RU2761272C1 - Drainage system for stabilising the roadway on thawed soft soils - Google Patents

Abstract

FIELD: construction of roads.

SUBSTANCE: invention relates to the field of construction of earthworks in complicated natural and climatic and engineering and geological conditions. The drainage system for stabilising the roadway on thawed soft soils comprises an upper and a lower longitudinal trenches and a waterproof screen. The trenches are made along the subgrade outside of the drained area. The upper and lower longitudinal trenches are filled with coarse-pored fractional drainage soil. The upper longitudinal trench is located directly behind the lower longitudinal trench higher uphill from the high part of the relief, forming a single stepped trench. The waterproof screen is laid on the side stepped face of the single trench, wherein a reinforcing screen is laid along the entire perimeter of the single stepped trench on top of said screen. The coarse-pored fractional drainage soil of the upper longitudinal trench is enveloped in a reinforcing screen, forming a drain. The upper longitudinal trench is made in the upper part of the seasonal thawing layer. The lower longitudinal trench is made to the full depth of the seasonal thawing layer and is overlapped with a heat insulation screen at the level of the step of the single stepped trench, wherein a waterproof layer is laid above said screen to the level of relief of the drained area. On the low side, additionally, in the near-bottom zone of the subgrade, a heat insulation screen is laid under a waterproof layer on the daylight surface. The waterproof layers on both sides of the roadway constitute dewatering berms made of clay soils.

EFFECT: increase in the maintenance-free service life of the drainage system until the time of planned re-equipment of the roadbed.

1 cl, 1 dwg

Description

The invention relates to the field of construction of linear structures on permafrost and in areas of deep seasonal freezing in difficult engineering and geological conditions and is intended primarily for the release of groundwater, in particular, in conditions of possible global warming.

The main reason for the loss of stability of the roadbed in difficult climatic, engineering-geological and permafrost-soil conditions is the deformations of the abyssal-ice nature. In most cases, this is due to the absence of small artificial structures at the intersection of the roadway with small local logs, sinuses, depression depressions located in weak-drainage areas of the terrain. In such areas, due to a small (less than 1.5%) longitudinal slope, as a rule, there is a malfunction of the drainage devices located along the embankment. In the event of a malfunction of the drainage devices, surface and ground waters from the slope flow into the bottom zone of the embankment along low relief areas such as the mouths of logs, sinuses, depression depressions. In summer, water freely filters through the body of the roadway, without significantly violating the integrity of the soil massif. During the period of the onset of negative temperatures, a violation of the water-thermal regime occurs due to uneven freezing of the bottom zones of their narrowing of the living section of the water flow and the occurrence of a pressure of the water flow due to the narrowing of its living section. As a result, as a rule, in the pre-winter period, at the beginning of soil freezing at the intersection of the roadway with local logs, sinuses, depression depressions with a high water pressure, moisture is squeezed out and soil particles are carried out through the draining soils of the roadway and base.

With the complete freezing of the bottom zones of the roadway, the voids in the body of the roadway are filled with water on the submontane side, which, when frozen, increases in volume and forms abyssal humps. In this case, subsidence of the base occurs due to the squeezing of water from the base soils into the bottom zones of the embankment, depressions are formed, which are filled with water, the soils lose strength, and the earthen structure is deformed. In the spring, during thawing, under the influence of a static load from the roadbed and vibrodynamic load from a train load, there is a reverse osmotic "suction" of squeezed water from the bottom zones of the subgrade into its base, which again overmoistens the base soils, they lose strength, and the sediment deforms due to the consolidation and plastic extrusion of soils of the base of the subgrade, which lasts for decades.

As a result of the settlement of the road bed, the profile of the railway track is distorted, which causes a violation of the safety and uninterrupted movement of trains.

To prevent waterlogging and deformation of the soils of the base of the roadway, various drainage devices are arranged, aimed at the release of surface and groundwater using, for example, traditional drainage systems and drainage systems: ditches, anti-ice "thermal" and "frozen" belts, drainage slots from sorted rocky soil, trays and others.

The use of a drainage system leads to soil hardening due to the collection and removal of water and, as a result, stabilization of the roadway on thawed soft soils, as well as an increase in the service life of the drying devices themselves.

However, in the process of repeated collection of water, the drying devices become clogged and become inoperable, and therefore, during the period of the stage-wise rearmament of the railway, their repeated re-arrangement is required during the standard service life of the roadway.

The problem lies in the short-term service life of the drying devices, due to their periodic clogging, which requires, accordingly, periodic re-arrangement of the drying devices during the standard service life of the roadway itself.

Known drainage system for stabilizing the roadway on thawed soft soils, based on the unhindered release of surface and groundwater through the body of the roadway, described in patent No. 3553738, (Patent holder - JSC "Russian Railways"; authors Krapivny V.A., Zhdanova S.M. ., Voronin V.V., Serenko A.F.)

The system consists of longitudinal and transverse trenches and dewatering berms. The longitudinal trench is made from the upland side along the slope of the roadway. Transverse trenches are made on both sides of the roadbed, from the upland and submontane sides, in one cross section and are connected to the upland longitudinal trench.

The transverse trenches are filled with crushed stone to the depth of seasonal freezing; on top of them is laid heat-insulating material, for example, expanded polystyrene.

Water-squeezing berms are made of finely dispersed clay soil in the bottom zones of the roadway, and in the locations of the transverse trenches they are laid on transverse drainage trenches.

The drainage system works as follows.

In spring, ground and surface water is collected in a longitudinal trench and is completely discharged outside the roadway through adjacent culverts: for example, bridges, pipes or filter embankments, which leads to drainage of the upland area near the roadbed.

In the event of an overflow of a longitudinal trench, water enters the transverse trenches, freely filtered through the soils of the roadway body, then it is diverted along the transverse trenches to the submontane side of the roadway. At the same time, the area near the roadbed is drained.

In the pre-winter period, ground and surface water is also collected by a longitudinal trench and discharged to adjacent culverts. With the onset of negative temperatures as a result of contact of the soil with cold ambient air in a longitudinal trench, uneven freezing of soils occurs due to their dimensional diversity and various physical properties.

At the same time, in transverse trenches, thanks to the insulating layer and berm, the soils maintain a positive temperature. In this case, the soils of the base of the body of the roadway are in a thawed state.

Uneven freezing of soils in a longitudinal trench leads to the accumulation of groundwater in the lower part of the relief in the bottom zone of the roadway and, as a consequence, to the occurrence of a pressure regime of groundwater.

Under the action of the pressure, the groundwater of the longitudinal trench enters the insulated transverse trenches, from which, through the thawed soils of the base of the roadway, enter the insulated transverse trenches. Of these, water is gravity diverted outside the roadway, which leads to drainage of the area near the roadway and the elimination of deformations.

In addition, the groundwater that has entered the basement soils from the upland side is completely removed from it. Thus, the base of the roadway maintains a constant water-thermal regime. At the same time, free filtration of ground water through the soils of the roadway is ensured, regardless of the season of the year.

The process of drainage of ground and surface water from the upland side of the roadway to the upland side continues until the ground water of the slope freezes completely, which leads to its absence in drainage systems, thereby ensuring continuous operation of the drainage drainage systems themselves on thawed weak soils as a whole for 5- 7 years.

However, after 5-7 years, draining drainage systems become clogged, which disrupts their normal operation. To restore normal operation of the drainage drainage systems, it is necessary to periodically carry out major overhauls.

Thus, the disadvantage of the known drainage system for stabilizing the subgrade on thawed weak soils consists in the repeated complete reorganization of the drainage drainage systems during the standard overhaul life of the subgrade itself.

The closest in technical essence and the expected result is a drainage system for stabilizing the subgrade on thawed weak soils and releasing surface and ground waters described in Patent No. 2618108 RF, (Patentee - (FVGUPS), Zhdanova S.M., Tukmakova O.V., Serenko A.F.)

The drainage drainage system is a two-stage drainage upper and lower longitudinal trench with large-porous fractional drainage soil, a watertight layer, a reinforcing layer, an insulating layer, and dewatering berms.

The lower longitudinal trench is located in the upland part of the relief, along the slope of the roadbed, directly behind the upper longitudinal trench up the slope, to form a single stepped trench with the upper trench.

The waterproof layer is made, for example, of geospan TN and laid on the side step of a single trench.

The reinforcing layer is made, for example, of a synthetic non-woven material (SNM) and is laid over the waterproof layer and around the entire perimeter of the stepped trench.

In this case, the lower longitudinal trench is made above the depth of the seasonal thaw layer, and the upper longitudinal trench is below the seasonal thaw layer.

In the section of the upper and lower trenches, a step is formed with the formation of a stepped trench.

The heat-insulating layer was laid at the level of the step in the upper part of the lower trench over the reinforcing layer of SNM.

The upper trench along its perimeter is reinforced with fractional rock soil, for example, rubble.

Water-squeezing berms are made of finely dispersed clay soil in the bottom zones on both sides of the roadway.

Thus, the drainage drainage system is reinforced with a waterproof layer, a reinforcing layer, an insulating layer and filled with fractional rocky soil, for example, crushed stone.

The drainage system works as follows. In the spring, ground and surface water is collected by longitudinal trenches, upper and lower, located on the upland side along the slope of the roadway and is completely diverted outside the roadway through adjacent culverts: for example, bridges, pipes or filter embankments, which leads to drainage of the upland area near the roadway.

In case of overflow of the upper longitudinal trench, water enters the lower trench thanks to the waterproof screen, freely filtered into the lower trench and is diverted to the submontane side of the roadway. At the same time, the area near the roadbed is drained.

In the pre-winter period, ground and surface water is also collected by the upper and lower longitudinal trenches and diverted to adjacent culverts. With the onset of negative temperatures as a result of the contact of the soil with cold ambient air in the upper longitudinal trench, uneven freezing of soils occurs due to their diversity and various physical properties.

At the same time, in the lower trench, thanks to the heat-insulating layer and berm, the soils maintain a positive temperature, and the soils of the base of the roadway body are in a thawed state.

Under the action of the pressure, groundwater flows into the insulated lower trench, from which it is discharged without pressure beyond the limits of the roadway, which leads to drainage of the area near the roadway and the elimination of deformations.

Thus, the groundwater additionally supplied from the upland side to the basement soils is completely removed from it, it maintains a constant water-thermal regime, and provides free filtration of groundwater through the soils of the roadbed, regardless of the season of the year.

The process of drainage of ground and surface waters from the upland side of the roadway continues until the ground water of the slope freezes completely. This leads to ensuring the stability of the operation of the drying devices themselves and the subgrade on thawed soft soils in general for at least 10 years.

This leads to ensuring the stability of the operation of the drainage devices themselves and the subgrade on thawed soft soils as a whole for 10 years.

However, over time, the drainage system to stabilize the subgrade on thawed soft soils reduces the amount of water they collect. This is due to silting and stagnation of water in the subsoil zone of the subgrade due to a waterproofing layer in a two-stage drainage system during annual cyclic processes of squeezing out of the base soils in the autumn and absorbing moisture (in the form of a suspension) in the spring, which is located between the berm and the lower drainage ditch, which contributes to the lowering of the permafrost boundary and the resumption of deformations of the subgrade.

After 10 years, as a result of lowering the boundary of permafrost soils, the active zone increases, which leads to an increase in the volume of thawed soils, the drainage system ceases to cope with the release of the resulting volume of water.

Thus, the disadvantage of the known drainage system for stabilizing the subgrade on thawed soft soils is its insufficient service life, which is much less than the standard service life of the subgrade itself.

The inventive solution differs from the prototype by the location of the upper longitudinal trench directly behind the lower longitudinal trench higher along the slope of the upland part of the relief, and from the foothill side, in addition, in the bottom zone of the roadbed, by laying a heat-insulating screen on the day surface under a waterproof layer, while waterproof layers from both the sides of the roadway, which are water-squeezing berms from clay soils.

The location of the upper longitudinal trench directly behind the lower longitudinal trench higher along the slope of the upland part of the relief, as well as additional laying of a heat-insulating screen on the day surface under a waterproof layer on the submontane side in the subsoil zone of the subgrade, which on both sides of the roadway are water-squeezing berms from clay soils , will allow unhindered drainage of the bottom zone of the embankment in the late autumn period and drain water in the late autumn period outside the subgrade, and in the spring period, reverse osmotic absorption will not occur due to the absence of a freezing front, eliminated by the presence of thermal insulation, which causes the effect of osmotic "absorption" moisture.

The presence of significant distinctive features indicates the compliance of the proposed solution with the criterion of patentability of the invention "novelty".

At the same time, the drainage system itself works without repair for a period equal to the period of stage re-equipment of the roadbed of the railway track due to the stability of temperature regimes in the soils of the trench, in the soils of the layer of seasonal freezing of the drained area near the roadbed and on a slope in the upland (upper) part of the relief.

Causal relationship "The location of the upper longitudinal trench directly behind the lower longitudinal trench, higher along the slope of the upland part of the relief, and on the foothill side, in addition, in the bottom zone of the roadbed, by laying a heat-insulating screen on the day surface under a waterproof layer, while waterproof layers from both the sides of the roadway, which are water-squeezing berms from clay soils, will make it possible to freely drain water outside the subgrade in the late autumn period, and in the spring period - reverse osmotic “suction” will also be excluded by the presence of thermal insulation ”, which was not found in the prior art and does not explicitly follow from it. Consequently, the above causal relationship is new, and the claimed solution meets the criterion of patentability of the invention "inventive step".

The figure shows a cross-section of the drainage system on permafrost soils, illustrating the operability and "industrial applicability" of the claimed device.

The drainage system on permafrost contains the upper 1 and lower 2 longitudinal trenches made as a whole, waterproof 3, reinforcing 4 and heat-insulating 5 screens and a waterproof berm layer 6.

The upper longitudinal trench 1 is made on the slope of the upland part of the relief 7 along the roadbed 8 outside the drained area 9 in the upper part of the seasonal thawing layer 10.

The lower longitudinal trench 2 is made close to the upper longitudinal trench 1 to the entire depth of the layer of seasonal thawing 10, in contact with permafrost 11.

The upper and lower longitudinal trenches 1, 2 contact along the entire length of the drainage system, forming a single stepped trench 12. In this case, the lower longitudinal trench 2 is located along the slope below the upper longitudinal drainage trench 1.

On the side stepped edge 13 of a single stepped trench 12, a waterproof screen 3 is laid out of a waterproof material, for example, geospan TN (or PVC - film).

In this case, the waterproof screen 3 contacts the soil of the slope of the upper longitudinal trench 1 from the field side 7 and the soil of the lower longitudinal trench 2 from the field side.

Along the entire perimeter of a single stepped trench 12, a reinforcing screen 4 made of synthetic nonwoven material, for example, kanvalan, is laid on top of the waterproof screen 3.

The lower longitudinal trench 2 is filled with fractional drainage soil, which is laid on a synthetic non-woven material 4 and wrapped around it to form a drain 14.

The lower longitudinal trench 2 at the level of step 15 of a single stepped trench 12, which is the bottom of the upper longitudinal trench 1, is covered with a heat-insulating screen 5, for example, made of expanded polystyrene, on which a waterproof layer 6 of clay soil is laid, forming the side wall of the upper longitudinal trench 1.

The upper longitudinal trench 1 along the perimeter is reinforced with fractional drainage material, for example, crushed stone.

The drainage system on permafrost soils works as follows.

In the spring, the surface water in the upper longitudinal trench 1 and ground water coming from the upland part of the relief 7 flow down along the drained area 9 and the subgrade 8 into the culvert. Waterproof screen 3 prevents the penetration of the main flow of suprapermafrost groundwater into the drained area and into the base of the subgrade 8. In the summer, when seasonal thawing reaches a maximum, the groundwater is intercepted by drain 14 of the lower longitudinal trench 2 and is discharged outside the drained area 9, without overmoistening the soil layer of seasonal thawing 10 and permafrost 11.

The waters in the trenches 1 and 2 are wetted, the reinforcing screen 4 located in them, which, due to the capillary properties of the synthetic nonwoven material, is constantly in a wet state. In the summer and winter periods, moisture evaporates from the surface of the reinforcing screen 4. Moisture evaporation leads to a decrease in the temperature of the soils of the seasonal freezing layer 10 under the lower trench 2 and the upper trench 1.

In addition, in the lower trench 2 between the large-porous fractional soil of the drain 14 and the soils of the seasonal thawing layer 10, as well as the permafrost soils 11, convective heat exchange takes place. The presence of convective heat exchange leads to a change in temperature in the large-porous fractional soils of the drain 14 synchronously with the natural change in the temperature of the soils of the layer of seasonal thawing 10. Moreover, the created temperature regime in the soils of the drain 14 is maintained by a heat-insulating screen 5, a waterproofing screen 3 and a reinforcing screen 4 made of synthetic non-woven material.

Ensuring the same temperature in the soils of the drain 14 and in the soils of the seasonal freezing layer 10 leads to the maintenance of thermodynamic equilibrium in the soils of the seasonal thawing layer 10 within the radius of action of a single stepped trench 12.

Thermodynamic equilibrium in soils within the radius of action of a single stepped trench 12, located in the upland part of the relief (slope) 7 and within the drained area 9, leads to a stable state of these soils without waterlogging and disturbing their structure.

As a result, the soils of the drain 14 and the soils of the seasonal thawing layer 10 work as a whole, which contributes to the preservation of the integrity of these soils in natural conditions for a long time. The annual soil regime of the layer of seasonal thawing 10 to the border of permafrost soil 11 occurs naturally constantly at the same depth for a long period comparable to the period of stage-wise re-equipment of the railway.

The location of the upper longitudinal trench 1 and the lower longitudinal trench 2 and the location of the waterproof screen 3 on the side of the lower longitudinal trench on the upland side of the roadbed of the railway track, as well as additional laying of the heat-insulating screen 17 made of expanded polystyrene plates at the base of the waterproof layer 16 of the berm located on the foothill side with the subsequent laying of berm 6 from the upland side from the subgrade 8 onto the heat-insulating screen 5 to the lower longitudinal trench, and from the upland side - onto the heat-insulating screen 17 at the base of the waterproof layer of the berm 16 will allow to drain the base and bottom zones without hindrance for 1-2 years railway road bed, to strengthen the soil and eliminate deformation of the road bed.

Additional laying of the heat-insulating screen 17 made of expanded polystyrene plates at the base of the berm from the foothill side will make it possible to freely drain water outside the subgrade in the late autumn period, and in the spring period, reverse suction will not occur due to the absence of a freezing front, eliminated by the presence of thermal insulation, which causes the effect of osmotic "absorption" of moisture.

The annual thawing of soils in the layer of seasonal thawing 10 to the border with permafrost 11 occurs naturally constantly at the same depth for a long period comparable to the period of stage re-equipment of the railway and remains practically the same in all measurement periods.

Mathematical modeling of the soil cooling process using convection in time made it possible to conclude that the claimed drainage system is operable, which allows us to conclude that the maintenance-free service life of the drainage system on permafrost soils will increase until the stage of the stage re-equipment of the subgrade due to the preservation of the permafrost boundary and the depth of seasonal thawing, located in the upland part of the relief (slope) within the drained territory, as in natural conditions.

The drainage system has been implemented at 24 distances along the Eastern range of the Far Eastern Railway on the Marevaya - Zmeika stretch.

Claims (1)

A drainage system for stabilizing the roadway on thawed soft soils, containing an upper, lower longitudinal trench and a waterproof screen, while the trenches are made along the roadbed outside the drained area, the upper and lower longitudinal trenches are filled with large-porous fractional drainage soil, the upper longitudinal trench is located directly behind the lower longitudinal trench down the slope of the upland part of the relief with the formation of a single stepped trench, a waterproof screen is laid on the side stepped edge of a single trench, on top of which a reinforcing screen is laid along the entire perimeter of a single stepped trench, a large-porous fractional drainage soil of the upper longitudinal trench is wrapped with a reinforcing screen with the formation of a drain , while the upper longitudinal trench is made in the upper part of the seasonal thawing layer, and the lower longitudinal trench is made to the entire depth of the seasonal thawing layer and at the level of the step of a single stepped trench and is covered with a heat-insulating screen, above which a waterproof layer is laid to the level of the relief of the drained area, characterized in that the upper longitudinal trench is located directly behind the lower longitudinal trench higher along the slope of the upland part of the relief, and from the upland side, in addition, in the bottom zone of the roadbed, on The day surface is covered with a heat-insulating screen under the waterproof layer, while the waterproof layers on both sides of the roadway are water-squeezing berms from clay soils.

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