JP2007113333A - Method of managing facing of tunnel using spring water pressure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of managing the facing of a tunnel using a spring water pressure on the basis of the level and pressure of underwater around the facing together with the physical properties of a natural ground. <P>SOLUTION: In this method of managing the facing of the tunnel using the spring water pressure, the presence or absence of underground water is checked and the spring water pressure is measured at the front of the facing of the tunnel repeatedly each time the facing advances by a predetermined distance. When the spring water pressure exceeds a specified value when it is measured or the amount of the spring water is large, a tunneling construction is suspended and draining is performed. After it is confirmed that the level and pressure of underwater are sufficiently lowered, the tunneling construction is re-started. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a tunnel face management method using a spring pressure that measures a spring pressure near a tunnel face using a simple spring pressure measuring device and manages the tunnel face based on the spring pressure value. It is.

Conventional face management in a sandy mountain tunnel is performed by physical characteristics such as the grain size of sandy soil that constitutes the face of the tunnel, evaluation of deformation of the face caused by excavation, evaluation of external force generated by excavation, etc. I came. However, since the groundwater flow is greatly involved in the stability of the face of the sandy land mountain tunnel, the need for evaluation has been pointed out (see Non-Patent Document 1 below).
Applied Geology, Vol.40, No.5, “Study on Self-sustainability Evaluation Test of Sandy Soil Tunnel Face” P270-280, 1999 “Design standard for railway structures, etc. Urban mountain tunnel”; Railway Research Institute, 2002

  As described above, when tunnel excavation is performed in sandy ground, in order to evaluate the stability of the face, in addition to the physical properties of the stratum constituting the face as described above, the situation of groundwater existing around the face is determined. It is essential to understand. Until now, however, the physical properties of the natural ground have been mainly used for the management of the face, and the face management based on the groundwater level and groundwater pressure around the face has hardly been performed.

  In view of the above situation, an object of the present invention is to provide a face management method using spring water pressure based on groundwater level and groundwater pressure around the face along with physical properties of natural ground.

In order to achieve the above object, the present invention provides
[1] In the face management method using spring pressure, the presence of groundwater and the spring pressure at the face of the tunnel are measured at the face of the tunnel, and this is repeated every time the face advances by a predetermined distance. If the spring water pressure exceeds the specified value or there is a large amount of spring water, the tunnel excavation work will be interrupted and groundwater level will be lowered. After confirming that the groundwater level and spring water pressure have dropped sufficiently, tunnel excavation work will be carried out. It is characterized by restarting.

  [2] In the face management method using the spring pressure described in [1] above, the predetermined value of the spring pressure is 0.1 MPa.

  [3] In the face management method using the spring pressure described in [1] or [2] above, a position in front of the face is about 20 m, and a predetermined distance traveled by the face is about 10 m.

  According to the present invention, tunnel excavation work can be proceeded safely by capturing groundwater near the face of the tunnel and sufficiently lowering the groundwater level.

  In the tunnel face management method using spring pressure of the present invention, when the geology is composed of unconsolidated earth and sand, the groundwater is localized due to the heterogeneity of the geology, so only the groundwater level lowering work to be performed in advance Then, there is a possibility that groundwater will remain near the face and destabilize the face. In such a case, the presence of groundwater and the spring pressure in front of the face are measured at the face of the tunnel, and this is repeated every time the face advances a predetermined distance, and when the spring pressure is measured, the spring pressure exceeds a predetermined value, If there is a large amount of spring water, the tunnel excavation work will be interrupted and groundwater level lowering work will be carried out. After confirming that the groundwater level and spring pressure have sufficiently decreased, the tunnel excavation work will be resumed.

  Hereinafter, embodiments of the present invention will be described in detail.

  First, an outline of a spring pressure measuring device for measuring spring pressure will be described.

  FIG. 1 is a configuration diagram of a spring pressure measuring apparatus according to the present invention, FIG. 2 is a front view of the measuring device, and FIG. 3 is a side view of the measuring device.

  In FIG. 1, 1 is an iron cross bit (diameter φ 45 mm), 2 is a self-drilling lock bolt (diameter φ 28.5 mm) having the iron cross bit 1 at the tip, 3 is an adapter, and 4 is an adapter to the self-drilling lock bolt 3. Branch hollow tube (cheese) connected through 3, 5 is a first valve connected to the branch hollow tube 4, 6 is an operating lever of the first valve 5, and 7 is a branch hollow tube. 4 is a second valve connected to 4, 8 is an operation lever of the second valve 7, 9 is a bushing, 10 is a pipe adapter, 11 is an O-ring, 12 is a water pressure gauge connected to the second valve 7, 13 Is a connection portion, and 14 is a cable connected to the water pressure gauge 12 via the connection portion 13. The branched hollow tube (cheese) 4 is formed of a T-shaped hollow tube, and the front end of each hollow tube is the rear end of the self-drilling lock bolt 2, the front end of the first valve 5, and the first It is comprised so that it may be screwed together and connected with the front-end | tip part of the 2 valve | bulb 7, respectively.

  The cable 14 is connected to the connection portion 16 of the measuring instrument 15 shown in FIGS. 2 and 3, and the spring pressure is digitally displayed on the display portion 17.

  This spring pressure measuring device in the vicinity of the face measures the water pressure of groundwater localized near the face. That is, since this apparatus can be connected to the self-drilling lock bolt 2 used at the construction site via the adapter 3, it can be applied at various sites. Moreover, this apparatus can measure a water pressure up to about 2 MPa.

  Here, the front face of the tunnel is drilled using a self-drilling lock bolt 2 with an iron cross bit 1. Therefore, when the operation lever 6 is operated to open the first valve 5, spring water flows out through the self-piercing lock bolt 2 -branch hollow tube 4 -first valve 5. Thereby, the state of spring water can be seen.

  Furthermore, when the operation lever 8 of the second valve 7 is operated to open the second valve 7 and the operation lever 6 of the first valve 5 is operated to close the first valve 5, the spring water pressure is changed to the water pressure. Since the load is applied to the meter 12, the spring pressure can be measured with the water pressure meter 12. In other words, the spring pressure output from the water pressure gauge 12 is taken into the measuring device 15 via the cable 14 -connecting portion 16 and is digitally displayed on the display portion 17.

  It was found that the spring pressure near the face can be measured with this spring pressure measuring device. Based on these facts, the face management method based on spring pressure measurement is shown below.

  FIG. 4 is a tunnel excavation flowchart using the face management method using spring water pressure according to the present invention.

  First, a preliminary survey is performed in step S1, and based on the result of the preliminary survey, the necessity of groundwater level lowering work by ground level classification and groundwater level is examined in step S2. If it is determined in this step S2 that a groundwater level lowering work is necessary (YES in step S3), a first-stage groundwater level lowering work (long drainage boring) is performed (step S4). . If it is determined in step S2 that groundwater level lowering work is not necessary (NO in step S3), the process proceeds to step S13.

  Next, in step S5, spring pressure is measured. As a result, when the spring water pressure is equal to or higher than the reference value (NO in step S6), a second-stage groundwater level lowering work (short drainage boring) is performed (step S7). In step S6, when the spring pressure is below the reference value, the process proceeds to step S10.

  Here again, in step S8, the spring pressure is measured. As a result, when the spring water pressure is equal to or higher than the reference value (NO in step S9), it is determined in step S15 whether or not it is possible to cope with drain boring. If it is determined that the response is not possible, the groundwater level lowering work / water stop work is separately examined and constructed in step S16, and the process proceeds to step S13. On the other hand, if it is determined in step S15 that the response is possible, it is determined in step S17 whether the amount of spring water is large. If the amount of spring water is large (YES in step S17), the first stage groundwater level lowering work (step S4). If the amount of spring water is small (NO in step S17), the second stage groundwater level. Return to the lowering work (step S7).

  In step S9, when the spring water pressure is equal to or lower than the reference value (YES in step S9), probe drilling is performed in step S10.

  Next, in step S11, the spring pressure is further measured. As a result, if the spring pressure is equal to or lower than the reference value (YES in step S12), the tunnel is excavated in step S13. When the spring water pressure is equal to or higher than the reference value (NO in step S12), the process proceeds to step S15, and it is determined whether or not it is possible to cope with drain boring.

  The above steps are repeated until excavation is completed. That is, in step S14, when excavation is not completed, the process returns to step S2, and when excavation is completed, the process ends.

  Next, the setting of the management reference value will be described.

  In the natural ground classification in the sandy land (see Non-Patent Document 2 above), the application condition is that the head in front of the face of the tunnel is less than +10 m from the center of the face. From this, it is conceivable that the spring pressure (0.1 MPa) corresponding to about 10 m at the head in the spring pressure measurement is set as the management reference value.

  When this 0.1 MPa is used as a reference value and applied to the measurement result in the Iiyama tunnel (Hokuriku Shinkansen), one location on the right shoulder of the 141 km 541 m face shows a reference value or more (see FIG. 7). In the Iiyama Tunnel, the management standard value is set to 0.1 MPa, so the excavation was interrupted here, and draining boring was performed toward the right front in the traveling direction. As a result of measuring the spring pressure again after draining boring, the amount of spring water and the spring pressure (0.00 MPa) were confirmed to decrease, so excavation was resumed and the face was not destabilized. Up to now, there is no example where the face is destabilized at a spring pressure of 0.1 MPa or less, which is a management reference value, and therefore it can be judged that the current reference value is generally appropriate.

  In addition, if a density test and a seepage collapse test are conducted on a sandy mountain that is the subject of a prior survey, etc., and the distribution of relative density and critical hydraulic gradient is clarified, it corresponds to the critical hydraulic gradient. It is also conceivable to set the spring pressure as a management reference value.

  The management criteria set in this way are changed as follows.

(1) Downward revision of management standards When excavation is carried out while managing at the reference value, and the face is unstable due to spring water, an auxiliary method for stabilizing the face and groundwater level lowering work will be performed. Consider correcting the value.

(2) Upward revision of management standards If the spring pressure is higher than the management standard value, groundwater level lowering work will be performed to lower the water level, and excavation will start after the water level falls below the standard value. Therefore, it is not possible to confirm the change in the state of the face when excavating at a spring pressure higher than the reference value, and the reference value cannot be corrected upward only by measuring the spring pressure and observing the state of the face.

  In order to revise the management standard upward, it is necessary to separately evaluate the resistance of the distributed sandy soil to spring pressure by a sample test such as a seepage collapse test.

  Note the following points.

  The main purpose of the forward survey by exploration drilling is basically to confirm that there is no groundwater around the face. On the other hand, if the presence of groundwater is confirmed by exploration drilling, it is highly possible that the groundwater level could not be lowered sufficiently by long and short boring such as a lenticular aquifer sand layer. It is necessary to judge the stability based on geological information, spring volume and spring pressure at that time. The simple spring pressure measurement around the working face that is implemented in the present invention is the stability of the working face, especially by investigating the presence or absence of groundwater that cannot be lowered by long and short boring, and measuring the water pressure. The purpose is to evaluate sex.

In consideration of such a purpose, exploration drilling and simple spring pressure measurement around the face are carried out based on the following basic concept.
(1) It shall always be implemented.
(2) The perforation length shall be an extension (about 10 m or more) that allows the ground between the face and the formation to become a bulkhead even in the presence of high-pressure groundwater in the front and a layer that tends to collapse.
(3) Even when the face is stable, it is carried out to confirm the local groundwater distribution due to the heterogeneity of the front geology.
(4) Carry out within the cross section of the face centering on the shoulder from the top where the collapse is most likely to occur.
(5) Be sure to perform the test where there is a new drop of water.
(6) Even when patterning the measurement, the pattern such as the execution position and frequency is changed according to the result of the long boring.
(7) If high-pressure springs are confirmed, stop excavation and examine necessary measures.

  Next, a simple spring pressure measurement method will be described.

  FIG. 5 is a view showing a simple spring pressure measurement position according to the present invention, FIG. 5 (a) is a side sectional view thereof, FIG. 5 (b) is a front sectional view thereof, and FIG. It is a figure which shows a state.

  Simple spring water pressure measurement uses FIT pipe (outside diameter: about 76mm, inside diameter: about 60mm, construction length: about 18.5m) used for the receiving work. A total of four locations were conducted. Note that the measurement is performed at a pitch of 9 m as shown in FIG. However, after the face position: 151 km 537 m (upper half), the drilling length in the upper half is set to 15.5 m for the convenience of construction.

  Hereinafter, the simple spring pressure measurement result concerning this invention is demonstrated.

  Simple spring water pressure measurement was carried out from April 1, 2004, and a total of 23 measurements have been performed so far. The result of the simple spring pressure measurement is shown in FIG. 7, and the geology and the state of spring water summarized from the drilling results are shown in FIG.

  The measurement results of spring pressure and spring volume by exploration are as follows.

  (1) The measured spring pressure is 0 to 0.033 MPa at the upper left shoulder, 0 to 0.115 MPa at the upper right shoulder, 0 to 0.018 MPa at the lower left side, and 0 to 0 at the lower right side. 0.03 MPa, and a high spring pressure was often observed in the right shoulder.

  (2) The amount of spring water is 0-40 l / min at the upper left shoulder, 0-53 l / min at the upper right shoulder, 0-25 l / min at the lower left side, and 0-63 l / min at the lower right side. is there.

  (3) Even when a high spring pressure is shown at one location in the face, there are many cases where almost no spring is observed from other locations.

  (4) The spring pressure tends to decrease as excavation progresses toward the starting point except for the upper right shoulder. Also, the amount of spring water tends to decrease with the progress of excavation toward the starting point in the lower half of the drilling.

  (5) The highest spring pressure was measured in the exploration drilling when it was carried out at the upper right shoulder of the face position 151 km 541 m. Here, since it became impossible to pierce at a point of 10 m depth due to spring water with high water pressure (spring pressure: unmeasurable, spring volume: 70 l / min), as a result of drilling again from the vicinity, spring pressure 0.115 MPa, The amount of spring water was 43 l / min. As described above, since the management reference value of the spring water pressure is set to 0.1 MPa, the excavation is interrupted here, and draining boring is performed toward the right front in the traveling direction (13-2 and 13-3 in FIG. 7). ). The amount of spring water and the spring pressure at the end of excavation were 16 l / min and 0.01 MPa for 13-2, and 93 l / min and 0.05 MPa for 13-3. After draining boring, simple spring pressure measurement was performed again near the right shoulder of 151 km 541 m face. As a result, it was confirmed that the spring pressure was 0.000 MPa, the amount of the spring water was about the level of seepage, and the spring pressure was reduced, so excavation was resumed.

  (6) Spring water from the face is often not seen, and even when there is spring water, it is at most about 5 l / min. However, even when no spring water was seen from the face, there were cases where spring water was seen from the rock bolts on the top and side walls.

  Among the measurement results of the simple spring water pressure described above, the characteristic items are described below.

  (1) There was a case where a relatively high spring pressure was shown even if the amount of spring was small.

  (2) In spite of the fact that almost no spring water was observed at the face, there was a case where spring water was observed from the top end, shoulder and side wall rock bolts.

  (3) As a result of simple spring pressure measurement, a relatively high spring pressure was observed on the right shoulder of the face.

  (4) A large amount of spring water and a high spring pressure were found in the measurement at the right shoulder of the face of 151 km 541 m. However, both the spring pressure and the amount of spring water were shown to be extremely low in the measurement at the left shoulder and lower half of the same face. As a result, in the draining boring conducted at two locations from the right side of the face, a relatively large amount of spring water was confirmed at 16 l / min and 93 l / min. As a result of this draining boring, there is almost no spring water on the right shoulder of the 151 km 541 m face.

  About said (1), even if the amount of spring water is small, it shows that the groundwater which has a high head exists. FIG. 9 shows the relationship between the amount of spring water and the spring pressure, but no significant correlation is found overall. As a cause of such a feature, a case where a low-permeability stratum has a high water head and is inundated, or a case where groundwater is under pressure is considered.

  About said (2)-(4), it is thought that it has suggested that the groundwater is localized with the heterogeneity of geology. There is a high possibility that the locally distributed groundwater that cannot be lowered by the pre-drained boring that has been particularly noticed in the face management method of the present invention is caught by searching and drilling.

  In particular, the spring water in the exploration drilling of the upper right shoulder of 151 km 541 m shown in (4) above is a spring volume of 180 l / min, which is captured at an excavation depth of about 70 to 75 m in advanced boring (11) (with ○). This corresponds to an aquifer having a water pressure of 1.00 MPa (see FIG. 8). The groundwater remaining in this aquifer was confirmed only by the exploration drilling of the right shoulder, but not by other exploration drilling. The reasons are as follows: i) local distribution of groundwater due to the inhomogeneity of geology as described above, ii) the difference in the geometrical relationship between the groundwater detectable position and the aquifer by exploration drilling, etc. Can be considered.

  As described in (3) above, there is a tendency for the spring pressure to be high in the upper right shoulder. In addition, when the relationship between the spring pressure and the spring volume was investigated and looked at each position in the cross section of the face of the perforation, there was a certain relationship between the upper right shoulder and lower lower right, but there was a clear relationship on the left. Absent. This is thought to be due to the fact that all of the local groundwater happens to be distributed in the right shoulder of the face. It is presumed that there is a strong possibility of a relationship.

  Next, the effectiveness of the present invention will be described from FIG.

  First, the tunnel is excavated from north-northwest to northwest to south-southeast to southeast, while the stratum strikes north-north-south-south-west or north-east-south-west, and its slope is almost the same, tilting south, against the face. It is a base structure. For this reason, the stratum appears from the left with respect to the face and moves to the right as the excavation progresses. Because of this geological structure, the drainage boring on the left side is preceded by the face to reduce the groundwater level earlier. Therefore, a large amount of spring water and spring pressure are observed in the drain boring on the left side. In the right draining boring and exploration drilling, the amount of spring water and the spring pressure are both small, so it can be judged that the draining boring on the left side effectively reduces the groundwater level. In addition, as a result of multiple water boring, water boring is effective because a large amount or high-pressure spring water is seen in the layer where the water boring has reached for the first time by the latest boring. I can see. Further, in the direction from the disturbance zone near 151 km to 500 to 540 m, the spring water pressure is high due to the search drilling that reaches the level corresponding to the formation where the relatively high spring water pressure was confirmed by draining boring on the left side. This is because groundwater that could not be sufficiently lowered by draining boring was caught by exploration and drilling, and the exploration drilling played a role of draining water and was judged to be effective in stabilizing the face.

  Starting from 151 km 525 m, the stratum direction is the same as the direction of the end point, but the slope is not constant, and it is presumed that the geology has been crushed by deformation and shearing associated with faults distributed around it. Even in this section, a certain amount of spring water and spring pressure have been confirmed in the drain boring on the left side toward the face, but the spring here has a tendency to rapidly decrease / decrease. In addition, almost no spring water has been confirmed in the drilling of the face. From this, it is presumed that the groundwater level was sufficiently lowered in this section by draining boring on the left side.

  As described above, as a result of simple spring pressure measurement, it was confirmed that the water level in groundwater distributed in a relatively wide area has decreased due to preliminary draining boring. In addition, it becomes clear that locally remaining groundwater that cannot be lowered by this drain boring can be confirmed by probe drilling, and the water level is lowered using the probe drilling or new drain hole. . Therefore, in the tunnel excavation based on the tunnel face management method of the present invention, it is considered that the water level around the face is reliably lowered by the combined use of draining boring and probe drilling, and the face is maintained in a substantially stable state. It is done.

  In addition, this invention is not limited to the said Example, Based on the meaning of this invention, a various deformation | transformation is possible and these are not excluded from the scope of the present invention.

  The tunnel face management method using spring pressure of the present invention can be used as a simple and practical tunnel face management method.

It is a block diagram of the spring pressure measuring apparatus concerning this invention. It is a front view of the measuring device of the spring pressure measuring apparatus concerning this invention. It is a side view of the measuring device of the spring pressure measuring apparatus concerning this invention. It is a excavation flowchart of the tunnel using the face management method using the spring pressure of this invention. It is a figure which shows the simple spring pressure measurement position concerning this invention. It is a figure which shows the use condition of the simple spring pressure measurement concerning this invention. It is a figure which shows the result of the simple spring pressure measurement concerning this invention. It is a figure which shows the performance of excavation concerning this invention, and the condition of spring water. It is a figure which shows the relationship between the amount of springs concerning this invention, and a spring pressure.

Explanation of symbols

1 Iron cross bit 2 Self-drilling lock bolt 3 Adapter 4 Branch hollow tube (cheese)
5 1st valve 6 1st valve operation lever 7 2nd valve 8 2nd valve operation lever 9 Bushing 10 Piping adapter 11 O-ring 12 Water pressure gauge 13,16 Connection part 14 Cable 15 Measuring instrument 17 Display part

Claims (3)

  Measure the presence of groundwater and the spring pressure in front of the face at the face of the tunnel, and repeat this every time the face advances by a predetermined distance. When measuring the spring pressure, the spring pressure exceeds the specified value or the amount of spring is large. In some cases, the tunnel excavation work was interrupted, groundwater level lowering work was performed, and after confirming that the groundwater level and the spring water pressure were sufficiently lowered, the tunnel excavation work was resumed, and spring pressure was used. Face management method.   The face management method using the spring pressure according to claim 1, wherein the predetermined value of the spring pressure is 0.1 MPa.   3. A face management method using spring water pressure according to claim 1 or 2, wherein a position in front of the face is about 20 m, and a predetermined distance traveled by the face is about 10 m. .