  waterproofing the joint, in order to grant a free sliding movement of the same membrane in respect to the joint. Both the protection substrate  18  and the sliding substrate  19  are fastened at spaced apart points to the concrete existing surface  10  by means of anchoring rods  20 . 
     Therefore the two substrates  18  and  19  have a double function, namely: the protection layer or layers  18 , in geotextile or other suitable material, avoid that the mutual sliding of the two supporting plates  14  and  15  interferes with the waterproofing strip  13 , damaging it for example because of the puncturing action of the edges of the plates themselves, while the sliding substrate  19 , besides constituting a further mechanical support and additional protection for strip  13  of the waterproofing membrane, allows also a free sliding of the membrane over substrates  18  and  19  and over the supporting plates  14  and  15  during the dilatation and contraction movements of joint  11 . 
     As shown in the enlarged section of FIG. 2, strip  13  of the waterproofing membrane is watertight fastened against the concrete existing surface of the facing, along its lateral edges, in a way totally independent from the substrates  18  and  19  and the supporting plates  14  and  15 . 
     For this purpose, metal profiles  21  have been applied along the lateral edges of membrane  13 ; these profiles tightly press the edges  13 ′ of the membrane against the surface of the upstream face  10 , also foreseeing the interposition of a suitable watertight gasket  22 . 
     The face or surface on which the watertight fastening is constructed is previously regularised by the application of proper material  22 ′, such as epoxy resins and similar. 
     The metal profiles  21  are fastened by means of threaded rods  23  anchored in the concrete, on which the blocking nuts  24  are screwed with interposition of suitable washers. 
     In this way a continuous watertight line is constructed along the two edges of the waterproofing membrane  13 . 
     As previously described, the waterproofing method employs, as a waterproofing element, a flexible synthetic, elastically yieldable, in form of a strip comprising one or more sections suitably welded one to the other, which extends for the whole length of the contraction joint  11 ; the waterproofing membrane  13  is preferably composed by a geocomposite consisting of a low permeability synthetic geomembrane coupled to a geosynthetic material having different properties. Therefore only the waterproofing geomembrane is exposed to the action of the reservoir, while the coupled geocomposite is suitably protected and constitutes a further antipuncturing and supporting layer which increases the dimensional stability of the geomembrane itself. 
     The flexibility and the elasticity of the synthetic geomembrane and of the system by which it is fastened to the dam concrete face, over joint  11  to be protected, are such as to allow the membrane to elastically deform along its entire extension, following the opening and closing movements of joint  11  under the maximum foreseen hydraulic load, or due to other causes. 
     As shown in FIG. 2, over the waterproofing membrane  13 , slightly detached from it, it is possible to add an additional protection which substantially consists of a shield  25  which extends for the entire length of the waterproofing membrane and beyond its lateral edges, for example a steel slab separately and independently fastened to the upstream face by means of anchoring rods  26 , slab  25  being supported by means of spacers  27  and bolts  28  that can be screwed on the threaded end of the rods. 
     In order to allow the protection shield  25  a sliding movement independent from the movement of the protection membrane, on one side of shield  25  the anchoring rods  26  are placed through holes  29 , which are oval-shaped or have larger dimensions, to allow a relative movement in transverse and/or longitudinal direction in respect to the protection shield  25  as seen in FIG.  3 . 
     Connection to the foundation beam 
     As previously described, the membrane  13  for the waterproofing of the joint can be extended in correspondence of the dam heel so as to allow the connection with the waterproofing system of a curb or a foundation beam, as schematically represented in the example of FIGS. 5 and 6 of the attached drawings. 
     The connection is executed by extending and positioning membrane  13  over the foundation beam  30  to which it is fastened by means of proper mechanical anchoring profiles. 
     The flat  13 ″ of the membrane is extended on the beam  30  for a brief stretch of 30-40 cm, in any case so long as to be sufficient to overlap on area  31  where the waterproofing of a joint in the foundation beam may have been executed, for example by injection into a proper sump of epoxy resins or similar, or by waterstops in PVC or similar. 
     As shown in FIGS. 5 and 6, flap  13 ″ of the membrane is watertight anchored along its three edges by means of metal profiles  32  which are fastened by means of anchoring rods  33 . A ballast  34  can be placed on the folded part  13 ″ of the waterproofing membrane, upon previous interposition of further protection synthetic material  35 , in order to allow a close contact between the waterproofing membrane and the grout curtain. 
     The flap  13 ″ of the membrane can be physically connected to material  31  waterproofing the beam joints, for example by means of an adhesive  36  or by welding, according to the material employed. 
     With this configuration, the waterproofing of the joint is connected with the beam at the dam heel, achieving a continuity between the waterproofing of the joint on the upstream face, the waterproofing of the foundation beam, and the grout curtain that is generally provided in the foundation beam towards the underlying ground. 
     The upper fastening of membrane  13  is similar to the lateral ones which have already been described. 
     Other applications 
     The waterproofing method for joints, previously described, beside being suitable for waterproof the contraction joints in RCC dams, can also be employed for restoring waterproofing in correspondence of deteriorated construction joints of concrete dams, or of cracks which should occur over time, for different causes, in the faces of concrete dams, or in the concrete face of embankment dams, or in the faces of other concrete or masonry structures. 
     The waterproofing method results substantially identical to the previously described one and can be applied both at the end of construction of the dam, and as a rehabilitation intervention to waterproof joints of existing hydraulic structures, as well as cracks produced by the deterioration of concrete. Should the waterproofing not be extended over the foundation beam, the perimeter fastening of the membrane at bottom is similar to the one adopted for watertight fastening the lateral edges. 
     FIGS. 7 and 8 of the attached drawings show the perimeter anchorage  37  at the bottom of a waterproofing membrane  13  should this membrane not reach the foundation beam  30  or the heel of the hydraulic structure. In this case it is possible to connect the waterproofing obtained with membrane  13  in the above-mentioned way, to a pre-existing joint  39  which has deteriorated, or to a crack, by means of injecting a sealing material  38  into a hole which has been put in contact with the crack or the defective joint  39 . 
     From what has been said and shown in the attached drawings, it will therefore be evident that we have provided a method for the waterproofing of joints for roller compacted concrete dams, concrete dams, or embankment dams with a concrete upstream face, and for the waterproofing of deteriorated joints and/or cracks in concrete and/or masonry structures. 
     Hence, what has been said and shown with reference to the attached drawings has been given as a mere example of the general principles of the invention and of some of its preferential constructive configurations; other modifications or variants can be made without departing from what claimed.