A system for applying a liquid, such as a deicing liquid, to a surface material, such as soil, sand, gravel, concrete, and asphalt. The system includes a mat possessing an array of upstanding tubular members and a pipe system maintained in the interstitial regions between the tubular members. In addition, a series of ports or nozzles may extend upwardly from the pipe such that the liquid drips or is sprayed on the surface of the material.

CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of application Ser. No. 09/169,532 filed on Oct. 9, 1998, now U.S. Pat. No. 6,095,718, which is a divisional application of Ser. No. 08/796,304 filed on Feb. 7, 1997, and now U.S. Pat. No. 5,848,856. The disclosures of the above-mentioned applications are hereby incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention generally relates to a system for applying a liquid, such as a deicing liquid, upon a pavement surface. The present invention also relates to a pavement for facilitating the movement of traffic thereon, to a molded mat for stabilizing a material in which the mat is disposed and for supporting and maintaining a pipe beneath a surface of the material, and to a system for heating a material, such as a pavement material, and to a method of delivering a fluid to a material surface. 
     Many surfacing materials, such as soil, sand, gravel, concrete, and asphalt are subject to migration and erosion, as well as damage from vehicular and pedestrian traffic. Mats, such as mats possessing an array of upstanding tube segments, have been utilized to stabilize such surfacing materials and to help prevent migration and erosion, as well as to inhibit compaction, cracking, etc. 
     The prior art mats including an array of upstanding tubular segments have been applied in the following manners, for example. Such a mat is laid upon a bed of gravel, and then sod with grass or other vegetation is rolled over the mat and pressed into the tubular segments of the mat. Because the tubular segments prevent the soil from being compacted and thereby killing the grass, the sod may be subject to vehicular and pedestrian traffic without killing the grass or other vegetation. Such a mat has also been designed for employment in paving roads with asphalt. The mat is first laid on the road bed, and then asphalt is rolled over the mat and into the tubular segments. The tubular segments help prevent the asphalt from migrating, which might produce ruts in the road, and also are believed to help minimize disintegration and cracking of the asphalt. 
     The aforementioned types of mats have been described in the inventor's U.S. Pat. No. 5,250,340 and the patent applications and patents mentioned therein, the disclosures of every one of which are incorporated herein by reference. 
     The present invention generally relates to the use of such mats or modified versions of such mats in combination with pipe systems for delivering a fluid to the material in which the mat is embedded. 
     SUMMARY OF THE INVENTION 
     The present invention generally relates to a system for applying a liquid, such as a deicing liquid, to a surface material, such as soil, sand, gravel, concrete, and asphalt. The system includes a mat possessing an array of upstanding tubular members, and a pipe system maintained in the interstitial regions between the tubular members. In addition, a series of ports or nozzles may extend upwardly from the pipe such that the liquid drips or is sprayed on the surface of the material. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be described with reference to the accompanying drawings, wherein like reference numerals refer to the same item. 
     FIG. 1 is a bottom plan view of a portion of a mat in accordance with one embodiment of the present invention; 
     FIG. 2A is a top plan view of a socket utilized in the mat as shown in FIG. 1; 
     FIG. 2B is a side view of the socket shown in FIG. 2A; 
     FIG. 2C is a cross-sectional view of the socket shown in FIG. 2A, taken along the line  2 C— 2 C; 
     FIG. 2D is a side view of a pair of prongs utilized in the mat as shown in FIG.  1  and which is designed to cooperate with the socket as shown in FIGS. 2A-C in an adjacent mat; 
     FIG. 2E is another side view of the prongs shown in FIG. 2B; 
     FIG. 3 is a fragmented side schematic illustration of a mat and pipe system in accordance with one embodiment of the present invention taken in the direction of arrow  70  in FIG. 1; 
     FIG. 4 is another fragmented side schematic illustration of a mat and pipe system in accordance with one embodiment of the present invention; 
     FIG. 5 is another fragmented side schematic illustration of a mat and pipe system in accordance with one embodiment of the present invention; and 
     FIG. 6 is a side schematic illustration of a pipe that may be used in an embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     There is shown in FIG. 1 a portion of a mat for stabilizing particulate materials, which mat includes a plurality of tubular members which, in the illustrated embodiment, take the form of cylindrical rings designated by reference numerals  10 - 25  disposed in a uniform rectangular array defined by a plurality of perpendicular rows and columns. For example, as shown in FIG. 1, tubular members  10 ,  11 ,  12 , and  13  define the upper-most row, while tubular members  10 ,  14 ,  18 , and  22  define the left-most column. It should be noted that the use of tubular members of other than cylindrical shape may be employed within the scope of the present invention. For example, tubular members having oval, hexagonal, rectangular, square, triangular, octagonal, and other cross-sectional shapes may be utilized. Further, the tubular members may be disposed in non-rectangular arrays, for example in circular patterns, or randomly distributed. 
     In order to allow a plurality of the mats to be secured together to form a large mat, first and second cooperating fasteners are formed on the side edges of the mat. Although the cooperating members may take the form as disclosed in U.S. Pat. No. 5,250,340, in the illustrated embodiment, the first fastener members may take the form of a plurality of sockets, designated by reference numerals  28 , spread along two opposing sides of a quadrilateral mat. The second fastener members in the illustrated embodiment take the form of a pair of upstanding prongs, designated by reference numerals  30 , spaced along the other two sides of the mat, such that the prongs  30  are located opposite the sockets  28 . 
     Two of the mats may be secured in an adjacent relation by inserting the prongs  30  spaced along one side edge of one mat through the sockets  28  spaced along a side edge of another mat. 
     As shown in FIG. 2A, each socket may include a centrally positioned, substantially square aperture  32  therethrough, which is adapted to receive the pair of prongs  30  As shown in FIG. 2D, each one of the prongs  30  extends generally upright from a base  34 , and includes, a trunk section  36  and a distal flange section  38  having a clasping lip  40 . As best shown in FIG. 2B, the distance between the outermost sections of the trunks  36  of the prongs  30  is only slightly less than width of the square shaped aperture  32  in the socket  28 . When the prongs  30  are pressed centrally against the socket  28 , the distal ends of the flange sections  38  will extend slightly into the aperture  32  of the socket  28  and will abut opposing walls of the socket  28  that define the aperture  32 . By further forcing the prongs  30  toward the socket  28 , the flange sections  38  of the prongs  30  will resiliently deflect toward each other so that the prongs  30  may be further inserted into the aperture  32  of the socket  28 . Since the width of the socket  28  is approximately equal to the height of the trunk  36  of each of the prongs  30 , when the prongs  30  are sufficiently inserted through the aperture  32  of the socket  28 , the flange portions  38  of the prongs  30  will spring away from each other, back to their original upstanding position, such that the lip  40  of each of the flange sections  34  overlaps a surface of the socket  28  adjacent to the aperture  32 . As shown in FIG. 2C the opposing edges of the aperture  32  along one surface of the socket  28  are indented to form a pair of opposing indentations  42 ,  44 , which are designed to accommodate the lip  40  of a corresponding flange section  38  of each of the prongs  30 . In such a condition, the prongs are maintained in a cooperative fastening relationship with the socket  28 . The prongs  30  may be disengaged from the associated socket  28  by manually compressing the flange portions  38  toward each other and then withdrawing the prongs  30  from the aperture  32  and the socket  28 . 
     The tubular members  10 - 25  are preferably integrally molded with a planar grid formed by a plurality of intersecting perpendicular struts. For example, the tubular member  10  is disposed centrally with respect to an intersection  50  of perpendicular struts  52  and  54 . It is contemplated that the struts may be disposed in other than a perpendicular rectangular grid pattern, for example, concentric ring struts with intersecting radially extending struts may be employed. Additionally, the struts may be arranged such that the grid openings are circular, oval, triangular, hexagonal, octagonal, etc. within the spirit and scope of the present invention. 
     In order to add strength and rigidity to the grid and tubular members, a plurality of longitudinal ribs (not shown) may extend along internal cylindrical side walls of the tubular members such that each of the ribs intersects one of the struts. In the illustrated embodiment, each cylindrical tubular member would possess four such longitudinal ribs disposed at 90° angular intervals. 
     The mat shown in FIG. 1 is preferably integrally molded from a semi-rigid thermal plastic material, preferably high density polyethylene, in an injection molding process. Polypropylene, thermoplastics, or plastic resins may also be suitable materials. The material selected should provide sufficient rigidity to resist undesired deformation and lateral shifting, but also be sufficiently flexible to allow the mat to be rolled for shipment and also to accommodate uneven terrain and base materials. 
     It will be seen that the columns and rows of tubular members are spaced so that a series of parallel, linear passages or pathways are formed between the columns (i.e., the pathways indicated by the arrows  60 ,  62 , and  64  in FIG. 1) and also between the rows (i.e., as indicated by the arrows  70 ,  72 , and  74  in FIG. 1) of tubular members. Although the embodiment as shown in FIG. 1 depicts a series of parallel, linear passageways that are orthogonal to each other, it should be appreciated that in a different array of tubular members, the pathways may be non-linear and may be non-orthogonal. 
     FIG. 3 depicts a fragmented, cross-sectional view of the mat as shown in FIG. 1 taken in a direction generally along the line of arrow  70  and depicting a portion of tubular member  10  and of tubular member  14  and interconnecting struts  52 ,  54 . In addition, FIG. 3 generally illustrates a length of pipe  76  extending along the pathway  70 . The pipe  76  may be fashioned of metal, plastic, or elastomer material and may be substantially rigid or deformable, for example. The pipe  76  generally possesses a cylindrical cross-sectional configuration, with the outer diameter of the pipe  76  being slightly less than the shortest distance between the tubular member  10  and the tubular member  14 . Also preferably, when the pipe  76  rests upon the struts  52 ,  54 , the upper peripheral edge of the pipe  76  is disposed slightly below the topmost edge of the tubular members  10 ,  14 . In such a preferred relationship, when the mat is covered with material such as soil or asphalt, and traffic upon the material tends to wear away the upper most layer of material, it will be appreciated that the upper edges of the tubular members  10 ,  14 , and not the pipe, will bear the weight of any traffic, thus protecting the pipe  76  from damage. 
     As shown in FIG. 1, a series of stiffening ribs  78  may extend between tubular members in a row of tubular members. Such ribs  78  may also, alternatively, extend between tubular members in a column of tubular members. The stiffening ribs  78  generally extend along a line interconnecting the centers of the tubular members. FIG. 4 shows a fragmented, cross-sectional view of the mat, generally taken in the direction of the arrow  60 , showing the tubular member  10  and the tubular member  11  as well as a stiffening rib  78  extending therebetween. Preferably the stiffening rib  78  is integrally molded with the other portions of the mat. The stiffening rib  78  as shown in FIG. 4 includes an upper, generally linear surface or edge  80  spaced a short distance  82  below the upper edges of the tubular members  10 ,  11 . The upper edge  80  also includes a recess or depression that is located mid-way along the upper edge  80  and that is shaped as an arcuate portion of a circle. It should be appreciated that the arcuate portion of the circle may range from a few degrees to 360°, and may be in the range of 45 to 120°, and may be in the range of 160 to 270°. As shown in FIG.  4 , the arcuate recess is about 250°. The arcuate configuration is adapted to receive a pipe (not shown) having a cylindrical configuration in which the radius of the outer peripheral surface of the pipe is slightly less than the radius of the arcuate configuration of the rib  78 . Thus, the rib  78  is designed to maintain and hold a pipe. When the pipe is placed within the arcuate recess of the rib  78 , then the upper peripheral edge of the pipe will be spaced a short distance  84  below the upper edges of the tubular members  10 ,  11 . Again, such positioning helps to protect the pipe from damage due to traffic. 
     The invention contemplates that non-cylindrical pipes may be employed and that the recess in the upper edge  80  may possess a configuration that conforms with the configuration of a portion of the pipe periphery. 
     Although it is contemplated that the mat may be slightly flexible so that the rib  78  also flexes to receive the pipe, the invention also contemplates that the upper edge  80  of the rib  78  shown in FIG. 4 forms a pair of opposing corners or ears  86  that may be resiliently flexed relative to the remaining portion of the rib  78  so that the pipe may be inserted into the arcuate recess in a slightly “snap fit” retention due to the ears  86  assuming their normal position after deflection. 
     It should also be appreciated that the pipe  76  as shown in FIG. 3 may be made sufficiently small in diameter so that when the pipe  76  rests upon the struts  52 ,  54 , the pipe  76  will be located below the pipe (not shown) that occupies the arcuate recess in the rib  78  as shown in FIG.  4 . Thus, the pipes may also form an orthogonal grid in the directions of the pathways  60 ,  62 ,  64  and  70 ,  72 ,  74 , as shown in FIG.  1 . It should be further appreciated, however, that only pipes disposed along the vertical passageway  60 ,  62 ,  64  might be employed, or that pipes disposed in alternating passageways or at regularly spaced passageways may be employed. 
     FIG. 5 shows a variation of a mat, tubular members, and rib  78  shown in FIG.  4 . The variation is especially adapted to facilitate the movement of a particulate or viscous material, such as soil or asphalt, throughout all interstitial regions of the mat. As shown in FIG. 5, the tubular members  10 ′,  11 ′ include arched apertures  90  extending upwardly from the bottom edge of each tubular member  10 ′,  11 ′. Also, the rib  78 ′ includes an upper surface or edge  80 ′ that is beveled downwardly from the upper edge of each adjacent tubular member  10 ′,  11 ′. Such configuration provides more strength to the rib  78  than is created by the linear upper edge  80  of the rib  78  as shown in FIG.  4 . The lower edge of the rib  78 ′ as shown in FIG. 5 includes a lower edge comprising a central horizontal surface  94  connected through beveled surfaces  92  to a corresponding lower edge of each tubular member  10 ′,  11 ′. The lower edge of the rib  78 ′ thus creates a lower aperture beneath the rib  78 ′. It will be appreciated that when particulate or viscous material covers or is spread over the mat, the mat construction of FIG. 5 permits the material to more readily migrate through and to completely fill the interstitial regions of the mat, whereby there are no voids, and whereby weight from traffic applied to an upper surface of the material will be firmly supported. Otherwise, a material with voids might result in depression, cracks, and other deformities of the upper surface of the material. 
     There is shown in FIG. 6 a schematic illustration of a pipe  76  maintained within a pathway of the mat. The dashed line  100  above the pipe  76  represents the plane formed by the upper edges of the various tubular members of the mat. The dashed line  102  above the pipe  76  represents the upper surface of the material in which the mat and pipe  76  are disposed. Segments of the pipe  76  may be joined together by a cylindrical collar  104 , which is threadably secured, adhesively secured, or otherwise secured to adjacent ends of the segments of the pipe  76 . A valve stem  106  or a nozzle may extend generally perpendicularly from the pipe  76 /collar  104  in a generally vertical or upward direction so that the upper edge of the valve stem  106  is approximately coextensive with the upper surface  102  of the material. The valve stem  106  is preferably ring-shaped, and may be formed of plastic, metal, or an elastomer. Preferably a hard-wear elastomer is utilized. Preferably there is a substantially open area or void in the material substantially immediately above the valve stem  106  or nozzle. The valve is preferably a one-way valve which permits liquid within the pipe  76  to escape through the valve stem  106  when liquid pressure within the pipe  76  reaches a predetermined magnitude or level. The valve may simply permit liquid from the pipe  76  to ooze through the valve and onto the upper surface of the material  102 , or more preferably, may spray the liquid above and onto the upper surface  102  of the material. When the instant invention is employed in the environments of sod or concrete or asphalt pavings for a driveway, then the valve may be a “pop up” valve such as valves conventionally used for sprinkler systems for lawns. When the invention is employed with asphalt or concrete airport runways or asphalt or concrete roads, then the valve is preferably not a “pop up” type valve, since when the valve is exposed above the upper surface  102  of the material, the wheels of frequent vehicular traffic might damage the valve. 
     It should be appreciated that instead of a valve being located at the location where liquid from the pipe  76  is to be discharged upwardly and onto the upper surface  102  of the material, a main valve may be used to permit or prevent liquid from entering the pipe system. When such a main valve allows liquid to enter the pipe system, then the liquid may automatically pass through the pipe  76 , through a passive port or nozzle, and upwardly onto the upper surface  102  of the material. 
     The present invention may be used to deliver water, or a combination of water and fertilizer to sod. It may also employed to deliver a deicing fluid, such as ethyl glycol, onto a pavement such as a sidewalk, a driveway, an airport runway, or a road. 
     It should be further appreciated that in an alternative embodiment of the present invention, liquid within the pipe need not escape outside the pipe and that the pipe may be used to deliver a relatively hot liquid or fluid (such as steam) to a material surrounding the mat and pipe  76 . For example, if the mat and pipe system of the present invention is disposed in sod beneath a football or soccer field, then a hot gas or liquid may be passed through the pipe system so as to heat the sod and keep the field from freezing or thaw a frozen field. In such an embodiment, it is preferred that the temperature of the fluid be hotter than the freezing point of water, and even more preferably, be at least about 60° F. In such a system, the fluid may be recirculated and passed through a heater to elevate the temperature of the fluid. 
     Although particular embodiments of the particular invention are described and illustrations herein, it should be recognized that modifications and variations may readily occur to those skilled in the art and that such modifications and variations may be made without departing from the spirit and scope of my invention. Consequently, my invention as claimed below may be practiced otherwise than as specifically described above.