JP2903502B2 - System and method for predicting groundwater ahead of face - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a system and method for predicting groundwater in front of a face for predicting the presence of groundwater in front of the face from the temperature of the face.

[0002]

2. Description of the Related Art In tunnel excavation work, it is very important information to detect in advance whether or not there is protruding groundwater in order to efficiently promote the work. Conventionally known methods for predicting groundwater include, for example, "A method for investigating groundwater by measuring landslide geothermal temperature" by Atsuo Takeuchi (Yoshii Shoten, first edition issued on August 15, 1983) and "Method for investigating flowing groundwater by measuring temperature". (Kokin Shoin, March 1, 1996
The first report issued on March 2), Masahiro Hasegawa, "Experimental research on methods for predicting soil and geological properties of face and ground in front of face in tunnel excavation work" are reported.

[0003] In the former two methods, the ground temperature in the deep underground is theoretically estimated by a 1m deep ground temperature measurement survey.
By comparing this with the measured ground temperature, information on a thermal abnormality caused by groundwater or the like existing underground is grasped in advance. Here we extend this theory, which was designed for groundwater near the surface of the ground, and show the possibility of predicting the presence of groundwater by comparing estimated and measured rock temperature along the tunnel route.

[0004] The latter study predicts an aquifer by comparing a measured ground temperature of a face with an estimated ground temperature. The concept of this method is almost the same as the case of the above-mentioned investigation method, but specifically shows a method of measuring the face temperature. Here, a method is used in which a ground temperature measurement hole having a depth of 2 m is drilled in the face face, and the temperature in the pit is measured with a contact-type thermometer.

[0005]

However, the above-mentioned conventional survey method qualitatively indicates the possibility of groundwater exploration, such as the tendency of the relative temperature difference, but how and under what conditions It is not clear how (such as location) it can be predicted that groundwater will be present if the temperature measurements are accurate. In addition, temperature distribution prediction considering differences in various conditions (groundwater temperature, groundwater scale, groundwater form, presence or absence of groundwater flow, underground temperature, etc.) related to groundwater and rock temperature has not been studied. Further, in the case of the above survey method, the temperature measurement is performed on the side wall surface after excavation, but the temperature value may be affected by long-time contact with the downhole air. In a recent case, the effectiveness of face measurement is also suggested, but no specific method is given.

[0006] In the above-mentioned conventional research, the possibility of groundwater exploration is also qualitatively indicated, such as the tendency of the relative temperature difference. It is not clear how groundwater can be predicted. In addition, prediction of temperature distribution due to the presence of groundwater has not been studied at all. Furthermore, since temperature measurement by drilling is premised, it takes time and effort to conduct the survey, and since it is measured at a single point near the face, it may be affected by local trends.

As other methods, there have been conventionally used electric sounding methods and elastic wave sounding methods, but the information obtained by these methods does not directly indicate the presence of groundwater. In addition, since the presence of groundwater is indirectly predicted by capturing the geological structure and the like, the reliability of the groundwater prediction method is poor.

[0008]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and enables highly reliable prediction of the presence, size, direction, distance, etc. of groundwater in front of a face.

For this purpose, the present invention provides a front face groundwater prediction system for predicting the presence of groundwater in front of a face from a face temperature, a face temperature measuring means for measuring the face temperature, and environmental conditions affecting the rock temperature. A heat conduction analysis means for performing a heat conduction analysis by changing the above-mentioned variable elements by a rock temperature prediction model incorporating a variable element relating to the condition of groundwater to be predicted and predicting a rock temperature distribution of a plurality of cases; A matching means for comparing the measured temperature profile in the face advancing direction measured by the measuring means with the predicted temperature profile of the rock temperature distribution predicted by the heat conduction analyzing means and selecting a matching case; Groundwater presence based on the predicted matching groundwater variables in the matched case It is characterized in that an output means for outputting the prediction result of the situation.

Further, the heat conduction analysis means performs a heat conduction analysis by a finite element method, and the basic elements include parameters relating to the topography of the ground and the thermal characteristics of the ground, parameters relating to groundwater, rocks and groundwater. The heat transfer coefficient, the variable element is the presence or absence of groundwater, the scale, the position, the face temperature measuring means measures the face temperature immediately after the start of the construction cycle and before spraying concrete, It is characterized by using a contact measurement technique.

Further, as a method for predicting groundwater in front of a face,
Immediately after the start of the construction cycle of tunnel excavation, which repeatedly performs drilling, blasting, shearing, concrete spraying, shoring, etc., the face temperature is measured to obtain the actual measured temperature profile in the face advancing direction. Performing a heat conduction analysis using the element model to predict the rock temperature distribution in the direction of face movement to obtain predicted temperature profiles for multiple cases, comparing the measured temperature profile with the predicted temperature profile, performing pattern matching and selecting a matching case And the presence, location, scale, etc. of groundwater are estimated.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a view showing an embodiment of a system for predicting groundwater in front of a face according to the present invention, wherein 1 is a temperature measuring section, 2 is an actually measured temperature profile creation processing section, 3 is an actually measured temperature profile storage section, and 4 is an analysis element setting. A processing unit, 5 is a heat conduction analysis processing unit, 6 is a predicted temperature profile storage unit, 7 is a pattern matching processing unit, and 8 is a groundwater prediction result output unit.

In FIG. 1, a temperature measuring section 1 measures a face temperature for obtaining an actually measured temperature profile in a face traveling direction along with the progress of tunnel excavation. Using a thermal infrared remote sensing (non-contact measurement) method such as an infrared video camera, the surface temperature of the face and the temperature inside the borehole are measured. Of course, if the non-contact measurement method as described above is used, work such as drilling the face face is not required at all, so that the measurement can be easily performed. However, it is also possible to use another measurement method such as a thermocouple. Not even. In conventional rock temperature measurement, drilling is performed on the face and side walls, and the internal temperature distribution is measured with a contact-type thermometer.However, drilling requires time and does not conform to the construction cycle at the site In addition, there is a problem that the measurement points are limited, and the temperature may be affected by local temperature trends.
On the other hand, the thermal infrared remote sensing method that employs a thermal infrared video camera or a simple radiation thermometer can measure the face temperature immediately after digging in a face-to-face and non-contact manner. Less and more efficient,
In addition, the temperature can be measured a plurality of times as the construction proceeds without disturbing the construction cycle at the site. The actually measured temperature profile creation processing unit 2 creates an actually measured temperature profile from the wellhead to the face based on the temperature data measured by the temperature measuring unit 1, and stores the measured temperature profile in the measured temperature profile. The profile storage unit 3.

The analysis element setting processing unit 4 is an analysis element for performing a predictive analysis by a steady / unsteady heat conduction analysis method of the finite element method according to a finite element model (rock temperature prediction model) of the ground to be investigated. Is input and set, and there are a basic element (environmental condition) and a variable element (variable to be predicted) as elements related to this prediction model. The basic element is an environmental condition element that affects the rock temperature and can be fixedly set for prediction within a predetermined section (however, it is adjusted if there is a change with the progress of construction). These are obtained based on the results of geological surveys, etc. For elements for which actual values cannot be obtained in the field, values based on past documents or values estimated on average are used. The variable element is a variable relating to “the condition of groundwater” to be actually predicted in the present invention, and is used for heat conduction analysis in order to obtain estimated rock temperature in a plurality of cases predicted by changing various conditions relating to groundwater and the like. Change the setting condition of.

The heat conduction analysis processing unit 5 performs a heat conduction analysis by the finite element method using the set basic elements and variable elements. Here, a constant (heat conduction) related to the rock obtained from the geological survey results is obtained. Rate, specific heat, etc.) and conduct analysis by changing conditions such as geological differences, estimated groundwater scale and location. The predicted temperature profile storage section 6 stores a plurality of predicted temperature profiles before and after the face, which are predicted by changing various conditions by such heat conduction analysis. The pattern matching processing unit 7 selects a temperature prediction result that is most matched by comparing the measured temperature profile with the predicted temperature profiles of a plurality of cases in which the temperature prediction of the plurality of cases is performed by changing the variable factors.
The groundwater prediction result output unit 8 outputs, as the groundwater condition prediction result, the setting condition of the variable element when calculating the temperature prediction result selected as the temperature prediction result most matched by the pattern matching processing unit 7. It is.

Next, a method for predicting groundwater in front of a face according to the present invention will be described. FIG. 2 is a diagram for explaining a relationship between rock temperature and groundwater, FIG. 3 is a diagram for explaining a relationship between a tunnel digging construction cycle and a timing of measuring a face temperature, and FIG. 4 is an example of an arrangement state of measurement points. , FIG. 5 is a diagram for explaining the flow of the groundwater prediction process, FIG. 6 is a diagram showing an example of a variable element, and FIG. 7 is a diagram showing an outline of a rock temperature prediction model and a groundwater diagnosis algorithm.

Since groundwater generally shows a temperature different from the normal temperature of the rock, its presence affects the temperature of the surrounding rock and forms a temperature field different from the normal temperature. Therefore, when the rock surface temperature of the face is measured as the tunnel excavation progresses, by comparing the rock surface temperature with the normal temperature as shown in FIG. 2, it is possible to catch the abnormality of the temperature field and predict the presence of groundwater. The present invention predicts the rock temperature distribution in a predetermined section in the face advancing direction by changing the presence conditions (position, scale, etc.) of the groundwater, measures the temperature of the face as the face advances, and compares these. In this way, the position, scale, etc. of the groundwater are predicted.

As shown in FIG. 3, the construction cycle of tunnel excavation includes drilling, blasting, shearing out, and concrete spraying / supporting work.
Assuming that the blasting time is about 2 m and 3 times a day, about 5 to 5 times a day
It is about 6 m. In the present invention, the measuring time of the face temperature is performed immediately after the start of the construction cycle and before the spraying of the concrete, whereby the blasting heat and the drilling water, the temperature due to the heat of hardening of the sprayed concrete. It is possible to eliminate the influence on the distribution and the influence on the work by the heavy equipment or the like at the time of observation. The measurement points are shown in FIG.
By setting multiple points on the top, bottom, left and right of the face as shown in, the influence of local temperature distribution is eliminated, and the average temperature of the entire face can be grasped. If there is a bias in the temperature distribution over the entire surface, it can be used to estimate the location of groundwater, etc.

As described above, as the tunnel excavation progresses, the face temperature is repeatedly measured immediately after the start of the construction cycle, and the measured temperature profile is obtained as the measured value of the face temperature change. The presence / absence and position of the groundwater are estimated by comparing the estimated temperature profile in the traveling direction of the face as an estimated value of a plurality of cases where the existence position and the like of the groundwater are changed by the model and selecting a matching case. FIG. 5 shows the flow of the processing.

First, a finite element model representing the shape of the ground along the tunnel route, which is the basis of groundwater prediction, is created (step S21). Here, ground surface data is created from a topographic map or the like, and the underground portion is equally divided into elements of an appropriate size based on the data. Then, a prediction section of about several tens of meters is set around the current face point (step S2).
2) Then, basic elements (rock ground thermal characteristics, heat transfer coefficient, groundwater shape, water temperature, etc.) which can be set almost fixed thereto are set (step S23). These are based on the results of preliminary surveys such as boring surveys, etc., except when there are multiple possibilities and when no case is found that matches the pattern matching between the predicted values and the actually measured values at the subsequent stage.
Basically do not change within the prediction interval. At the same time, the variables related to groundwater to be predicted (presence, size, and location of groundwater)
Is set (step S24). FIG. 6 shows an example of the setting of this variable element. In the case of the setting with groundwater as shown in FIG. 6, the position (front, diagonal, side) and the like are changed, and the condition of a plurality of cases is changed. Set. In addition, for comparison and verification, a case without groundwater indicating normal rock temperature is also set.

Next, according to the setting results of the basic element and the variable element, the physical property values of the respective elements of the finite element model of the ground are set, such as the setting of the groundwater existence range and the water temperature, and the setting of the rock physical property value. Settings are made (step S25). In this way, a finite element model for conducting heat conduction analysis is prepared. Subsequently, using the finite element model in which the physical property values are set, the heat conduction analysis is repeatedly performed while changing the variable element based on the setting condition of the basic element (analysis period and the like) (step S2
6). Then, a predicted temperature profile along the tunnel route corresponding to each case is created from the obtained temperature distribution data of a plurality of cases (step S27).

By comparing the predicted temperature profiles of the rock temperatures in a plurality of cases obtained by the above steps with the actually measured temperature profiles obtained by measuring the face temperature as the excavation progresses, an estimated case matching the actual measurement by pattern matching is selected. (Step S29). It is determined whether or not an appropriate estimated case has been found (step S32). If no appropriate estimated case has been found, the process returns to step S23, where the basic elements are set again, and the same processing is repeated again. Then, when an appropriate estimation case is found, the setting condition of the variable element is output as a groundwater prediction result (step S33). As a result, a diagnosis result regarding the presence / absence, scale, location, etc. of the groundwater can be obtained.

Next, basic elements and fluctuation elements related to the groundwater prediction model will be described in detail. As shown in FIG. 7, the basic elements which are elements of environmental conditions that affect the rock temperature include the topography of the ground, parameters related to groundwater, and the ground (rock).
And the heat transfer coefficient between bedrock and groundwater. The topography of the ground is specifically determined using topographic maps, etc., along the tunnel route (elevation data)
Is measured, and a finite element model of the ground (rock) is constructed based on the measured values, and this finite element model serves as a basis for rock temperature prediction. As parameters related to groundwater,
Shape, flow / non-flow distinction, groundwater temperature, water temperature change, existence period are listed, and parameters related to the thermal characteristics of the ground (rock) include heat conduction coefficient, specific heat, and density. The heat transfer coefficient between rock and groundwater is a coefficient representing the heat exchange performed between rock and groundwater, and is W / m ^2.
・ It is given by K, and it is set based on the previous literature and sample measurement as well as the thermal conductivity coefficient.

Each element of the parameters relating to groundwater will be described in more detail. The existence form of groundwater in the rock may be massive, linear or planar along the crush zone. The groundwater shape is selected based on the distribution of shatter zones within the prediction range based on the results of geological surveys, etc., based on these three types of forms. Incorporate into the finite element model. Groundwater can be considered to exist in two forms, that is, when the groundwater stays in the bedrock and when it is constantly recharged and flowing. For example, it is considered that groundwater deep in the ground is non-fluid because it is gradually recharged over a long period of time, and groundwater in a shallow layer is constantly recharged with surface water and is fluid. flow·
Since the non-flow distinction affects the amount of heat that the groundwater gives to the surrounding rock for a long time, that is, the rock temperature distribution, one of the forms is selected with reference to the results of the geological survey, the topography (cover thickness), and the existing literature. The groundwater temperature defines the degree of influence of the presence of groundwater on the rock temperature distribution (shape of the temperature profile along the tunnel route) and is an important factor in groundwater prediction. The groundwater temperature is set based on the temperature logging in the preliminary survey and the measurement of the groundwater temperature flowing out as the excavation progresses. Deep groundwater is generally considered to be at a constant temperature, but shallow groundwater may be affected by the annual change in the temperature of incoming surface water. As a result, the rock temperature distribution near the groundwater (the shape of the temperature profile along the tunnel route) is particularly affected, and it may be different from the case where there is no annual change. The groundwater temperature is based on the results of temperature logging in the preliminary survey and the like, and the presence or absence of the change in the groundwater temperature and its degree are given by a sin function or the like. The selection of the flow / non-flow classification and the presence / absence of the groundwater temperature change determines whether to use the steady-state analysis (flow and no water temperature change) or the unsteady analysis (others) during the heat conduction analysis. The existence period is an element that sets how much time has passed since the inflow of groundwater. If the existence period is long, the influence of groundwater on the rock temperature will be wide. The existence period is set based on the results of geological surveys, groundwater surveys, and existing literature.

Each element of the parameters relating to the thermal characteristics of the ground (rock) will be described in more detail. The coefficient of thermal conductivity is a coefficient that regulates the ease with which heat can be transmitted through rock.
Given by W / m · K,
The value obtained by actual measurement for a rock sample is adopted. The specific heat is a coefficient defining the easiness of the temperature change of the rock, and is given in J / kg · K.
It is set based on existing literature and sample measurements. Density is a coefficient representing the weight per unit volume of rock mass, and is expressed in kg / m.
It is given by ³ and, together with the specific heat (by multiplication), defines the easiness of temperature change of the rock. This density is also set based on past literature and sample measurements, as with the thermal conductivity coefficient.

As shown in FIG. 6, the variables include the presence or absence of groundwater, the scale of groundwater, and the position of groundwater. Of these, the presence or absence of groundwater is the most basic variable related to diagnosis that determines whether to incorporate groundwater into the rock temperature prediction model (a finite element model of the ground). If groundwater exists, temperature distribution prediction is performed by incorporating the various elements described above into the model. However, when groundwater does not exist, the elements related to groundwater including basic elements are excluded from the model. That is, only the normal rock temperature is estimated. The scale of groundwater is an element representing the thickness and spread of groundwater, and is an element related to the calorific value of the groundwater. This factor affects the rock temperature distribution, especially when there is no groundwater flow (such as groundwater in the rock). On the rock temperature prediction model (ground element finite element model), the range of the groundwater element expressed there is changed, and the temperature distribution according to the difference in scale is predicted. The position of groundwater depends on the current face position,
It is an element that determines whether or not it exists in the distance. This is a highly important element that is the main prediction target in the present invention. On the rock temperature prediction model (the finite element model of the ground), the position expressing the groundwater element is changed, and the temperature distribution according to the difference in the position is predicted.

It should be noted that the present invention is not limited to the above embodiment, and various modifications are possible. For example, in the above embodiment, the heat conduction analysis by the finite element method was performed. However, as long as a predicted temperature profile of the face temperature change can be obtained, another analysis method may be adopted, and a plurality of rock masses may be used. After matching the predicted temperature profile of temperature, pattern matching with the measured temperature profile was performed, but pattern matching was performed each time the predicted temperature profile of rock temperature in each case was obtained by heat conduction analysis using the finite element method. It may be. In addition, there are four basic elements: ground terrain, parameters related to groundwater, parameters related to thermal characteristics of ground (rock), heat transfer coefficient between rock and groundwater.
Although the description has been made with reference to the scale of the groundwater and the position of the groundwater, these can be appropriately changed according to the situation. Further, the description has been given of the case where the present invention is applied to the construction of a tunnel excavation. However, it is needless to say that the present invention can be similarly applied to the prediction of groundwater at the time of the construction of an excavation including an underground cavity such as a shaft, a tunnel, and a large underground space. .

[0028]

As is apparent from the above description, according to the present invention, a face in consideration of various conditions relating to groundwater and the environment, such as groundwater existence form, scale, distance, fluidity, rock properties, underground temperature, etc. Multiple cases are predicted by a rock temperature prediction model (a finite element model of ground) that can perform temperature prediction.
Based on the comparison (inverse analysis) between the prediction result and the actual measurement, the existence and the distance of the groundwater are estimated, so that the groundwater in front of the face based on an objective and quantitative criterion can be predicted.
In addition, in the measurement of rock temperature, the temperature of the face immediately after cutting is reduced efficiently and efficiently by adopting a thermal infrared remote sensing method using a simple radiation thermometer or thermal infrared video camera. In addition, the temperature can be measured in a non-contact manner, and the surface temperature can be measured in a short time in consideration of the construction cycle. Furthermore, according to the rock temperature prediction model (ground element finite element model), parameters such as groundwater temperature and rock physical properties can be set organically according to the information acquisition level. Predictable. In other words, under the condition where the parameters are not sufficiently obtained, the warning level prediction for determining only the presence or absence of the groundwater is performed, and under the condition where the parameters such as the groundwater temperature are sufficiently obtained, the groundwater shape and the scale are included. It is possible to respond flexibly, for example, by making accurate predictions.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of a front face groundwater prediction system according to the present invention.

FIG. 2 is a diagram for explaining the relationship between rock temperature and groundwater.

FIG. 3 is a diagram for explaining a relationship between a construction cycle of tunnel excavation and a timing of measuring a face temperature.

FIG. 4 is a diagram showing an example of the arrangement of measurement points.

FIG. 5 is a diagram for explaining the flow of groundwater prediction processing.

FIG. 6 is a diagram illustrating an example of a variable element.

FIG. 7 is a diagram showing an outline of a rock temperature prediction model and a groundwater diagnosis algorithm.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Temperature measurement part, 2 ... Measured temperature profile creation processing part, 3 ... Measured temperature profile storage part, 4 ... Analysis element setting processing part, 5 ... Heat conduction analysis processing part, 6 ... Predicted temperature profile storage part, 7 ... Pattern Matching processing unit, 8 ... Groundwater prediction result output unit

Claims (7)

(57) [Claims] 1. A face front groundwater prediction system for predicting the presence of groundwater in front of a face from a face temperature, a face temperature measuring means for measuring the face temperature, and basic factors and prediction of environmental conditions affecting rock temperature. Heat conduction analysis means for performing a heat conduction analysis by changing the above-mentioned variable elements by a rock temperature prediction model incorporating a variable element relating to the condition of groundwater to be measured, and predicting a rock temperature distribution of a plurality of cases, and measuring by the face temperature measuring means. A matching means for comparing the measured temperature profile in the traveling direction of the face and the predicted temperature profile of the rock temperature distribution predicted by the heat conduction analyzing means to select a matching case, and a matching selected by the matching means. Outputs the prediction result of groundwater existence status based on the variables related to the groundwater status to be predicted in the case And a groundwater predicting system in front of the face. 2. The system for predicting groundwater in front of a face according to claim 1, wherein said heat conduction analyzing means performs a heat conduction analysis by a finite element method. 3. The basic element includes a parameter related to the topography of the ground and a thermal characteristic of the ground, a parameter related to groundwater,
2. The face front groundwater prediction system according to claim 1, comprising a heat transfer coefficient of rock and groundwater. 4. The variable element includes presence or absence of groundwater, scale,
The front face groundwater prediction system according to claim 1, comprising a position. 5. The system for predicting groundwater in front of a face according to claim 1, wherein the face temperature measuring means measures the face temperature immediately after the start of the construction cycle and before the spraying of the concrete. 6. The system for predicting groundwater in front of a face according to claim 1, wherein said face temperature measuring means uses a non-contact measurement method. 7. A face temperature is measured immediately after the start of a construction cycle of a tunnel excavation in which drilling, blasting, shearing, concrete spraying / supporting, etc. are repeated, to obtain an actually measured temperature profile in the face advancing direction. Performing a heat conduction analysis by a finite element model of the ground to predict the rock temperature distribution in the face traveling direction to obtain a predicted temperature profile of a plurality of cases, comparing the measured temperature profile with the predicted temperature profile and performing pattern matching. A method for estimating groundwater in front of a face, comprising selecting a matching case and estimating the presence, location, scale, etc. of groundwater.