RU2581851C1 - Method for reinforcement of linear objects on sink hole-hazardous areas - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: invention relates to construction and repair of linear objects located in dangerous karst zones, namely, to strengthening soil foundation. Reinforcement method for linear objects in dangerous karst zones consists in determination of linear object zone where formation of at least one karstic cavity with diameter no more than 4 m is possible, driveway is removed in this zone, soil layer is cut with formation of trench width of which is not less than width of driveway to provide loam content in soil from 25 % to 35 % and sand of average size ranging from 75 % to 65 % respectively , soil is treated in trench and cut soil layer is treated in pile by adding to it loam or sand depending on the initial composition of soil, after which the soil in trench and pile is treated with polifilizator “PGSZH 1” in liquid form and polifilizator “PGSP 3” in the form of powder and stirs it. Steel galvanised corrugated sheets are placed on the treated in pit soil in a projection under applied movable loads and connected, layers of geoweb are laid above on which soil layer, treated in the pile is placed, it is compacted in the pit, one more layer of geoweb is laid on compacted soil, on which soil treated in pile is laid in several layers, each layer is compacted and driveway is arranged.

EFFECT: technical result of the disclosed solution is increased safety of linear objects located in dangerous karst zones.

8 cl

Description

The invention relates to the field of construction and repair of linear facilities located in karst hazardous areas, namely to strengthen the soil base.

A known method of strengthening the soil, including drilling wells, installing injectors having a perforated portion therein, injecting injected cement slurry into the soil through injectors under pressure to ensure its hydraulic fracturing at a pressure of 5-20 atm, the injectors being not removed from it after strengthening the soil. Three injectors of different heights are installed in one well, designed for cementation of different depth layers of soil, and when three injectors are installed in the well, it is carried out in such a way that the perforated part of each subsequent injector is located below the perforated part of the previous one, without blocking it, while a cement mortar consisting of cement and water, add either bentonite clay, or liquid glass, or bentonite clay and liquid glass, or cement dust and liquid glass, or cement dust, bentonite clay and water glass or cement dust, sand fines and water glass (RF patent №2439246, E02D 3/12, published on 10.01.2012, at -. analogue).

A disadvantage of the known solution is the following. The injection of cement mortar is carried out in limited masses of soil that are not interconnected. As a result, karst failure can occur in the space between the massifs of fortified soil and the safety of linear objects will not be ensured.

A known design for perceiving the impact of the karst failure, which can form under the ballast layer during the passage of the train - "anti-karst bed". The design is a system of interconnected steel-concrete beams in which old-year materials were used - rails and sleepers (Tolmachev V.V., Leonenko M.V., Yurgin O.V. On the history of the study of karst on the Gorky railway (Section Art. The Sejm - Doskino station of the Moscow-Gorky line.) Modern problems of designing, building and operating the subgrade of railways. Sixth scientific and technical conference with international participation (November 11-12, 2009). Proceedings. Readings on the 105th anniversary of the professor G.M.Sakhunyantsa. M. 2009. - S. 81-86, - anal g).

A disadvantage of the known solution is the lack of connection of interconnected steel-concrete beams in the longitudinal direction, which could ensure the perception of the applied moving loads without realizing deformations over the dip.

The technical result, the achievement of which the claimed solution is directed, is to increase the safety of linear objects located in karst hazardous areas.

The specified technical result is achieved by the fact that in the method of enhancing linear objects in karst hazardous areas, a section of a linear object is determined where at least one karst cavity with a diameter of not more than 4 m is possible to be formed, in this section the carriageway is removed, the soil layer is cut to form under it, a pit, the width of which is not less than the width of the roadway, to ensure the content of loam in the soil from 25% to 35% and sand of medium size in the range from 75% to 65%, respectively, they process the soil in the excavation pit and cut out soil layer in the dump by adding loam or sand to it, depending on the initial soil composition, after which the soil in the excavation pit and in the dump is treated with the “ПГСЖ 1” polyphilizer in liquid form and “ПГСП 3” polyphilizer in the form of powder and mixed it, on the soil processed in the pit, is laid in the projection under the applied moving loads, steel galvanized corrugated sheets and connected, layers of geogrid are laid on top, on which the soil layer processed in the dump is laid, compacted it was in the pit, in compacted soil laid another layer of geogrid on which several layers stacked in a heap treated soil layer is compacted and arrange each roadway.

A method in which the width of the pit exceeds the width of the carriageway by at least 30%.

The method in which the carriageway is removed to a depth of 0.4-0.6 m

A method in which a soil layer is cut under a remote carriageway with the formation of a pit to a depth of 0.65-1.05 m.

A method in which a reinforced layer of at least 0.15 m thick is formed from the soil processed in the foundation pit.

A method in which the total thickness of all layers of reinforced soil is 0.8-1.2 m.

A method in which a geogrid with a breaking load of at least 120 kN / m in the longitudinal and transverse directions is used.

“PSGI 1” polyphilizer concentrate - “Consolid 44” - is a brown liquid with a characteristic odor, including quaternary ammonium compounds 25-50%, higher fatty amines 10-25%, alkoxylate less than 2.5% and other chemical compounds, pH = 4,5-5. The concentrate is completely mixed with water. The product is not explosive and does not ignite spontaneously.

PGSP 3 polyphilizer concentrate - Solidray - a mixture of cationic surfactants, is a light yellow powder with an ammonia odor, including sterilamine 25-100%, dialkyl ether triethanolammonium methyl sulfate 25-100%, isopropanol 5-10 %, as well as other complex substances with a density of 0.858 g / cu. cm, pH = 9-10, insoluble in cold water. The product is not explosive and is not self-igniting. The Solidray concentrate does not change properties over time (the product is stable) and does not decompose. The melting point of the Solidray concentrate is 50-52 ° C, the ignition temperature is more than 170 ° C.

Ready-to-use PFSA 1 polyphilizer is a yellow-brown liquid with a characteristic odor, including the Consolid 44 concentrate mixed with water in a 1: 4 ratio. It is completely dissolved in water. The product is not explosive and does not ignite spontaneously.

Ready-to-use PGSP 3 polyphilizer is a gray powder, does not change properties over time (the product is stable) and does not break up. The composition of the ready-to-use "ПГСП 3" includes:

- Solidray concentrate - a mixture of cationic surfactants;

- cement (in accordance with GOST 31108-2003, GOST 10178-85);

- lime (in accordance with GOST 9179-77, GOST 22688-77, GOST 4.204-79);

- blast furnace slags (in accordance with GOST 3476-74);

- sludge metallurgy;

- fly ash (in accordance with GOST 25818-91).

Karst is a combination of natural processes and phenomena caused by the dissolution of rocky rocks, which results in changes in the structure and condition of these rocks, the formation of a system of interconnected cavities, highly fractured zones in these rocks, decompaction zones in the soils covering them and the associated deformations of the earth surface and foundations of structures (dips, subsidence, karst subsidence, etc.). Soluble (karst) rocks are carbonates (limestone, dolomite, chalk), sulfates (gypsum, anhydrite), chlorides (rock, potassium salts). In the first case, karst is called carbonate, in the second - sulfate, in the third - chloride (hydrochloric). Currently existing karst cavities in these rocks can develop to critically dangerous sizes in several decades. The rate of dissolution of salt rocks is hundreds of times higher than sulfate. As a result, in the areas of salt karst, the cavity can re-form and develop to critically dangerous sizes even within a few months (especially with unacceptable technogenic influences). Karst cavities can intensively develop not only by dissolution, but also due to other processes (partial or complete collapse of the roof of the cavity, suffusion, underground erosion, etc.). In this regard, not every discovered (without special research) karst cavity should be considered dangerous. In the case of the presence of water-saturated sands in the cover soil stratum under certain conditions, these sands can be carried out (suffusion) into the lower cavities or fractured zones with the formation of intermediate cavities and decompaction zones in the cover thickness with their subsequent exit to the surface in the form of dips, subsidence, local subsidence . Such a process is karst-suffusive. It can become significantly more active due to unacceptable technological impacts on the geological environment (for example, due to unsatisfactory functioning of drainage and culvert facilities). The above processes have a significant impact on the reliable functioning of linear objects located in the zone of karst-hazardous surface areas.

Data for determining the likelihood of occurrence of karst cavities are obtained during engineering and geological surveys of karst areas, including surveying and decoding of space and aerial photographs. In this case, surface manifestations of karst are established. Using geophysical exploration, larger karst cavities, zones of increased fracturing, cavernousness and watering of rocks, as well as tectonic faults and decompaction zones in the cover layer are revealed.

If there are several cavities in a certain area, then the method is used within all cavities.

The inventive method of enhancing linear objects on karst hazardous areas can be used for the following linear objects - roads, railway lines, runways, tram lines, etc. The carriageway of linear objects for the proposed method includes:

for railways and tram tracks - the upper structure of the track (rails, sleepers and ballast);

for roads - road surface;

for runways - coating.

If the diameter of one karst cavity exceeds 4 m, then this method will not ensure the achievement of a technical result, since deformations of the roadway of linear objects will occur.

If the width of the pit will be less than the width of the carriageway, then the bearing capacity of the constructed structure will be insufficient to ensure traffic safety.

If the loam content in the soil is less than 25% or more than 35%, then the strength of the strengthened soil will not be achieved, sufficient for the safe passage of the moving load.

If the sand content of medium size according to GOST 25100-2001 is less than 65% or more than 75%, then the necessary strength of the strengthened soil will not be achieved.

Other types of soils are unsuitable for strengthening by their physical and mechanical properties.

Processing of soil containing loam and medium-sized sand with liquid polyphilizers and in the form of powder leads to an increase in soil strength.

If the loam is characterized by a moisture content at the yield strength w _{L of} more than 0.28, the necessary soil strength will not be achieved.

Additives are distributed evenly over the thickness and width of the reinforced layer. The water flow rate to bring the soil (mixture) to the optimum humidity according to GOST 22733-2002 (Soils. Laboratory method for determining the maximum density) is determined by the formula

where M is the mass of soil (mixture); w ₁ - the natural moisture content of the soil (mixture),%; w ₂ - optimal soil moisture (mixture),%.

The simultaneous use of joined galvanized steel sheets, which are laid on the ground processed in the pit in the projection under the applied moving loads, and several layers of the geogrid, between two of which a layer of the treated soil of the claimed composition is laid, leads to the joint work of the structure. The geogrid layers located at the bottom of the reinforced layer reinforce this layer and work in tension. In the upper part of this layer, reinforcement is not required due to the compression of the soil. In the cells of the geogrid, meshing of the fortified soil is realized. Coupling occurs due to the adhesion of reinforced and compacted soil to the geogrid. The soil located in the corrugations of galvanized steel sheets also engages with them. The deformation is hindered by high strength and low flexibility of the geogrid.

The projection under the attached moving loads is a geometric reflection of the position of the moving loads on a plane passing at the bottom of the pit.

An example of a specific implementation for a linear object - a railway track

A method for reinforcing the basement in karst hazardous areas is described, in which a layer of soil with liquid and powder additives of reinforcing compounds is arranged under the ballast to prevent rolling stock and ensure the safety of train traffic when a karst dip is formed up to 4 m in diameter. For what:

- the reinforced soil layer is reinforced with geogrid layers and galvanized steel corrugated sheets;

- the liquid additive is the "PSG 1" polyphilizer, which includes the "Consolid 44" concentrate mixed with water in a ratio of 1: 4;

- the powder additive is a PGSP 3 polyphilizer containing Solidray concentrate, cement, lime, blast furnace slags, metallurgical sludge, fly ash, etc .;

- in the hardened layer, mixtures of soils containing 30% loam, characterized by humidity at the yield strength w _L = 0.28, and 70% sand of medium size, in which liquid and powder additives are added, are used; - the consumption of ПГСЖ 1 "(concentrate" Consolid 44 ") is 1.2 l / m ³ , the consumption of" ПГСП 3 "is 54 kg / m ³ , additives are distributed evenly over the thickness and width of the reinforced layer;

- a reinforced soil layer is placed at a depth of 0.5 m below the base of the sleepers;

- on the reinforced layer have a ballast layer;

- the distance from the top of the ballast layer to the level of the curb should not exceed 0.6 m, a layer of rubble is placed on the curb;

- the thickness of the reinforced soil layer should be 1 m, the slope at the top of the layer should be equal to 0.04 towards the side of the road, the layer width at the single-track section should be equal to 6.5 m, at the double-track under one track - 5.2 m, the distance from the track axis to the edge of the layer from the side of the double-joint at the double-track section should be (in _mp - 0.15 m) / 2, where in the _MP - the width of the double-blast, m;

- use steel galvanized corrugated sheets 1160 mm wide, 2000 mm long, 5 mm thick, corrugation height 50 mm, corrugation distance 150 mm, corrugations oriented along the long side of the sheet;

- corrugated sheets are placed in two rows in the projection under the rail threads symmetrically relative to the axis of the track onto a layer of unconsolidated reinforced soil with a thickness of 0.15 m;

- on the short sides of the sheet holes should be arranged with a diameter of 24 mm in two rows through 125 mm, the sheets are joined together by an overlap with bolts;

- the geogrid has mesh sizes of 50 × 50 mm, a breaking load of at least 120 kN / m in the longitudinal and transverse directions, an elongation at break of not more than 3% in these directions; the geogrid is laid in two layers in the lower part of the reinforced layer on top of the corrugated sheets, the geogrid stripes are oriented perpendicular to the longitudinal axis of the path with an overlap of at least 0.3 m, another geogrid layer with the indicated overlap of the bands is placed 0.2 m above these two layers.

The main works to strengthen the basement in karst hazardous areas:

- ballast cut to a depth of 0.5 m below the base of the sleepers;

- cleaning of rail-sleeper grid;

- cutting the soil layer with a thickness of 0.85 m to a width of 6.5 m on a single track and 5.2 m on a double track with removal to a dump on an equipped site;

- soil planning in the pit and dump;

- making loam / sand and reinforcing additives in the pit to create a reinforced layer with a thickness of 0.15 m with loosening of the soil;

- laying of corrugated sheets with their connection;

- laying of the geogrid in two layers;

- the introduction of loam / sand and reinforcing additives on the site in the soil of the dump to a layer thickness of 0.2 m with loosening;

- soil transportation with additives to create a layer with a thickness of 0.2 m from the site to the pit;

- soil compaction in the pit;

- laying of the upper layer of the geogrid;

- the introduction of loam or sand (depending on the initial composition of the excavated soil) and reinforcing additives on the site into the soil of the dump to a layer thickness of 0.3 m with loosening;

- soil transportation with additives to create a layer with a thickness of 0.3 m from the site to the pit;

- soil compaction with additives in a layer 0.3 m thick in the pit;

- soil transportation to create a layer with a thickness of 0.35 m from the site to the pit;

- introduction of loam / sand and reinforcing additives in the pit with loosening;

- soil compaction with rollers;

- laying of rail-sleeper lattice;

- unloading crushed stone and performing track lifting with straightening and tamping operations in three stages.

Claims (8)

1. A method for enhancing linear objects in karst-hazardous areas, which consists in determining a section of a linear object in which at least one karst cavity with a diameter of not more than 4 m is possible, in this section the carriageway is removed, a soil layer is cut to form under it a pit, the width of which is not less than the width of the roadway, to ensure the content of loam in the soil from 25% to 35% and sand of medium size in the range from 75% to 65%, respectively, the soil is processed in the pit and cut I soil in the dump by introducing loam or sand into it, depending on the initial composition of the soil, after which the soil in the foundation pit and in the dump is treated with the PSGI 1 polyphilizer in liquid form and the PGSP 3 polyphilizer in the form of powder and mixed, onto the treated in a foundation pit, the soil is laid in a projection under the applied moving loads, steel galvanized corrugated sheets and connected, layers of geogrid are laid on top, on which a layer of soil processed in the dump is laid, it is compacted in the foundation pit, on the seal One more layer of the geogrid is laid on this soil, onto which the soil treated in the dump is laid in several layers, each layer is compacted and a roadway is arranged. 2. The method according to p. 1, characterized in that the width of the pit exceeds the width of the carriageway by at least 30%. 3. The method according to p. 1, characterized in that the roadway is removed to a depth of 0.4-0.6 m 4. The method according to p. 1, characterized in that the soil is cut out under a remote carriageway with the formation of a pit to a depth of 0.65-1.05 m. 5. The method according to p. 1, characterized in that a fortified layer of at least 0.15 m is formed from the soil processed in the foundation pit. 6. The method according to p. 1, characterized in that the total thickness of all layers of reinforced soil is 0.8-1.2 m 7. The method according to p. 1, characterized in that they use a geogrid with a breaking load of at least 120 kN / m in the longitudinal and transverse directions. 8. The method according to p. 1, characterized in that they use loam with moisture at the yield strength w _L not more than 0.28.