RU2618108C2 - Drainage system on permafrost soils - Google Patents

Abstract

FIELD: mining.

SUBSTANCE: drainage system on permafrost soils refers to the construction of earthworks in difficult climatic and geotechnical conditions and is intended for surface and ground water discharge mainly on permafrost soils and in areas of deep seasonal thawing. The drainage system at the permafrost soils contains an upper 2, lower 1 longitudinal trenches made outside the drained territory and filled with coarse-pored fractional draining soil, watertight barrier 3, reinforced shield 4, heat protection shield 5 and waterproof layer 6. The upper longitudinal trench 1 is located directly behind the lower longitudinal trench 2 below the slope of the mountainous terrain 7 with forming of a single stepline trench 12 and formed in an upper part of the seasonal thawing 10 layer. Lower longitudinal trench 2 is formed over the entire depth of seasonal thawing layer 10. Watertight barrier 3 is laid on the side stepped back 13 of a single trench 12, a reinforced shield 4 is laid on the top of it around the perimeter of the single stepline trench 12. A coarse-pored fraction drainage soil of the lower longitudinal trench 2 is wrapped with reinforced shield 4 with forming the drain 14. Lower longitudinal trench 2 at the level of a step 15 of the single stepline trench 12 is covered with heat protection shield 5 above which a waterproof layer 6 is laid to the level of the drained area relief. A waterproof geosynthetic woven material is selected by way of the watertight barrier, and a geosynthetic nonwoven material is selected by way of reinforced shield.

EFFECT: increased maintenance-free service life of the drainage system up to subgrade rearmament landmark duration due to permafrost soil delimitation preservation and seasonal thaw depth, located in the mountainous part of the relief within the drained area, and in natural conditions.

3 cl, 1 dwg

Description

The invention relates to the field of construction of earthworks in difficult climatic and engineering-geological conditions and is intended for the release of surface and groundwater mainly on permafrost soils and in areas of deep seasonal thawing.

Often, the main reason for the loss of the bearing capacity of earthworks in difficult climatic, engineering, geological and permafrost conditions is the deformation due to the natural weathering of rocks located in the upland part of the relief (slope) within the drained territory, which leads through 10- 12 years of operation to increase the depth of seasonal thawing of these soils. One of the reasons for thawing of icy soils and underground ice, which leads to deformations of the soil base of the subgrade, is their overmoistening due to the absence or malfunction of drainage and drainage systems.

As a result of waterlogging, the temperature-humidity regime in the soil mass is disturbed. The temperature of seasonal thawed soils rises, at the border with permafrost soils, the integrity of the massif is violated, the border of permafrost soils decreases, depressions are formed that are filled with moisture, soils lose strength. Under the action of the static load of the subgrade, deformation of the sedimentation of the soil of the base and subgrade occurs. As a result of the settlement of the subgrade, a distortion of the railway track profile occurs, which causes a violation of the safety and uninterrupted movement of trains.

To prevent waterlogging and deformation of soils of the subgrade base, various drainage structures are arranged to discharge surface and groundwater using, for example, drainage systems and drainage systems: ditches, anti-ice "thermal" and "permafrost" belts draining slots from sorted rock soil and others.

The problem of the known drainage facilities lies in the short life of the drainage facilities, amounting to 5-7 years, during which the subgrade is in a stable condition.

In the subsequent period, the drainage facilities become inoperable, and therefore, for the period of the stage re-equipment of the railway, their repeated repair is required.

Known drainage system on permafrost soils on a slope, the principle of operation of which is based on the preservation of permafrost soils from thawing [patent for invention of the Russian Federation No. 2152483, IPC ⁷ E02D 31/02, E02B 3/18, F25D 21/00 1998. A method of preventing ice formation on slopes in snowy areas of permafrost. Belyakov A.E., Babello V.A., Petrov BC Chita State Technical University. Stated July 27, 1998. Publ. 07/10/2000, Bull. No. 19. - 11 pp.].

The drainage system on permafrost soils contains a drainage trench and a line of drainage pipes.

The drainage trench is an ordinary trench, which is made outside the drained territory of the subgrade of the railway track on the slope of the mountainous part of the relief along the railway track to the depth of the seasonal thawing layer.

The drainage pipe line consists of vertical drainage pipes and a longitudinal drainage pipe. Each vertical drainage pipe is installed in a drainage trench in the upper part of the trench located on the slope of the upland part of the relief to the depth of the seasonal freezing layer. Vertical drainage pipes are connected in the upper part by a longitudinal drainage pipe into a single highway.

In the drainage trench, in its lower part, a waterproof screen is made to a depth below the depth of the seasonal thawing layer.

The drainage trench is filled with large-pore drainage material, such as crushed stone and sand.

The device operates as follows.

During negative temperatures, under the influence of gravity and hydrostatic pressure, underground permafrost groundwater flows from the upstream side through cracks in soils into a longitudinal drainage pipe and is diverted by it outside the drained territory, for example, outside the drained territory along the subsoil zone of the subgrade of the railway track.

The waterproof screen prevents the penetration of groundwater into the drained territory at the base of the subgrade of the railway track.

Thus, most of the underground permafrost groundwater is removed from the soils of the upland part. As a result, the debit of the flow of groundwater to the drained territory near the subgrade of the railway track decreases. At the same time, the filtration effect of groundwater on the subgrade of the railway track is reduced, the temperature and humidity conditions in the subgrade of the subgrade are equalized, and as a result, further thawing of underground ice is stopped.

In the initial period of 2-3 years after the construction of the known drainage device, the probability of receipt of permafrost ground water and, accordingly, thawing of permafrost reaches about 60-70%. With this amount of permafrost thawing, the probability of soil deformations at the base of the subgrade is about 20-30%.

The well-known drainage system is working properly all of its standard life, which is 5-7 years.

Over time, the drainage pipes of the system become clogged, which reduces the rate at which they collect water. Due to a decrease in the speed and pressure of water, the collection, removal and drainage of the upland part of the relief is significantly slowed, which leads to disruption of the drainage system. A decrease in the flow rate of water causes its faster freezing in pipes, which leads to waterlogging of the soil base of the subgrade and violation of the temperature-humidity regime in them. As a result, thawing of permafrost soils of the drained territory occurs, violation of the integrity of the massif on the border with permafrost soils, cracks form that are filled with moisture, soils lose strength, which leads to uneven deformations of the subgrade.

This is due to the difference in the temperature regime in trench soils and in the soils of the seasonal thawing layer, which leads to an increase in the depth of seasonal thawing of these soils and a violation of the integrity of the massif on the border with permafrost soils. The difference in temperature conditions leads to degradation of permafrost, deformation of the drainage system and subgrade, which begin 2-3 years after the start of operation of the drainage system.

The occurrence of deformations of the subgrade leads to the need to repair the drainage system after 5-7 years of operation of the system, while the standard non-repairable service life of the subgrade of the railway track is 10 years.

The advantage of the well-known drainage system on permafrost soils is a good non-repairable service life equal to the standard service life of 5-7 years. This is due to ensuring compliance with the design parameters of the collection and drainage of the supra-permafrost underground water entering the drainage system from the drained territory during its standard service life of 5-7 years.

However, the standard service life of the known drainage system is less than the unrepaired service life of the subgrade of the railway track (10 years), which is a disadvantage of the known drainage system. This is due to the occurrence of deformations of the subgrade, firstly, as a result of waterlogging and thawing of permafrost soils of the drained territory due to disruption of the drainage system and, secondly, as a result of degradation of permafrost due to differences in temperature conditions in trench soils and in soils layer of seasonal freezing due to violation of the integrity of the seasonal freezing layer.

The closest in technical essence is a drainage system on permafrost soils, the principle of operation of which is based on the preservation of permafrost soils from thawing [patent for invention of the Russian Federation No. 2449084, IPC EV 02/11 (2006.01). Application 2010133853/03, 08/12/2010. Drainage system / Zhdanova S.M., Gorshkov N.I., Voronin V.V., Serenko A.F. Federal State Budgetary Educational Institution of Higher Professional Education "Far Eastern State University of Railway Engineering" (FENU) (RU). Publ. 08/12/2010; Bull. No. 12. - 11 p.].

The drainage system on permafrost soils contains upper, lower longitudinal trenches and at least two transverse drainage trenches.

The upper longitudinal drainage trench is made on the slope of the upland part of the relief along the railway track within the drained territory.

A drainage pipe is laid at the bottom of the upper drainage trench, and a waterproof screen is installed in its submountain part below the depth of the seasonal thawing layer. The upper trench is made to the depth of the seasonal thawing layer and is filled with large-pore fractional drainage material.

The lower longitudinal drainage trench is made on the slope of the upland part of the relief (slope) along the subgrade of the railway track within the drained territory. It is made below the depth of the seasonal thawing layer and is filled with large-pore fractional drainage material.

The upper and lower longitudinal trenches in the drainage bands are interconnected by transverse drainage trenches, forming a drainage system. Transverse drainage trenches are made below the depth of the seasonal thawing layer and are filled in the lower part with absorbent material.

The drainage system on permafrost soils works as follows.

In summer, the upper longitudinal drainage trench intercepts free ground and surface water from a slope from the soil of a layer of seasonal thawing, which is drained by a drain pipe outside the drained territory. The waterproof screen keeps the free ground flow in the upper longitudinal drainage trench and prevents the penetration of permafrost ground water into the drained territory between the transverse trenches from the elevated part of the relief. The drained area between the transverse trenches is protected from waterlogging by groundwater.

In the pre-winter period, the soils of the seasonal thawing layer of the drained territory along the subgrade freeze unevenly due to their different thermal conductivity and depth. First, the soil of the subgrade is frozen between the transverse drainage trenches. As a result of the freezing of a large area along the subgrade, runoff of permafrost ground water from the upland part of the relief into the subsoil zone of the subgrade between transverse drainage trenches stops. This leads to an increase in the hydrostatic pressure of permafrost ground water in transverse drainage trenches.

Permafrost ground water with an increased hydrostatic pressure transfers particles of absorbent material from the transverse drainage trenches to the base of the subgrade, which cement the dusty and clay particles of the subgrade base. The soils compacted in the base and body of the subgrade form a solid monolithic structure that ensures long-term stable operation of the drainage system, which is comparable to the standard non-repairable service life of the subgrade of the railway track for at least 10 years.

Over time, the thermodynamic equilibrium in the natural-technogenic system changes, the natural natural process is violated, which leads to a decrease in the permafrost boundary and an increase in the depth of seasonal thawing of the upland part of the relief (slope) within the drained territory. An increase in the depth of seasonal thawing leads to the formation of bumps below the layer of seasonal thawing.

Part of the permafrost groundwater with increased hydrostatic pressure is discharged through the lower drainage trench, and the other is dispersed in irregularities below the seasonal thawing layer. Under the influence of permafrost ground water in irregularities, soils are deformed, which leads to deformation of the drainage pipe in the upper trench and a decrease in the hydrostatic pressure of permafrost ground water in it.

As a result of the decrease in the hydrostatic pressure of permafrost ground water in the upper trench, its work and the work of the transverse drainage trenches are disturbed. The lower drainage trench continues to operate normally, removing the incoming water stream from the upper trench.

The drainage system as a whole remains operational for 10-12 years. The service life of the drainage system in 10-12 years is comparable to the maintenance-free subgrade life of 10 years. The uninterrupted operation of the drainage system for 10-12 years ensures the stability of the subgrade of the railway track during this period.

The advantage of the well-known drainage system on permafrost soils is its extended service life up to 10 years, which allows the drainage system to be operated without intermediate repairs during the standard maintenance-free service life of the railway subgrade, during which the railway subgrade remains stable.

However, even the extended non-repairable service life of the known drainage system is not comparable with the stage-by-stage re-equipment of the subgrade itself, which is 20 years or more.

This is due to the lowering of the boundary of permafrost soils located in the upland part of the relief (slope) within the drained territory, which after 10-12 years of operation leads to an increase in the depth of seasonal thawing of these soils. At the same time, lowering the border of permafrost soils causes deformation of the drainage pipe in the upper trench and a decrease in the hydrostatic pressure in it and, accordingly, a disruption in the normal operation of the drainage system itself and loss of stability of the subgrade of the railway track.

The problem solved by the invention is to develop a drainage system on permafrost soils, which allows to increase its maintenance-free service life until the stage of re-equipment of the subgrade by preserving the boundaries of permafrost soils and the depth of seasonal thawing located in the upland part of the relief (slope) within the drained territory, as in vivo.

To solve the problem in a drainage system on permafrost soils containing upper, lower longitudinal trenches and a waterproof screen, the trenches are made along the subgrade of the railway track outside the drained territory, the upper and lower longitudinal trenches are filled with large-pore fractional drainage soil, the upper longitudinal trench is located directly behind the lower longitudinal trench lower on the slope of the upland part of the relief with the formation of a single step trench, waterproof The first screen is laid on the lateral step face of the single trench, over which the reinforcing screen is laid around the entire perimeter of the single step trench, the large-pore fractional drainage soil of the lower 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 is blocked by a heat-insulating screen at the level of the step of a single step trench, above which ovnya drained relief area is laid a waterproof layer.

In addition, in the drainage system on permafrost soils, a waterproof geosynthetic woven material and a geosynthetic non-woven material are selected as a waterproof screen.

The claimed solution differs from the prototype by the location of the upper longitudinal trench directly behind the lower longitudinal trench lower on the slope of the upland part of the relief with the formation of a single step trench, laying a waterproof screen on the side step face of a single trench, over which a reinforcing screen is laid around the entire perimeter of the single trench, by wrapping a large-pore drainage soil of the lower longitudinal trench with a reinforcing screen with the formation of a drain, the implementation of the upper longitudinal trench in the upper h part of the seasonal thawing layer, and the lower longitudinal trench to the entire depth of the seasonal thawing layer and covering it at the step level of a single step trench with a heat-insulating screen and laying a waterproof layer on it to the relief level of the drained territory.

The presence of significant distinguishing features indicates the conformity of the proposed solution to the patentability criterion of the invention of "novelty."

The location of the upper longitudinal trench directly behind the lower longitudinal trench below the slope of the upland part of the relief with the formation of a single step trench, laying a waterproof screen on the lateral step face of the single trench, on top of which a reinforcing screen is laid around the entire perimeter of the single trench, and the large longitudinal pore drainage soil is wrapped around it with reinforcing screen with the formation of a drain, the implementation of the upper longitudinal trench in the upper part of the seasonal thawing layer, and the lower longitudinal A trench to the entire depth of the seasonal thawing layer and its overlapping at the level of a single step trench with a heat-insulating screen and laying a waterproof layer on it to the relief level of the drained territory ensures an increase in the maintenance-free life of the drainage system on permafrost soils until the stage of re-equipment of the subgrade by storing in under natural conditions, the boundaries of permafrost soils and the depth of seasonal thawing located in the upland part of the relief (slope) within drainage territory, as in natural conditions without thawing.

This is due to the fact that due to convective heat transfer between coarse-grained fractional and permafrost soils, cold air accumulates in the drainage system and, in the radius of its influence on surrounding soils, which contacts seasonal thawed soils and lowers their temperature. As a result, the temperature is maintained in seasonal thawed soils, as in natural conditions. At the same time, the drainage system itself works without repair for a period equal to the stage of stage re-equipment of the subgrade of the railway track due to the stability of temperature conditions in the trench soils, in the soils of the seasonal freezing layer of the drained territory near the subgrade 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 lower on the slope of the upland part of the relief with the formation of a single step trench, laying a waterproof screen on the side step face of a single trench, over which a reinforcing screen is laid around the entire trench, wrapping a large-pore drainage soil of the lower longitudinal trench with a reinforcing screen with the formation of a drain, the implementation of the upper longitudinal trench in the upper part of the seasonal layer about thawing, and the lower longitudinal trench to the entire depth of the seasonal thawing layer and overlapping it at the step level of a single step trench with a heat-insulating screen and laying a waterproof layer on it to the relief level of the drained territory provides an increase in the maintenance-free life of the drainage system on permafrost until the stage of re-equipment of earthen canvases due to the preservation in natural conditions of the border of permafrost soils and the depth of seasonal thawing located in the upland lefa (slope) within the territory drained as in vivo without thawing "was not found in the prior art and does not obviously follow from it. Therefore, the above causal relationship is new, and the claimed solution meets the criteria of patentability of the invention "inventive step".

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

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

The upper longitudinal drainage trench 1 is made on the slope of the upland part of the relief 7 along the subgrade of railway track 8 within the drained territory 9 in the upper part of the seasonal thawing layer 10.

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

The upper and lower longitudinal drainage trenches 1, 2 are in contact along the entire length of the drainage system, forming a single step trench 12. Moreover, the lower longitudinal drainage trench 2 is located on a slope above the upper longitudinal drainage trench 1.

A waterproof screen 3 of waterproof geosynthetic material, such as a geospan, is laid on the lateral stepped face 13 of a single trench 12.

When this waterproof screen 3 is in contact with the slope of the upper longitudinal trench 1 from the subgrade 8 and with the soil of its bottom, as well as with the slope of the lower longitudinal drainage trench 2 from the subgrade 8.

Around the perimeter of a single step trench 12, a reinforcing screen 4 made of geosynthetic non-woven material, such as a canalan, is laid over a waterproof screen 3.

The lower longitudinal trench 2 in the lower part is filled with fractional drainage material, which is laid on the geosynthetic nonwoven material 4 and wrapped with it to form a drain 14.

The lower longitudinal trench 2 at the level of step 15 of the single step trench 12, which is the bottom of the lower longitudinal trench 1, is covered by a heat-insulating layer 5 at the level of step 15, for example, from polystyrene foam.

The lower longitudinal trench 2 is filled to the relief level 7 with a waterproof layer 6, for example, clay soil, which is laid on a heat-insulating layer 5, which forms the side wall of the upper longitudinal drainage trench 1.

The upper longitudinal drainage trench 1 is filled with fractional drainage material, such as crushed stone.

The drainage system on permafrost soils works as follows.

In the summer, surface water located in the upper longitudinal drainage trench 1 and permafrost groundwater entering the lower longitudinal drainage trench 2 flow into the drained territory 9 from the elevated upland part of the relief 7. The waterproof screen 3 prevents the penetration of these waters into the drained territory. The waters are intercepted by the lower and upper longitudinal drainage trenches 1, 2 and are diverted outside the drained territory 9 without wetting the soils of the seasonal thawing layer 10 and permafrost soils 11.

The waters in trenches 1 and 2 are wetted by the reinforcing screen 4 located in them, which, due to the capillary properties of the geosynthetic non-woven material, is constantly in a wet state. In summer and winter, evaporation of moisture from the surface of the reinforcing screen 4 occurs. Evaporation of moisture leads to a decrease in the soil temperature of the seasonal freezing layer 10 under the lower drainage trench 2 and the lower trench 1.

In addition, in the lower trench 2 between the coarse-grained soils of the drain 14 and the soils of the seasonal thawing layer 10, as well as the permafrost soils 11, convective heat transfer occurs. The presence of convective heat transfer leads to a temperature change in the fractional coarse-grained soils of the drain 14 simultaneously with the natural change in the temperature of the soils of the seasonal thawing layer 10. Moreover, the temperature regime in the soils of the drain 14 is maintained by a heat-insulating screen 5, a waterproofing screen 3, and a geosynthetic woven material 4.

Ensuring the same temperature in the soils of the drain 14 and in the soils of the seasonal freezing layer 10 leads to the preservation of thermodynamic equilibrium in the soils of the seasonal freezing layer 10 within the radius of the drainage system 12.

Thermodynamic equilibrium in soils within the radius of the drainage system 12, located in the upland part of the relief (slope) 7 and within the drained territory 9, leads to a stable state of these soils without overmoistening and disturbance of their structure.

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

The use of the inventive drainage system in 2004 led to the conclusion about its feasibility. Temperature measurements near drain 14 and in the drain, as well as in the wells in the seasonal thawing layer, showed the same temperatures in the trench soils, in the soils of the seasonal freezing layer of the drained territory near the subgrade and on the slope in the upland (upper) part of the relief.

Checking the operability of the drainage system was carried out at 3223 km of BAM railway. For this purpose, temperature measurements were carried out in the drain, in the layer of seasonal thawing on the drained territory and on the slope of the upland part of the relief during each season. The measurement results showed an average convergence of soil temperature values. The results of dynamic sounding of the upper boundary of permafrost confirm the fact that the boundary of permafrost soils remains at the level, as in natural conditions, and the depth of the layer of seasonal thawing is constant in all sections and is almost the same in all periods of measurements. Mathematical modeling of the soil cooling process using convection in time allowed us to conclude that the inventive drainage system is working, which allows us to conclude that the drainage system will be repaired without permanent service on permafrost soils until the stage of re-equipment of the subgrade by preserving the boundaries of permafrost soils and the depth of seasonal thawing, located in the upland part of the relief (slope) within the drained territory, as in natural conditions.

Claims (3)

1. The drainage system on permafrost soils, containing the upper, lower longitudinal trenches and a waterproof screen, the trenches being made along the subgrade of the railway track outside the drained territory, the upper and lower longitudinal trenches are filled with large-pore fractional drainage soil, characterized in that the upper longitudinal trench located directly behind the lower longitudinal trench below the slope of the upland part of the relief with the formation of a single step trench, waterproof screen wives on the lateral step face of the single trench, over which the reinforcing screen is laid around the entire perimeter of the single step trench, the large-pore fractional drainage soil of the lower longitudinal trench is wrapped with a reinforcing screen with the formation of a drain, the upper longitudinal trench made in the upper part of the seasonal thawing layer, and the lower longitudinal the trench is made to the entire depth of the seasonal thawing layer and at the level level of a single step trench is covered by a heat-insulating screen, above which to the level of relief fa drained area laid waterproof layer. 2. The drainage system on permafrost soils according to claim 1, characterized in that a waterproof geosynthetic woven material is selected as a waterproof screen. 3. The drainage system on permafrost soils according to claim 1, characterized in that a geosynthetic non-woven material is selected as the reinforcing screen.

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