JP4973051B2 - Method of excavating small earth covering section by earth pressure type shield machine and pressure management method in chamber - Google Patents

Description

  The present invention relates to a method for excavating a small earth covering section by an earth pressure type shield machine and a pressure management method in a chamber.

  In recent years, when constructing underground structures in urban areas, shield construction methods have been adopted in order to smoothly perform construction on roads with heavy traffic and reduce the impact of construction on surrounding residents. It is often used during tunnel construction. In addition, since it is difficult to secure a sufficient work base area on the ground in urban areas, construction using earth pressure type shields that require a small area for equipment placement space compared to a muddy water type shield that requires a large area for equipment placement space. Needs are growing.

  Generally, as shown in Non-Patent Document 1, the minimum soil covering depth of a tunnel excavated by the shield method is about 1.0D to 1.5D (D: outer diameter of excavation). In the natural ground in front of the tunnel when the tunnel covering depth is 1.0D to 1.5D or more, as shown in FIG. 8, the lump of the wedge-shaped portion 30 around the face is affected by the adhesiveness of the ground. Is moving toward the tunnel along the sliding surface (black arrow), and earth pressure (white arrow) is acting on the face at this time. In such a case, the face is supported by managing the pressure in the chamber of the earth pressure type shield machine so as to be slightly larger than the earth pressure. The pressure in the chamber is managed based on a measured value of a soil pressure gauge installed near the center of the partition wall as a representative value.

In addition, when the tunnel cover depth is less than 1.0D, the ground cover is improved by an auxiliary method such as a chemical injection method before excavating the tunnel to prevent ground deformation due to tunnel excavation. Method is used.
"Tunnel Standard Specification [Shield Method] / Comment" August 1994, pages 18 and 183, Japan Society of Civil Engineers

  As shown in FIG. 9, the method of managing the pressure in the chamber with the measured value of the earth pressure gauge installed near the center of the partition wall as a representative value is the distribution of the pressure of the earth pressure acting on the face and the pressure distribution in the chamber. , There may be some pressure difference between the upper part of the face and the lower part of the face. When the tunnel covering depth is 1.0D to 1.5D or more, the depth of the covering is large even if there is a slight difference between the earth pressure acting on the face and the pressure in the chamber. The amount of soil mass in the shaped portion 30 is large. For this reason, this difference can be absorbed by the adhesiveness of the soil, and ground subsidence and uplift do not occur.

  On the other hand, when the tunnel covering depth of the tunnel is smaller than 1.0D, as shown in FIG. 10, the mass of the natural ground portion 21 immediately above the face is going to move downward. At this time, if a pressure difference is generated at the upper part of the face as described above, the soil covering depth is small and the amount of the soil mass in the natural ground portion 21 is small, so that the effect of the adhesiveness of the soil is also small. There is a problem that the natural ground portion 21 may sink without being able to absorb water.

  Also, if the tunnel covering is less than 1.0D, using an auxiliary method such as the chemical injection method requires ground work, so it is necessary to secure a working space on the ground part. There is a problem that it is difficult to secure this working space. Furthermore, although the shield method is adopted to eliminate the work on the ground, there is a problem that the ground work using the auxiliary method is contrary to the original purpose.

  Therefore, the present invention has been made in view of the conventional problems as described above, and can dig a section where the tunnel covering depth is smaller than 1.0D by the shield method without performing the auxiliary method. The purpose is to provide an excavation method.

In order to achieve the above object, the method of digging a small earth covering section by the earth pressure type shield machine of the present invention is formed between the cutter head and the partition wall, and applies a predetermined pressure to the excavated earth and sand to hold the face. In the excavation method of the small earth covering section by the earth pressure type shield machine equipped with the chamber, the vertical earth pressure immediately above the face is calculated based on the earth covering depth and the unit weight of the ground, and the pressure in the chamber is calculated. The present invention is characterized in that the ground is excavated while being controlled so as to be substantially the same as the vertical earth pressure or increased by a predetermined pressure (first invention).
According to the excavation method of the small earth covering section by the earth pressure type shield machine according to the present invention, the small earth covering section can be excavated by the earth pressure type shielding machine without using the auxiliary construction method. Further, by controlling the pressure in the chamber so as to be substantially the same as the vertical earth pressure immediately above the face or by a predetermined pressure during excavation, subsidence or uplift of the ground can be reliably prevented.

According to a second invention, in the first invention, a displacement meter is installed on the ground to measure the amount of displacement of the ground surface, and the pressure in the chamber is adjusted based on the measurement result. .
According to the excavation method of the small earth covering section by the earth pressure type shield machine according to the present invention, the displacement amount of the ground surface is measured by the displacement meter, and the pressure in the chamber is reduced based on the measurement result. Since the adjustment is performed, it is possible to reliably prevent the ground surface from sinking or rising.

A third invention is characterized in that, in the first or second invention, the pressure in the chamber is managed based on a result of measurement by a pressure gauge installed at the uppermost part of the partition wall.
According to the method of digging a small earth covering section by the earth pressure type shield machine according to the present invention, the vertical earth pressure immediately above the face is measured by a pressure gauge installed at the top of the partition wall, and the pressure in the chamber is compared with the vertical earth pressure. Therefore, it is possible to reliably prevent subsidence or uplift of the ground directly above the face.

A fourth invention is characterized in that, in any one of the first to third inventions, the pressure in the chamber is adjusted by controlling at least one of a soil removal speed and a propulsion speed of the earth pressure shield machine. To do.
According to the excavation method of the small earth covering section by the earth pressure type shield machine according to the present invention, it is possible to easily adjust the pressure in the chamber by controlling at least one of the earth discharging speed or the propulsion speed of the earth pressure type shield machine. Is possible.

The fifth invention is characterized in that, in the first invention, the earth covering depth of the small earth covering section is smaller than an outer diameter of the excavation by the earth pressure type shield machine.
According to the excavation method of the small earth covering section by the earth pressure type shield machine according to the present invention, the earth covering depth is larger than the outer diameter of excavation by the earth pressure type shield machine (hereinafter referred to as 1.0D (D: outer diameter of excavation)). Since tunnels can be excavated to a small depth, it is possible to improve the work efficiency during tunnel excavation work, shorten the approach construction period, and facilitate tunnel maintenance management after construction. .

The pressure management method in the chamber by the earth pressure type shield machine according to the sixth aspect of the present invention provides a predetermined pressure applied to the earth and sand in the chamber formed between the cutter head and the partition wall when excavating a tunnel with the earth pressure type shield machine. In the pressure management method in the chamber for holding the working face, the vertical earth pressure immediately above the working face is calculated based on the earth covering depth and the unit weight of the ground, and the earth pressure speed or propulsion of the earth pressure type shield machine is calculated. By controlling at least one of the speeds, the pressure in the chamber is managed so as to be substantially the same as or larger than the calculated vertical earth pressure by a predetermined pressure.

  A seventh invention is characterized in that, in the sixth invention, a displacement meter is installed on the ground to measure the amount of displacement of the ground surface, and the pressure in the chamber is adjusted based on the measurement result.

  An eighth invention is characterized in that, in the sixth or seventh invention, the pressure in the chamber is managed based on a result of measurement with a pressure gauge installed at the uppermost part of the partition wall.

  As described above, according to the excavation method of the small earth covering section by the earth pressure type shield machine of the present invention, the earth covering type shield machine is used to make the small earth covering section whose tunnel covering depth is smaller than 1.0D. It is possible to dig without auxiliary construction.

  The excavation method of the small earth covering section by the earth pressure type shield machine is to prevent the deformation of the ground surface when constructing the tunnel of the small earth covering, and hereinafter, the excavation method of the small earth covering section according to the present invention A preferred embodiment will be described in detail with reference to the drawings.

  FIG. 1 is a front view of an earth pressure shield machine having a rectangular cross section according to an embodiment of the present invention, and FIG. 2 is a side sectional view of the earth pressure shield machine. In addition, illustration of the part considered unnecessary for description of this invention is abbreviate | omitted. As shown in FIGS. 1 and 2, the earth pressure type shield machine 1 includes a machine main body 2 having a cutter head 8 for excavating the ground, a power unit 25 for propelling the machine main body 2, It is comprised from the connection means 4 which connects the machine main-body part 2 and the motive power part 25. FIG.

  The machine main body 2 is arranged in parallel with the rectangular cylindrical front body 3 and the width direction in the front body 3, and each machine body 2 can be independently propelled from the front body 3, and each is independently driven. Two possible rectangular main shields 6 are provided between the main shield 6 and the front body 3 at both ends in the width direction, and each can be independently propelled from the front body 3, and each is independent. And a plurality of rectangular side shields 15 having a width smaller than that of the main shield 6.

  Inside the front body 3, each main shield 6 and each side shield 15 are provided movably back and forth, and are configured to be able to propel from the front body 3 toward the front thereof. Each main shield 6 and each side shield 15 are configured to be propelled independently from the front body 3.

  Each main shield 6 includes a rectangular shield main body 7 provided in the front body 3 so as to be movable back and forth, a slide jack 10 for moving the shield main body 7 back and forth, and a rectangular area of the main shield 6 on the front side of the shield main body 7. The cutter head 8 to be excavated, the drive source 11 provided in the shield body 7, the power transmission mechanism 12 for transmitting the drive force of the drive source 11 to the cutter head 8, and the earth pressure gauge for measuring the pressure in the chamber 5 20.

  Five earth pressure gauges 20 (20a to 20e) are installed on the partition wall 13 of each main shield 6, and two of them (20a, 20c) are installed on the top of the partition wall 13. In the natural ground in front of the tunnel when the earth covering depth is smaller than 1.0D, as described above (FIG. 10), the ground mass 21 just above the face is going to move so as to fall, and just above the face. Since the vertical earth pressure is acting, earth pressure gauges 20a and 20c were installed at the top of the partition wall 13 for the purpose of measuring the vertical earth pressure as accurately as possible. And the fall of the natural ground part 21 is prevented by managing the pressure in the chamber 5 so as to be larger than the value of the vertical earth pressure measured by the earth pressure gauges 20a and 20c by a predetermined pressure (a management method will be described later). . In the present embodiment, five units are installed on the partition wall 13 and two of them are installed on the top of the partition wall 13. However, the number and installation position are not limited to this, and the design is not limited to this. Change appropriately based on the above.

  Each side shield 15 is rotatable to the front side of the shield body 16, a rectangular shield body 16 slidably provided in the front body 3, a slide jack (not shown) for moving the shield body 16 back and forth. A cutter 17 provided, a drive source (not shown) provided on the shield body 16, and a power transmission mechanism (not shown) for transmitting the drive force of the drive source to the cutter 17 are provided. 15 is configured to be independently drivable.

  The power unit 25 is a rectangular cylindrical rear body 26 connected to the rear part of the front body 3 of the machine body 2 via the connection means 4, and the earth pressure type shield machine 1 is provided in an annular shape in the rear body 26. A plurality of shield jacks 27 to be propelled are provided.

  The rear body 26 includes an erector 29 for assembling the segment 28, and the segments 28 are sequentially assembled by the erector 29 in the rear body 26, and an annular inner wall by the segment 28 is constructed. After the segment 28 is constructed, the earth pressure type shield machine 1 is propelled to construct the tunnel 19.

  A method for excavating the small earth tunnel 19 with the earth pressure shield machine 1 configured as described above will be described below.

  FIG. 3 is a flowchart for managing the pressure in the chamber 5. In S10 of FIG. 3, the pressure in the chamber 5 when excavating the ground with the earth pressure shield machine 1 is set. The pressure in the chamber 5 is calculated by calculating a vertical earth pressure P immediately above the face based on the relationship between the soil covering depth and the unit volume weight of the ground, and a predetermined set pressure P0 that is higher than the vertical earth pressure P by a predetermined pressure. Set as follows. The predetermined pressure varies depending on the site depending on the depth of the earth covering, the geology, etc., and is appropriately determined based on the design and the like. In the present embodiment, the set pressure P0 in the chamber 5 is set to be larger than the vertical earth pressure P by a predetermined pressure. However, the present invention is not limited to this, and the set pressure P0 in the chamber 5 is set to the vertical pressure. You may set so that it may become substantially the same as the earth pressure P.

  FIG. 4 is a side sectional view showing a state in which the main shield 6 is propelled when excavating the tunnel 19.

As shown in FIG. 4, when excavating the tunnel 19, the cutter head 8 of the main shield 6a disposed on the left side of the earth pressure shield machine 1 is driven to rotate to excavate the ground, and the slide jack 10 is extended. Thus, the main shield 6a is propelled from the front body 3. The earth and sand excavated by the cutter head 8 is agitated in the chamber 5, and a mud-making agent for promoting plastic fluidization of the excavated earth and sand is injected as needed. The soil fluidized plastically in this way is sent to the back of the shield body 7 by the soil removal screw 18.
Further, when excavating the tunnel 19, a plurality of ground subsidence meters 14 as displacement meters are installed on the road, and the main shield 6a is promoted while constantly monitoring the amount of displacement on the road surface.

  And in S12 of FIG. 3, while digging with the main shield 6a, the actual vertical earth pressure P1 is measured with the earth pressure gauges 20a and 20c. Based on the measurement result, the pressure in the chamber 5 is managed by the following method.

  First, in S14 of FIG. 3, the rotational speed of the soil removal screw 18 is set. Specifically, when the result measured by the earth pressure gauges 20a and 20c is higher than the set pressure P0, the rotation of the earth removal screw 18 is increased, the amount of earth removal is increased, and the pressure in the chamber 5 is lowered. . On the other hand, when the result measured by the earth pressure gauges 20a and 20c is lower than the set pressure P0, the rotation of the earth removal screw 18 is made low speed, the amount of earth removal is reduced, and the pressure in the chamber 5 is increased.

  Next, in S16 of FIG. 3, the propulsion speed of the slide jack 10 is set. If the result measured by the earth pressure gauges 20a and 20c does not reach the set pressure P0 even if the rotation speed of the earth discharging screw 18 is adjusted in S14, the propulsion speed of the slide jack 10 is adjusted to adjust the pressure in the chamber 5. Specifically, when the result measured by the earth pressure gauges 20a and 20c is higher than the set pressure P0, the propulsion speed of the slide jack 10 is decreased, the propulsion speed of the main shield 6a is decreased, and the pressure in the chamber 5 is decreased. Reduce. On the other hand, when the result measured by the earth pressure gauges 20a and 20c is lower than the set pressure P0, the propulsion speed of the slide jack 10 is increased, the propulsion speed of the main shield 6a is increased, and the pressure in the chamber 5 is increased. .

  Next, in S18 of FIG. 3, the ground subsidence meter 14 measures the amount of displacement due to ground subsidence or uplift. If the measurement result of the ground subsidence meter 14 is within a predetermined range determined in advance by design or the like, in S20 in FIG. 3, the measurement result by the earth pressure gauges 20a and 20c is constantly monitored while the set pressure P0 is maintained. It digs up with the shield 6a. On the other hand, if the measurement result of the ground subsidence meter 14 is outside the predetermined range, the set pressure P0 in the chamber 5 is changed in S30 of FIG. Specifically, when the ground surface is sinking, the set pressure P0 is slightly increased. On the other hand, when the ground surface is raised, the set pressure P0 is slightly decreased. .

  And while pushing the main shield 6a, as mentioned above, the rotational speed of the earth removal screw 18 and the propulsion speed of the slide jack 10 are adjusted repeatedly, and the pressure in the chamber 5 is managed.

  Next, in the same manner as the operation method of the left main shield 6a described above, the cutter head 8 of the main shield 6b disposed on the right side of the earth pressure shield machine 1 is driven to rotate, and the slide jack 10 is extended to extend the main shield 6a. The shield 6b is propelled from the front body 3, and the ground located in front of the main shield 6b is excavated by rotating the cutter head 8. While propelling the right main shield 6b, the pressure in the chamber 5 is managed by the ground subsidence meter 14 and the earth pressure gauges 20a and 20c so that the ground portion 21 directly above the face does not sink or rise in the same manner as described above. .

  Then, with both main shields 6a and 6b protruding, a reaction force is applied to the rear segment 28 by the shield jack 27, and the shield jack 27 is extended to extend the earth pressure type shield composed of the front body 3 and the rear body 26. The machine 1 is propelled. After the earth pressure shield machine 1 main body is propelled, the shield jack 27 is contracted and a new segment 28 is assembled in the body 26.

  As described above, when excavating the main shields 6a and 6b, the rotational speed of the earthing screw 18 and the propulsion speed of the slide jack 10 are repeatedly adjusted while measuring the amount of displacement of the ground surface with the ground subsidence meter 14. Thus, the tunnel 19 is constructed by a method for managing the pressure in the chamber 5.

  Next, the result of measuring the displacement amount of the road surface when the tunnel 19 underpassing the actual road is excavated by the excavation method of the small covering section according to the present invention will be shown.

  In this measurement, first, the earth pressure type shield machine 1 is started from the ground, and a downward approach section having a downward slope until reaching a predetermined excavation depth (2.2 m = 1.0 D) is constructed, A tunnel section underpassing the road is constructed from the end point of the down approach section, and an up approach section having an ascending slope from the end section of the tunnel section to the ground part is constructed. Was carried out using the excavation method to reach the ground.

  FIG. 5 is a diagram showing the earth covering depth of the tunnel section propelled by the earth pressure shield machine 1, and the horizontal axis indicates the face position (m) indicating the distance from the starting point of the earth pressure shield machine 1 to the face. The vertical axis represents the soil covering depth (m).

  As shown in FIG. 5, all the tunnel sections have a soil covering depth of 1.0 D or less. In addition, illustration and description are abbreviate | omitted in the above-ground part and the descent | fall approach section (face position 0m-23m) and the up approach section (face position 72m-102m) since there is no earth covering.

  FIG. 6 is a diagram showing the relationship between the vertical earth pressure P calculated from the earth covering depth and the unit volume weight of the ground, and the vertical earth pressure P1 measured by the earth pressure gauges 20a and 20b during excavation. Indicates the face position (m), and the vertical axis indicates the earth pressure (KPa). In addition, the vertical earth pressure P1 has shown only the value to the face position 30m-70m which is a measurement object area. In the present embodiment, the set pressure P0 is set to be approximately equal to the vertical earth pressure P. However, the set pressure P0 may be set to be larger than the vertical earth pressure P by a predetermined pressure so that the ground does not rise. The predetermined pressure in such a case is appropriately set because it varies depending on the geological conditions of each site.

  As shown in FIG. 6, the vertical earth pressure P1 at the time of actual excavation becomes larger as the earth covering depth becomes deeper, and becomes smaller as the earth covering depth becomes shallower, and is almost the same as the change in the vertical earth pressure P. Showed the trend. Moreover, although the vertical earth pressure P1 at the time of actual excavation has the width | variety of some increase and decrease, the pressure value comparable as the vertical earth pressure P was shown.

  FIG. 7 is a diagram showing the amount of displacement of the ground surface in the tunnel section accompanying the propulsion of the earth pressure shield machine 1, the horizontal axis shows the face position (m), and the vertical axis shows the amount of displacement (mm).

  As shown in FIG. 7, in the section where the earth covering is smaller than 1.0D, the amount of displacement of the ground surface is generally within the range of minus 5 mm to plus 5 mm, and no subsidence or uplift occurred on the road. In addition, although the amount of subsidence was about 10 mm at the points 38 m and 56 m and the amount of protrusion was about 10 mm at the points 50 m and 65 m, there was no problem in running cars and people. Therefore, it was confirmed that the excavation method in the earth pressure type shield machine 1 of the present invention prevents the ground surface from being deformed when the tunnel 19 with a small earth covering is constructed.

  According to the excavation method of the small earth covering section in the earth pressure type shield machine 1 in the present embodiment described above, without using an auxiliary construction method for the small earth covering section in which the earth covering depth of the tunnel 19 is smaller than 1.0D, It is possible to dig up with the earth pressure shield machine 1. Then, by controlling the pressure in the chamber 5 so that the vertical earth pressure P1 becomes the set pressure P0 during excavation, it is possible to reliably prevent ground subsidence or uplift.

  In addition, the ground subsidence meter 14 always measures the amount of displacement of the ground surface, and in order to adjust the pressure in the chamber 5 so as to reduce the amount of displacement based on the measurement result, the ground subsidence or uplift is reliably ensured. It becomes possible to prevent.

  Furthermore, since the pressure in the chamber 5 is adjusted by controlling at least one of the earth discharging speed and the propulsion speed of the earth pressure shield machine 1, the pressure in the chamber 5 can be reliably managed.

  In addition, since the tunnel 19 can be excavated to a depth of less than 1.0D, the work efficiency during tunnel excavation work is improved, the construction period of the approach part is shortened, and the tunnel maintenance management after construction It is possible to obtain effects such as ease of use.

  Further, since the vertical earth pressure P1 directly above the face is measured by the earth pressure gauges 20a and 20c installed at the uppermost part of the partition wall 13, the vertical earth pressure P1 immediately above the face can be accurately measured. Then, in order to manage the pressure in the chamber 5 so that the vertical earth pressure P1 becomes the set pressure P0, it is possible to surely prevent the ground subsidence or uplift just above the face.

It is a front view of the earth pressure type shield machine which has the rectangular section shape concerning the embodiment of the present invention. It is a sectional side view of an earth pressure type shield machine. It is a flowchart for managing the pressure in a chamber. It is a sectional side view which shows the state which pushed the main shield when excavating a tunnel. It is a figure which shows the earth covering depth of the tunnel area which the earth pressure type shield machine propelled. It is a figure which shows the relationship between the vertical earth pressure calculated by the earth covering depth and the unit volume weight of the ground, and the vertical earth pressure measured with the earth pressure gauge at the time of excavation. It is a figure which shows the displacement amount of the ground surface of a tunnel area accompanying the propulsion of earth pressure type shield machine. It is a figure which shows the earth pressure which acts on a face when the soil covering depth of a tunnel is 1.0D-1.5D or more. It is a figure which shows the pressure distribution of the earth pressure which acts on a face, and the pressure distribution in a chamber. It is a figure which shows the earth pressure which acts on the face directly when the earth covering depth of a tunnel is smaller than 1.0D.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Shield machine 2 Machine body part 3 Front body 4 Connection means 5 Chamber 6 Main shield 7 Shield body 8 Cutter head 10 Slide jack 11 Drive source 12 Power transmission mechanism 13 Bulkhead 14 Ground subsidence meter 15 Side shield 16 Shield body 17 Cutter 18 Exhaust screw 19 Tunnel 20 Earth pressure gauge 21 Ground part 25 Power part 26 Rear body 27 Shield jack 28 Segment 29 Electa 30 Triangle part P Vertical pressure P0 Set pressure P1 Measured vertical pressure

Claims (8)

In the excavation method of the small earth covering section by the earth pressure type shield machine formed between the cutter head and the partition wall and having a chamber for applying a predetermined pressure to the excavated earth and sand and holding the face,
Based on the soil covering depth and the unit weight of the ground, calculate the vertical earth pressure just above the face,
Excavation in a small earth covering section by an earth pressure type shield machine characterized by excavating the ground while managing the pressure in the chamber to be substantially the same as the calculated vertical earth pressure or to be increased by a predetermined pressure. Method. Install a displacement meter on the ground to measure the amount of displacement on the ground surface,
The method for digging a small earth covering section by an earth pressure type shield machine according to claim 1, wherein the pressure in the chamber is adjusted based on the measured result.   3. The excavation of a small earth covering section by an earth pressure type shield machine according to claim 1, wherein the pressure in the chamber is managed based on a result of measurement with a pressure gauge installed at an uppermost part of the partition wall. Method.   4. The earth pressure shield machine according to claim 1, wherein the pressure in the chamber is adjusted by controlling at least one of a discharge speed and a propulsion speed of the earth pressure shield machine. The method of digging the small earth covering section.   2. The method of digging a small earth covering section with an earth pressure shield machine according to claim 1, wherein the earth covering depth of the small earth covering section is smaller than an outer diameter of excavation by the earth pressure type shielding machine. In the pressure management method in the chamber for holding a face by applying a predetermined pressure to the earth and sand in the chamber formed between the cutter head and the partition wall when excavating the tunnel with the earth pressure shield machine,
Based on the soil covering depth and the unit weight of the ground, calculate the vertical earth pressure just above the face,
By controlling at least one of the earth discharging speed and the propulsion speed of the earth pressure shield machine, the pressure in the chamber is managed to be substantially the same as the calculated vertical earth pressure or increased by a predetermined pressure. A method for pressure management in a chamber using an earth pressure shield machine. Install a displacement meter on the ground to measure the amount of displacement on the ground surface,
The pressure management method in the chamber by the earth pressure type shield machine according to claim 6, wherein the pressure in the chamber is adjusted based on the measured result. The pressure in the chamber by the earth pressure type shield machine according to claim 6 or 7, wherein the pressure in the chamber is managed based on a result of measurement with a pressure gauge installed at the top of the partition wall. Method.