with coefficient of filtration of 3m per day and more with capillarity raising of 25cm height.

At fills widening from coarse-grained soils it is necessary to use filler from clay soils wherein upper part of the thickness not less than working layer is recommended to construct from fragments up to 250mm size. In coarse –grained soils the content of clay filler is about 30% with moistening equal to optimal value. Adherence of this requirement protects pockets. In coarse-grained soils or in industrial wastes the humidity of fractured fine grade part should coincide to tough consistence (C cons is about 0.3%).

Coarse-grained soils with ultimate compression strength is more 0.5 MPa compact in two stages: in first stage there are used tampers of mass more than 25tonne, in the second one – vibrator roller of mass less than 10-12 tonne with 10-12 passes along one track.

Because of the limiting possibility of earth allotment for soil carries in some cases for subgrade widening there can be used different industrial wastes: metallurgical slags and ash slag wastes of thermal power plants. Their application needs special attention to structure homogeneity, technology of industrial works, compaction and quality control.

UNIT IV

CORRECTION OF VERTICAL ALIGNMENT OF ROAD

4.1.Construction technology at fill height increase. Calculation of subgrade geometrical parameters.

4.2.Construction technology at excavation depth change.

4.3.The layout of the subgrade slopes.

4.4.Slop soling.

4.1. Fills height is increased in the following cases: on snowbound plots in order to raise subgrade edge up to the snowbound fill; on heaving area and on the sections with high level of ground water or stagnant surface waters up to the mark overtop capillary ascension of water; on the longitudinal gradient reduction

The choice of the work order at fills height raise significantly depends on many factors: the height of old fill and its slopes steepness; size of fill raise and steepness of new slopes, road axis location before and after fill raise; type and condition of road surfacing, soils and drainage system etc.

While raising fill height old road surfacing is unpaved, recycled and enriched with material and then used during construction of new road surfacing or at other road works.

As a rule slope base of the fill with small height is 1:1 or 1:1,5. At the same time according to Building Norms and Regulations 2.05.02-85 slopes steepness of the ills with the height up to 3m on the roads of I-III categories is as a rule to be designed

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not steeper than 1:4 and or the roads of other categories at fill height up to 2m – not steeper than 1:3 with account of traffic safe ramp in accident situations.

At fill raise more than 0,5m the works are done upwards from a toe of fill slope up to the subgrade edge of existing road.

At fills height raise it is necessary to comply with the requirements for soils their disposition and degree of compaction which are the same at subgrade widening.

Further fill raise is executed according to the common technology of subgrade construction.

At fills height raise it is necessary to comply with the requirements for soils their disposition and degree of compaction which are the same at subgrade widening.

At fill raise up to 0,5m an old road surface can be used as a bed on which new road surface is constructed. In this case the raise of subgrade is the soil backfill on to the edges and soil compaction. The final decision is taken after technical – economical comparison of variants where there is considered the expenditure for old road surface removal, recycling and enriching of obtained materials, re-laying of these materials into road pavement. These expenditures are compared with the expenditures for new road surface construction.

At fill raise (up to 0,5m) and removal of existing road the following works are executed:

–plant removal from shoulders and from upper slop part up to the height of 0,5-0,6 m;

–layerwise wrecking and removal of the materials of the old road bed course;

–layerwise filling in of the roadbed with soil and its compaction;

–sand course filling, construction of new road pavement;

–roadsides topping up and their hardening;

As you can see in fig. 4.1 at fill height raise there is compulsory happened its widening onto the subgrade and along the whole height in comparison with existing road due to slope base.

Fig. 4.1. Diagram of subgrade size determination at embankment height increase

The magnitude of widening on the level of existing road subgrade shoulder can be found according to the formula:

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where m2 – slop embankment base after its reconstruction; ∆h – raise of embankment height, м.

Magnitude of widening along the embankment is:

where h1 – embankment height before the reconstruction, м; h2 – total height of embankment after its reconstruction, м; m1 – slop embankment before reconstruction.

In the cases when during gravel and crushed stone removal the materials are happened to be so crushed and polluted the expenditure for their recycling and enriching exceeds the cost of new road construction, then the road pavement is not removed but filled up with soil (“bury” in subgrade).

4.2. An excavation depth increase usually connects with the necessity of longitudinal slop softening, increase of the visibility of the longitudinal profile on vertical convex curves, and also according to the conditions of viaduct construction over the existing road for the other motor way or railway.

The depth of the existing excavation is increased rarely than the increase of embankment height which is explained by the most complicated conditions of such works realization.

The change of design line in excavation courses the change of design line at its approaches (see fig. 4.2).

Fig. 4.2. Diagram of location of adjacent sections of change of excavation depth and embankment height while grade reduction of the longitudinal slope

1 – line of earth surface; 2 – red line location before reconstruction; 3 – the same after reconstruction; i1 и i2 – maximal longitudinal slop before and after the reconstruction.

In this case we can mark out some specific sections of longitudinal profile change:

–section of excavation depth increase-I;

–section of excavation depth decrease –II;

–section where the excavation is changed by embankment – III;

–section of embankment height increase on the approach to the excavation – IV. In real conditions some from the mentioned sections can be absent, but work

organization on excavation reconstruction is remained complicated, At increasing depth of excavations it is to be increasing of their width at the top, removal of existing road pavement, reconstruction of the drainage.

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In some cases simultaneously with excavation deepening for slop stability or snowdrift extant slop steepness is increased (slop flattening).

In fig. 4.3 there is a diagram for determination of geometrical parameters of cut deepening.

Fig. 4.3. Diagram for determination of geometrical parameters of cut deepening

Increase of cut width on the top from one side is:

where m1, m2 – slop depth before and after reconstruction; h1, h2 – cut depth before and after reconstruction, m.

If slop steepness after reconstruction becomes the same as before

where m – slop depth.

Cut deepening works begin with arrangement of bypass, removal of vegetation layer from cut slops and earth surface on the lane of widening.

After that there is made cut widening up to the mark of existing road edge first from one side and then from the other one or from the both sides simultaneously.

Vehicles at that period can travel along the both lanes of carriage way without interruption.

At the width of 2m cut slop development can be done by bulldozer with longitudinal soil removal. At smaller width the slop cut is removed by excavator – dragline or excavator with backhoe, which is placed on the slop top and removes soil with its further loading into transport vehicle or into disposal.

Excavator can be also used for slop removal at big widening and depth. In this case excavator with front shovel can be used, developing a tiered slope with further loading into vehicles.

After the cut slops developed into depth up to the existing road edge mark the cut deepening up to the design mark is started.

By that time traffic should be stopped along the main road and transferred on bypass or the traffic is organized along one side of carriage way part. The pavement is taken off.

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Deepening works are executed by scrapers or bulldozers. Work technology practically does not differ from the road construction works.

4.3.Embankments are widened with the soil reservation on slops equal to 5- 10cm in order to be limited with soil cutting out while leveling. In the case of vegetation soil placing on slops the reservation for leveling is not provided.

Cut slops of 2 m depth and embankments of 2m height at slop steepness 1:3 and 1:4 are leveled by motor grader. First of all slop is finished at upper edges by one or two motor grader pass. If slops wide motor grader levels the rest part while passing lower edges.

At embankment height and depth up to 4m slops are leveled by hanged special slop levelers on track tractors or by bulldozers. Wherein upper slop part is leveled by bulldozer with put down slop leveler and then lower part is finished by raised slop leveler.

Excavator –dragline is used at high embankment height and cuts depth. Scraper is fastened to its rod at firm soils and trough is fastened at soft ground.

While slops finishing by excavator there is projected the line of their traffic on 2.5-2.8 m from embankment edge.

For slops leveling an excavator with telescopic boom is applied. Firest the upper slop part is leveled at that excavator moves along road profile on the distance of 1.5-1.8 m from edge. Then there is made the pass to the same section on the distance of 0,5 m from edge with the help of excavator boom leveling the lower slop part. On bottom excavator levels the slop of 7m width for two passes. Scraper moving from top to bottom cuts the soil, which rolls down along the slop. Excavator with telescopic boom efficiency 1,3 times as excavator of dragline type. Excess of soil at slop bottom is cleaned by motor grader and removed.

High embankment slops and deep cuts sometimes are leveled by excavator equipped with two-shaft scraper – leveller.

4.4.Roadbed slop protection with account of natural factor affect and presence of local materials suitable for protection works.

In road construction there are applied the following techniques of roadbed for slops protection.

1.Mechanized sowing of perennial herbs is applied for protection of embankment slop and cuts with working marks not more that 3m. Method is used during construction of roadbed from any soils at favorable conditions for grass growing.

Hydrosowing of perennial herbs is used for protection of 24 m width slop without applacation of vegetation soil.

2.Ramp is used for slop protection against running water at its slow low.

3.Airspray is used for protection of roadbed slop of the height more that 2m and bid slop steepness of soil with high intensity of weathering.

4.Courses from reinforced soil is applied for slop protection from weathering during the construction or during the first year of roadbed service.

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6.Reinforced concrete slabs are applied for slops protection on the area of intensive water affect.

7.Synthetic materials are applied for local and total stability increase.

8.Synthetic materials are applied for local and total stability increase.

Mechanized sowing of perennial grass.

Mix of seeds consists of three biological groups. 1) bunch grasses, timothy, fescue grass, wheatgrass broadleaf and Siberian, couch grass etc. 2) rhizomatous – red fescue, meadow grass, quitch; 3) legumes-clover, lucerne, melilot, holy clover, etc.

Slop surface subjected to stabilization by grasses is to be loosen into 10-15cm depth for better adhesion with vegetation soil.

Hydrosowing

Working mix for hydrosowing consists of seeds of perennial grasses, mineral fertilizers.

Film forming materials: bitumen emulsions, latexes.

Working mix is distributed by two vehicle passes: during the first one there is distributed half of it, and then – the rest.

Turfing

а) continuous flat.

Local greensward is used if possible. Greensward width is from 6 up to 12 cm in dependence of depth, thickness and strength of grass root system. Length and width of some sod covers and soft cover strips is 25х40, 20х50 and 40х60 cm.

Greensward is cut and placed on slops by greensward placer at the height up to 4m. Turfing is started from the bottom of slop by horizontal rows along the whole length.

b) squared turfing.

Squared turfing needs smaller amount of greensward and it is laboriousness. Checks have the size not more than 1.5х1.5 m, there are filled with soil and sowed with grasses. Checks are placed by greensward strips of 15 cm width and 2-3m length (fig. 4.4).

Turfing is started from embankment bottom along which three greensward strips are put. On slop strips are put along the two mutually perpendicular directions under the angle of 45о towards horizontal slop surfaces. One greensward strip is put along the embankment edge. The lower greensward strip is embedded into soil on 10cm and closed up soil and then tamped into one level with earth surface.

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Fig. 4.4. Slope pitching with squared turfing

Drip irrigation

Materials of drip irrigation:

- Gunned material and gunite is used at plane and steep slop surface and possibility of landfall.

The structures finished by drip irrigation are divided into light-weighed of 25mm thickness, average -40-60mm, reinforced up to 100mm with metal lattice

Before drip irrigation slop surface is cleaned from dust and mud by water or water-air jet of watering machines, cement gun, concrete gun – machine.

Reinforced soil

Soil mixes treated by bindings are prepared in mixer and delivered on the operation place by trucks. Sandy and sandy loan mixes are used for finishing.

Mix is delivered onto surface and consolidated by excavator –dragline with special rigging equipment. Leveler on tractor T-100M can be used instead of excavator-dragline. Thickness of the course is 10cm. Consolidated soil course on slop is treated by watering machines during 2-10 days.

Material consumption is 100м3 of soil: concrete – 2 t, 2t of bitumen emulsion.

Prefabricated lattice structures

Prefabricated structure cells are filled with monolithic concrete, crashed stone, reinforced soil, vegetation soil with grasses sowing and other materials.

Technological process includes the following operations: slab leveling and compaction, transporting and loading of prefabricated materials, assembling of prefabricated horizontal beams, assembling of prefabricated structure elements, packing of cells by materials.

Reinforced concrete slabs

Slabs are placed on gravel, crushed stone or sandy bed beginning from slop bottom by truck crane. Protuberance of some slabs should not be more than 1cm.

Synthetic materials are used in combination with other types of strengthening – biological, bearing, protective or isolated.

If synthetic materials are combined with biological types of strengthening the road bed are laid directly onto slop surface or onto vegetation soil.

In the first case there is created solid grass cover.

In the second case synthetic material prevents grass washout and protects slop against erosion for the period of grass cover formation and it services as temporary element.

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