CN115660420B - Grading method for bottom bulge deformation risk level of ballastless track railway tunnel - Google Patents
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Abstract
The invention discloses a grading method of a ballastless track railway tunnel bottom bulge deformation risk grade, which is used for pointedly selecting and adjusting factors which can influence the tunnel bottom bulge deformation according to the requirements of ballastless tracks on railway foundations, so that the bottom bulge deformation of a tunnel section to be researched can be graded more accurately, the grading method is also more suitable for judging the ballastless track railway tunnel bottom bulge deformation, and further technical support is provided for adopting a supporting structure which is more beneficial to improving the safety and stability of the tunnel section to be researched, and the grading method has positive effects of reducing the probability of the bottom bulge deformation disasters which can influence the normal operation of the ballastless track and ensuring the normal operation of high-speed rails.
Description
Technical Field
The invention relates to the field of tunnel engineering geological investigation, in particular to a grading method for a ballastless track railway tunnel bottom bulge deformation risk grade.
Background
The ballastless track structure is mainly adopted in the high-speed railway in China, but the deformation sensitivity of the ballastless track to the track foundation is extremely high, namely the deformation of the track foundation in millimeter level can influence the smoothness of the ballastless track, potential safety hazards appear, and therefore the normal operation of the high-speed railway (the state of the ballastless track directly influences the running speed, safety and comfort of a high-speed railway train) is influenced, and therefore the deformation control requirement of the construction of the ballastless track on the track foundation structure is very strict. Particularly, the problem of controlling the uplift deformation of the bottom of the ballastless track tunnel is more difficult when safety judgment is carried out due to the comprehensive influence of a plurality of parts and factors such as a tunnel side wall, a vault, a bow and the like, and the problem is a difficult problem which needs to be faced in the construction process of the conventional ballastless track railway tunnel engineering.
Meanwhile, as new railway tunnels built or prepared in China gradually develop towards the trend of larger section, faster speed, larger burial depth, higher ground stress and more complex geological conditions in recent decades, the tunnel construction difficulty is also increased. Particularly in mountain areas of western complex geology, along with the excavation of long, large and deep buried tunnel engineering under more complex geological conditions and higher ground stress environments, in order to reduce the influence of the large deformation characteristics of soft rocks with large displacement, large deformation and long duration, more targeted implementation measures capable of effectively controlling the large deformation problem of the tunnel are given out, and domestic scholars develop a great deal of researches on the deformation damage mechanism, the arch rising reason and the repair measures of the bottom of the tunnel and acquire a plurality of research results, and also put forward a plurality of judgment methods and control techniques for the large deformation of the bottom of the tunnel, such as: a method for classifying large deformation of soft rock in tunnel construction of patent publication No. CN 111425252A; patent publication No. CN112832863A is suitable for grading the deformation grade of a soft rock tunnel under the action of ultrahigh ground stress; patent publication No. CN110513146A is a method for classifying large deformation of tunnel surrounding rock in the investigation design stage.
However, the deformation classification method also belongs to the judgment of tunnel deformation, but is the judgment of large tunnel deformation; in addition, in the grading method, the bulge deformation of a few millimeters to a few centimeters (5-100 mm) belongs to the category of small deformation, and the tunnel structure and the common train operation are not influenced, but the bulge deformation of a few millimeters to a few centimeters (more than 5 mm) can obviously influence the ballastless track, so that the normal operation of the high-speed rail is influenced, wherein 5-20 mm can eliminate the influence of the bulge deformation by adjusting the track fastener, and the deformation of more than 20mm needs to be subjected to disease special treatment. Therefore, the existing grading method for the tunnel deformation grade is not suitable for judging the risk of the bulge deformation at the bottom of the ballastless track railway tunnel, namely the existing grading method for the bulge deformation at the bottom of the ballastless track railway tunnel cannot accurately grade the risk of the bulge deformation at the bottom of the ballastless track railway tunnel, so that the safety and stability of a supporting structure adopted in the tunnel excavation or later-period tunnel maintenance process are insufficient, and the risk of the bulge deformation disaster at the bottom of the ballastless track railway tunnel is caused.
Disclosure of Invention
Aiming at the defect that the existing tunnel deformation grading method cannot accurately grade the tunnel bottom uplift deformation according to the deformation requirement of the ballastless track on the tunnel foundation, the invention provides a grading method of the ballastless track railway tunnel bottom uplift deformation risk grade, and the grading method can pertinently select and adjust factors which can influence the tunnel bottom uplift deformation according to the requirement of the ballastless track on the railway foundation, so that the bottom uplift deformation of a tunnel section to be researched can be graded more accurately, and the grading method is also more suitable for judging the tunnel bottom uplift deformation of the ballastless track railway, further provides technical support for adopting a supporting structure which is more beneficial to improving the safety and stability of the tunnel section to be researched, and has positive effects on reducing the probability of the bottom uplift deformation disaster which can influence the normal operation of the ballastless track and ensuring the normal operation of high-speed rail.
In order to achieve the aim of the invention, the invention provides a grading method of a ballastless track railway tunnel bottom uplift deformation risk grade, which comprises the following steps:
s1, obtaining the designed excavation span, the horizontal maximum initial ground stress, the rock stratum thickness, the rock stratum inclination angle and the rock uniaxial saturation compressive strength of a tunnel section to be researched;
s2, screening the tunnel to be researched according to the designed excavation span, the horizontal maximum initial ground stress, the rock stratum thickness, the rock stratum inclination angle and the rock uniaxial saturation compressive strength which are obtained in the step S1, so as to obtain a tunnel section with possible bottom bulge deformation;
the tunnel paragraph screening conditions of the possible bottom rising deformation are as follows: the excavation span is designed to be medium, large or super-large, the thickness of the rock stratum is not more than 1.0m, the inclination angle of the rock stratum is not more than 30 degrees, the uniaxial saturated compressive strength of the rock is not more than 30Mpa, and the horizontal maximum initial ground stress is not less than 8Mpa;
s3, calculating the rock strength stress ratio of the tunnel section with the possible bottom bulge deformation according to the horizontal maximum initial ground stress and the rock natural saturation compressive strength of the tunnel section with the possible bottom bulge deformation obtained by screening in the step S2, and dividing the risk level of the tunnel section with the possible bottom bulge deformation according to the rock strength stress ratio and the rock layer thickness of the tunnel section with the possible bottom bulge deformation.
According to the grading method of the bottom uplift deformation risk grade of the ballastless track railway tunnel, provided by the invention, the tunnel section is initially judged by pertinently selecting from the excavation span, the horizontal maximum initial ground stress, the rock stratum thickness, the rock stratum inclination angle and the rock uniaxial saturation compressive strength based on the requirement of the ballastless track on the track foundation and the influence factor of the bottom uplift deformation of the tunnel, under the condition that the possibility of the bottom uplift deformation which has a remarkable influence on the ballastless track is determined in the tunnel section, the bottom uplift risk grade is determined according to the rock strength stress ratio and the rock stratum thickness, so that the grading accuracy of the risk grade of the bottom uplift deformation of the tunnel section to be researched is remarkably improved, the grading efficiency is remarkably improved, and meanwhile, the grading method is more suitable for judging the bottom uplift deformation of the ballastless track railway tunnel, so that technical support is provided for adopting a supporting structure which is more beneficial to improving the safety and stability of the tunnel section to be researched, the possibility of the bottom uplift deformation disaster of the tunnel can be effectively reduced, and the normal operation of high-speed rail is ensured.
The design excavation span in the step S1 refers to the horizontal maximum width of the tunnel excavation cross section, and is divided by referring to the 'railway tunnel design Specification' TB 10003-2016; the specific division criteria are as follows: the excavation span is more than 5m and less than or equal to 8.5m and is a small span; the excavation span is more than 8.5m and less than or equal to 12m and is medium span; the excavation span is larger than 12m and smaller than or equal to 14m and is a large span; the excavation span is larger than 14 and is an extra-large span. According to the statistical analysis of the excavation span of the tunnel with the bottom bulge (the deformation amount is more than or equal to 5 mm), the whole structure of the small-span tunnel is more stable, the bottom deformation is very small, the operation of the ballastless track cannot be influenced, and the bottom bulge deformation is all generated in the middle span or above, so that the possibility that the ballastless track is obviously influenced due to the bottom bulge deformation of the small-span tunnel is eliminated.
The horizontal maximum initial ground stress in step S1 refers to the maximum horizontal stress existing in the soil before the load under consideration is applied, and is one of factors causing the tunnel bottom to bulge and deform. For the horizontal lamellar soft rock stratum, when the local stress field is mainly based on self-weight stress, the bulge deformation of the bottom of the inverted arch of the tunnel is smaller, and the bulge deformation of the bottom of the inverted arch can not be caused in a normal deformation range. The local stress field is mainly based on horizontal structural stress, the tunnel inverted arch bottom uplift deformation is increased along with the increase of horizontal initial stress, and the risk level is correspondingly increased. When the horizontal initial stress is below 8MPa, the possibility of the tunnel bottom bulge deformation (the deformation amount is more than or equal to 5 mm) is avoided; when the initial horizontal ground stress is not less than 8MPa, there is a possibility that the tunnel bottom is deformed by bulging (deformation amount is not less than 5 mm). It can be seen that for a horizontal layered rock mass, the horizontal initial ground stress factor has a large influence on the tunnel bottom bulging deformation, and when the maximum horizontal initial ground stress is not less than 8MPa, the tunnel has a possibility of bottom bulging deformation and has a significant influence on the ballastless track. The horizontal maximum initial ground stress is obtained by adopting an actual measurement method or a numerical inversion method, wherein the actual measurement method comprises a hydraulic fracturing method, an acoustic emission method and a flat jack method; preferably, the horizontal maximum initial ground stress is obtained by adopting an actual measurement method preferentially, and if the horizontal maximum initial ground stress cannot be obtained by adopting the actual measurement method, the horizontal maximum initial ground stress is obtained by adopting a numerical inversion mode; the maximum initial horizontal stress obtained by the actual measurement method is more accurate, and the risk grade of the bottom rising deformation paragraph possibly occurs is also more accurately graded.
Wherein, the thickness of the rock stratum in the step S1 refers to the vertical distance between two parallel interfaces of the rock stratum; the horizontal lamellar rock mass at the bottom of the tunnel can be regarded as a combined beam structure, the rigidity of the combined beam structure influences the bending effect of the combined beam structure, under the action of horizontal structural stress, the tunnel inverted arch shows a bottom bulge deformation phenomenon, the bottom bulge deformation amount at the middle part of the tunnel inverted arch is maximum, and the bottom bulge deformation at the two side wall feet is minimum. Under high ground stress conditions, the magnitude of the effect of the lamellar rock formation type on the maximum compressive stress of the inverted arch is as follows: thin layer > medium layer > thick layer > giant layer, and the smaller the layer thickness of the layered formation, the greater the compressive stress experienced by the inverted arch, and the greatest compressive stress all occurs in the middle of the inverted arch. The formation thickness of the tunnel bottom bulge deformation phenomenon (deformation amount is more than or equal to 5 mm) is mostly a thin layer to a medium thick layer, a small amount of the formation thickness is a thicker layer to a thicker layer, and the probability of the tunnel bottom bulge deformation of the giant thick layer formation is small (deformation amount is less than 5 mm). The rock layer thickness is divided by referring to the geotechnical engineering prospecting Specification GB50021-2001, and specific division standards are as follows: the thickness of the rock layer is larger than 1.0m to be a huge thick layer; the thickness of the rock stratum is more than 0.5m and less than or equal to 1.0m and is thick; the thickness of the rock stratum is more than 0.1m and less than or equal to 0.5m and is a medium thickness layer; the thickness of the rock stratum is less than or equal to 0.1m and is a thin layer; thus, when the formation thickness is not more than 1.0m, the tunnel has a possibility that the bottom ridge is deformed and has a significant influence on the ballastless track.
The rock stratum inclination angle in the step S1 refers to an acute angle projected by an inclination line of a rock stratum layer and a horizontal plane, and represents the inclination degree of the rock stratum at a space inclination angle; the dip angle of the layered rock layer is different, the tunnel damage mode is also different, and the steep dip rock layer along the tunnel axis is easy to bend and bulge after splitting at the side wall part; the inclined rock stratum loses support during excavation unloading, and shearing sliding along a structural surface or bedding bias on the other side is easy to occur at the arch part of the tunnel; the gently inclined rock stratum is prone to sinking or rising in the arch or inverted arch after excavation. By counting the inclination angles of tunnel basement rock strata with the deformation amount of more than or equal to 5mm of bottom bulge deformation of a plurality of seats (not less than 10 seats), the rock stratum inclination angles are mostly produced in a nearly horizontal or smaller than 15 degrees and are generally not more than 30 degrees, so that when the tunnel rock stratum inclination angles are not more than 30 degrees, the bottom bulge deformation of the tunnel is possible and the ballastless track is obviously influenced.
The uniaxial saturated compressive strength of the rock in the step S1 refers to the uniaxial compressive strength of the rock sample in a saturated water-containing state according to standard rules (GBT 50266-2013 of engineering rock mass test method); the formation lithology of the tunnel bottom is mainly soft rocks such as chalk (K), dwarf (J), triad (T) shale, sandstone and the like, the uniaxial saturated compressive strength of the rock is 8.4-26.75 MPa, the average value is 14.90MPa, and the standard value is 12.86MPa. It can be seen that the tunnel bottom bulge deformation rock is mainly soft rock or softer rock, namely when the uniaxial saturation compressive strength of the tunnel rock is not more than 30MPa, the tunnel has the possibility that the bottom bulge deformation and the ballastless track are obviously influenced.
Preferably, the specific method for screening the tunnel paragraphs to be studied in step S2 includes the following steps:
s21, judging whether the designed excavation span of the tunnel paragraph to be researched is a medium, large or super-large span, if so, performing a step S22; if not, the tunnel paragraph to be researched is not likely to have bottom bulge deformation, and screening is finished;
s22, judging whether the rock stratum thickness of the tunnel section to be researched along the tunnel axis is not more than 1.0m, if so, performing a step S23; if not, the tunnel paragraph to be researched is not likely to have bottom bulge deformation, and screening is finished;
s23, judging whether the rock stratum inclination angle of the tunnel section to be researched is not more than 30 degrees, if so, performing a step S24; if not, the tunnel paragraph to be researched is not likely to have bottom bulge deformation, and screening is finished;
s24, judging whether the uniaxial saturated compressive strength of the rock of the tunnel section to be researched is not more than 30MPa, if so, performing a step S25; if not, the tunnel paragraph to be researched is not likely to have bottom bulge deformation, and screening is finished;
s25, judging whether the horizontal maximum initial ground stress of the tunnel section to be researched is not less than 8MPa, if yes, performing a step S3; if not, the tunnel paragraph to be researched is not likely to have bottom bulge deformation, and screening is finished.
In the preferred method for screening tunnel paragraphs to be studied in step S2, the sequence of steps has no influence on the screening result and also has no influence on the risk level classification result of the bottom bulge deformation paragraphs, but the sequence in the preferred method is performed according to the influence importance degree of the characteristics of the tunnel paragraphs to be studied on the bottom bulge deformation of the tunnel, and the earlier screening characteristics are easier to obtain and easier to screen, so that the possible tunnel paragraphs without bottom bulge deformation can be removed more quickly, the screening time is saved, and the classification speed is faster.
In the step S3, the rock strength stress ratio is a quantitative index of the relative relation between the uniaxial saturated compressive strength of the rock and the initial ground stress; the rock strength stress ratio well represents the condition of a rock body relative to an initial stress field, reflects the capability of the tunnel bottom rock to resist extrusion deformation, generally has the larger risk of occurrence of tunnel bottom bulging deformation, is smaller than 4 according to case analysis on multi-seat (not less than 10) tunnel bottom bulging deformation (deformation amount is more than or equal to 5 mm), is generally positioned at 0.5-2, belongs to extremely high stress, and can be divided into four sections of 4-2, 2-1, 1-0.5 and less than or equal to 0.5.
In step S3, the principle of grading the risk level of the bottom rising deformation section which may occur by the rock strength stress ratio and the rock layer thickness is as follows: the rock strength stress ratio represents the condition of a rock body relative to an initial stress field, the initial ground stress field of a bottom bulge deformation tunnel (the deformation amount is more than or equal to 5 mm) is in a high ground stress region (the rock strength stress ratio is less than 4), and the ground stress directly influences the risk and the deformation amount of the bottom bulge deformation of the tunnel; under high ground stress conditions, the effect of the formation thickness on the maximum compressive stress of the inverted arch is as follows: the thinner layer > the medium layer > the thicker layer > the giant layer, and the smaller the single layer thickness of the layered rock layer, the larger the compressive stress of the inverted arch, the higher the risk of bottom uplift deformation, the larger the deformation amount, the maximum compressive stress all appears in the middle part of the inverted arch, and the bottom uplift deformation also appears in the middle part of the inverted arch with a higher probability. The thickness of rock stratum with the deformation of the tunnel bottom (deformation amount is more than or equal to 5 mm) is mostly a thin layer to a medium thick layer, a small amount of rock stratum with the deformation of the tunnel bottom is a thicker layer to a thicker layer, and the probability of the giant thick layer rock stratum to generate the tunnel bottom bulge deformation is minimum. Therefore, the risk level of the tunnel bottom bulge is directly related to the rock strength stress ratio and the rock layer thickness, and is two key indexes for grading the risk level of the tunnel bottom bulge.
In step S3, the method for dividing risk levels includes the following steps:
step S31: performing grading assignment on the rock stratum thickness and the rock strength stress ratio;
step S32: the assignment of rock layer thickness and rock strength stress ratio is used as index factorηAndλby a logical relationFHR=0.6η+0.4λAnd obtaining a deformation risk value, and grading the deformation risk of the bulge at the bottom of the tunnel by taking the deformation risk value as a grading index.
In step S31, by classifying and assigning the rock layer thickness and the rock strength stress ratio, the risk of the tunnel bottom rising deformation can be classified more accurately and more intuitively, and the specific classification and assignment are as follows:
| hierarchical assignment | Formation thickness | Rock strength stress ratioR/σ max |
| 1 | Thick layer | 2＜R/σ max ≤4 |
| 2 | Medium thick layer | 1＜R/σ max ≤2 |
| 3 | Medium thick layer-thin layer | 0.5＜R/σ max ≤1 |
| 4 | Thin layer | R/σ max ≤0.5 |
In step S32, the specific risk level classification is as follows:
| FHR | [ 1 , 1.6 ] | ( 1.6 , 2.2 ] | ( 2.2 , 3 ] | ( 3 , 4 ] |
| risk level | Slight | Medium and medium | Strong intensity | Extremely strong |
Preferably, the specific risk level dividing method further includes step S33: judging and obtaining the corresponding deformation degree of the bottom bulge of the tunnel, surrounding rock, deformation characteristics and treatment plans according to the risk level and the degree of accumulated strain energy in the basement rock; the specific contents are as follows:
| bottom ridge Risk level | Surrounding rock and deformation characteristics, treatment plan |
| Slight | The tunnel surrounding rock is mainly soft rock and soft rock, and is thick-thick to medium-thick, and is coreThe cake phenomenon exists; bottom bulge deformation phenomenon is not generated Obviously, the bottom bulge with deformation displacement less than 20mm can occur, the duration is short (less than 3 months), and the deformation displacement can be communicated The track fastener is adjusted to eliminate the influence of the uplift deformation, so that the deformation monitoring is performed without improving the supporting strength of the tunnel. |
| Medium and medium | The surrounding rock of the tunnel is mainly softer rock and soft rock, and is mainly a medium-thick layer, and the diameter shrinkage phenomenon exists in drilling holes; the bottom of the container is raised and deformed, bottom bulge with deformation displacement of 20-50mm can occur and the duration is long (about 1 year), and proper lifting is recommended The tunnel inverted arch sagittal ratio is 1/14 with high tunnel supporting strength. |
| Strong intensity | The tunnel surrounding rock mainly comprises soft rock and extremely soft rock, and has a medium-thick layer to a thin layer, so that the phenomenon of hole drilling and diameter shrinkage is obvious; with a pronounced bottom elevation Deformation, the bottom of which may occur with a deformation displacement of 50-100mm, has a long duration (about 5 years), and is recommended The tunnel supporting strength is improved, the thickness of the tunnel inverted arch is properly increased, and the reinforced concrete inverted arch and the tunnel inverted arch sagittal-span ratio are adopted 1/10 of the total weight of the material was used. |
| Extremely strong | The tunnel surrounding rock mainly comprises soft rock and extremely soft rock, and is mostly thin, so that the phenomenon of hole drilling and diameter shrinkage is obvious; with significant bottom bulging deformation As an example, a bottom bulge with a deformation displacement of > 100mm may occur, and the duration is long (more than 5 years), suggesting reinforcement The tunnel supporting strength is increased, the thickness of the tunnel inverted arch is increased, the reinforced concrete inverted arch is adopted, and the sagittal ratio of the tunnel inverted arch is 1/8. |
Compared with the prior art, the invention has the beneficial effects that:
1. the grading method of the tunnel bottom bulge deformation risk level can determine the bottom bulge risk level according to the rock strength stress ratio and the rock layer thickness, so that the evaluation accuracy of the bottom bulge deformation risk level of the tunnel section to be researched is obviously improved, and the grading method is more suitable for judging the bottom bulge deformation of the ballastless track railway tunnel.
2. The grading method of the tunnel bottom uplift deformation risk grade is based on the requirements of the ballastless track on the track foundation and the influence factors of the tunnel bottom uplift deformation, and the tunnel paragraphs are primarily judged by pertinently selecting from the excavation span, the horizontal maximum initial ground stress, the rock stratum thickness, the rock stratum dip angle and the rock uniaxial saturation compressive strength, so that the workload can be effectively reduced, the grading time can be shortened, and the grading efficiency can be improved.
3. The grading method of the tunnel bottom bulge deformation risk level has high precision, strong pertinence and simple and reliable grading method, provides technical guarantee for the safe construction of the ballastless track tunnel engineering, and particularly can effectively reduce the possibility of tunnel bottom bulge deformation disasters and ensure the normal operation of high-speed rails.
Description of the drawings:
fig. 1 is a flow chart of a grading method of the bottom bulge deformation risk grade of the ballastless track railway tunnel.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to test examples and specific embodiments. It should not be construed that the scope of the above subject matter of the present invention is limited to the following embodiments, and all techniques realized based on the present invention are within the scope of the present invention.
Example 1:
s1: when the special design of the West adult is carried out, the speed is 250km/h, and the Zhao Guyan tunnel is a two-wire tunnel. Acquiring relevant data of a tunnel section to be researched, wherein the formation lithology of the section to be researched is copper street subgroup two-section calcareous shale of a three-stack system, the surrounding rock grade is III-IV, the rock stratum thickness is mainly an extremely thin layer, the layer thickness is 1-5mm, the bonding between layers is good, the rock stratum dip angle is 10 degrees at minimum, the uniaxial saturated compressive strength standard values of the calcareous shale, the argy shale and the argy limestone are 13.0 MPa, 21.3MPa and 17.9MPa respectively, and the horizontal maximum initial ground stress is 11.3MPa on average and is perpendicular to the tunnel axis;
s2: and (2) carrying out preliminary screening and judging on whether the bottom bulge deformation occurs to the section to be researched of the Zhao Guyan tunnel according to the tunnel section screening condition that the bottom bulge deformation possibly exists in the step (S2): (1) The tunnel is a 250km/h double-line tunnel, and belongs to an extra large span; (2) a horizontal maximum initial ground stress of 11.3MPa > 8MPa; (3) the thickness of the rock stratum is 1-5mm < 1m; (4) the rock stratum inclination angle is 10 degrees less than 30 degrees at minimum; (5) The maximum uniaxial saturation compressive strength of the rock is 21.3MPa < 30MPa; therefore, the section to be studied of the Zhao Guyan tunnel is judged to be a tunnel section with possible bottom bulge deformation;
s3, grading the bottom bulge deformation of the section to be researched of the Zhao Guyan tunnel according to the grading standard of the bulge deformation: (1) The thickness of the rock stratum is 1-5mm, and the rock stratum is a thin layer and the thickness factor of the rock stratumη4; (2) According to the maximum initial horizontal stress and the natural saturated compressive strength of the rock, the rock strength stress ratio of the calcareous shale, the marl and the marl is calculated to be 1.2, 1.9 and 1.58 respectively, and the rock strength stress ratio factor is in the range of 1 < R/sigma max less than or equal to 2λFor 2, the bottom bump risk rating FHR was calculated to be 3.2, and therefore, the bottom bump risk rating of the Zhao Guyan tunnel section under study was evaluated as a "very strong" rating.
Example 2
S1, forming a railway design speed per hour of 200km/h, wherein the cloud top tunnel is a double-track tunnel. Acquiring relevant data of a tunnel section to be researched, wherein the stratum lithology of the tunnel section to be researched is Jurassic system Lai town mudstone and mudstone sand-holding rock, the gangue gypsum is 1-3mm, the surrounding rock level is level III, the stratum is a medium-thickness layer, the stratum is nearly horizontal, the uniaxial saturation compressive strength of the rock is 4.4MPa, the horizontal maximum initial ground stress is 9.5-13.7MPa, and the included angle between the stratum and the axis is 49-90 degrees;
s2, carrying out preliminary screening and judging on whether the bottom bulge deformation occurs in the section to be researched of the cloud top tunnel according to the tunnel section screening conditions that the bottom bulge deformation possibly exists in the step S2: (1) The tunnel is a 200km/h double-track tunnel, and belongs to a large span; (2) a horizontal maximum initial ground stress of 9.5-13.7MPa > 8MPa; (3) the rock stratum is a medium thick layer, and the thickness of the rock stratum is 0.1-0.5 m < 1m; (4) the stratum is nearly horizontal, and the inclination angle is less than 30 degrees; (5) The maximum uniaxial saturation compressive strength of the rock is 4.4MPa < 30MPa. Therefore, judging the cloud top tunnel as a tunnel section with possible bottom bulge deformation;
s3, grading the bottom bulge deformation of the section to be researched of the cloud top tunnel according to the grading standard of the bulge deformation: (1) Thick layer in formation thickness, formation thickness factorηIs 2; (2) According to the horizontal maximum initial ground stress and the natural saturated compressive strength of the rock, the stress ratio of the rock strength is calculated to be 0.9-1.0 respectively, and the stress ratio is less than 0.5R/σmaxIn the range of less than or equal to 1, the stress ratio factor of the rock strengthλFor 3, the bottom bump risk level FHR is calculated to be 2.4, and therefore, the bottom bump risk level of the section to be studied of the cloud-top tunnel is evaluated as a "strong" level.
In actual engineering, the risk grades which can be judged by referring to the grading description of the risk grades of the bottom uplift deformation phenomenon of the section of the West Cheng patent Zhao Guyan tunnel and the section of the tunnel forming the railway cloud roof tunnel in construction are respectively extremely strong and strong, and the bottom uplift risk grade obtained by adopting the grading method disclosed by the invention is completely matched with the actual situation, so that the bottom uplift deformation situation of the tunnel to be researched can be accurately confirmed, and further, the accurate supporting mode is adopted according to the bottom uplift risk grade in the tunnel construction and maintenance process, and the safety of the tunnel is ensured.
Comparative example 1
Adopting the regulations in the tunnel design Specification TB10003-2016, wherein the surrounding rock stratum of the section to be researched of the Zhao Guyan tunnel is a thin layer, taking 0.35 according to the rock integrity index of the table B.1.3-1, and respectively converting the rock strength stress ratio of calcareous shale, marl and marl into the rock strength stress ratios of 0.42, 0.67 and 0.55 according to the rock strength stress ratios of 1.2, 1.9 and 1.58; according to table 12.5.3, rock mass strength stress ratio of 0.25-0.5 is divided into class I large deformations, 0.15-0.25 is divided into class II large deformations, less than 0.15 is divided into class III large deformations, only a small portion of the to-be-studied paragraphs with lithology of calcareous shale having a rock mass strength stress ratio of 0.42 can be identified as class I large deformations, and the remaining paragraphs with bottom bulging possibly are identified as no large deformation risk.
Comparative example 2
The method comprises the steps that the regulation in the tunnel design specification TB10003-2016 is adopted, the surrounding rock stratum of a section to be researched of a cloud top tunnel is a medium-thick layer, the rock integrity index is 0.55 according to the table B.1.3-1, the rock strength stress ratio is respectively 0.9-1.0, and the rock strength stress ratio is 0.5-0.55; according to table 12.5.3, rock mass strength stress ratio of 0.25-0.5 is divided into I-level large deformation, 0.15-0.25 is divided into II-level large deformation, less than 0.15 is divided into III-level large deformation, and the section to be studied is considered to have no large deformation risk.
The comparison analysis of the risk assessment process and the result of the embodiment and the comparative example can find that the result of classifying and judging the western adult patent Zhao Guyan tunnel and the tunnel-to-railway cloud top tunnel by adopting the existing large deformation classification method is that most paragraphs have no large deformation risk, namely, no targeted deformation prevention and control measures are needed, but in practice, all the paragraphs have bottom bulge phenomenon, and the normal operation of the ballastless track is obviously influenced: the cloud roof tunnel has 6 sections to shake vehicles, crack lining and the like, wherein the rail surface elevation with the maximum change is raised by approximately 17mm after being finely adjusted, and after disease treatment is carried out by adopting anchor cable and anchor rod reinforcing measures, the arch rising speed is slowed down, the deformation is still developed, and the maximum accumulated deformation monitored later is 69.75mm; the bottom of 7 sections 351m of the Zhao Guyan tunnel is raised, the maximum deformation is approximately 60mm, and the deformation is basically controlled after the tunnel is treated by adopting measures such as replacing an inverted arch, adding a prestressed anchor rod, resetting a ballastless track and the like.
Therefore, the grading method for the tunnel bottom bulge deformation can evaluate the grade of the tunnel bottom bulge deformation more accurately, is more suitable for evaluating the ballastless track tunnel bottom bulge deformation with higher requirements on foundation accuracy, can provide technical support for adopting a supporting structure which is more beneficial to improving the safety and stability of a tunnel section to be researched, effectively reduces the possibility of occurrence of bottom bulge deformation disasters of the tunnel, and has higher matching degree of evaluation results and actual conditions.
The foregoing examples merely represent specific embodiments of the present application, which are described in more detail and are not to be construed as limiting the scope of the present application. It should be noted that, for those skilled in the art, several variations and modifications can be made without departing from the technical solution of the present application, which fall within the protection scope of the present application.
Claims (1)
1. The grading method of the ballastless track railway tunnel bottom uplift deformation risk level is characterized by comprising the following steps of:
s1, obtaining the designed excavation span, the horizontal maximum initial ground stress, the rock stratum thickness, the rock stratum inclination angle and the rock uniaxial saturation compressive strength of a tunnel section to be researched;
s2, screening the tunnel to be researched according to the designed excavation span, the horizontal maximum initial ground stress, the rock stratum thickness, the rock stratum inclination angle and the rock uniaxial saturation compressive strength which are obtained in the step S1, so as to obtain a tunnel section with possible bottom bulge deformation;
the specific method for screening comprises the following steps:
s21, judging whether the designed excavation span of the tunnel paragraph to be researched is a medium, large or super-large span, if so, performing a step S22; if not, the tunnel paragraph to be researched is not likely to have bottom bulge deformation, and screening is finished;
s22, judging whether the rock stratum thickness of the tunnel section to be researched along the tunnel axis is not more than 1.0m, if so, performing a step S23; if not, the tunnel paragraph to be researched is not likely to have bottom bulge deformation, and screening is finished;
s23, judging whether the rock stratum inclination angle of the tunnel section to be researched is not more than 30 degrees, if so, performing a step S24; if not, the tunnel paragraph to be researched is not likely to have bottom bulge deformation, and screening is finished;
s24, judging whether the uniaxial saturated compressive strength of the rock of the tunnel section to be researched is not more than 30MPa, if so, performing a step S25; if not, the tunnel paragraph to be researched is not likely to have bottom bulge deformation, and screening is finished;
s25, judging whether the horizontal maximum initial ground stress of the tunnel section to be researched is not less than 8MPa, if yes, performing a step S3; if not, the tunnel paragraph to be researched is not likely to have bottom bulge deformation, and screening is finished;
s3, calculating the rock strength stress ratio of the tunnel section with the possible bottom bulge deformation according to the horizontal maximum initial ground stress and the rock natural saturation compressive strength of the tunnel section with the possible bottom bulge deformation obtained by screening in the step S2, and grading the risk level of the tunnel section with the possible bottom bulge deformation according to the rock strength stress ratio and the rock layer thickness of the tunnel section with the possible bottom bulge deformation;
the specific dividing method of the risk level comprises the following steps:
step S31: performing grading assignment on the rock stratum thickness and the rock strength stress ratio; specific hierarchical assignments are as follows:
Step S32: the assignment of rock layer thickness and rock strength stress ratio is used as index factorηAndλby a logical relationFHR=0.6η+0.4λThe deformation risk value is obtained, and the deformation risk of the bottom bulge of the tunnel is classified by taking the deformation risk value as a classification index; the specific risk level classification is as follows:
Step S33: judging and obtaining the corresponding deformation degree of the bottom bulge of the tunnel, surrounding rock, deformation characteristics and treatment plans according to the risk level and the degree of accumulated strain energy in the basement rock in the step S32; the concrete contents of the deformation degree of the bottom bulge of the tunnel, surrounding rock, deformation characteristics and treatment plans are as follows:
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