CN111778959A - Construction method for treating loess collapse in tunnel site area by adopting cement stabilized soil - Google Patents

Construction method for treating loess collapse in tunnel site area by adopting cement stabilized soil Download PDF

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Publication number
CN111778959A
CN111778959A CN202010468903.8A CN202010468903A CN111778959A CN 111778959 A CN111778959 A CN 111778959A CN 202010468903 A CN202010468903 A CN 202010468903A CN 111778959 A CN111778959 A CN 111778959A
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China
Prior art keywords
stabilized soil
cement stabilized
construction
soil
cement
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Inventor
王雅红
贺晓峰
胡平
刘红梅
张鸣
尹玉林
冯静
刘磊
刘毅
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Yulin Tianyuan Road Industry Co ltd
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Yulin Tianyuan Road Industry Co ltd
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Priority to CN202010468903.8A priority Critical patent/CN111778959A/en
Publication of CN111778959A publication Critical patent/CN111778959A/en
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    • EFIXED CONSTRUCTIONS
    • E02HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02DFOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
    • E02D3/00Improving or preserving soil or rock, e.g. preserving permafrost soil
    • E02D3/12Consolidating by placing solidifying or pore-filling substances in the soil
    • EFIXED CONSTRUCTIONS
    • E02HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02DFOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
    • E02D17/00Excavations; Bordering of excavations; Making embankments
    • E02D17/06Foundation trenches ditches or narrow shafts
    • E02D17/12Back-filling of foundation trenches or ditches

Abstract

The invention provides a construction method for treating loess collapse holes in a tunnel site area by adopting cement stabilized soil, wherein the loess collapse holes with larger depth are water collapse holes, and before a tunnel enters the tunnel, (1) for the collapse holes with the caliber smaller than 70cm, drainage outcrops are firstly blocked, and then the collapse holes are treated by a method of filling fluid cement stabilized soil; (2) for the crater with the caliber larger than 70cm, compacting and backfilling by using 3% of cement stabilized soil semi-rigid material; (3) for the crater with the lower half part aperture smaller than 70cm and the upper half part aperture larger than 70cm, firstly plugging the excretion outcrop, then pouring fluid cement stabilized soil into the lower half part with the aperture smaller than 70cm, and then compacting and backfilling the upper half part with the aperture larger than 70cm by adopting 3% cement stabilized soil semi-rigid material. According to the principle of ' active treatment ', the loess cave (water falling hole ') is treated by adopting cement stabilized soil before entering the hole, so that the construction quality and safe operation of tunnel engineering are ensured.

Description

Construction method for treating loess collapse in tunnel site area by adopting cement stabilized soil
Technical Field
The invention relates to the field of tunnel engineering, in particular to a construction method for treating loess collapse in a tunnel site area by adopting cement stabilized soil.
Background
Loess areas often develop loess collapse holes with different scales in the hills and the pit areas due to geological conditions of the loess areas, and the loess collapse holes are a typical engineering geological problem in the loess areas and are caused by the erosion and the corrosion of loess collapsible water and the potential effect of underground water to form blind ditches, blind holes and the like which are collectively called collapse holes. The loess collapse hole with larger depth is called as a water falling hole, the water falling hole is a loess layer which develops in a vertical joint way, and the loess on the surface layer is formed after the loess collapses or collapses under the action of surface water and underground water and the lower part is eroded by water flow.
Most of the geometrical shapes of the water falling hole are in a shape of being thick at the top and thin at the bottom, and if the water falling hole is not processed in time, geological disasters such as collapse, mud burst and the like often occur in the construction or operation stage, so that unexpected difficulties and obstacles are brought to the construction and safe operation of tunnel engineering.
Disclosure of Invention
The invention provides a construction method for treating loess collapse in a tunnel site area by adopting cement stabilized soil, which treats the loess collapse (water falling hole) by adopting the cement stabilized soil before a tunnel enters the hole according to the principle of 'active treatment', ensures the construction quality and safe operation of tunnel engineering, and receives good economic benefit and engineering benefit.
The technical scheme for realizing the purpose of the invention is as follows:
a construction method for treating loess collapse in a tunnel site area by adopting cement stabilized soil,
dividing all loess collapse holes in a tunnel site area into collapse holes with the caliber of less than 70cm, collapse holes with the caliber of more than 70cm and water falling holes, wherein the water falling holes are the loess collapse holes with larger depth, thick upper parts and thin lower parts;
the construction method for treating loess collapse in the tunnel site area by adopting cement stabilized soil comprises the following steps:
(1) for a sunk hole with the caliber of less than 70cm, firstly plugging the drainage outcrop, and then pouring fluid cement stabilized soil for treatment;
(2) for the crater with the caliber larger than 70cm, compacting and backfilling by using 3% of cement stabilized soil semi-rigid material;
(3) for the water falling hole with the thick upper part and the thin lower part, the caliber of the lower half part of the water falling hole is smaller than 70cm, the caliber of the upper half part of the water falling hole is larger than 70cm, the excretion outcrop is blocked firstly, then the lower half part with the caliber smaller than 70cm is filled with fluid cement stabilized soil, and then the upper half part with the caliber larger than 70cm is compacted and backfilled by adopting 3% cement stabilized soil semi-rigid material.
As a further improvement of the invention, the disposal method of the overboard cave comprises the following steps:
firstly, plugging a drainage outcrop for the lower half part of a water falling hole with the aperture smaller than 70cm, and then pouring fluid cement stabilized soil;
secondly, compacting and backfilling 3m of 3% cement stabilized soil semi-rigid material to form a second filling section for the upper half part of the water falling hole with the aperture larger than 70cm after the fluid cement stabilized soil is solidified into the first filling section;
thirdly, compacting and backfilling the part above the second filling section in the second step by using plain soil;
and step four, carrying out grass planting and greening on the backfilled top surface in the step three.
As a further improvement of the invention, in the second step and the third step, an excavator is adopted to carry a plate compactor for compacting and backfilling.
As a further improvement of the invention, the step three adopts plain soil layer-by-layer retreat backfilling.
As a further improvement of the present invention, said step four is followed by: and step five, arranging drainage ditches at the periphery of the backfill area in the step three to avoid the surface water from being washed again.
According to a further improvement of the invention, the mixing ratio of the fluid cement-stabilized soil is cement-soil =3:97, and the cement-soil mixture water =1: 1-1: 2.
As a further improvement of the invention, during the construction of the cement stabilized soil semi-rigid material, the top end of the water falling hole is firstly dug to be square, then the water falling hole is filled by adopting a horizontal layering method from bottom to top, the virtual pavement thickness of each layer of cement stabilized soil is not more than 30cm, and the compaction coefficient is not less than 93%.
As a further improvement of the invention, the size of the square is not less than 1.5m × 1.5 m.
As a further improvement, during construction of the cement-stabilized soil, the mixing ratio of the cement-stabilized soil is that cement-soil =3:97, and the plasticity index of the soil is not more than 17.
As a further improvement of the invention, during the construction of the cement stabilized soil, a manual matching excavator is adopted for mixing, a bucket of the excavator is utilized to pave the mixture to a site to form a paving layer, then the bucket is replaced by a flat plate type vibrating tamper, and a movable arm of the excavator is utilized to carry the flat plate type vibrating tamper for tamping and paving;
and repeating the steps until the cement stabilized soil is backfilled layer by layer to the specified elevation.
As a further improvement of the invention, during the compaction and backfilling construction of the plain soil in the third step, the loess on site is used as the filler, and the water content of the filler is manually made to reach the standard of the optimal water content; spreading the filler by using a bucket of an excavator, then replacing the bucket with a flat plate type vibration tamper for rolling, and backfilling layer by layer from bottom to top, wherein the thickness of each layer is not more than 30cm, and the compaction coefficient is not less than 93%.
Compared with the prior art, the invention has the beneficial effects that:
1. according to the principle of ' active treatment ', the loess cave (water falling hole ') is treated by adopting cement stabilized soil before entering the hole, so that the construction quality and safe operation of tunnel engineering are ensured.
2. The invention adopts the fluid cement stabilized soil to backfill the pitted holes with the caliber less than 70cm, and is based on good fluidity of the material, guaranteed quality, moderate manufacturing cost and convenient construction.
3. The proportion of cement to soil in the cement stabilized soil is 3:97, the plasticity index of the soil is not more than 17, and the water addition amount is determined according to the optimal water content determined by a compaction test.
4. The backfill thickness of the cement stabilized soil is determined to be 3m, so that the treatment quality cannot be guaranteed if the backfill thickness is too thin, and the economic cost is increased if the backfill thickness is too thick.
5. The construction machine tool used by the invention adopts the excavator with the specification not more than 300 type to carry the hydraulic flat plate type vibratory tamper, and aims to adapt to the characteristics of narrow and steep site and incapability of entering large-scale construction machinery.
6. According to the development rule of 'thick upper part and thin lower part' presented by loess caves (water falling holes), the invention treats the caves (or the lower half part of the water falling hole) with the caliber of less than 70cm by adopting a method of filling fluid cement to stabilize soil, is beneficial to completely backfilling loess small caves and forming hardening strength, avoids the defects of high cost, long period, incomplete treatment, serious damage to original landform and the like caused by the traditional construction method, and has good social benefit and economic benefit.
Drawings
FIG. 1 is a schematic view of the natural development of a water falling hole;
FIG. 2 is an enlarged view of a portion of FIG. 1;
FIG. 3 is a construction flow chart of loess collapse (water falling cave) in a treatment tunnel site area;
FIG. 4 is a flow chart of the construction of the water falling cave;
FIG. 5 is a schematic view after disposal of a overboard cavern;
FIG. 6 is an enlarged view of a portion of FIG. 5;
fig. 7 is an enlarged view of a portion a in fig. 6.
1. A lower half; 2. an upper half; 3. a tunnel; 100. a first filling section; 200. a second filling section; 210. compacting the layer; 220. a loose layer; 300. a plain soil backfill layer; 400. plugging the excretion outcrop; 500. an original earth surface; 600. the points are small.
Detailed Description
The present invention is described in detail with reference to the embodiments shown in the drawings, but it should be understood that these embodiments are not intended to limit the present invention, and those skilled in the art should understand that functional, methodological, or structural equivalents or substitutions made by these embodiments are within the scope of the present invention.
The traditional construction method of the loess collapse in the tunnel site area comprises the following steps: and (4) expanding and excavating the sinking points from top to bottom, and then backfilling by grouting or concrete layer by layer. Therefore, the original landform is excessively damaged, and the defects of high treatment measure cost, long period, incomplete disease treatment and the like exist.
The design concept of the invention is as follows: firstly, backfilling loess collapse holes in advance to avoid possible geological disasters of the tunnel in the construction and operation processes; secondly, for the caves with the caliber less than 70cm (or the lower half part of the water falling cave), firstly plugging the drainage outcrop, then pouring fluid cement stabilized soil, and filling the tiny caves of the loess caves in a 'chasing' manner by utilizing the good fluidity of the fluid cement stabilized soil; thirdly, for the sinking hole (or the upper half part of the water falling hole) with the caliber larger than 70cm, 3 percent of cement stabilized soil semi-rigid material is compacted and backfilled for 3m, so that the site construction condition is met, and the engineering quality is ensured; fourthly, the part above the second filling section is backfilled layer by adopting plain soil, so that the treatment cost is reduced, and the engineering quality is ensured; the transportation, mixing and paving machines in the invention adopt an excavator with the size not larger than 300, and the compaction machines adopt a method of carrying a plate compactor by the excavator, and mainly utilize the advantages of strong climbing capability, good maneuverability, small occupied area and the like.
The invention provides a quick, high-quality and low-cost loess cave (water falling hole) treatment mode for engineering technicians, and the fine cave paths of the loess caves are filled in a 'chasing' manner by filling fluid cement stabilized soil into the lower parts of the caves in advance and utilizing the good fluidity of the fluid cement stabilized soil; the upper part of the sinking hole is compacted and backfilled for 3m by adopting a semi-rigid material of 3% cement stabilized soil, and the gap part is backfilled layer by adopting plain soil. Therefore, the traditional loess cave treatment form and the construction process are optimized, and the aims of smooth construction and safe operation of tunnel engineering are fulfilled.
Specifically, as shown in fig. 3, the invention provides a construction method for treating loess collapse at a tunnel site area by using cement stabilized soil, wherein the loess collapse with a larger depth is a water collapse hole, and before entering the tunnel, all the loess collapse at the tunnel site area are divided into collapse holes with the caliber of less than 70cm, collapse holes with the caliber of more than 70cm and water collapse holes with thick upper parts and thin lower parts; (1) for the crater with the caliber less than 70cm, firstly plugging the excretion outcrop 400, and then treating by a method of pouring fluid cement stabilized soil; (2) for the crater with the caliber larger than 70cm, compacting and backfilling by using 3% of cement stabilized soil semi-rigid material; (3) for the water falling hole with the thick upper part and the thin lower part, the caliber of the lower half part 1 of the water falling hole is smaller than 70cm, the caliber of the upper half part 2 of the water falling hole is larger than 70cm, the drainage outcrop 400 is firstly blocked, then the lower half part 1 with the caliber smaller than 70cm is filled with fluid cement stabilized soil to form a first filling section 100, and then the upper half part 2 with the caliber larger than 70cm is compacted and backfilled by adopting 3% cement stabilized soil semi-rigid material to form a second filling section 200.
According to the principle of ' active treatment ', the loess cave (water falling hole ') is treated by adopting cement stabilized soil before entering the hole, so that the construction quality and safe operation of tunnel engineering are ensured. According to the development rule of 'thick upper part and thin lower part' presented by loess caves (water falling holes), the invention treats the caves (or the lower half part of the water falling hole) with the caliber of less than 70cm by adopting a method of filling fluid cement stabilized soil, is beneficial to completely backfilling loess small caves and forming hardening strength, avoids the defects of high cost, long period, incomplete treatment, serious damage to original landform and the like caused by the traditional mortar protection, and has good social benefit and economic benefit.
The first implementation mode comprises the following steps:
as shown in fig. 3, for a cave with a caliber of less than 70cm, the embodiment provides a construction method for treating a loess cave in a tunnel site area by using cement stabilized soil, wherein drainage outcrops are blocked first, then fluid cement stabilized soil is poured into the cave, the fluid cement stabilized soil flows to a fine cave path along the cave, and hardening strength is formed after the fluid cement stabilized soil is solidified. The fluid cement-stabilized soil is prepared from cement and soil =3:97, and a cement-soil mixture and water =1: 1-1: 2. When the fluid cement stabilized soil is constructed on site, cement and soil can be mixed firstly, then water is added to the fluid state, and the mixture is filled into the cave.
As shown in fig. 3, for a cave with a caliber of more than 70cm, the embodiment provides a construction method for treating a loess cave in a tunnel site area by using cement stabilized soil, wherein the excretion outcrop is blocked firstly, and then compacted and backfilled by using a semi-rigid material of 3% cement stabilized soil.
In the embodiment, when compacting and backfilling, an excavator is adopted to carry a plate compactor to tamp and backfill, when the semi-rigid material of the cement stabilized soil is constructed, the top end of a cave needs to be firstly expanded and dug into a square shape, then the cave is filled by adopting a horizontal layering method from bottom to top, the virtual pavement thickness of each layer of the cement stabilized soil is not more than 30cm, and the compaction coefficient is not less than 93%.
When the semi-rigid material of the cement stabilized soil is constructed, the top end of the sunk hole can be firstly expanded and dug into a square shape (the size of the square shape is not less than 1.5m multiplied by 1.5 m), then the square shape is filled by adopting a horizontal layering method from bottom to top, the virtual pavement thickness of each layer of the cement stabilized soil is not more than 30cm, and the compaction coefficient is not less than 93%. When the cement stabilized soil is constructed, the mixing proportion of the cement stabilized soil is that cement and soil =3:97, and the plasticity index of the soil is not more than 17. During construction of cement stabilized soil, manually matching an excavator to mix, spreading the mixture to a site by using a bucket of the excavator to form a spreading layer, then replacing the bucket with a flat plate type vibrating tamper, and tamping the spreading layer by using a movable arm of the excavator to carry the flat plate type vibrating tamper; and repeating the steps until the cement stabilized soil is backfilled layer by layer to the specified elevation.
According to the principle of ' active treatment ', the cement stabilized soil is adopted to treat ' loess collapse holes ' (water falling holes ') before entering the holes, so that the construction quality and safe operation of tunnel engineering are ensured. The embodiment selects the fluid cement stabilized soil to backfill the cave with the caliber less than 70cm based on good fluidity of the material, guaranteed quality, lower manufacturing cost and convenient construction. The proportion of cement to soil in the cement stabilized soil of the embodiment is 3:97, the plasticity index of the soil is not more than 17, and the water addition amount is determined according to the optimal water content determined by a compaction test. The backfill thickness of the cement stabilized soil is determined to be 3m, the treatment quality cannot be guaranteed if the backfill thickness is too thin, and the economic cost is increased if the backfill thickness is too thick. The type of the excavator used in the embodiment is not more than 300, and the excavator is adopted to carry the flat plate type vibratory tamper for the construction machine tool, so that the excavator is suitable for the characteristics of narrow and steep site and incapability of entering large construction machinery. According to the development rule of 'thick upper part and thin lower part' presented by loess collapse points (water falling holes), for the collapse points (or the lower half parts of the water falling holes) with the caliber smaller than 70cm, the method of filling the fluid cement for stabilizing the soil is adopted for treatment, so that the loess thin and small cave paths can be completely backfilled, the hardening strength can be formed, the defects of high cost, long period, incomplete treatment, serious damage to original landforms and the like caused by the traditional mortar protection are avoided, and the social benefit and the economic benefit are good.
The second embodiment:
fig. 1 and 2 are schematic structural views of a downpipe cave with a thick upper part and a thin lower part. When the water falling hole is in a shape of thick upper part and thin lower part, as shown in fig. 3 and 4, the construction method of the loess collapse at the tunnel site area comprises the following steps:
firstly, plugging a drainage outcrop 400 for the lower half part 1 of a water falling hole with the aperture smaller than 70cm, and then pouring fluid cement stabilized soil;
secondly, compacting and backfilling 3m by using 3% of cement stabilized soil semi-rigid material to form a second filling section 200 for the upper half part 2 of the water falling hole with the aperture larger than 70cm after the fluid cement stabilized soil is solidified into the first filling section 100;
thirdly, compacting and backfilling the part above the second filling section 200 in the second step by using plain soil;
step four, carrying out grass planting and greening on the top surface backfilled in the step three;
and step five, arranging drainage ditches at the periphery of the backfill area in the step three to avoid the surface water from being washed again.
And in the second step and the third step, tamping and backfilling by adopting a mode of carrying a plate compactor by an excavator. And step three, adopting plain soil to retreat from the platform layer by layer and backfilling. The fluid cement-stabilized soil is prepared from cement and soil =3:97, and a cement-soil mixture and water =1: 1-1: 2. When the cement stabilized soil semi-rigid material is constructed, the top end of a water falling hole is firstly dug to be square (the size of the square is not less than 1.5m multiplied by 1.5 m), then a horizontal layering method is adopted for filling from bottom to top, the virtual pavement thickness of each layer of cement stabilized soil is not more than 30cm, and the compaction coefficient is not less than 93%.
When the cement stabilized soil is constructed, the mixing proportion of the cement stabilized soil is that cement and soil =3:97, and the plasticity index of the soil is not more than 17. During construction of cement stabilized soil, manually matching an excavator to mix, spreading the mixture to a site by using a bucket of the excavator to form a spreading layer, then replacing the bucket with a flat plate type vibrating tamper, and tamping the spreading layer by using a movable arm of the excavator to carry the flat plate type vibrating tamper; and repeating the steps until the cement stabilized soil is backfilled layer by layer to the specified elevation.
When the plain soil compaction and backfilling construction is carried out, on-site loess is used as a filler, and the water content of the filler is manually enabled to reach the standard of the optimal water content; spreading the filler by using a bucket of an excavator, then replacing the bucket with a flat plate type vibration tamper for rolling, and backfilling layer by layer from bottom to top, wherein the thickness of each layer is not more than 30cm, and the compaction coefficient is not less than 93%.
According to the principle of ' active treatment ', the cement stabilized soil is adopted to treat ' loess collapse holes ' (water falling holes ') before entering the holes, so that the construction quality and safe operation of tunnel engineering are ensured.
The third embodiment is as follows:
as shown in fig. 5 and 6, the present embodiment discloses a structure after disposal of a large-upper and small-lower shaped water falling hole.
The upper thick and lower thin water falling hole is defined by 700mm, the lower half part of the water falling hole is arranged from 700mm to the bottom end, and the upper half part of the water falling hole is arranged from 700mm upwards. The structure after the disposal of the upper-thick-lower-thin-shaped water falling hole comprises a plug, a first filling section 100 and a second filling section 200, wherein the plug is positioned at the bottom end of a loess cave of a tunnel site area and is used for plugging a bottom end leakage opening; pouring fluid cement stabilized soil into the lower half part 1, and forming a first filling section 100 after the fluid cement stabilized soil is solidified; and 3% of cement stabilized soil is filled into the upper half part 2 to form a second filling section 200, and the height of the second filling section 200 is 3 +/-0.5 m. In order to shorten the filling and compacting time of the second filling section 200 and further shorten the disposal period, the second filling section 200 of the present embodiment is composed of a compacted layer 210 and a loose layer 220, as shown in fig. 5, the loose layer 220 is positioned below the compacted layer 210, the fluid cement stabilized soil is solidified into the first filling section 100, the cement stabilized soil semi-rigid material is laid on the first filling section 100 until the cement stabilized soil semi-rigid material is laid to a certain thickness to form the loose layer 220, and then the cement stabilized soil semi-rigid material is filled back to the first filling section 100 in a layered compacting manner to form the compacted layer 210. The compacted layer 210 and the unconsolidated layer 220 collectively comprise the second fill segment 200.
The densified layer 210 has a thickness greater than 2 m. The plain soil backfill layer 300 adopts layer-by-layer retreat and backfill. The vegetarian soil backfill layer 300 is provided with drainage ditches at the periphery thereof, which prevents the vegetarian soil backfill layer 300 from being washed away again. Grass planting and greening are planted on the plain soil backfill layer 300.
The fourth embodiment:
on the basis of the first to third embodiments, the present embodiment discloses the following:
a construction method for treating loess collapse in a tunnel site area by adopting cement-stabilized soil is disclosed, wherein the mixing proportion of fluid cement-stabilized soil is cement-soil =3:97, and the mixing proportion of cement-soil is water =1: 1-1: 2. The cement-soil ratio in the cement-stabilized soil semi-rigid material is =3:97, the plasticity index of the soil is not more than 17, and the water addition amount is determined according to the optimal water content determined by a compaction test. When the cement stabilized backfill soil is constructed, the sunk holes can be firstly dug into squares (the size is not less than 1.5 multiplied by 1.5 m), then the squares are filled by adopting a horizontal layering method from bottom to top, the virtual pavement thickness of each layer of cement stabilized soil is not more than 30cm, and the compaction coefficient is not less than 93%. The semi-rigid material of the cement stabilized soil is mixed by manually matching with an excavator, the mixture is spread to the site by utilizing an excavator bucket, and then the bucket is replaced by a flat plate type vibration rammer for rolling. And repeating the steps until the semi-rigid material of the cement stabilized soil is backfilled layer by layer to the specified elevation.
In the embodiment, the backfill thickness of the cement stabilized soil is determined to be 3m, the treatment quality cannot be guaranteed if the backfill thickness is too thin, and the economic cost is increased if the backfill thickness is too thick.
In the embodiment, the loess on site is used as the filler, and the water content of the filler is artificially enabled to reach the standard of the optimal water content; spreading the filler by using a bucket of an excavator, then replacing the bucket with a flat plate type vibration tamper for rolling, and backfilling layer by layer from bottom to top, wherein the thickness of each layer is not more than 30cm, and the compaction coefficient is not less than 93%. The type of the excavator is not more than 300, and the compactor adopts a method that the excavator carries a plate compactor, aiming at adapting to the characteristics of narrow and steep field and inconvenient movement. And planting grass and greening the backfilled top surface, and arranging drainage ditches at the periphery of the backfilled area to recover the vegetation on the earth surface and avoid the scouring of the surface water again.
The fifth embodiment:
the embodiment provides a specific application example:
the tunnel has a total length of 620m from K6+200 to + 820. Due to the inherent characteristics of loess geological conditions, loess collapse holes (water falling holes) are respectively developed at tunnel site areas K6+714, K6+664 and K6+641, the loess collapse holes (water falling holes) are basically located above a tunnel structure through on-site verification, the collapse hole tops are buried at a depth of about 10-15 m away from the tunnel structure, and small cave paths below the collapse holes possibly invade the tunnel structure, so that the collapse holes (water falling holes) are subjected to active treatment before tunnel engineering construction, and smooth construction and safe operation of the tunnel engineering are ensured.
The traditional treatment technology for the water falling hole mostly adopts a 'top-down' large excavation method, the water falling hole is expanded and excavated, and then is backfilled layer by adopting a mortar-masonry or concrete pouring method from bottom to top, so that the hidden danger that the fine and small holes at the lower part of the water falling hole cannot be treated exists, and the defects of high treatment cost, long construction period, large environmental damage and the like also exist.
And after on-site inspection, carefully analyzing the geological cause and development characteristics of the loess collapse. The following treatment methods were determined:
1, K6+714 water falling holes with the caliber less than 70cm can be used for blocking the excretion outcrop first and then pouring fluid cement stabilized soil for treatment; in the fluid cement-stabilized soil, the ratio of cement to soil is =3:97, and the ratio of cement to soil mixture is 1: 1-1: 2. When in site construction, cement and soil are mixed, and then water is added to fill the pits until the pits are filled.
2, K6+664 and K6+641 water falling holes with the calibers respectively reaching 2.5m and 5.2m and being larger than 70cm, wherein the drainage outcrop can be firstly plugged, then the water falling holes are dug from top to bottom until the calibers of the water falling holes are smaller than 70cm, and a square construction platform (the size is not smaller than 1.5 multiplied by 1.5 m) is trimmed; secondly, pouring fluid cement stabilized soil, and filling the fluid cement stabilized soil to a square construction platform; thirdly, 3% of semi-rigid material of the cement stabilized soil is adopted to fill, compact and backfill 3m from bottom to top by adopting a horizontal layering method, the virtual pavement thickness of each layer of the cement stabilized soil is not more than 30cm, and the compaction coefficient is not less than 93%. In the cement stabilized soil, the ratio of cement to soil is =3:97, the plasticity index of the soil is not more than 17, and the water addition amount is determined according to the optimal water content determined by a compaction test; fourthly, backfilling the top surface of the backfill layer by adopting plain soil, wherein the width of the top surface of the backfill is 3.0-4.0m so as to meet the basic requirements of the operation of the excavator. The thickness of each layer is not more than 30cm, and the compaction coefficient is not less than 93%; after backfilling to the top surface of the original surface, leveling and greening, and arranging drainage ditches at the periphery of a backfilling area to avoid scouring again by surface water; sixthly, during construction, the cement stabilized soil (containing plain soil) is transported, mixed and paved by adopting an excavator, and the compaction machine adopts a method that the excavator carries a plate compactor.
By adopting the treatment method, the construction cost is low, the construction period is short, the environmental damage is small, and the fine cave roads at the deep part of the loess cave are filled in a 'chasing' manner by utilizing the good 'fluidity' of the fluid cement stabilized soil, so that the treatment quality is ensured, and the purpose of good engineering benefit, economic benefit and ecological benefit is realized.
The above-listed detailed description is only a specific description of a possible embodiment of the present invention, and they are not intended to limit the scope of the present invention, and equivalent embodiments or modifications made without departing from the technical spirit of the present invention should be included in the scope of the present invention.
It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned.
Furthermore, it should be understood that although the present description refers to embodiments, not every embodiment may contain only a single embodiment, and such description is for clarity only, and those skilled in the art should integrate the description, and the embodiments may be combined as appropriate to form other embodiments understood by those skilled in the art.

Claims (9)

1. A construction method for treating loess collapse holes in a tunnel site area by adopting cement stabilized soil is characterized in that all the loess collapse holes in the tunnel site area are divided into collapse holes with the caliber of less than 70cm, collapse holes with the caliber of more than 70cm and water falling holes, wherein the water falling holes are loess collapse holes with larger depth, thick upper parts and thin lower parts;
the construction method for treating loess collapse in the tunnel site area by adopting cement stabilized soil comprises the following steps:
(1) for a sunk hole with the caliber of less than 70cm, firstly plugging the drainage outcrop, and then pouring fluid cement stabilized soil for treatment;
(2) for the crater with the caliber larger than 70cm, compacting and backfilling by using 3% of cement stabilized soil semi-rigid material;
(3) for the water falling hole, the excretion outcrop is blocked, then the lower half part with the aperture smaller than 70cm is filled with fluid cement stabilized soil, and then the upper half part with the aperture larger than 70cm is compacted and backfilled by adopting 3% cement stabilized soil semi-rigid material.
2. The construction method according to claim 1, wherein the disposal method of the overboard cave comprises the steps of:
firstly, plugging a drainage outcrop for the lower half part of a water falling hole with the aperture smaller than 70cm, and then pouring fluid cement stabilized soil;
secondly, compacting and backfilling 3m of 3% cement stabilized soil semi-rigid material to form a second filling section for the upper half part of the water falling hole with the aperture larger than 70cm after the fluid cement stabilized soil is solidified into the first filling section;
thirdly, compacting and backfilling the part above the second filling section in the second step by using plain soil;
and step four, carrying out grass planting and greening on the backfilled top surface in the step three.
3. The construction method according to claim 2, wherein in the second step and the third step, the compactor is tamped and backfilled by using an excavator carrying a plate compactor.
4. The construction method according to claim 2 or 3, wherein step three is implemented by adopting plain soil layer-by-layer retreat backfilling.
5. The construction method according to claim 2, wherein the fourth step is followed by further comprising: and step five, arranging drainage ditches at the periphery of the backfill area in the step three to avoid the surface water from being washed again.
6. The construction method according to any one of claims 1 to 3, wherein the fluid cement-stabilized soil is cement-soil =3:97, and cement-soil mixture-water =1:1 to 1: 2.
7. The construction method according to any one of claims 1 to 3, wherein during the construction of the cement stabilized soil semi-rigid material, the top end of the water falling cave is firstly dug to be square, then the water falling cave is filled by adopting a horizontal layering method from bottom to top, the virtual pavement thickness of each layer of cement stabilized soil is not more than 30cm, and the compaction coefficient is not less than 93%.
8. The construction method according to claim 7, wherein the square has a size of not less than 1.5m x 1.5 m.
9. The construction method according to claim 7, wherein during the construction of the cement stabilized soil, a manual excavator is adopted for mixing, a bucket of the excavator is used for spreading the mixture to the site to form a spreading layer, then the bucket is replaced by a flat plate type vibrating tamper, and a movable arm of the excavator is used for carrying the flat plate type vibrating tamper to compact and spread the mixture;
and repeating the steps until the cement stabilized soil is backfilled layer by layer to the specified elevation.
CN202010468903.8A 2020-05-28 2020-05-28 Construction method for treating loess collapse in tunnel site area by adopting cement stabilized soil Pending CN111778959A (en)

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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN108487228A (en) * 2018-03-20 2018-09-04 中国建筑西北设计研究院有限公司 A kind of method of collapsibility that capableing of Compaction variables loess
CN108959189A (en) * 2018-06-07 2018-12-07 长安大学 A method of it calculating Canal in Loess Area roadbed and underlies dark cave marginal stability
CN110241830A (en) * 2019-07-19 2019-09-17 高建伟 A kind of backfilling apparatus and earth-filling method
CN110306529A (en) * 2019-06-21 2019-10-08 中国十七冶集团有限公司 A kind of method that bridge pile foundation solution cavity layering throwing blocks
CN110409464A (en) * 2019-07-12 2019-11-05 榆林市交通工程质量监督站 A kind of method for tunnel construction across coombe location
CN110671132A (en) * 2019-10-31 2020-01-10 中铁二十局集团有限公司 Deformation control construction structure and method for deep-buried loess tunnel based on arch sheathing

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN108487228A (en) * 2018-03-20 2018-09-04 中国建筑西北设计研究院有限公司 A kind of method of collapsibility that capableing of Compaction variables loess
CN108959189A (en) * 2018-06-07 2018-12-07 长安大学 A method of it calculating Canal in Loess Area roadbed and underlies dark cave marginal stability
CN110306529A (en) * 2019-06-21 2019-10-08 中国十七冶集团有限公司 A kind of method that bridge pile foundation solution cavity layering throwing blocks
CN110409464A (en) * 2019-07-12 2019-11-05 榆林市交通工程质量监督站 A kind of method for tunnel construction across coombe location
CN110241830A (en) * 2019-07-19 2019-09-17 高建伟 A kind of backfilling apparatus and earth-filling method
CN110671132A (en) * 2019-10-31 2020-01-10 中铁二十局集团有限公司 Deformation control construction structure and method for deep-buried loess tunnel based on arch sheathing

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