JP2016216984A - Management method and management device for penetration of lining element into natural ground - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a management method and a management device for penetration of a lining element into a natural ground that avoid an influence of an obstacle and others for certain and enable construction work to be performed safely and efficiently.SOLUTION: A lining element 1, having a cutting edge 2 for excavation connected at a tip, is penetrated into a natural ground 12 in each of penetration sections S, S, ..., S, ...Sformed by dividing a penetration route into a plurality of sections from a start side 10 toward an arrival side 11. The method includes the following steps for: setting a prediction-related equation for penetration force relative to a penetration distance from the start side 10, before penetrating the lining element 1 at each of the penetration sections; measuring the penetration distance of the lining element 1 and calculating actual penetration force at the penetration distance position, at a plurality of positions, during the penetration work at each of the penetration sections; calculating predicted penetration force by substituting the measured penetration distance into the prediction-related equation, during the penetration work at each of the penetration sections; and comparing the actual penetration force with the predicted penetration force. Penetration speed of the lining element 1 is varied to suit deviation of the actual penetration force from the predicted penetration force.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an intrusion management method and a management apparatus for a lining element.

   As one of the underpass construction methods for constructing underground structures that three-dimensionally intersect the ground below the vehicle driving path such as railway tracks and roads, many long steel lining elements are penetrated into the ground to cover the ground. HEP & JES (High Speed Element Pull & Jointed Element Structure) method to perform is known.

  This method is, for example, to fit a long steel lining element provided with a special joint along the longitudinal direction so as to divide the cross section of the structure on the ground under the vehicle traveling path, After parallel insertion by towing and inserting into the ground, concrete is placed inside the lining element to construct a box-type ramen type or circular lining wall, and then the inner ground is excavated and covered. This is a construction method using a construction wall as a structural body (see, for example, Patent Documents 1 and 2).

  The lining element has a cutting edge connected to the tip, and in the case of a mechanical excavation method, the lining element penetrates into the natural ground while excavating the natural ground in front of the cutting edge using the excavator installed at the cutting edge. Is done. In the case of a manual excavation method, excavation by manpower at the blade edge and penetration of the lining element are alternately repeated, and the lining element is penetrated into the ground.

  The traction force of the lining element is determined by the resistance from the ground in front of the blade edge during towing, the friction resistance from the ground in the peripheral edge of the blade edge and the lining element, and the fitting of the existing lining element. It is the resistance as the sum of the frictional resistance (fitting resistance) between the joints. Therefore, the traction force is proportional to the penetration distance (towing distance), since the initial length is the resistance in front of the blade edge, and then the length of penetration of the lining element into the ground becomes longer as the traction construction progresses. It is known that there is.

  On the other hand, when towing the lining element, there may be obstacles in front of the lining element in the penetration direction. If this interferes with the blade edge or the lining element, the obstacle should be pushed into the ground. Therefore, the traction force increases rapidly.

  Based on the background described above, when towing the lining element, conventionally, the traction force is calculated from the hydraulic pressure of the traction jack, and the penetration distance and the traction speed from the starting side by a distance meter provided on the starting side. Each is measured, and construction is performed while the operator confirms these as construction data in the central control room.

  Specifically, while comparing the penetration distance and the traction force, stop the traction when the traction force suddenly increases, check for obstacles on the face, and remove any obstacles I'm going to tow you again. However, the conventional method relies on the operator's senses, and if the tendency to increase the traction force is overlooked, the obstacle will be forced into the ground and will adversely affect the ground surface.

JP 2000-120372 A JP 2000-179282 A

The present invention has been made based on the technical background as described above, and achieves the following object.
An object of the present invention is to provide an intrusion management method and a management device for a lining element to a natural ground that can reliably avoid the influence of obstacles and the like and can be safely and efficiently constructed. .

The present invention employs the following means in order to achieve the above object.
That is, according to the present invention, the lining element having a cutting edge connected to the tip is divided into a plurality of penetration sections divided from the starting side to the reaching side into a plurality of sections from the starting side to the reaching side. In the method of penetrating the natural ground,
Before the penetration of the lining element in each penetration section, setting a predictive relational expression of penetration input to the penetration distance from the start side of the lining element;
During the penetration construction of the lining element in each penetration section, measuring the penetration distance from the start side of the lining element, and calculating the actual penetration input at the penetration distance position at a number of positions,
Calculating the predicted penetration input by substituting the measured penetration distance into the predicted relational expression during the penetration construction of the lining element in each penetration section;
Comparing the actual penetration input and the predicted penetration input;
According to the penetration management method of a lining element into a natural ground, the penetration speed of the lining element is changed in accordance with a deviation of the actual penetration input from the predicted penetration input.

  In the case of the mechanical excavation method, the cutting edge is equipped with an excavator, and the excavation speed of the natural ground by the excavator is changed so as to synchronize with the change of the penetration speed.

The management method further includes an actual relationship between the penetration distance measured at multiple positions after the penetration distance of the lining element reaches the end point of each penetration section and the actual penetration input at those penetration distance positions. Calculating an equation;
Comparing the prediction relation set for one penetration section with the actual relation obtained as a result of penetration of the lining element in the penetration section,
When the deviation of the actual relational expression from the prediction relational expression is within a predetermined range, the prediction relational expression of the penetration section is applied as a prediction relational expression of the next penetration section, and when the deviation is not within the predetermined range, The real relational expression is applied as a prediction relational expression for the next intrusion section.

  In the case of the towing method, the through force is given to the lining element by a towing jack installed on the reaching side.

Further, according to the present invention, a lining element having a tip for excavation connected to the tip is divided into a plurality of penetration sections divided into a plurality of portions between the starting side and the reaching side from the starting side toward the reaching side. An intrusion management device for penetrating natural ground,
A hydraulic jack that gives the lining element a penetration input to the natural ground;
A hydraulic unit that supplies hydraulic oil to the hydraulic jack and outputs hydraulic data;
A penetration distance measuring member that measures a penetration distance from the start side of the lining element and outputs penetration distance data;
An arithmetic and control unit,
The arithmetic and control unit is a predictive relational expression setting unit that sets a predictive relational expression of a penetration input with respect to a penetration distance from the start side of the lining element before penetration of the lining element in each penetration section;
A prediction penetration calculation unit that calculates a prediction penetration by substituting the penetration distance data into the prediction relational expression during penetration construction of the lining element in each penetration section,
During penetration construction of the lining element in each penetration section, an actual penetration input calculation unit that calculates actual penetration input from the hydraulic pressure data,
A through input comparison unit that compares the predicted through input and the actual through input;
The ground element of the lining element is characterized by outputting a penetration speed adjustment command to the hydraulic unit so as to change a penetration speed of the lining element in accordance with a deviation of the actual penetration input from the predicted penetration input. In the intrusion management device.

In the case of a mechanical excavation method, the cutting edge is equipped with an excavator that is operated by hydraulic oil fed from the hydraulic unit,
The arithmetic and control unit outputs an excavation speed adjustment command to the hydraulic unit so as to synchronize with the penetration speed.

After the penetration distance of the lining element reaches the end point of each penetration section, the arithmetic and control unit calculates an actual relational expression of both from the penetration distance data and the data group of the actual penetration input data. And
A relational expression comparison unit that compares the prediction relational expression set for one penetration section and the actual relational expression obtained as a result of penetration of the lining element in the penetration section;
When the deviation from the prediction relational expression of the actual relational expression is within a predetermined range, the prediction relational expression setting unit applies the prediction relational expression of the penetration section as a prediction relational expression of the next penetration section, and the divergence Is not within the predetermined range, the real relational expression is applied as a prediction relational expression for the next intrusion section.

  In the case of the towing method, the hydraulic jack is a towing jack installed on the reaching side.

  There are two methods of penetrating the lining element into the ground: a method in which the lining element is towed from the arrival side with a towing jack, and a method in which the lining element is propelled (pushed) with a propulsion jack from the starting side. Input is a concept that includes both of these types of forces, ie, traction and propulsion.

  According to this invention, the penetration input with respect to the penetration distance from the start side of the lining element is predicted, and the penetration speed is changed according to the difference between the predicted penetration input and the actual penetration input, so that the influence of obstacles and the like can be reliably confirmed. Therefore, construction can be performed safely and efficiently.

It is sectional drawing which shows embodiment of this invention and shows the penetration construction state to the natural ground of a lining element. It is a block diagram which shows the structure of a calculation control apparatus. It is a flowchart which shows the procedure of the management method. 4 is a flowchart showing a procedure subsequent to FIG. 3. A prediction equation of penetration section S _j, is a graph showing a determination area for setting the prediction equation in the next penetration section S _{j + 1.} It is a graph which shows the prediction relational expression in penetration section _{Sj + 1} .

  Embodiments of the present invention will be described below with reference to the drawings. The embodiment shown below is an example in which a lining element is penetrated into a natural ground by towing from the reaching side (towing method). FIG. 1 is a cross-sectional view showing a state in which a lining element penetrates into a natural ground. The lining element 1 is a square-shaped steel member or a U-shaped steel member that penetrates into a natural ground while being sequentially connected in parallel to this through a joint (see Patent Documents 1 and 2 for details). The lining element 1 is divided into a plurality along the longitudinal direction, and each divided element 1a is connected to the last one on the starting side (starting shaft) 10 as it penetrates into the natural ground.

  A blade edge 2 is connected to the tip of the lining element 1. In the case of the mechanical excavation method, the cutting edge 2 is equipped with an excavator 3 such as an auger excavator operated by a hydraulic motor 4. The earth retaining wall 5 on the arrival side (reach shaft) 11 is provided with a hydraulic towing jack 6. One end of a tensile material (PC steel stranded wire) 7 is connected to the blade 2, and the other end of the tensile material 7 is held by the traction jack 6 through the inside of the ground 12. The lining element 1 is inserted into the natural ground 12 by the operation of the towing jack 6. The hydraulic oil for the traction jack 6 and the hydraulic motor 4 is supplied from a hydraulic unit 13 including a hydraulic pump, an oil tank, and the like.

The penetration of the lining element 1 into the natural ground 12 is performed every intrusion section S ₁ , S ₂ ,..., S _{j ,.} Done. The length of each penetration section is a length (for example, 2 m) obtained by dividing the length (for example, 6 m) of the dividing element 1a into a plurality of sections. In the case of the mechanical excavation method, the lining element 1 is inserted into the natural ground while excavating the natural ground in front of the blade edge 2 by the excavator 3. On the other hand, in the case of a human-powered excavation method in which an operator enters the blade mouth 2 and excavates, the lining element is a natural ground by alternately repeating several tens of centimeters of excavation and penetration of the lining element 1 into the natural ground. Intruded.

  The apparatus for managing the penetration of the lining element 1 as described above includes the penetration distance measuring member 14 and the arithmetic control device 15 in addition to the above-described towing jack 6 and hydraulic unit 13. The hydraulic unit 13 outputs hydraulic data of a hydraulic pump that supplies hydraulic oil to the towing jack 6 and the hydraulic motor 4, and this hydraulic data is input to the arithmetic and control unit 15.

  As the penetration distance measuring member 14, for example, a rotary encoder attached to the earth retaining wall 5 on the starting side 10 is used. The rotary encoder 14 comes into contact with the circumferential surface of the lining element 1 and rotates as it penetrates, and outputs penetration distance data (traction distance data) from the start side 10. This penetration distance data is input to the arithmetic and control unit 15.

  For example, a personal computer having an input / output unit, a calculation control unit (CPU), and a storage unit is used as the calculation control device 15. FIG. 2 shows a functional block diagram of the arithmetic and control unit 15. The arithmetic and control unit 15 includes a traction speed setting unit 16, a predicted relational expression setting unit 17, a predicted traction force calculation unit 18, an actual traction force calculation unit 19, a traction force comparison unit 20, an actual relational expression calculation unit 21, and a relational expression comparison unit. 22 is provided.

Traction speed setting unit 16, before the start penetration at each penetration section S _j, presetting the previous pulling speed immediately before the end of the penetration section S _j-1 as traction speed of the penetration section S _j. Predictive equation setting unit 17, before the start penetration at each penetration section S _j, equation P = a _j traction P against penetration distance L from equation predicted in the penetration section S _j ie starting side Set L + b _j

The predicted traction force calculating unit 18 calculates the predicted traction force P _culk by substituting the input penetration distance data L _k into the prediction relational expression P = a _j · L + b _j during the penetration work in each penetration section S _j. . The actual traction force calculation unit 19 calculates the actual traction force P _k from the input hydraulic data of the traction jack 6 during the penetration work in each penetration section S _j .

The traction force comparison unit 20 compares the calculated predicted traction force P _culk and the actual traction force P _k , respectively, and calculates the degree of divergence d _k = P _k / P _culk . In accordance with the deviation degree d _k , the arithmetic control device 15 outputs a traction speed adjustment command to the hydraulic unit 13 so as to change the traction speed. That is, the flow rate of the hydraulic oil fed from the hydraulic pump for the towing jack 6 is changed.

  In the case of the mechanical excavation method, the arithmetic and control unit 15 outputs an excavation speed adjustment command to the hydraulic unit 13 so as to change the excavation speed of the excavator 3 in synchronization with the towing speed. That is, the flow rate of the hydraulic oil fed from the hydraulic pump for the hydraulic motor 4 of the excavator 3 is changed.

After the lining element 1 reaches the end point of each penetration section S _j , the actual relational expression calculation unit 21 calculates from the data group of the penetration distance data L _k and the actual traction force data P _k obtained in the penetration section S _j. Then, the real relational expression P = a _o · L + b _o of the traction force P with respect to the penetration distance L is calculated by the method of least squares. The relational expression comparison unit 22 compares the predicted relational expression P = a _j · L + b _j set for the intrusion section S _j and the calculated actual relational expression P = a _o · L + b _o to set the prediction relational expression. The part 17 sets the prediction relational expression of the next penetration section S _{j + 1} according to those divergences.

That is, when the deviation of the actual relational expression P = a _o · L + b _{o from} the prediction relational expression P = a _j · L + b _j is within a predetermined range, the prediction relational expression setting unit 17 determines the next penetration section S _{j +.} as predicted relationship _{P = a j + 1 · L} + b j + 1 of ₁ applying the predictive equation _{P = a j · L + b} j of the penetration section _{S j (a j + 1 =} a j, b j + 1 = b _j). When the deviation is not within the predetermined range, the actual relational expression P = _ao * L + _bo is applied as the prediction relational expression P = _{aj +} 1.L + bj _{+ 1} of the next penetration section _{Sj + 1} ( a _{j + 1} = a _o , b _{j + 1} = b _o ).

Next, the management method will be specifically described with reference to the flowcharts shown in FIGS. 3 and 4 and the graphs shown in FIGS. 5 and 6. In penetrating the penetration section S _j , first, the traction speed setting unit 16 sets the traction speed, and the prediction relational expression setting unit 17 sets the prediction relational expression P = a _j · L + b _j for the penetration section S _j ( Step S1). The towing speed to be set is the towing speed immediately before the end of penetration in the previous penetration section S _j-1 . The prediction relational expression P = a _j · L + b _j to be set is determined after the penetration of the previous penetration section S _j−1 , as will be described later. For the initial intrusion section S ₁ , the traction speed and the predictive relational expression P = a ₁ · L + b ₁ based on the conventional construction results taking the soil quality and the like into consideration are applied.

After starting the penetration (step S2), the penetration distance measurement member 14 measures the penetration distance L _k from starting side and the actual traction force P at the penetration distance from the hydraulic data real traction calculation unit 19 that is input _k is calculated (step S2). The penetration distance data L _k and the actual traction force data P _k are acquired at a number of distance positions from the start side in the penetration section S _j (see FIG. 5).

Then, each time the penetration distance data L _k is acquired, the predicted traction force calculation unit 18 calculates the predicted traction force P _culk by substituting the penetration distance data L _k into the prediction relational expression P = a _j · L + b _j ( step S4), and further traction comparison unit 20 calculates the penetration distance L _k in the actual traction P _k and predicted traction P _Culk by comparing the degree of deviation _{d k = P k / P culk} ( step S5).

As a result of calculating the divergence degree d _k , the arithmetic and control unit 15 outputs a traction speed adjustment command to the hydraulic unit 13 according to the divergence degree d _k , and in the case of the mechanical excavation method, the excavation speed synchronized with the traction speed Therefore, an excavation speed adjustment command is output to the hydraulic unit 13. That is, when level 1: d _k <0.8, the traction speed is increased by 20% (step S6-1). Further, in the case of the mechanical excavation method, the excavation speed is increased so as to synchronize with the towing speed (step S7-1). Further, when level 2: 0.8 ≦ d _k <1.0, the traction is continued at the set speed without changing the traction speed (step S6-2). At this time, the excavation speed is not changed.

Level 3: When 1.0 ≦ d _k <1.2, the traction speed is reduced by 50% (step S6-3). In the case of the mechanical excavation method, the excavation speed is further lowered so as to synchronize with the towing speed (step S7-3). Level 4: When 1.2 ≦ d _k , the arithmetic and control unit 15 issues a warning for emergency stop measures. Then, after confirming the presence or absence of abnormalities in the face and the towing equipment, the suspension is canceled and the towing is resumed (step S7-4).

When the above steps are repeated and the penetration distance L _k reaches the end point of the penetration section S _j (step S8), the penetration is finished (step S9), and the prediction relationship for the next penetration section S _{j + 1} The equation P = a _{j + 1} · L + b _{j + 1} is set.

Therefore, firstly, the actual relationship from the data set of both the least squares method resulting penetration distance data L _k and actual traction data P _k of penetration of the real relationship calculating section 21 penetrating segment S _j P = a _o · L + b _o is calculated (step S10). The relational expression comparison unit 22 compares the calculated actual relational expression P = a _o · L + b _o with the predicted relational expression P = a _j · L + b _j set in the penetration section S _j , and the actual relational expression is within a predetermined range. It is determined whether it is in.

Here, the predetermined range as shown in FIG. 5 in this embodiment, the prediction equation P = a _j · L + b _j of gradient a _j and the intercept b _j respectively ± 1 / 2a in _rng and ± 1 / 2b width _rng The upper limit expression P = (a _j + 1 / _2arng ) · L + (b _j + 1 / _2brng ) and the lower limit expression P = (a _j −1 / _2arng ) · L + (b _j −1 / _2brng) ) As a range between.

That is, the relationship comparator 22, the deviation is a predetermined range from the gradient a _j tilt a _o whether a _{(| | a o -a j <} a rng) ( step S11), and also sections of intercept b _o It is determined whether or not the deviation from b _j is within a predetermined range (| b _o −b _j | <b _rng ) (step S12).

Consequently, when none of the slope a _o and the intercept b _o is within a predetermined range, the prediction equation setting unit 17 prediction relationship of the penetration section S _j as the prediction relationship of the following penetration section S _{j + 1} Apply the expression as is. That is, in the relational expression P = a _{j + 1} · L + b _{j + 1} of the next penetration section S _{j + 1} , a _{j + 1} = a _j and b _{j + 1} = b _j are set (step S13-1).

On the other hand, one of the tilt a _o and the intercept b _o is when not within the predetermined range, applying the actual relationship as predicted relationship of the following penetration section S _{j + 1.} That is, in the relational expression P = a _{j + 1} · L + b _{j + 1} of the next penetration section S _{j + 1} , a _{j + 1} = a _o and b _{j + 1} = b _o are set (step S13-2). FIG. 6 shows a case where an actual relational expression is applied as a prediction relational expression for the next penetration section S _{j + 1} .

  According to the above embodiment, the traction force with respect to the penetration distance from the start side is predicted, and the traction speed is changed according to the difference between the predicted traction force and the actual traction force, so that the influence of obstacles and the like is reliably avoided. It is possible to carry out construction safely and efficiently. Moreover, the actual relational expression calculated from the data group of the penetration distance data and the actual traction force data is compared with the prediction relational expression set in the penetration section, and the prediction relational expression of the next penetration section is determined according to the deviation. Since it is set, it is possible to set a rational prediction relational expression according to changes in construction conditions such as changes in soil conditions.

  The above embodiment is merely an example, and the present invention can take various aspects. For example, the rate of change of the traction speed that is changed according to the difference between the predicted traction force and the actual traction force is an example and varies depending on the construction conditions. Similarly, the upper and lower limit formulas used to determine the prediction relational expression of the next intrusion section are only an example.

  Further, as described above, the present invention is not limited to a traction method in which the lining element is penetrated into the ground by towing from the arrival side, but can also be applied to a propulsion method in which the lining element is propelled from the start side.

1: Covering element 2: Cutting edge 3: Excavator 4: Hydraulic motor 6: Hydraulic jack 7: Tensile material 10: Starting side 11: Arrival side 12: Ground mountain 13: Hydraulic unit 14: Penetration distance measuring member 15: Calculation Control device

Claims (8)

A method of penetrating a lining element having a cutting edge connected to the tip thereof into a natural ground for each penetration section divided into a plurality of sections between the start side and the reach side from the start side toward the reach side In
Before the penetration of the lining element in each penetration section, setting a predictive relational expression of penetration input to the penetration distance from the start side of the lining element;
During the penetration construction of the lining element in each penetration section, measuring the penetration distance from the start side of the lining element, and calculating the actual penetration input at the penetration distance position at a number of positions,
Calculating the predicted penetration input by substituting the measured penetration distance into the predicted relational expression during the penetration construction of the lining element in each penetration section;
Comparing the actual penetration input and the predicted penetration input;
A penetration management method of a lining element into a natural ground, wherein a penetration speed of the lining element is changed according to a deviation of the actual penetration input from the predicted penetration input.   The ground of the lining element according to claim 1, wherein the cutting edge is equipped with an excavator, and the excavation speed of the natural ground by the excavator is changed so as to synchronize with the change of the penetration speed. Intrusion management method. After the penetration distance of the lining element reaches the end point of each penetration section, calculating the actual relational expression of both from the penetration distance measured at multiple positions and the actual penetration input at those penetration distance positions;
Comparing the prediction relation set for one penetration section with the actual relation obtained as a result of penetration of the lining element in the penetration section,
When the deviation of the actual relational expression from the prediction relational expression is within a predetermined range, the prediction relational expression of the penetration section is applied as a prediction relational expression of the next penetration section, and when the deviation is not within the predetermined range, The method for managing penetration of a lining element into a natural ground according to claim 1 or 2, wherein the actual relational expression is applied as a prediction relational expression of a next penetration section.   The penetration management method to the natural ground of the lining element of Claim 1, 2, or 3 which provides the said penetration input to the said lining element with the tow jack installed in the said reach | attainment side. In order to penetrate the lining element, which has a cutting edge connected to the tip thereof, into the ground for each penetration section divided into a plurality of sections between the starting side and the reaching side from the starting side to the reaching side Intrusion management device,
A hydraulic jack that gives the lining element a penetration input to the natural ground;
A hydraulic unit that supplies hydraulic oil to the hydraulic jack and outputs hydraulic data;
A penetration distance measuring member that measures a penetration distance from the start side of the lining element and outputs penetration distance data;
An arithmetic and control unit,
The arithmetic and control unit is a predictive relational expression setting unit that sets a predictive relational expression of a penetration input with respect to a penetration distance from the start side of the lining element before penetration of the lining element in each penetration section;
A prediction penetration calculation unit that calculates a prediction penetration by substituting the penetration distance data into the prediction relational expression during penetration construction of the lining element in each penetration section,
During penetration construction of the lining element in each penetration section, an actual penetration input calculation unit that calculates actual penetration input from the hydraulic pressure data,
A through input comparison unit that compares the predicted through input and the actual through input;
The ground element of the lining element is characterized by outputting a penetration speed adjustment command to the hydraulic unit so as to change a penetration speed of the lining element in accordance with a deviation of the actual penetration input from the predicted penetration input. Intrusion management device. The blade is equipped with an excavator that is operated by hydraulic oil fed from the hydraulic unit,
The intrusion management device for lining elements according to claim 5, wherein the arithmetic control device outputs an excavation speed adjustment command to the hydraulic unit so as to synchronize with the penetration speed. After the penetration distance of the lining element reaches the end point of each penetration section, the arithmetic and control unit calculates an actual relational expression of both from the penetration distance data and the data group of the actual penetration input data. And
A relational expression comparison unit that compares the prediction relational expression set for one penetration section and the actual relational expression obtained as a result of penetration of the lining element in the penetration section;
When the deviation from the prediction relational expression of the actual relational expression is within a predetermined range, the prediction relational expression setting unit applies the prediction relational expression of the penetration section as a prediction relational expression of the next penetration section, and the divergence 7. The penetration management device for a lining element to a natural ground according to claim 5 or 6, wherein the actual relational expression is applied as a prediction relational expression of the next penetration section when the is not within a predetermined range.   The intrusion management device for lining elements according to claim 5, 6 or 7, wherein the hydraulic jack is a towing jack installed on the reaching side.

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