A METHOD AND APPARATUS FOR RESTRICTING LOCAL VARIATIONS IN GROUND LEVEL IN THE VICINITY OF SURFACE WATER DRAINS AND MANHOLES

Abstract: Method and arrangement for restricting local variations in ground level in the vicinity of surface water drains and manholes, at locations where the freezing and unfreezing of the ground causes the ground and parts of the drainage system located therein to move. To this end, the arrangement comprises a drain cover-support means (2) arranged to be anchored in the surface ground layer (5) in a conventional manner, and provided with a tubular part (6) which projects down into the drain (1) and is axially moveable relative thereto. A supporting element (8) is arranged around the tubular part (6) of the drain cover-support means (2), the supporting element being axially displaceable relative to the tubular part (6), while being guided by the upper part (1) of the drain, and is arranged to be anchored in the surrounding ground layer (5). The supporting element preferably has the shape of a circular plate or disc (8), which abuts the tubular part (6) substantially tightly, and the outer diameter of the plate or disc (8) is about twice that of the diameter of the drain.

Description: A method and apparatus for restricting local variations in ground level in the"vicinity of * * surface water drains and manholes 5 Technical field . The present invention relates to a method for restricting local variations in ground level in the vicinity of surface-water drains and manholes, at loca¬ tions where the freezing and unfreezing of the ground 10 causes the ground and parts of drainage systems located •therein to move. The invention also relates to apparatus for use when carrying out the method. Background of the invention When subjected to rapid variations in tempera- 15 ture, the level between the cover-support means of a sur¬ face-water drain or manhole and the surrounding ground surface will often vary quite considerably. Since this type of drain is normally located in drive ways, such as roads, .such variations in- level present a driving 20 hazard and are expensive to rectify. Such variations in level are mainly caused by the ground freezing during the Autumn and Winter month ' s, the ground, which contains water, expanding when frozen, with subsequent lifting of the ground level, and by par- 25 tial unfreezing of the ground in the vicinity of the drain or manhole during the Spring months, with reduced firmness of the ground as a result. By way of example, it can be mentioned that when ground which contains a lot of water is subjected to extreme cold over a long - 30 period of time, the ground level can rise from 30-40 cm. The aforementioned local variations in level can occur, among other things, as a result of the ground freezing at different depths at different moments in time, and also because the extent to which the ground 35 unfreezes varies with depth and with distance from a drain or manhole. The following events can take place in the case of a conventional drain or manhole, hereinafter O PI referred to generally as water drain. When the ground freezes, the level of the ground rises, causing the drain cover-support means to be lifted, so that the ground sur¬ face remains substantially flat. In warmer weather, the ground in the immediate vicinity of the drain will often unfreeze more rapidly than the surrounding ground, con¬ sequently reducing the firmness or supporting power of the ground adjacent the water drain, which may either result in the whole of the drain sinking relative to the surrounding ground, to form a pit, or as is more usual, causing the ground layer immediately surrounding the drain cover to disintegrate and sink to form a crater around the drain cover. The reason why the ground around a water drain will unfreeze more rapidly than ground more- dis¬ tance therefrom is sometimes because of the water from melted snow or ice entering the outside or inside of the drain, thereby heating the same. Air currents in the drain are also liable to heat the same. This is particu¬ larly noticeably when steam is used to unfreeze a frozen drain. Sometimes a drain will remain in a lifted position when the level of the surrounding ground has fallen, as a result, among other things, of ground which remains frozen at a deeper level, the raised drain constituting an obstacle and a hazard to traffic. Object of the invention The main object of the present invention is to provide a method and an arrangement for eliminating or reducing the aforementioned problems. Brief summary of the invention relative to the upper part of the drain. Hence, such a ., supporting element will carry out several different func- tions. Among other things, it will prevent the surface layer from disintegrating and forming craters around the drain cover should the ground unfreeze locally during 5 warmer weather, e.g. in the Spring, since it improves the supporting power of underlying material. The supporting element will also lead away water deriving from frozen ice and snow, thereby preventing local unfreezing of the ground layer surrounding the well. Since the supporting 10 element will accompany movement of the ground layer imme¬ diately beneath the surface layer, said element will also exert a downwardly pressing force on the drain when the surface layer sinks. This is of particular importance in the case of light drains located in regions of ligth 15 traffic, since otherwise such drains may remain in a lifted position. A corresponding effect will also prevent light drains, for example drains made of plastic pipes, from being pressed upwardly be earth pressure; The use of a supporting-element structure has 20 previously been suggested, c.f. SE 7712565-6 and NO 141 319. These supporting elements, however, have only been intended for supporting the drain cover-support means, among other things to prevent forces being trans¬ mitted to the drain itself. Such a supporting element 25 cannot fulfil the function of the supporting element according to the present invention. In accordance with the present invention a method of the kind mentioned in the introduction is particularly characterized by anchoring the drain cover-support means -» 30 in the surface layer in a conventional manner, and so that a tubular part of the cover-support means projects down into the drain axially moveable relative thereto; and by placing a supporting element around said tubular part of the drain cover-support means, so that said sup- 35 porting element is axially displaceable relative to the drain cover-support means while guided by the upper part __O H of the drain; and by anchoring the supporting element in the surrounding ground. Preferably, the supporting element is arranged so as to be telescopically displaceable relative to the upper part of the drain, substantially in tight peri¬ pheral abutment with the tubular part of the drain. In a preferred embodiment of the invention, the supporting element comprises a circular disc, whose outer diameter is of the order of twice the drain diameter. It is important that the supporting element extends over a relatively long distance outside the drain, so as to in¬ crease the carrying power and to obtain a reliable an¬ chorage in the ground. Suitably, the supporting element is designed so that it can be fixed to a holder displace- ably arranged on the upper edge of the drain, without using loose attachment means. In order to reduce still further the risk of ' the drain being heated by water deriving from, snow or. ice, the tubular part of the drain cover projecting down into the drain is suitably provided with a throat. The invention will now be described in detail with reference to the accompanying drawing. Brief description of the drawings Figure 1 is a side view, partly in section taken on the line I-I in Figure 2 , of an arrangement according to the invention mounted on a surface-water drain. Figure 2 is a horizontal, part-sectional view of the arrangement according to Figure 1. Description of a preferred embodiment of the invention The reference 1 identifies the upper part of a water drain, while reference 2 identifies a drain cover- support means supporting a grating 3. The drain cover- support means 2 is provided with a peripheral flange 4, by means of which said support menas can be fir_ιly an- chored in the surface layer 5, for example an asphalt coating, so as to produce a perfectly smooth ground sur- face. As will be seeen, the drain cover-support means 2 is provided with a lower, tubular part 6, which projects 4 " down into the drain 1. The lower part of the tubular por¬ tion 6 is provided with a throat 7, which among other 5 things prevents warm, melted ice or snow from running along the wall of the drain 1 and warming the same. The throat also greatly reduces the amount of dirt deposited on the wall of the drain, said dirt otherwise forming a good ger¬ minating substrate for fungi, moss and the like. 10 The tubular portion 6 of the drain cover-support means is encircled by a supporting or bearing element 8, which extends outwardly into the surrounding ground layer 9 over a relatively long distance, thereby to provide a good anchorage for the supporting element and a high 15 bearing power, even though the material in the layer 9 is relatively loose. The supporting element 8 peripheral¬ ly abuts the tubular portion 6 quite tightly, but shall be able to move up and down relative to said tubular portion, whereat said element also effectively conducts 20 away arywaterpenetrating down the outside of the drain cover 2. Thus, this water will not contribute towards heating the actual drain 1. In the illustrated embodiment the supporting element 8 has the form of an annular plate which, in 25 order to have sufficient rigidity, is arched. As will be understood, sufficient rigidity can be imparted to a flat plate by corrugating the same. A flat, corrugated plate may be preferred from the aspect of manufacture. Preferably, the outer diameter of the plate is about ij, 30 twice the diameter of the dain. In the illustrated embodiment, the supporting element 8 is fixed to a holder arranged on the upper part 1 of the drain, without the use of loose attachment means. In the illustrated case, the holder comprises a 35 sleeve having double walls 10 and 11 joined together by OMH means of a ring-shaped part 12 and slided over the upper end part 1 of the drain. The connecting part 12 is provided with an outer flange 13 which, as will be seen from Figure ' 2, is provided with recesses 14. The support- ing element 8 is provided underneath with mounting tongues 15, which fit into the recesses 14 and which when rotating the supporting element 8 lock said element to the flange 13. In this way, the supporting element 8 retains its ability to move vertically relative to both the tubular part 6 of the drain cover-support means 2 and the upper part 1 of the drain, since the double-wall sleeve 10, 11, 12 can be displaced telescopically relative to the drain whilst being guided by the upper part 1 of said drain. Thus, in the illustrated arrangement the drain cover-support means 2 will accompany the movement of the ground as it is lifted when the earth i.n the outer layer 5 freezes during the cold Autumn months, resulting in a flat ground surface. As beforementioned, when the ice and snow melts in warmer weather, the water is prevented from running down along the inner and outer surfaces of the drain 1, as a result of the throat 7 and the supporting element 8. If the ground layer around the drain 1 should, nevertheless, partially unfreeze, the supporting element 8 will obtain sufficient support from the material 9 lo- cated beneath the surface layer, thereby preventing the surface layer 5 from disintegrating with the resultant formation of craters and pits around the outer flange 4 of the dain cover 2. The supporting element 8 also pre¬ vents any tendency of the drain cover 2 when loaded to sink beneath the level of the outer layer 5, when the ground layer 9 therebeneath unfreezes, and also serves to relieve the drain of any load exerted thereon, which is significant when the drain is made of plastic pipes. Because the supporting element 8 has a relative- ly large area, the element is also able to exert a down- wardly pressing force on the drain 1 as a result of the weight of the ground material located on top of said element, among other times in conjunction with the un¬ freezing and sinking of the level of the surface layer 5 and the ground layer 9 located immediately therebeneath. Thus, the supporting element 8 will accompany the move¬ ment of the ground layer. To permit a certain amount of movement of the drain 1, the supporting element 8 is suitably positioned so that initially there is a clearance between the upper end of the drain 1 and the connecting part 12. Optionally, a fixing mass can be pressed down through holes 16 in the connecting part 12, to hold the supporting element at a given level relative to the drain 1. When the drain is made of a light material, usually a plastics material, the supporting element 8 can also serve to prevent the drain from being urged upwardly by surrounding ground pressure. Light drains not provid¬ ed with a supporting element are liable to be lifted by pressures acting in the surrounding ground. In this case, the counter-acting force which the supporting element 8 is able to exert on the drain plays an important role. As will be understood from the aforegoing, all parts are axially moveable relative to one another, al- though so guided as to prevent radial displacement between said parts. The described embodiment is not limitive of the invention, but can be modified in several respects. For example, the holder for mounting the supporting element on the drain can be varied as desired. In the illustrated holder, the outer and inner pipe walls can, for example, have mutually different heights and one wall optionally excluded altogether.. Neither need the guide means of the holder have the form of closed tubular walls. Although it is preferred to secure the supporting element to the holder without the use cf loose attachment means, as with the illustrated embodiment, other attachment methods can be used, for example bolts or like fasteners. The design of the supporting element can be modified as desired. For example, the supporting element can be made in one piece and. provided with means which guide or abut the drain. Preferably, instead of being completely rigid, the support¬ ing element is able to yield a little. As will be under¬ stood, the use of a supporting element arrangement according to the invention can also be used with other types of dains and drain cover-support means, irrespective of their geometric shape. Those problems solved by means of the invention, however, are ' particularly found with surface water drains, and can also exist with manholes.

Claims: # Claims 1. A method of restricting local variations in ground level in the vicinity of surface water drains and man- 5 holes, at locations where the freezing and unfreezing of the ground causes the ground and parts of drainage sy¬ stems located therein to move, characterized in that the drain cover-support means is anchored in the surface ground layer in a conventional manner, and so that a 10 tubular part of the drain cover-support means extends down into the drain so as to be axially moveable relative thereto; that a supporting element is placed around the tubular part of the drain cover-support means, so as to be axially moveable relative, thereto while being guided 15 by the upper part of the drain; and in that the supporting element is anchored in the surrounding ground layer. 2. A method according to Claim 1, characterized in that the supporting element -is telescopically displace- able relative to the upper part of the drain. 20 3. A method according to Claim 1 or Claim 2, charac¬ terized in that the supporting element is so arranged that when a load is placed on its upper side said element is able to exert a downwardly pressing force on the under¬ lying drain. 25 4. A method according to any one of Claims 1-3, characterized in that the supporting element is arranged substantially tightly around the tubular part of the drain cover-support means. 5. An arrangement in surface water drains and man- 30 holes for restricting local variations in ground level in the vicinity of surface water drains and manholes at locations where the freezing and unfreezing of the ground causes the ground and parts of drainage systems located therein to move, characterized in that said arrangement includes a drain cover-support means (2) arranged to be anchored in the surface ground layer (5) in a conventional manner and provided with a tubular part (6) which pro¬ jects down into the drain (1) and is axially moveable re- lative to said drain; and a supporting element (8) v/hich is arranged around the tubular part (6) of said drain cover-support means (2) and which is . axially displaceable relative to said part (6) while being guided by the upper part (1) of the drain, and which supporting element is arranged to be anchored in the surrounding ground layer ' (5) . 6. An arrangement according to Claim 5, characterized in that the supporting -element has the form of a circular disc (8) , in a substantially tight peripheral abutment with the tubular part (6) . 7. An arrangement according to Claim 6, characterized in that the outer diameter of the plate, or disc (8). is about twice that of the diameter of said drain. 8. An arrangement according to any one of Claims 5- 7, characterized by a holder means (10, 11, 12) displace¬ able mounted on the upper part (1) of the drain, said supporting element (8) being connected to said holder means. 9. An arrangement according to Claim 8, characterized in that the holder means (10, 11, 12) is arranged to be slided onto the upper part (1) of said drain. 10. An arrangement according to any one of Claims 5-9, characterized in that the lower part of the tubular part (6) of the drain cover-support means (2) is provided with a throat (7) .

Inventors: ARNTYR OSCAR SVEN, ENGSTROEM THORD INGEMAR
Applicants: ARNTYR OSCAR SVEN, ENGSTROEM THORD INGEMAR
Application year: 1982
Main classification: E03F5
IPC codes: E02D29