CN117454466B - Factory dam safety distance quantitative control method for arranging underground factory building on near arch dam abutment - Google Patents

Abstract

The present invention discloses a method for quantitatively controlling the safe distance of a plant dam with an underground plant near the abutment of an arch dam, comprising the following steps: obtaining characteristic parameters; establishing a numerical simulation model and performing static analysis; obtaining a curve of the change of the principal compressive stress along the arch dam toe corner point of a typical monitoring line segment; drawing a stress attenuation curve of the arch dam toe corner point; calculating the inflection point of the stress attenuation curve; dividing the arch dam load concentration transfer area and diffusion area; drawing the boundary of the arch dam load concentration transfer area and diffusion area; preliminarily arranging the underground plant cavern group; calculating the safety degree of the arch seat rock mass point; and accurately arranging the underground plant cavern group. The present invention has the advantages of low cost, scientific rationality, good safety, and quantitative accuracy, breaking through the limitation of the traditional underground plant cavern group being arranged far away from the dam and not less than 2 times the thickness of the arch end, and realizing the quantitative arrangement of the underground plant cavern group near the abutment of the arch dam.

Description

Quantitative control method for safe distance between powerhouse and dam when underground powerhouse is arranged near the abutment of arch dam

Technical Field

The invention relates to the technical field of water conservancy and hydropower engineering design, and in particular to a method for quantitatively controlling the safe distance between a plant and a dam in which an underground plant is arranged near an arch dam abutment.

Background technique

Most hydropower stations built in mountainous and canyon areas adopt the layout of arch dams combined with large underground powerhouse caverns. The traditional hub layout method is "dam first, avoidance first", that is, under the premise of ensuring the safety of the main buildings of the project, the dam is arranged in good strata first, followed by the underground powerhouse caverns, and the dam and powerhouse try to avoid bad strata. According to relevant statistics, the underground powerhouse caverns of large underground power stations in China are all arranged away from the dam, with a thickness of no less than 2 times the arch end, to ensure the long-term stability of the underground powerhouse caverns. However, in mountainous canyon areas, the geological structure is complex and there is a limited range of good strata. Under the condition that the dam gives priority to occupying good rock mass, if the underground powerhouse cavern group adopts the traditional layout method, it needs to be far away from the dam, that is, not less than 2 times the thickness of the arch end, and arranged against the inner side of the mountain, which leads to a significant increase in the length of the water transmission line, a substantial increase in project investment, and a reduction in economic efficiency; if the underground powerhouse cavern group is arranged close to the arch dam shoulder, that is, less than 2 times the thickness of the arch end, then under the influence of the thrust of the arch dam shoulder, the stability and safety of the cavern surrounding rock in the local range of the underground powerhouse cavern is difficult to ensure, and the instability of the cavern surrounding rock will affect the safety of the arch dam. According to the "Design Code for Underground Powerhouses of Hydropower Stations" (NB/T 35090-2016), underground powerhouses should not be arranged within the load transfer range of the dam.

At present, the existing technology has made some research on the reasonable utilization range of the resisting rock mass of the arch dam abutment foundation, but has not given a quantitative arrangement method for the underground powerhouse cavern group near the arch dam abutment. Therefore, when the range of good strata is limited, how to determine the powerhouse-dam distance can not only ensure the stability and safety of the dam and the underground caverns, but also reduce the length of the water transmission line and save investment. It is of great significance to propose a scientific and reasonable quantitative control method for the powerhouse-dam safety distance of the underground powerhouse arranged near the arch dam abutment.

Summary of the invention

The purpose of the present invention is to provide a method for quantitatively controlling the safe distance of an underground powerhouse near the abutment of an arch dam, which can solve the technical problem of arranging an underground powerhouse cavern group near the abutment of an arch dam under the condition of limited good stratum range, break through the limitation that the safe distance between the traditional underground powerhouse cavern group and the arch dam is not less than 2 times the thickness of the arch end, and realize the quantitative arrangement of the underground powerhouse cavern group near the abutment of the arch dam.

To achieve the above purpose, the technical solution adopted by the present invention is as follows:

A quantitative control method for the safe distance between a powerhouse and a dam with an underground powerhouse arranged near an arch dam abutment is characterized by comprising the following steps:

Step 1: Obtain feature parameters;

Obtain characteristic parameters of the arch dam and the characteristic parameters of the resisting rock mass around the arch dam abutment;

Step 2: Establish a numerical simulation model and perform static analysis;

Establish two-dimensional numerical simulation models of arch rings and resisting rock masses at different elevations, and conduct static analysis;

Step 3: Obtain the variation curve of the principal compressive stress at the toe corner of the arch dam along the monitoring line segment;

Taking the arch dam toe corner point as the reference point, draw radial line segments along the arch dam toe corner point as monitoring line segments, read the principal compressive stress value σ of each node on the monitoring line segment, and draw the principal compressive stress variation curve along the arch dam toe corner point;

Step 4: Draw the stress attenuation curve of the arch dam toe corner;

Calculate the stress attenuation degree η of the arch dam toe corner point at each node, and draw the stress attenuation degree curve of the arch dam toe corner point according to the stress attenuation degree η of the arch dam toe corner point;

Step 5: Calculate the inflection point η _key of the stress attenuation curve;

Step 6: Divide the arch dam load concentration transfer area and diffusion area;

According to η _key , the arch dam load concentration transfer area and diffusion area are divided:

η≤η _key is the arch dam load concentrated transfer area, η＞η _key is the arch dam load diffusion area;

Step 7: Draw the boundaries of the arch dam load concentration transfer area and diffusion area;

Connect the inflection points of the stress attenuation curve of each monitoring line segment to form the boundary between the arch dam load concentration transfer area and the diffusion area;

Step 8: Preliminary layout of underground powerhouse caverns;

The underground powerhouse caverns are preliminarily arranged at any position within the arch dam load diffusion zone;

Step 9: Calculate the safety factor _Kp of the abutment rock mass point;

According to the preliminary layout of the underground powerhouse cavern group, the safety degree of the arch abutment rock mass point under the interaction between the underground powerhouse cavern group and the arch dam is calculated as K _p =((2c×cosφ)/(1-sinφ))/((1+sinφ)/(1-sinφ)×σ ₁ -σ ₃ ), where c and φ are the cohesion and internal friction angle of the abutment rock mass material, and σ ₁ and σ ₃ are the maximum and minimum principal stresses of the Mohr stress circle of the abutment rock mass when the underground powerhouse cavern group interacts with the arch dam;

Step 10: Accurately arrange the underground powerhouse cavern groups.

Preferably, in step one, the characteristic parameters include the size of the arch dam, the reservoir water level, the mechanical parameters of the surrounding rock, the elastic modulus of the arch dam concrete and the Poisson's ratio.

Preferably, in step three, the number of monitoring line segments is determined according to actual accuracy requirements of the project.

Preferably, the number of monitoring line segments is n, where n=180/β+1, wherein β is the angle between two monitoring line segments.

Preferably, in step three, the length of the monitoring line segment is determined according to the attenuation of the principal compressive stress of the rock mass.

Preferably, in step 4, the calculation formula of the stress attenuation degree η at the toe corner of the arch dam is:

η＝(σ _max -σ)/(σ _max -σ _min )×100%, 0≤η≤1, where σ _max is the maximum stress value on the principal compressive stress variation curve along the process; σ _min is the minimum stress value on the principal compressive stress variation curve along the process, and σ is the principal compressive stress value of each node.

Preferably, in step 5, the calculation formula of the inflection point η _key of the stress decay curve is:

η _key =η _a (cη _b -b)/(η _a (cb) - a (1 - η _b )), where (a, η _a ), (b, η _b )

and (c, 1) represent three groups of typical characteristic points on the stress attenuation curve, (b, η _b ) and (c, 1) are the characteristic points at both ends of the nearly horizontal section of the stress attenuation curve; (a, η _a ) and the origin (0, 0) are the characteristic points at both ends of the stress attenuation steep change section; η _key is mainly obtained based on the intersection of the line connecting the characteristic point (a, η _a ) and the origin (0, 0) and the line connecting the characteristic points (b, η _b ) and (c, 1), and the abscissa of the corresponding intersection is the stress attenuation inflection point η _key .

Preferably, in step seven, the inflection points of the stress attenuation curves of the monitoring line segments are connected by smooth curves.

Preferably, in step ten, the underground powerhouse cavern groups are precisely arranged according to the following method:

When the underground powerhouse cavern group is arranged at any position within the arch dam load diffusion zone, _Kp >f always holds true. Then the minimum arrangement distance of the underground powerhouse cavern group near the arch dam abutment is the minimum distance between the arch dam load concentrated transfer zone, the diffusion zone boundary and the dam toe corner point. At the same time, the actual arch seat rock mass point safety degree _Kp can be calculated.

When the underground powerhouse cavern group is arranged within the arch dam load diffusion zone and K _p ≤ f, the underground powerhouse cavern group layout position is adjusted until the arch seat rock mass point safety degree K _p ＝f. At this time, the distance between the underground powerhouse cavern group and the arch dam abutment is the minimum layout distance near the arch dam abutment.

Among them, f is the preset safety value of the abutment rock mass point, and f≥1.

Preferably, in actual engineering applications, the value of f is determined comprehensively based on the engineering grade, the importance of the building, etc.

Compared with the prior art, the present invention has the following beneficial effects:

(1) It provides a process for dividing the concentrated transfer area and diffusion area of the arch dam load, providing a certain basis for the preliminary layout of the underground powerhouse cavern group;

(2) The method for determining the inflection point of the stress attenuation curve provided by the present invention is more scientific and reasonable than the prior art, and can more accurately reflect the stress attenuation change process;

(3) The technical difficulty of arranging underground powerhouse caverns near the abutment of the arch dam under the condition of limited good strata was solved, and the quantitative arrangement of underground powerhouse caverns near the abutment of the arch dam was realized;

(4) It breaks through the limitation of traditional underground powerhouse cavern groups that are far away from the dam and have a thickness not less than twice the arch end, shortens the water supply line, reduces the project investment cost, and provides a new research idea for the layout of large underground powerhouse cavern groups near arch dams.

In summary, the quantitative control method of the plant dam safety distance of the underground powerhouse cavern group arranged near the arch dam abutment of the present invention has the advantages of low cost, scientific rationality, good safety, high degree of quantification and strong operability. It breaks through the limitation of the traditional underground powerhouse cavern group that is far away from the dam and has a thickness of not less than 2 times the arch end, and realizes the quantitative arrangement of the underground powerhouse cavern group near the arch dam abutment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is an analysis flow chart of a method for quantitatively controlling the safe distance between an underground powerhouse and a dam in accordance with the present invention when an underground powerhouse is arranged near an arch dam abutment.

FIG. 2 is a curve showing the variation of the principal compressive stress along the toe corner of the arch dam according to the present invention and a stress attenuation curve.

FIG3 is a schematic diagram of determining the inflection point of the stress attenuation curve of the present invention.

FIG4 is a schematic diagram of an underground powerhouse cavern group arranged in the load diffusion zone of an arch dam according to the present invention.

FIG5 is a schematic diagram for verifying the scientific rationality of the method for determining the inflection point of the stress attenuation curve of the present invention.

In the figure: 1-arch dam, 2-dam toe corner point, 3-arch dam load concentration transfer area, 4-arch dam load concentration transfer area and diffusion area boundary, 5-arch dam load diffusion area, 6-main powerhouse, 7-main transformer tunnel, 8-surge chamber, 9-minimum layout distance of underground powerhouse cavern group near the arch dam abutment.

Detailed ways

The following detailed description of the implementation of the present invention is made in conjunction with the accompanying drawings, but they do not constitute a limitation of the present invention and are only given as examples. At the same time, the advantages of the present invention are made clearer and easier to understand through the description.

The applicant found that when the reservoir water pressure is transmitted to the dam shoulders on both sides, the bearing characteristics of the resisting rock mass are generally distributed in a "stress diffusion and value attenuation" manner, and there is an obvious attenuation inflection point. Based on this, the present invention divides the arch dam load concentrated transfer area and the diffusion area, and provides corresponding calculation formulas. Then, the safety of the arch seat rock mass point is comprehensively determined according to the engineering grade, the importance of the building, etc. The minimum layout distance of the underground powerhouse cavern group near the arch dam shoulder is determined by calculating the safety of the arch seat rock mass point, so as to accurately arrange the underground powerhouse cavern group, which can realize the quantitative layout of the underground powerhouse cavern group near the arch dam shoulder, and provide a quantitative control method and its specific calculation formula for the layout distance of the underground cavern group when the range of excellent strata is limited.

Specifically, the technical solution of the present invention is:

The quantitative control method of the safe distance between the powerhouse and the dam with underground powerhouse arranged near the abutment of the arch dam includes the following steps:

Step 1: Obtain feature parameters;

Obtain characteristic parameters of the arch dam and the characteristic parameters of the resisting rock mass around the arch dam abutment;

Step 2: Establish a numerical simulation model and perform static analysis;

Establish two-dimensional numerical simulation models of arch rings and resisting rock masses at different elevations, and conduct static analysis;

Step 3: Obtain the variation curve of the principal compressive stress at the toe corner of the arch dam along the monitoring line segment;

Taking the arch dam toe corner point 2 as the reference point, draw a radial line segment along the arch dam toe corner point 2 as the monitoring line segment, read the principal compressive stress value σ of each node on the monitoring line segment, and draw the principal compressive stress variation curve of the arch dam toe corner point along the process;

Step 4: Draw the stress attenuation curve of the arch dam toe corner;

Calculate the stress attenuation degree η of the arch dam toe corner point at each node, and draw the stress attenuation degree curve of the arch dam toe corner point according to the stress attenuation degree η of the arch dam toe corner point;

Step 5: Calculate the inflection point η _key of the stress attenuation curve;

Step 6: Divide the arch dam load concentration transfer area and diffusion area;

According to η _key , the arch dam load concentration transfer area and diffusion area are divided:

η≤η _key is the arch dam load concentrated transfer area 3, η＞η _key is the arch dam load diffusion area 5;

Step 7: Draw the boundary lines of the arch dam load concentration transfer area and diffusion area 4;

Connect the inflection points of the stress attenuation curve of each monitoring line segment to form the boundary line between the arch dam load concentration transfer area and the diffusion area 4;

Step 8: Preliminary layout of underground powerhouse caverns;

The underground powerhouse caverns are preliminarily arranged at any position within the arch dam load diffusion zone;

Step 9: Calculate the safety degree of the abutment rock mass point;

According to the preliminary layout of the underground powerhouse cavern group, the safety degree of the arch abutment rock mass point under the interaction between the underground powerhouse cavern group and the arch dam is calculated as K _p =((2c×cosφ)/(1-sinφ))/((1+sinφ)/(1-sinφ)×σ ₁ -σ ₃ ), where c and φ are the cohesion and internal friction angle of the abutment rock mass material, and σ ₁ and σ ₃ are the maximum and minimum principal stresses of the Mohr stress circle of the abutment rock mass when the underground powerhouse cavern group interacts with the arch dam;

Step 10: Accurately arrange the underground powerhouse cavern groups.

In step one, the characteristic parameters include the size of the arch dam, the reservoir water level, the mechanical parameters of the surrounding rock, the elastic modulus of the arch dam concrete and the Poisson's ratio.

In step three, the number of monitoring line segments is determined according to the actual accuracy requirements of the project.

In step three, the number of monitoring line segments is n, n=180/β+1, where β is the angle between two monitoring line segments.

In step three, the length of the monitoring line segment is determined according to the attenuation of the principal compressive stress of the rock mass.

In step 4, the calculation formula of the stress attenuation degree η at the toe corner of the arch dam is:

η＝(σ _max -σ)/(σ _max -σ _min )×100%, 0≤η≤1, where σ _max is the maximum stress value on the principal compressive stress variation curve along the process; σ _min is the minimum stress value on the principal compressive stress variation curve along the process, and σ is the principal compressive stress value of each node.

In step 5, the calculation formula of the inflection point η _key of the stress decay curve is:

η _key =η _a (cη _b -b)/(η _a (cb) - a(1 - η _b )), where (a, η _a ), (b, η _b )

and (c, 1) represent three groups of typical characteristic points on the stress attenuation curve, (b, η _b ) and (c, 1) are the characteristic points at both ends of the nearly horizontal section of the stress attenuation curve; (a, η _a ) and the origin (0, 0) are the characteristic points at both ends of the stress attenuation steep change section; η _key is mainly obtained based on the intersection of the line connecting the characteristic point (a, η _a ) and the origin (0, 0) and the line connecting the characteristic points (b, η _b ) and (c, 1), and the abscissa of the corresponding intersection is the stress attenuation inflection point η _key .

The method for determining the inflection point of the stress attenuation curve provided by the present invention is scientific and reasonable, and can more accurately calculate the inflection point of the stress attenuation curve than the prior art. According to Figure 5, it can be seen that when the σ _max and σ _min of two different stress attenuation curves 1 and 2 are the same, the inflection points of the two stress attenuation curves calculated by the prior art σ _n = (σ _max -σ _min ) × 5% are consistent, while the inflection points of the stress attenuation curve calculated by the method of the present invention are η _key1 and η _key2 respectively. According to the stress attenuation change in Figure 5, it can be seen that the method for calculating the inflection point of the stress attenuation curve proposed by the present invention is more scientific and reasonable, and can better reflect the stress attenuation change process. By comparing and analyzing two different stress attenuation curves, the rationality of the calculation formula for the inflection point of the stress attenuation curve of the present invention is fully explained.

In step seven, the inflection points of the stress attenuation curves of the monitoring line segments are connected by smooth curves.

In step 10, the underground powerhouse caverns are precisely arranged according to the following method:

When the underground powerhouse cavern group is arranged at any position within the arch dam load diffusion zone, _Kp >f always holds true. Then the minimum arrangement distance of the underground powerhouse cavern group near the arch dam abutment is the minimum distance between the arch dam load concentration transfer zone, the diffusion zone boundary (4) and the dam toe corner point (2). At the same time, the actual arch seat rock mass point safety degree _Kp can be calculated.

When the underground powerhouse cavern group is arranged within the arch dam load diffusion zone and K _p ≤ f, the underground powerhouse cavern group layout position is adjusted until the arch seat rock mass point safety degree K _p ＝f. At this time, the distance between the underground powerhouse cavern group and the arch dam abutment is the minimum layout distance near the arch dam abutment.

Among them, f is the preset safety value of the abutment rock mass point, and f≥1.

In actual engineering applications, the value of f is determined comprehensively based on the project grade, building importance, etc.

The present invention is now described in detail by taking the present invention being tried in a certain hydropower station as an example, which also has a guiding role in the application of the present invention in other hydropower stations.

Embodiment 1:

The hub project of a hydropower station is mainly composed of a concrete hyperbolic arch dam, flood discharge and energy dissipation buildings, left and right bank water diversion and power generation systems, and diversion buildings, with a total installed capacity of 10,200MW and a total reservoir capacity of 7.408 billion m3. The maximum dam height of the concrete hyperbolic arch dam is 270m. The underground powerhouse cavern group adopts a parallel layout of the main powerhouse, main transformer tunnel and tailwater surge chamber. The maximum excavation dimensions (length × width × height) of the main powerhouse and main transformer tunnel are 333.00m × 32.50m × 89.80m and 272.00m × 18.80m × 35.00m respectively. The diameter of the surge chamber is 53m and the height is 113.50m. The layout area of the underground powerhouse cavern group on the right bank is affected by the geological structure and is limited to the narrow triangular space surrounded by "riverbed-Baigou fault-extremely thin layer of dolomite", which has the problem of arranging the underground powerhouse cavern group near the arch dam shoulder.

In order to quantitatively control the arrangement distance of underground powerhouse cavern groups, this embodiment adopts the quantitative control method of the plant-dam safety distance of underground powerhouse cavern groups arranged near the abutment of the arch dam of the present invention, as shown in Figures 1 and 4, and its implementation process includes the following steps:

Step 1: Determine the characteristic parameters of the arch dam and rock mass;

In this example, the calculation parameters are mainly arch dam size, water level, surrounding rock mechanical parameters, arch dam concrete elastic modulus and Poisson's ratio;

Step 2: Establish a numerical simulation model and perform static analysis;

Establish a typical two-dimensional numerical simulation model of arch rings and resisting rock mass at different elevations, and conduct static analysis to obtain the stress value of each node within the model range;

In this example, the calculation range is nearly 1.0 times the dam height upstream of the arch dam, nearly 2.5 times the dam height downstream, nearly 2.0 times the dam height on both banks, and about 1 times the dam height at the dam base;

In this embodiment, the numerical simulation model establishment platform is ANSYS;

Step 3: Obtain the principal compressive stress variation curve along the arch dam toe corner of the typical monitoring line segment;

As shown in FIG4 , taking the arch dam toe corner point 2 as the reference point, n radial line segments are drawn along the arch dam toe corner point 2 as monitoring line segments; the principal compressive stress value σ of each node on the monitoring line segment is read, and the principal compressive stress variation curve along the line is drawn, as shown in FIG2 ;

In step 3, the number of monitoring line segments is n, n=180/β+1, where β is the angle between two monitoring line segments;

In this example, β=20, n=10; taking the arch dam toe corner point 2 as the reference point, 10 monitoring line segments were selected in the range of 180° in the clockwise direction at an interval of 20 degrees, and the line segment length was about 300m, as shown in Figure 4. In the figure, n is the number of detection line segments, B1, ..., Bn represent detection line segments, and β is the angle between two monitoring line segments; the stress change curves along each line segment are drawn, such as the principal compressive stress curves shown in Figures 2 and 3. In the figure, the abscissa of the principal compressive stress curve is the distance of the line segment from the arch dam toe corner point 2, in m, and the ordinate is the principal compressive stress value, in MPa;

Step 4: Draw the stress attenuation curve of the arch dam toe corner;

The stress attenuation degree η of the arch dam toe corner at each node is calculated according to the following formula:

η＝(σ _max -σ)/(σ _max -σ _min )×100%, 0≤η≤1, where σ _max is the maximum stress value on the principal compressive stress variation curve along the process; σ _min is the minimum stress value on the principal compressive stress variation curve along the process, and σ is the principal compressive stress value of each node;

And according to the stress attenuation degree η of the arch dam toe corner point, a stress attenuation curve of the arch dam toe corner point is drawn;

In this example, the stress attenuation curves of the arch dam toe corner are shown in Figures 2 and 3, where the abscissa of the stress attenuation curve is the distance between the line segment and the arch dam toe corner, in meters, and the ordinate is the stress attenuation, in dimensionless units;

Step 5: Calculate the inflection point η _key of the stress attenuation curve;

The inflection point η _key of the stress attenuation curve is calculated according to the following formula:

η _key =η _a (cη _b -b)/(η _a (cb) - a(1 - η _b )), where (a, η _a ), (b, η _b )

and (c, 1) represent three groups of typical characteristic points on the stress decay curve, (b, η _b ) and (c, 1) are the characteristic points at both ends of the nearly horizontal section of the stress decay curve; (a, η _a ) and the origin (0, 0) are the characteristic points at both ends of the stress decay steep change section; η _key is mainly obtained based on the intersection of the line connecting the characteristic point (a, η _a ) and the origin (0, 0) and the line connecting the characteristic point (b, η _b ) and (c, 1), and the abscissa of the corresponding intersection is the stress decay inflection point η _key ;

As shown in FIG3 , in this example, a=50, η _a =0.6, b=150, η _b =0.97, c=300, that is, (a, η _a ), (b, η _b ) and (c, 1) are (50, 0.6), (150, 0.97) and (300, 1) respectively, and η _key =0.95 is obtained according to the formula.

Step 6: Divide the arch dam load concentration transfer area and diffusion area;

According to step 5, the classification standards of arch dam load concentration transfer zone and diffusion zone are: η≤0.95 is arch dam load concentration transfer zone 3, η＞0.95 is arch dam load diffusion zone 5;

Step 7: Draw the boundary lines of the arch dam load concentration transfer area and diffusion area 4;

A smooth curve is used to connect the inflection points of the stress attenuation curve of each monitoring line segment to form the boundary between the arch dam load concentration transfer area and the diffusion area 4;

In this example, the stress attenuation inflection points η1, η2, ..., η10 of the 10 monitoring line segments are calculated. The 10 monitoring line segment inflection points are sequentially connected using a spline curve to obtain the boundary 4 between the arch dam load concentration transfer area and the diffusion area;

Step 8: Preliminary layout of underground powerhouse caverns;

The underground powerhouse caverns are preliminarily arranged at any position within the arch dam load diffusion zone;

In this example, the main powerhouse 6, main transformer tunnel 7 and surge chamber 8 of the underground powerhouse cavern group are preliminarily arranged within the arch dam load diffusion and transfer area 5, with a distance of 100m from the arch dam abutment;

Step 9: Calculate the safety degree of the abutment rock mass point;

According to the preliminary layout of the underground powerhouse cavern group, the safety degree of the arch seat rock mass point under the interaction between the underground powerhouse cavern group and the arch dam is calculated as _Kp = ((2c×cosφ)/(1-sinφ))/((1+sinφ)/(1-sinφ)× _σ1 - _σ3 ), where c and φ are the cohesion and internal friction angle of the arch seat rock mass material, and _σ1 and _σ3 are the maximum and minimum principal stresses of the Mohr stress circle of the arch seat rock mass when the underground powerhouse cavern group interacts with the arch dam;

In this embodiment, the safety degree of the arch seat rock mass point under the interaction condition between the underground powerhouse cavern group and the arch dam is calculated to be K _p =2;

Step 10: Accurately arrange the underground powerhouse caverns;

When the underground powerhouse cavern group is arranged at any position within the arch dam load diffusion zone, _Kp >f always holds true. Then the minimum arrangement distance of the underground powerhouse cavern group near the arch dam abutment is the minimum distance between the arch dam load concentration transfer zone, the diffusion zone boundary (4) and the dam toe corner point (2). At the same time, the actual arch seat rock mass point safety degree _Kp can be calculated.

When the underground powerhouse cavern group is arranged within the arch dam load diffusion zone and K _p ≤ f, the underground powerhouse cavern group layout position is adjusted until the arch seat rock mass point safety degree K _p ＝f. At this time, the distance between the underground powerhouse cavern group and the arch dam abutment is the minimum layout distance near the arch dam abutment.

Where, f is the preset safety value of the abutment rock mass point, and f≥1;

In actual engineering applications, the value of f is determined comprehensively based on the engineering level, the importance of the building, etc.

In this example, f is taken as 1.5; since the safety degree of the arch rock point _Kp ＝2>1.5 of the preliminary arranged underground powerhouse cavern group location, the location of the underground powerhouse cavern group is adjusted, and it is obtained that when the minimum distance 9 between the underground cavern group and the dam toe corner point 2 is 62m, _Kp ＝1.5. Therefore, in this example, the underground powerhouse cavern group is arranged 62m away from the arch dam abutment, which is only 1.2 times the corresponding arch end thickness (52m), breaking through the restriction of the traditional underground powerhouse cavern group not less than 2 times the arch end thickness. Compared with the conventional underground powerhouse cavern group not less than 2 times the arch end thickness technology, it effectively reduces the engineering volume of the water diversion power generation system and saves a total of about 1.25 billion yuan in engineering investment.

The invention discloses a quantitative control method for the safe distance of a dam and power plant in which an underground power plant cavern group is arranged near the abutment of an arch dam. The method determines the concentrated transfer area and diffusion area of the arch dam load by drawing a curve of the change of the principal compressive stress along the path and a curve of the stress attenuation. Finally, the underground power plant cavern group is accurately arranged according to the safety degree of the arch seat rock mass point, and a specific calculation method is given.

After demonstration, the method for quantitatively controlling the safe distance between the powerhouse and dam and the underground powerhouse cavern group arranged near the abutment of the arch dam proposed in the present invention has effectively solved the technical problem of arranging the underground powerhouse cavern group near the abutment of the arch dam under the condition of limited good stratum range, and has broken through the limitation of the traditional arrangement of the underground powerhouse cavern group far away from the dam and not less than 2 times the thickness of the arch end, so as to realize the quantitative arrangement of the underground powerhouse cavern group near the abutment of the arch dam, and has clear process, strong operability, low cost, scientific and reasonable, good safety, accurate quantification, and certain economic benefits, and provides a certain basis for the division of the concentrated transfer zone and diffusion zone of the arch dam load, and at the same time provides a new research idea for the arrangement of large underground powerhouse cavern groups near the arch dam.

As can be seen from the accompanying drawings, other parts not described belong to the prior art.

Claims (9)

1. The factory dam safety distance quantitative control method for arranging the underground factory building on the near arch dam abutment is characterized by comprising the following steps of: the method comprises the following steps:

Step one: acquiring characteristic parameters;

acquiring characteristic parameters of an arch dam and characteristic parameters of surrounding resistance rock mass of an arch dam abutment;

Step two: establishing a numerical simulation model and carrying out static analysis;

Establishing two-dimensional numerical simulation models of rock masses with different heights Cheng Gongjuan and resistance, and performing static analysis;

Step three: acquiring a main compressive stress along-way change curve of a toe corner of the monitoring line segment arch dam;

Using an arch dam toe corner point (2) as a reference point, drawing a radial line segment along the dam toe corner point (2) as a monitoring line segment, reading a main compressive stress value sigma of each node on the monitoring line segment, and drawing an arch dam toe corner point main compressive stress along-way change curve;

Step four: drawing a stress attenuation degree curve of the toe corner of the arch dam;

calculating the stress attenuation degree eta of the toe corner of the arch dam of each node, and drawing a curve of the stress attenuation degree of the toe corner of the arch dam according to the stress attenuation degree eta of the toe corner of the arch dam;

step five: calculating a stress attenuation degree curve inflection point eta _key;

Step six: dividing an arch dam load concentrated transfer area and a diffusion area;

dividing an arch dam load concentrated transfer area and a diffusion area according to eta _key:

Eta is less than or equal to eta _key and is an arch dam load concentrated transmission area (3), eta is more than eta _key and is an arch dam load diffusion area (5);

step seven: drawing an arch dam load concentrated transfer area and a diffusion area boundary line (4);

Connecting inflection points of stress attenuation curves of each monitoring line segment to form an arch dam load concentrated transfer area and a diffusion area boundary line (4);

step eight: initially arranging underground factory building cavern groups;

preliminarily arranging the underground factory building chamber group at any position in the range of the arch dam load diffusion area;

Step nine: calculating the safety K _p of the arch support rock mass points;

Calculating the safety K _p＝((2c×cosφ)/(1-sinφ))/((1+sinφ)/(1-sinφ)×σ₁-σ₃ of arch abutment rock mass points under the interaction condition of the underground plant cavity group and the arch dam according to the preliminary arrangement position of the underground plant cavity group, wherein c and phi are the cohesive force and the internal friction angle of arch abutment rock mass materials, and sigma ₁、σ₃ is the maximum and minimum principal stress of the arch abutment rock mass molar stress circle when the underground plant cavity group and the arch dam are interacted;

step ten: accurately arranging underground factory building cavern groups;

The underground factory building cavern group is precisely arranged according to the following method:

When the underground plant cavity group is arranged at any position within the range of the arch dam load diffusion area, K _p > f is constantly established, the minimum arrangement distance of the underground plant cavity group near the arch dam abutment is the minimum distance between the arch dam load concentrated transmission area, the diffusion area boundary line (4) and the dam toe corner point (2), and meanwhile the actual arch abutment rock mass point safety K _p can be calculated;

when the underground plant cavity group is arranged in the range of the arch dam load diffusion area and K _p is less than or equal to f, adjusting the arrangement position of the underground plant cavity group until the safety degree of the arch seat rock mass point is K _p =f, wherein the distance between the underground plant cavity group and the arch dam abutment is the minimum arrangement distance of the near-arch dam abutment;

Wherein f is a preset value of the safety degree of the arch rock mass point, and f is more than or equal to 1.

2. The factory dam safety distance quantitative control method for arranging an underground factory building on a near-arch dam abutment according to claim 1, wherein the method comprises the following steps of: in the first step, the characteristic parameters comprise the size of the arch dam, the reservoir water level, the surrounding rock mechanical parameters, the elastic modulus of the arch dam concrete and the poisson ratio.

3. The factory dam safety distance quantitative control method for arranging an underground factory building on a near-arch dam abutment according to claim 1, wherein the method comprises the following steps of: in the third step, the number of the monitoring line segments is determined according to the actual precision requirement of the engineering.

4. The factory dam safety distance quantitative control method for arranging an underground factory building on a near-arch dam abutment according to claim 3, wherein the method comprises the following steps of: in the third step, the number of the monitoring line segments is n, n=180/β+1, where β is an included angle between two monitoring line segments.

5. The factory dam safety distance quantitative control method for the near-arch dam abutment arrangement underground factory building according to claim 4, wherein the method comprises the following steps of: in the third step, the length of the monitoring line segment is determined according to the attenuation condition of the main compressive stress of the rock mass.

6. The factory dam safety distance quantitative control method for arranging an underground factory building on a near-arch dam abutment according to claim 1, wherein the method comprises the following steps of: in the fourth step, the calculation formula of the stress attenuation degree eta of the toe corner of the arch dam is as follows:

η= (σ _max-σ)/(σ_max-σ_min) x 100%, 0.ltoreq.η.ltoreq.1, where σ _max is the maximum stress value on the main compressive stress along the course change curve; σ _min is the minimum stress value on the main compressive stress along the path change curve, and σ is the main compressive stress value of each node.

7. The factory dam safety distance quantitative control method for arranging an underground factory building on a near-arch dam abutment according to claim 1, wherein the method comprises the following steps of: in the fifth step, the calculation formula of the inflection point η _key of the stress attenuation curve is:

η _key＝η_a(cη_b-b)/(η_a(c-b)-a(1-η_b), wherein (a, η _a)、(b,η_b) and (c,

1) Three groups of typical characteristic points on the stress attenuation curve are represented, wherein (b, eta _b) and (c, 1) are characteristic points at two ends of a near horizontal section of the stress attenuation curve; (a, eta _a) and the original points (0, 0) are characteristic points at two ends of the abrupt change section of the stress attenuation degree; η _key is mainly obtained from the intersection point of the connecting line of the feature point (a, η _a), the origin (0, 0) and the connecting line of the feature point (b, η _b), (c, 1), and the corresponding intersection point abscissa is the inflection point η _key of the stress attenuation degree.

8. The factory dam safety distance quantitative control method for arranging an underground factory building on a near-arch dam abutment according to claim 1, wherein the method comprises the following steps of: in the seventh step, the inflection points of the stress attenuation curves of the monitoring line segments are connected by adopting a smooth curve.

9. The factory dam safety distance quantitative control method for arranging an underground factory building on a near-arch dam abutment according to claim 1, wherein the method comprises the following steps of: in practical engineering application, the value of f is comprehensively determined according to the importance of the engineering and the like and the importance of the building.