FIELD OF THE INVENTION

This invention relates to road pavements, in particular pavements comprising layers of variable heights. BACKGROUND OF THE INVENTION

Usually for road pavements design, it is estimated that most (approximately 95%) of traffic heavy loads, move along the right lane of a road while the lanes, provide faster moving vehicles the opportunity to pass the slower traffic moving in the right lanes. Therefore the load carrying pavement can be thinner in the area of the left lane and thicker in the area of the right lane. In countries where the British transport system rules are used ('right side driving'), the above applies however with most traffic moving along the right lane, respectively.

A number of factors must be considered when designing pavement structures, or, more particularly, the pavement thickness, three of which include: (1) the ability of the underlying soils to support loads, (2) the type and availability of construction materials, and (3) the degree of loading to be accommodated - the traffic loads.

Traffic loading refers not only to the magnitude of the loads - the weight that is being applied to the pavement section - but also the nature or arrangement of the applied loads, and the frequency of the loading, that is, how many times that weight is applied, or the axle load accumulation.

Joint patterns that delineate adjacent lanes should be as continuous as possible to maintain uniformity of movement between longitudinal lanes, otherwise longitudinal joints (longitudinal lines of intersection between two adjacent lanes) may be subjected to differential deflections due to discontinuous and sudden changes of paving material. SUMMARY OF THE INVENTION

According to the present disclosed subject matter there is disclosed a pavement having a pavement top surface defined by a pavement longitudinal direction and a pavement traverse direction perpendicular to said longitudinal direction, the pavement comprising at least a first lane and a second lane, at least two pavement layers, of which at least one pavement layer has a first portion across said first lane, with a first bottom surface of a first slope, and a second portion across said second lane, with a second bottom surface of a second slope different from said first slope.

The term pavement according to the presently disclosed subject matter denotes any paved road, driveway etc.

A pavement according to the present disclosed subject matter may be configured with any one or more of the following designs and features:

^■ a fill layer formed between two adjacent pavement layers, said fill layer extending across the first lane along said traverse direction

^■ the fill layer varies in thickness across said first lane, having the lowest thickness at an intersection of said first lane with said second lane;

^■ the fill layer is of a gradually decreasing thickness;

^■ at least one pavement layer is of a uniform thickness along said traverse direction;

^■ at least one pavement layer is of a variable thickness along said traverse direction;

^■ the first portion is of a variable thickness and the second portion is of a uniform thickness;

^■ a thickness of said first portion is equal to the thickness of said second portion at the intersection between said first lane and said second lane, maintaining thereby the continuity of the whole layer thickness

^■ the first slope is greater than 2%;

^■ the first slope is greater than 3%;

^■ said first slope is about 5% greater than said second slope;

■ the top pavement surface is of a uniform slope along said traverse direction;

■ the uniform slope is at least 2%;

■ a lowermost pavement layer is a sub grade layer and the uppermost pavement layer is an asphalt layer;

■ the first pavement layer is a sub-grade layer, the second pavement layer is a sub-base layer, the third pavement layer is a base course layer and the fourth pavement layer is an asphalt layer. According to another aspect of the disclosed subject matter there is provided a method of paving of a pavement having a pavement top surface defined by a pavement longitudinal direction and a pavement traverse direction perpendicular to said longitudinal direction, said pavement comprising at least a first lane and a second lane, the method comprising:

a. forming a first pavement layer; and

b. forming at least a second pavement layer having a first portion extending across said first lane, said first portion comprising a first bottom surface of a first slope, and a second portion extending across said second lane, said second portion comprising a second bottom surface of a second slope different from said first slope.

The method may further comprise forming at least one fill layer between two adjacent pavement layers, so that said fill layer extends across the first lane along said traverse direction.

The above method can lead to significant material and cost savings yet maintain the desired load carrying requirements of said road. In particular, using a method of non parallel levelling cross-sections, mainly of the sub-grade, fill, sub-base, base course and asphalt layer - the material expenditure in the area of light traffic i.e. the left lanes is reduced, resulting in overall cost reduction.

Moreover, the thicknesses of the layers, according to the presently disclosed subject matter, are continuous along the whole width (the transverse axis) of the road, and in particular on the intersection line between the lanes, decreasing thereby the risk for differential deflections of the layers. Therefore, when forming the road layers according to the method of the presently disclosed subject matter, a special attention must be paid to the precise thicknesses of the layers.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to understand the invention and to see how it may be carried out in practice, embodiments will now be described, by way of non-limiting examples only, with reference to the accompanying drawings, in which:

Fig. 1 is a traverse cross section of a prior art method of pavement; Fig. 2 is a traverse cross section of a pavement according to an example of the present disclosed subject matter overlaid in dashed lines over the prior art method shown in Fig.l ;

Figs. 3A and 3B are traverse cross sections of pavements according to other examples or the presently disclosed subject matter; and

Fig. 4 is a traverse cross section of a pavement according to another example of the present disclosed subject matter overlaid in dashed lines over the prior art method shown in Fig.l.

DETAILED DESCRIPTION OF EMBODIMENTS

Referring first to Fig.l of the drawings there is shown a design of a known method of pavement of a road 1 extending across but not limited to, two lanes, namely a left lane 4 and a right lane 6 of a road. The road has a top surface 2 defined by a longitudinal axis Ai (along the road) and a traverse axis A ₂ .

The pavement 1 consists of several layers:

- a sub grade SG (i.e. the natural soil) which has a flattened and graded top surface 11 of slope Si;

a sub base SB of substantially uniform traverse thickness HSB with a flattened and graded top surface 13 of a slope S ₂ ;

- a base course BC of substantially uniform traverse thickness HBC with a flattened and graded top surface 17 of a slope S3; and

an asphalt layer AL, also of substantial uniform traverse thickness HAS with a flattened and graded top surface 19 of a slope S4, constituting the top surface 2 of the pavement 1.

It is thus noted that all layers constituting the pavement 1 are also of substantial uniform height along the axis Ai, and of substantial uniform and equal traverse slope, so that Si=S2=S3=S4. Therefore, angles ai, ₂ and ( 3 between portions 12, 14 and 16 extending across the lane 4 and portions 12', 14' and 16' extending across the lane 6, respectively, are equal to 180°.

Turning now to Fig.2 there is illustrated a cross section of a pavement 22 according to the presently disclosed subject matter, indicated by the dashed lines and for sake of exemplifying is superimposed over the prior art pavement discussed herein above in connection with Fig. 1.

The designed pavement 22 extends across but not limited to, two lanes, namely a right lane 26 and a left lane 24 of a road with an intersection line 9 therebetween. The pavement 22 may further comprise a left shoulder line SLi and a right shoulder line SL _r .

The pavement 22 consists of several layers extending between side edges 37 and

38.

The layers forming the road pavement 22 are:

a sub grade (SG) 25 having a top surface constituted of a top surface portion 31 across the lane 24 and a top surface portion 31' across the lane 26;

a fill layer 32 having a top surface 34 and a bottom surface 31 (part of the top surface of the sub grade layer 25) ranging in thickness across the sub grade level 25 from the point 30 on the intersection line 9, to a thickness ¾ at the side edge 37 of lane 24 (or up to the left shoulder line SL]) ;

- a sub base layer (SB) 35, having a first portion 35' with a top surface 42 across the lane 24 and a second portion 35" with a top surface 42' across the lane 26. The sub base layer 35 ranges in thickness, measured from the top surface 34 of the fill layer 32 at or near the edge 37 of lane 24, from a thickness HSBI _> to a thickness HSB2 adjacent edge 38 of lane 26. a base course layer (BC) 40, having a first portion 40' with a top surface 46 across the lane 24 and a second portion 40" with a top surface 46' across the lane 26, ranging in thickness, measured from the top surface 42 of sub base layer 35 at or near the edge 37 of lane 24, from a thickness HBCI, to a thickness of HBC2 adjacent edge 38 of lane 26; and

- an asphalt layer (AL) 55, having a flattened and graded top surface 19, ranging in thickness along the axis A ₂ , measured from the top surface 46 of base course layer 40, at or near the edge 37 of lane 24, from a thickness HASI to a thickness of HAS2 adjacent edge 38 of lane 26.

The above listed layers are constructed in the following manner.

The sub grade layer (SG) 25 is a natural soil which is uniformly flattened and graded along the traverse axis A ₂ with a uniform slope Si in the range of 2% to 10%, and usually is substantially parallel to the slope of the asphalt layer. The fill layer 32 composed of a low cost material, for example residual bedrock, is layered on top of the sub grade 25 surface 31 and graded to a slope X from its maximal thickness HF to its minimal thickness 0 at the point 30 on the intersection line 9, as mentioned above, forming the top surface 34 thereof. The slope X creates a gradient for the subsequent layers, in particular portions of the layers extending along the lane 24, so that an angle βι between the top surfaces 34 and 31 ' is less than 180°.

The sub base layer (SB) 35, composed of unbound granular material which can be crushed stone or crushed slag or crushed concrete or a combination thereof, is layered along the traverse axis A ₂ of lanes 24 and 26, from the thickness ¾BI to the thickness ¾Β2· The top surface 42 of the first portion 35' of the sub base layer 35 has a slope S ₂ ' and the top surface 42' of the second portion 35" has a slope S ₂ ", different from the slope S ₂ \ but equal to the slope Si. Consequently, an angle β ₂ between the top surfaces 42 and 42' is less than 180°.

The sub base layer 35 is designed so that its first portion 35' is of a variable thickness, increasing from the thickness ¾BI to the thickness ¾B2 at the intersection line 9, and its second portion 35" is of a uniform thickness ¾Β2· However, the first portion 35' may be of a uniform thickness as well, in which case the thickness thereof will be equal to the thickness of the second portion 35" . In any case, the continuity in thickness is maintained across the whole layer.

The base course layer (BC) 40, composed of newly quarried rock which is crushed to a specific recipe of graded aggregates, is layered on top of the sub base layer 35, and ranging in thickness from HBCI to HBC2> where usually ΗΒΟ2>·ΗΒΟΙ· The top surface 46 of the first portion 40' of the base course layer 40 has a slope S3' and the top surface 46' of the second portion 40" has a slope S3", different from the slope S ₃ ', but equal to the slope Si and S ₂ '. Consequently, an angle 3 between the top surfaces 46 and 46' is less than 180°.

The base course layer 40 is designed so that its first portion 40' is of a variable thickness, increasing from the thickness HBCI to the thickness ¾C2 at the intersection line 9, and its second portion 40" is of a uniform thickness ¾C2. However, the first portion 40' may be of a uniform thickness as well, in which case the thickness thereof will be equal to the thickness of the second portion 40". In any case, the continuity in thickness is maintained across the whole layer. The top asphalt layer (AL) 55 is spread on the top surfaces 46, 46' of the first and second portions 40' and 40" of the base course layer 40, and graded along the traverse axis A ₂ along the lanes 26 and 24 to a uniform slope S4. This leads to a thickness variation of the asphalt layer 55 ranging from the thickness of H _A si to the thickness H _A s2 _? as mentioned above, where usually HAS2 ^> HASI-

Eventually, the paved road according to the presently disclosed subject matter and comprising the layers described above, is of a variable height, decreasing between a first height Hi and the second height ¾ with the slope S4 that may vary between about 2% of a flat road to about 15% in sharp curves. However, the designed layers thickness remains substantially constant, as the inclination is usually imparted by the sub grade 25 and/or the fill layer 32.

In this connection, it should be noted that the paved road according to the present invention may comprise more than one fill layer (F _l5 F ₂ and F ₃ ), as shown in Fig. 3A or not comprise any fill layer, as shown in Fig. 3B. In the latter case the sub grade layer 25 is graded so as to create the required slope for the rest of the layers.

The use of a low cost material for the fill layer(s) (or decreasing the slope of the sub grade layer) decreases the amount of material used in the other layers, , resulting in overall cost reduction.

Turning now to Fig. 4 there is illustrated a cross section of a pavement 52 according to another example of the presently disclosed subject matter, indicated by the dashed lines and for sake of exemplifying is superimposed over the prior art pavement discussed herein above in connection with Fig. 1.

The designed pavement 52 extends across but not limited to, two lanes, namely a right lane 56 and a left lane 54 of a road. The pavement 1 may further comprise a left shoulder line SLi and a right shoulder line SL _r .

The pavement 52 consists of several layers extending between side edges 67 and

68.

The layers forming the road pavement 52 are:

- a sub grade (SG) 55 having a top surface constituted of a top surface portion

61 across the lane 54 and a top surface portion 61' across the lane 66;

- a fill layer 62 having a top surface 64 and a bottom surface 61 (part of the top surface of the sub grade layer 55) ranging in thickness across the sub grade level 55 from the point 60 on an intersection line 9 where the lane 56 merges with the lane 54, to a thickness Hp at the side edge 67 of lane 64 (or up to the left shoulder line SL|) ;

- a sub base layer (SB) 65, having a first portion 65' with a top surface 72 across the lane 54 and a second portion 65" with a top surface 72' across the lane 56. The sub base layer 65 ranges in thickness, measured from the top surface 64 of the fill layer 62 at or near the edge 67 of lane 54, from a thickness H _SBI» to a thickness H _SB2 adjacent edge 68 of lane 56. a base course layer (BC) 70, having a first portion 70' with a top surface 76 across the lane 54 and a second portion 70" with a top surface 76' across the lane 56, ranging in thickness, measured from the top surface 72 of sub base layer 65 at or near the edge 67 of lane 54, from a thickness H _BCI , to a thickness of ¾ _C2 adjacent edge 68 of lane 56; and

an asphalt layer (AL) 85, having a flattened and graded top surface 19, ranging in thickness along the axis A ₂ , measured from the top surface 76 of base course layer 70, at or near the edge 67 of lane 54, from a thickness H _ASI to a thickness of H _AS2 adjacent edge 68 of lane 56.

The above listed layers are constructed in the following manner.

The sub grade layer (SG) 55 is a natural soil which is uniformly flattened and graded across the portion of the surface 61 to a slope Ii of about 5% or less and across the portion of the surface 31' to a slope Ii', smaller than the slope I _l5 of about 2% or less.

The fill layer 62 composed of a low cost material, for example residual bedrock, is layered on top of the sub grade 55 surface 61 and graded to a slope X' from its maximal thickness ¾ to its minimal thickness 0 at the point 60, forming the top surface 64 thereof. The slope X' creates a gradient for the subsequent layers, in particular portions of the layers extending along the lane 54. The slope X' is different from the slope Ii' and may be about 4%.

The sub base layer (SB) 65, composed of unbound granular material which can be crushed stone or crushed slag or crushed concrete or a combination thereof, is layered along the traverse axis A ₂ of lanes 54 and 56, from the thickness H _SBI to the thickness ¾ _Β2 · The top surface 72 of the first portion 65' of the sub base layer 65 has a slope I ₂ and the top surface 72' of the second portion 65" has a slope I ₂ \ different from the slope I ₂ .

In order to maintain parallelism of each of the first and second portions 65' and 65" (i.e. so that the surface 64 is substantially parallel with the surface 72 and the surface 61' is substantially parallel with surface 72'), the slope I ₂ is substantially equal to the slope X', and the slope I ₂ * is substantially equal to the slope '. For this purpose, the slope I ₂ is usually about 3.5% and the slope I ₂ ' is about 3%.

In such case, the thickness of the portions 65 and 65" is uniform, so that the sub base layer 65 is of uniform thickness, namely HSBI = HSB2- However, depending on load requirements HSBI can be smaller (thinner) than

HSB2 but not larger (thicker). In such case, one or both portions 65' and 65" may be of a variable thickness, so that the slopes of these portions satisfy one of the following conditions: X'=I ₂ and I ₂ '≠ Ii', or X'≠ I ₂ and I ₂ '= Ιι', or X'≠ I ₂ and I ₂ '≠ Ι .

The base course layer (BC) 70, composed of newly quarried rock which is crushed to a specific recipe of graded aggregates, is layered on top of the sub base layer 65, and ranging in thickness from HBCI to HBC2> as mentioned above, where usually HBC2 ^> HBCI- The rightmost thickness HBC2 of the base course layer 70 may be greater than the rightmost thickness ¾Β2 of the sub base layer 65, or equal thereto 3.

The top surface 76, 76' of the base course layer 70 is substantially evenly graded along the lanes 52 and 56, so that the slope ¾ of the top surface 76 of the first portion 70' is equal to the slope I3' of the top surface 76' of the second portion 70". In such case this slope may be about 3%.

However, depending on load requirements, the slope I3 may be different from the slope I3'.

The top asphalt layer (AL) 85 is spread on the top surfaces 76, 76' of the first and second portions 70' and 70" of the base course layer 70, and graded along the traverse axis A ₂ along the lanes 56 and 54 to a slope I4, which is usually at least 2%. This leads to a thickness variation of the asphalt layer 55 ranging from the thickness of HASI to the thickness HAS2> as mentioned above, where usually HAS2 ^> HASI- With reference to all the above examples according to the presently disclosed subject matter, the slopes of the layer portions extending across the left lane are usually about 5% greater than the slopes of the layer portions extending across the right lane. It is appreciated that all the above given numeric values are set as examples only and may vary depending on different design parameters.

Employing the method of layering and paving according to the disclosed subject matter result in less base course (BC) and asphalt (AL) material being present in the area of the left lane ('fast lane') where traffic loads are light and lead to a significant cost savings during the constructing (or paving) of a road while maintaining the desired load bearing capacity of the road.

It should be noted that pavements shoulders structure design (i.e. right of line SL _r and left of line SLi) may be different than pavements structure for the driving lanes (i.e. between shoulder lines). However, depending on designer requirements, the shoulders may be paved in continuation with the layers of the respective driving lanes, as discussed herein above. In particular, this may be the case where design is made in consideration of intention to expand the road (pavement) at a later stage.

It is noted that the proposed design refers to paving a road with two or more lanes in one direction. However, a two-directional road is paved in compliance with the above disclosed method, i.e. with the lanes in each direction designed with inclinations in an opposite sense, so as to drain liquids (i.e. rain) off the road.

It is noted that this method creates a tailor-made pavement design cover for the predicted loads in each lane,

Those skilled in the art to which this invention pertains will readily appreciate that numerous changes, variations and modifications can be made without departing from the scope of the invention mutatis mutandis. For example, in a road comprising more than two lanes, there may be intermediate grading of the respective layers, etc.