CN111749064A

CN111749064A - Protection method for ice-rich cutting slope in permafrost region

Info

Publication number: CN111749064A
Application number: CN202010533956.3A
Authority: CN
Inventors: 李林; 蔡阳; 路毅
Original assignee: Nanjing Forestry University
Current assignee: Nanjing Forestry University
Priority date: 2020-06-10
Filing date: 2020-06-10
Publication date: 2020-10-09

Abstract

The invention provides a method for protecting an ice-rich cutting slope in a permafrost region, which comprises the following steps: cutting slope of the cutting slope, positioning of underground ice, removing of the underground ice, backfilling of the cavity, snow cleaning, ecological protection and slope maintenance management realize the protection of the ice-rich cutting slope in the permafrost region. Wherein, the underground ice is removed by adopting a method of combining direct excavation and high-temperature steam, and the melting depth is the local seasonal frozen soil depth. The method is suitable for the side slope with the gradient less than 1/1.5, and has the main advantages that: the cost is low, easy operation, protecting effect is good, has solved the difficult problem of the rich ice cutting side slope protection in permafrost region.

Description

Protection method for ice-rich cutting slope in permafrost region

Technical Field

The invention belongs to the technical field of road civil engineering safety, and particularly relates to a method for protecting an ice-rich cutting slope in permafrost regions.

Background

When the road construction is carried out, required longitudinal slopes are required to be achieved in different road sections in a filling or excavating mode according to terrains. In permafrost regions, cutting slopes formed on excavated road sections can directly expose underground ice in the air, if any treatment is not carried out or the treatment measures are not proper, the underground ice can melt (namely thermally erode) when coming in spring, cavities can be formed in slopes due to melting of the underground ice, and the cavities can be deepened and enlarged continuously along with the lapse of time; in addition, water formed after the underground ice melts can scour the slope, and the development and continuous scouring of the cavity can induce the collapse of the slope, so that the safe operation of the road is influenced.

In recent years, researchers are trying to protect ice-rich cutting slopes in permafrost regions by different methods. Disease characteristics and control measures of cutting slopes in existing permafrost regions are analyzed and summarized on the period 11 of volume 59 of Standard design of railways in Hutian Fei and Du Sheng 2015. At present, the commonly used measures include retaining walls, reinforced earth protection slopes, anchor shotcrete, precast concrete assembly and the like. The measures can effectively maintain the stability of the slope in a short time. However, each measure has the disadvantages of complicated process and high cost; in addition, the durability of the measures is poor due to the influence of water stagnation and freeze-thaw cycle of the slope caused by thermal erosion. The method for protecting the ice-rich cutting slope in the permafrost region is economic, simple, effective and environment-friendly and is one of the problems to be solved urgently in the technical field of road civil engineering safety.

Disclosure of Invention

The invention provides a thermal erosion protection method aiming at the problems in the prior art, and the method can solve the problems of safety and stability of the ice-rich cutting slope in the permafrost region.

1. In order to achieve the purpose, the technical scheme of the invention comprises the following steps: cutting slope of the cutting slope, positioning of underground ice, removing of the underground ice, backfilling of a cavity, snow cleaning, ecological protection and slope maintenance management are carried out to realize the protection of the ice-rich cutting slope in the permafrost region.

2. The invention relates to cutting of a cutting slope, which is carried out in the early winter of a permafrost region under the weather condition that the average temperature reaches near 0 ℃, the slope (vertical height/horizontal distance) cannot be larger than 1/1.5, and sundries and broken stones on an operation surface need to be cleaned after the slope is cut, so that the slope surface is basically flat.

3. The positioning of the underground ice is comprehensively realized by artificial observation and geological radar detection of cut slopes, the artificial observation is used for roughly positioning the underground ice, the geological radar is used for detecting the underground ice without outcrop, and the geological radar is used for carrying out detailed detection on places where the underground ice is found or suspected to be stored to determine the specific shape, size and depth of the underground ice.

4. The invention relates to a method for removing underground ice, which is realized by directly excavating shallow underground ice with the depth less than 1.5 meters or spraying high-temperature steam on the ice surface, wherein the high-temperature high-pressure steam is used for melting the underground ice with the depth more than 1.5 meters, and the melting depth value needs to be referred to the thickness of local seasonal frozen soil.

5. The invention relates to a method for backfilling a cavity, which uses earthwork generated by slope cutting, wherein different compaction methods are adopted in the backfilling process according to the specific depth of the cavity, specifically, a one-time compaction method is adopted for the cavity with the depth of less than 1 m, and a layer-by-layer compaction method is adopted for the cavity with the depth of more than 1 m, wherein the compaction is carried out while backfilling.

6. The accumulated snow cleaning is generally carried out in time after the snowfall is finished, if the thickness of the accumulated snow is less than 2 cm after the snowfall for one time, the accumulated snow is not cleaned, if the accumulated thickness of the snowfall on the slope is more than 2 cm, the slope needs to be cleaned in time after the snowfall, and the accumulated snow is cleaned by adopting a high-power blower to directly blow away the slope from the top to the bottom.

7. The ecological protection is carried out in early spring, and is realized by sowing grass seeds (such as ryegrass, blue grass and the like) which can grow in permafrost regions or directly paving cold-resistant commercial turf, soil loosening is carried out on a slope surface before the grass seeds are sowed, the soil loosening depth is controlled within 5 cm, the grass seeds are scattered after the soil loosening is finished, then nutrient solution is sprayed, a grass curtain is paved, the thickness of the grass curtain is less than 1 cm, certain light transmittance is realized, and the nutrient solution is sprayed on the commercial turf after the grass curtain is paved.

8. The slope maintenance management needs to regularly spray water to the slope and to ensure the normal growth of the surface turf by applying fertilizer and spraying pesticide according to the growth condition of the turf.

The invention provides a method for protecting an ice-rich cutting slope in a permafrost region, which has the main advantages that: low cost, simple operation, environmental protection and lasting protection effect.

Detailed Description

The technical solution of the present invention is explained below by a specific example.

Examples

This embodiment is a certain cutting section side slope protection process in high latitude permafrost region. The method specifically comprises the following steps:

1) the road section is in the north-south direction, the mountain body is positioned on the east side of the road, the length of the mountain body is about 62 meters along the road direction, the highest position of the mountain body is about 12 meters, the design gradient is 1/1.5, the excavation earth volume of a side slope is about 1470 cubic meter, the excavation working surface is about 730 square meters, the seasonal frozen soil depth is about 2 meters, and a permanent frozen soil layer is below 2 meters;

2) removing slope vegetation and excavating and leveling the mountain according to the set slope when the average temperature in the first week is-2.87 ℃ in the beginning of 10 months;

3) after the excavation is finished, underground ice is found through artificial observation, and the underground ice is relatively and intensively distributed in the range of about 67 square meters on the right side of the slope surface, and the number of the underground ice is 4;

4) after slope cutting is finished, the position with the underground ice is detected by a geological radar, and the detection result shows that the underground ice is locally connected in a slope body, has different depths and irregular shapes, most depths are greater than 1.5 meters, and the local depths reach 5-6 meters;

5) according to the detection and human observation results, the position and the range of the underground ice are marked on the slope;

6) the shallow underground ice at the edge part is removed by directly adopting an excavation method, the underground ice which is difficult to excavate and bury deeply is melted by spraying high-temperature steam, the ice melting process is firstly carried out from the upper part of a slope and is gradually carried out towards the direction of a toe, the underground ice with the width of 1 meter is melted each time, the melting depth value is controlled to be about 2 meters, and the melting water is drained to a drainage ditch of the toe in time during ice melting;

7) backfilling a cavity formed after removing the underground ice by using earthwork generated by slope cutting, and compacting layer by layer;

8) the snow is fallen for 14 times in the whole winter, the total thickness of the snowfall is about 0.8 meter, and the accumulated snow on the slope is cleared in time after each snowfall;

9) in early spring, loosening soil on the slope and sowing ryegrass, then spraying nutrient solution and paving a straw mat, wherein the straw mat is fixed on the side slope by soil nails;

10) regularly sprinkling water to the slope surface and fertilizing and spraying pesticides according to the growth condition of the turf to ensure the normal growth of the surface turf;

11) in 2 years up to now after the construction, the surface of the side slope is not obviously collapsed, and the slope surface is not obviously scoured due to the existence of the turf.

Finally, it should be noted that the above-mentioned contents are only used for illustrating the technical solutions of the present invention, and not for limiting the protection scope of the present invention, and that the simple modifications or equivalent substitutions of the technical solutions of the present invention by those of ordinary skill in the art can be made without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for protecting an ice-rich cutting slope in a permafrost region is characterized by comprising the following steps:

(1) cutting a cutting slope of the cutting slope;

(2) positioning of underground ice;

(3) removing underground ice;

(4) backfilling the hollow hole;

(5) clearing accumulated snow;

(6) ecological slope protection;

(7) and (5) slope surface maintenance management.

2. The method for protecting ice-rich cutting slope in permafrost region according to claim 1, wherein the cutting of the cutting slope in step (1) is performed in the early winter when the average air temperature reaches about 0 ℃, and the slope (vertical height/horizontal distance) is less than 1/1.5.

3. The method for protecting the ice-rich cutting slope in the permafrost region according to claim 1, wherein the positioning of the ice falling in the step (2) is comprehensively realized by x field observation and geological radar detection.

4. The ice-rich cutting slope protection method for permafrost regions according to claim 1, wherein the removal of the underground ice in the step (3) is realized by directly excavating shallow underground ice with a depth of less than 1.5m or spraying high-temperature water vapor on the ice surface, wherein the high-temperature water vapor is used for melting the underground ice with a depth of more than 1.5m, and the melting depth value is determined by the thickness of local seasonal frozen soil.

5. The method for protecting the ice-rich graben slope in the permafrost region according to claim 1, wherein earthwork generated by slope cutting is used for backfilling the hollow in the step (4).

6. The method for protecting the ice-rich graben slope in the permafrost region according to claim 1, wherein the accumulated snow cleaning in the step (5) is performed in time after the snow fall is completed.

7. The method for protecting the ice-rich cut slope in the permafrost region according to claim 1, wherein the ecological slope protection in the step (6) is performed in early spring, and is specifically performed by planting grass seeds, spraying nutrient solution, covering a protective layer or directly laying commercial turf.

8. The method for protecting the ice-rich cutting slope in the permafrost region according to claim 1, wherein in the step (7), slope maintenance management needs to regularly sprinkle water and fertilize the slope surface to ensure the normal growth of the surface turf.