CN109001808A - The recognition methods of the potential seepage channel of underground formula powerhouse of hydropower station based on micro seismic monitoring - Google Patents

Abstract

The present invention provides a method for identifying subsurface seepage channels of underground hydropower plant buildings based on microseismic monitoring. The steps are as follows: ① Delineate the monitoring area, arrange sensors and blast holes; ② Blast in each blast hole at different time points, record Calculate the average equivalent wave velocity of the rock mass at the take-off time of the elastic waves generated by each blasting; ③ Monitor the monitoring area through the microseismic monitoring system, measure the source position and occurrence time of the microseismic events generated in the monitoring area, and make the spatial distribution of the source position As shown in Fig. 1, when the source locations of microseismic events gather in one or some local areas of the monitoring area and present a strip or planar distribution, there are potential seepage channels in the corresponding local areas. The method of the invention can more accurately identify the potential seepage channels that appear during the construction and operation of the underground layout type hydropower plant, and is beneficial to better guide the safe construction and safe operation of the underground layout type hydropower plant.

Description

Identification of potential seepage channels in underground hydropower plant buildings based on microseismic monitoring method

technical field

The invention belongs to the field of geotechnical engineering, and relates to a method for identifying potential seepage channels of an underground layout type hydropower plant building based on microseismic monitoring.

Background technique

Many large hydropower stations are located in high mountains and valleys with limited ground space. Effective use of underground space can not only solve the problem of hub layout, but also make full use of head differences to improve water energy utilization efficiency. The Shuangjiangkou Hydropower Station, Baihetan Hydropower Station, and Lianghekou Hydropower Station currently under construction in my country, as well as the Wudongde Hydropower Station, Xiangjiaba Hydropower Station, and Ertan Hydropower Station that have been built, all adopt underground layouts, and are oriented toward large-span, large-scale excavation, etc. Develop in the direction of super-large caverns. Due to the underground layout, hydropower stations are mostly located below the natural water level formed by rainfall. During the excavation process, the surrounding rock of the hydropower station building is prone to groundwater seepage, threatening the safety of the project. Therefore, whether the excavation process of the underground hydropower plant is safe or not requires not only solving the stability of the surrounding rock of the cavern, but also accurately identifying potential seepage cracks in the rock, so as to provide a good guarantee for the safe construction of the hydropower station in the early stage and the stable operation in the later stage.

At present, the seepage problems of powerhouses of hydropower stations are mostly based on saturated-unsaturated seepage theory, combined with the basic properties of fractured rock mass, the physical experiment model or mathematical analysis model of the main powerhouse is established to provide solutions for the seepage problems of powerhouses. Physical experimental models include fracture network models, dual-media models, and porous media models. Mathematical calculation models have also made great progress in the development of seepage calculations in recent years, but these models are mostly based on data obtained from on-site geological surveys and hydrogeological surveys. First-hand data, including the physical and mechanical properties of rocks, the occurrence of fault joints, and the occurrence of groundwater, etc., did not take into account the cracks formed by the excavation of hydropower plant buildings, and the accuracy needs to be improved. Moreover, most of the underground hydropower plant buildings exist in a certain groundwater environment. During the excavation process of the underground hydropower plant buildings, drainage holes, drainage curtains and anti-seepage curtains are often used to solve the groundwater seepage problem in the main plant. Most of these are based on experience. Obtained, and adopt all-round, multi-scale construction to solve the seepage problem. It can be seen that if the seepage problem of the underground hydropower plant building cannot be accurately identified on the basis of the inability to accurately identify the rock seepage channel, it will waste manpower and material resources and delay the construction period.

The rock mass of the underground layout hydropower station building is under certain in-situ stress conditions. During the excavation and unloading process of the underground layout hydropower station building, the original in-situ stress is disturbed by the excavation, which will lead to stress redistribution and cause rock mass initiation Microcracks and the expansion of primary cracks. The development and expansion of primary fissures will not only cause the instability of surrounding rock, but the through fissures will also become potential seepage channels for groundwater. Therefore, during the excavation and unloading process of the powerhouse of the underground hydropower station and the subsequent operation of the hydropower station, it is necessary to accurately identify the expansion of primary cracks and the development and initiation of micro-cracks, and then accurately identify the potential seepage of the powerhouse of the underground hydropower station. The channel will be of great significance for solving the seepage problem of the underground layout hydropower station building and ensuring the safe construction and stable operation of the underground layout hydropower station building.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies of the prior art, and to provide a method for identifying subsurface seepage passages of underground hydropower plant buildings based on microseismic monitoring, so as to more accurately and effectively identify the hidden seepage channels of underground hydropower plant buildings during construction and operation. The potential seepage channel provides a basis for solving the stability problem of the underground hydropower plant, so as to better guide the safe construction and operation of the underground hydropower plant.

The method for identifying the submerged seepage channel of an underground layout type hydropower plant based on microseismic monitoring provided by the present invention has the following steps:

① Delineate the rock mass in the powerhouse area of the hydropower station to be identified as the potential seepage channel as the monitoring area, install the sensors of the microseismic monitoring system on the rock mass in the monitoring area, at least 4 sensors, and install the sensors on different surfaces at different elevations. The sensor is connected to the acquisition instrument of the microseismic monitoring system, and then the acquisition instrument is connected to the host part of the microseismic monitoring system; a three-dimensional rectangular coordinate system is established to measure the coordinates of each sensor, and the coordinates of the i-th sensor are marked as ( _xi , y _i , z _i ); set at least one blast hole on the rock mass in the tunnel, measure the coordinates at the center of the bottom of each blast hole, and denote the coordinate at the bottom center of the jth blast hole as (X _j , Y _j , Z _j );

②Install explosives at the bottom of each blast hole, carry out a blast in each blast hole at different time points, record the take-off time of the elastic wave generated by each blast through the sensor, and record the blasting time of the jth blast hole as t _j , the take-off time when the i-th sensor receives the elastic wave generated by the blasting after the j-th blasting hole is blasted is recorded as t _ji ;

According to the distance between the jth blast hole and each sensor, and the relationship between speed and time, corresponding to each blast hole, the following equations (1-1)~(1-i) are listed according to the two-point distance formula. The i in 1-i refers to the total number of sensors:

…

Substitute the values of the coordinates of the 1st, 2nd,...,j blastholes, the blasting time of the corresponding blasthole blasting, and the take-off time when the i-th sensor receives the elastic wave generated by the blasting after the corresponding blasthole blasting into the formula One of (1-1)～(1-i), the equivalent wave velocity of the rock mass can be obtained respectively, denoted as v ₁ , v ₂ ,…,v _j , and then the average equivalent wave velocity v of the rock mass can be calculated according to

③Monitor the monitoring area through the microseismic monitoring system, determine the source location and time of the microseismic events in the monitoring area, and make real-time statistics on the source location of the microseismic events in the monitoring area and mark the source location in the three-dimensional Cartesian coordinate system. Spatial distribution map of seismic source locations. When the seismic source locations of microseismic events gather in one or some local areas of the monitoring area and present a strip or planar distribution, there are potential seepage channels in the corresponding local areas; if microseismic events The hypocenter location of the source is discretely distributed in one or some local areas of the monitoring area, and there is no aggregation phenomenon, which means that there is no potential seepage channel in the corresponding local area;

The method of determining the source location and the moment of occurrence of microseismic events in the monitoring area is as follows:

Assuming that the coordinates of the source of the microseismic event are (X _k , Y _k , Z _k ), and the moment when the microseismic event occurs is t _k , define t _ki as the take-off time when the i-th sensor receives the elastic wave generated by the microseismic event. According to the microseismic event The distance between the source of the earthquake and each sensor, and the relationship between speed and time, the following equations (2-1)~(2-i) are listed according to the two-point distance formula, where i in 2-i refers to the sensor’s total:

…

At least 4 equations in the simultaneous equations (2-1)~(2-i) are substituted into the average equivalent wave velocity v of the rock mass, the coordinates of each sensor, and the take-off time when each sensor receives the elastic wave generated by the microseismic event value, the coordinates (X _k , Y _k , Z _k ) of the source of the microseismic event and the moment t _k of the microseismic event can be obtained.

In the technical solution of the above-mentioned microseismic monitoring-based subterranean seepage channel identification method for underground layout hydropower plant buildings, the microseismic monitoring system may adopt the ESG microseismic monitoring system or other microseismic monitoring systems.

In the technical scheme of the above-mentioned identification method for submerged seepage channels of underground hydropower plant buildings based on microseismic monitoring, the equivalent wave velocity of the rock mass can be measured and calculated by setting up one blast hole and performing one blast. Accuracy, preferably using more than one blast hole, more preferably, the number of blast holes is 2-5.

In the above-mentioned technical scheme of the identification method for the submerged seepage channel of the underground layout type hydropower plant building based on microseismic monitoring, the construction is stopped during the blasting so as not to interfere with the acquisition of the elastic wave signal generated by the blasting sensor. After the acquisition of the elastic wave signal generated by the blasting is completed, Resume normal construction.

The microseismic monitoring-based identification method for submerged seepage channels of underground hydropower plant buildings provided by the present invention uses the microseismic monitoring technology to obtain the accumulation of the source positions of the moderate earthquake events in the micro-monitoring area, and judges the monitoring according to the accumulation of the source positions of the microseismic events The development of micro-cracks in the rock body in the region: if the source location is gathered in one or some local areas of the monitoring area, it indicates that cracks are widely developed in these local areas; when the source location is in one or some local areas of the monitoring area When they are aggregated and distributed in a striped or planar form, it indicates that the fractures in the corresponding local area develop in a banded or planar form, that is, there are potential seepage channels in the corresponding local area. If the local area exists in groundwater, In other words, if there are water cavities in this local area, and the widely developed cracks can be used as potential seepage channels for groundwater, then this local area is a potential unstable area. During the construction process or the operation of the hydropower station, timely measures need to be taken to deal with it. The potential instability area is protected to ensure the construction safety and the operation safety of the underground layout hydropower plant.

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

1. The method for identifying potential seepage channels of underground hydropower plant buildings based on microseismic monitoring provided by the present invention, the method uses microseismic monitoring technology to obtain the accumulation situation of the source location of the microseismic event, and judges the location of the monitoring area according to the aggregation situation of the source location The development of micro-cracks in the rock mass, and then identify the potential seepage channels in the rock mass in the powerhouse area of the underground hydropower station. It solves the problem that the existing physical and mathematical model calculation methods are difficult to accurately identify the potential seepage channels of the underground layout hydropower plant. Compared with the existing physical and mathematical model calculation methods, the method of the present invention has advanced forecasting and convenience, and can accurately Potential seepage channels can be effectively identified, so as to better guide and guarantee the construction safety and operation safety of underground hydropower plant buildings.

2. The method provided by the present invention is a non-destructive monitoring method in a spatial range, especially capable of real-time monitoring of rock microcracks and the expansion of primary cracks caused by construction disturbances during the construction of underground hydropower plant buildings, and then judging the accumulation of microcracks Or whether the expansion of primary joints and fissures can form potential seepage channels, and it is also possible to monitor in real time whether potential seepage channels are generated during the operation of underground hydropower plant buildings.

Description of drawings

Fig. 1 is a schematic diagram of the present invention identifying potential seepage channels of an underground hydroelectric power plant building.

Fig. 2 is a sensor layout diagram in the monitoring area of the embodiment, in which S1, S2, S3, S4, S5, and S6 are sensor numbers.

Fig. 3 is a network topology diagram of the ESG microseismic monitoring system in the embodiment.

Fig. 4 is the spatial distribution diagram of the seismic source position made in the embodiment, wherein, (A) is a top view, (B) is a side view, and (C) is a partial enlarged view of (B).

Detailed ways

The method for identifying potential seepage channels of underground layout hydropower plant buildings based on microseismic monitoring according to the present invention will be further described below through specific embodiments and with reference to the accompanying drawings. It must be pointed out that the following examples are only used to further illustrate the present invention, and should not be construed as limiting the protection scope of the present invention. Those skilled in the art make some non-essential improvements and adjustments to the present invention based on the above-mentioned content of the invention. The specific implementation still belongs to the protection scope of the present invention.

Example 1

This embodiment takes the excavation construction process of the main powerhouse of a large-scale underground hydropower station as an example, and specifically explains the method for identifying the potential seepage channels of the powerhouse of the underground hydropower station based on microseismic monitoring. The present invention identifies the potential seepage channels of the powerhouse of the underground hydropower station. The schematic diagram is shown in Figure 1.

The microseismic monitoring system adopted in this embodiment is the ESG microseismic monitoring system (ESG Corporation of Canada). host part of the system). The network topology diagram of the ESG microseismic monitoring system is shown in Figure 3. Each acceleration sensor is connected to the Paladin digital signal acquisition system through cables, and the Paladin digital signal acquisition system is connected to the Hyperion digital signal processing system through a network cable. After connecting with Lianghekou Camp Office, connect with Chengdu Computing and Analysis Center through the network. The sensitivity of the sensor is 30V/g, and the frequency response range is 50Hz～5kHz. The sampling frequency of the Paladin digital signal acquisition system is 20kHz. The sensor converts the received stress wave into an electrical signal, and converts it into a digital signal through the Paladin digital signal acquisition system. The signal is then stored in the Hyperion digital signal processing system. In this embodiment, the take-off times of the elastic waves collected by the sensor are all the take-off times of the P waves.

The concrete steps of this embodiment are as follows:

①Delineate the area of about 200m×200m×200m (in three directions along the flow direction, vertical flow direction and vertical direction) of the upstream side wall of the main powerhouse of the large hydropower station as the monitoring area, and install the sensors of the ESG microseismic monitoring system in the Six sensors are installed in the drainage tunnel and air supply tunnel upstream of the main powerhouse in the monitoring area, and each sensor is numbered as S1, S2, S3, S4, S4, and S6, and each number corresponds to the first, second, and third respectively 1st, 4th, 5th, 6th sensors. The elevations of the sensors are different and form a spatial network structure respectively. The arrangement of the sensors prevents any three sensors from being located on the same straight line and any four sensors from being located on the same plane. The sensors cover the upstream side of the main building including the drainage tunnel and the air supply tunnel. The surrounding rock of the wall is shown in Figure 2. Each sensor is connected with the acquisition instrument of the microseismic monitoring system, and then the acquisition instrument is connected with the host part of the microseismic monitoring system.

Take the first machine nest along the water flow direction as the positive direction of the x-axis, take the vertical foot of the first machine nest vertical to the water flow direction as the 1100 coordinate point of the y-axis, and connect the first machine nest to the second and third machine nests The direction of the machine nest is the positive direction of the y-axis, and the absolute elevation is the positive direction of the z-axis as the coordinate reference, establish a three-dimensional rectangular coordinate system, measure the coordinates of each sensor, and denote the coordinates of the i-th sensor as (x _i , y _i , z _i ), i=1,2,3,...,6; set up two blast holes on the upstream side wall of the main building, measure the coordinates of the center of each blast hole bottom, and place the jth blast hole bottom The coordinates at the center are marked as (X _j , Y _j , Z _j ), j=1,2. Measure the coordinates of each sensor and the center of the bottom of each blast hole, and record them in Table 1 and Table 2 respectively.

Table 1 Coordinates of each sensor

Table 2 Coordinates at the bottom center of each blast hole

blast hole Easting(X)/m Northing(Y)/m Depth(Z)/m 1 -3.00 92.35 0.58 2 4.50 92.35 4.23

② Install emulsion explosives at the bottom of each blast hole, connect detonating wire and high-voltage electrostatic detonator, and seal the opening of each blast hole with loose soil particles on site to reduce energy loss during blasting. A blast is carried out in the first blast hole to the second blast hole respectively, and the interval between the two blasts is 4 days. The sensor records the take-off time of the elastic wave generated by each blast, and the blasting time of the jth blast hole is recorded as t _j , the take-off time when the i-th sensor receives the elastic wave generated by the blasting after the blasting of the j-th blasting hole is recorded as t _ji ; the excavation construction is stopped during the blasting so as not to interfere with the sensor’s collection of the elastic wave signal generated by the blasting. After completing the collection of elastic wave signals generated by blasting, normal excavation construction will resume.

According to the distance between the jth blasthole and each sensor, and the relationship between speed and time, corresponding to each blasthole, formula (1-1) is listed according to the two-point distance formula:

Substitute the coordinates of the first blast hole and the second blast hole, the blasting time of the corresponding blast hole, and the take-off time when the i-th sensor receives the elastic wave generated by the blast after the corresponding blast hole is blasted into the formula (1-1), respectively solve the rock mass equivalent wave velocity v ₁ =4028m/s, v ₂ =4034m/s, and then calculate the rock mass average equivalent wave velocity v,

③ During the construction of the hydropower plant, the monitoring area is monitored through the ESG microseismic monitoring system, and the source location and occurrence time of the microseismic events generated in the monitoring area are determined. The method of determining the source location and the moment of occurrence of microseismic events in the monitoring area is as follows:

Assuming that the coordinates of the source of the microseismic event are (X _k , Y _k , Z _k ), and the moment when the microseismic event occurs is t _k , define t _ki as the take-off time when the i-th sensor receives the elastic wave generated by the microseismic event. According to the microseismic event The distance between the seismic source and each sensor, and the relationship between speed and time, according to the two-point distance formula, the following six equations are listed:

Combining the above six equations, substituting the average equivalent wave velocity v of the rock mass, the coordinates of each sensor, and the value of the take-off time when each sensor receives the elastic wave generated by the microseismic event, the coordinates of the source of the microseismic event (X _k , Y _k , Z _k ) and the moment t _k of microseismic occurrence.

During the microseismic monitoring period, the source locations of the microseismic events in the monitoring area are counted in real time, and the source locations are marked in the three-dimensional rectangular coordinate system in real time to obtain the spatial distribution map of the source locations, which is combined with the distribution of the source locations in the spatial distribution map of the source locations. Judging, when the source locations of microseismic events are gathered in one or some local areas of the monitoring area and present a strip or planar distribution, then there are potential seepage channels in the corresponding local areas; if the source locations of microseismic events are in If one or some local areas in the monitoring area are discretely distributed and no aggregation phenomenon occurs, it means that there are no proven controlling faults and other structural planes in the corresponding local area, that is, there are no potential seepage channels in the corresponding local area.

In the monitoring process of the present embodiment, after monitoring for 45 days, 221 microseismic events occurred in total, and the spatial distribution map of the microseismic position events made, as shown in Figure 4, as can be seen from Figure 4, the epicenter position of the microseismic events occurred In a local area upstream of the main powerhouse (the local area framed by the dotted line in (C) of Figure 4) and presenting a strip-like distribution, it indicates that there are potential seepage channels in this local area. It is suggested that during the construction of the main powerhouse of the underground hydropower station, protective measures should be taken for the local area, such as concrete grouting and other measures to ensure the construction safety of the main powerhouse of the hydropower station.

Claims (3)

1. The seepage channel recognition methods 1. the underground formula powerhouse of hydropower station based on micro seismic monitoring is dived, it is characterised in that step is such as Under:

   1. drawing a circle to approve the powerhouse of hydropower station region rock mass of pending potential seepage channel identification as monitoring region, by micro seismic monitoring system The sensor of system is mounted on the rock mass in monitoring region, and sensor is at least 4, and each sensor antarafacial is installed on different elevations, Each sensor is connected with the Acquisition Instrument of Microseismic monitoring system, then by the host machine part of the Acquisition Instrument and Microseismic monitoring system Connection；Three-dimensional cartesian coordinate system is established, the coordinate of each sensor is measured, the coordinate of i-th of sensor is denoted as (x_i,y_i,z_i)； At least one blast hole is set on the rock mass in tunnel, the coordinate at each blast hole bottom hole center is measured, by j-th of blast hole Coordinate at bottom hole center is denoted as (X_j,Y_j,Z_j)；

   2. the bottom hole in each blast hole installs explosive, onepull is carried out in each blast hole respectively in different time points, is passed through Sensor records the take-off moment for the elastic wave that each separate explosion generates, and the blowing-up time of j-th of blast hole is denoted as t_j, by jth The take-off moment that i-th of sensor receives the elastic wave of explosion generation after a blast hole explosion is denoted as t_ji；

   According to the distance between j-th of blast hole and each sensor and the relationship of speed and time, correspond to each explosion Hole following equation (1-1)~(1-i) is listed according to two o'clock range formula:

   …

   Respectively by the 1,2nd ..., the coordinate of j blast hole, the blowing-up time of corresponding blast hole explosion and corresponding explosion After the explosion of hole i-th of sensor receive explosion generation elastic wave the take-off moment value substitute into formula (1-1)~(1-i) it One, the equivalent velocity of wave of rock mass can be solved respectively, be denoted as v₁,v₂,…,v_j, rock mass average equivalent velocity of wave v is then calculated,

   3. being monitored by Microseismic monitoring system to monitoring region, the hypocentral location for the microseismic event that measurement monitoring region generates And the moment occurs for microseism, hypocentral location is simultaneously shown in three-dimensional by the hypocentral location for the microseismic event that real-time statistics monitoring region occurs In rectangular coordinate system, obtain hypocentral location spatial distribution map, when the hypocentral location of microseismic event monitoring region a certain or certain When a little regional area aggregations and presentation ribbon or planar distribution, then i.e. there are potential seepage channels in corresponding regional area；

   It is as follows that the method at moment occurs for the hypocentral location for the microseismic event that measurement monitoring region generates and microseism:

   Assuming that the coordinate of the focus of microseismic event is (X_k, Y_k, Z_k), it is t at the time of microseism occurs_k, define t_kiIt is sensed for i-th Device receives the take-off moment of the elastic wave of microseismic event generation, according between the focus of microseismic event and each sensor away from From and speed and time relationship, following equation (2-1)~(2-i) is listed according to two o'clock range formula:

   …

   At least four equation in joint type (2-1)~(2-i), substitute into rock mass average equivalent velocity of wave v, each sensor coordinate, with And each sensor receives the value at the take-off moment of the elastic wave of microseismic event generation, can solve the seat of the focus of microseismic event Mark (X_k, Y_k, Z_k) and microseism occur at the time of t_k。
2. 2. the latent seepage channel recognition methods of the underground formula powerhouse of hydropower station based on micro seismic monitoring according to claim 1, It is characterized in that, the Microseismic monitoring system is ESG Microseismic monitoring system.
3. The seepage channel identification side 3. the underground formula powerhouse of hydropower station according to claim 1 or claim 2 based on micro seismic monitoring is dived Method, which is characterized in that the quantity of blast hole is 2~5.