EP4296431A1 - Method for laying out and forming a supporting wall in the ground and supporting wall - Google Patents

Abstract

The invention relates to a method for designing and forming a supporting wall in the ground with a required target wall stiffness from a soil mortar, which is produced in the ground by mixing soil material and a cement suspension, and vertically directed support beams, which are set in the ground mortar and arranged therein, wherein the arrangement of the support beams is designed with an overall beam stiffness. According to the invention, it is provided that the support beams are arranged in such a way that the designed overall beam stiffness is smaller than the required target wall stiffness, and that when designing and arranging the support beams, an additional stiffness component is included, which consists of at least one adjacent wall section made of floor mortar results.

Description

The invention relates to a method for designing and forming a supporting wall in the ground with a required target wall strength from a floor mortar, which is produced in the ground by mixing soil material and a cement suspension, and vertically directed support beams, which are set into the floor mortar and arranged therein , wherein the arrangement of the support beams is designed with an overall beam stiffness, according to the preamble of claim 1.

The invention further relates to a retaining wall in the ground with a required target wall strength made of a soil mortar which is produced in the ground by mixing soil material and a cement suspension and vertically directed supports which are set and arranged in the ground mortar to form the retaining wall, wherein the arrangement of the support beams is designed with an overall beam stiffness, according to the preamble of claim 10.

From the EP 1452645 B2 describes a method for creating a diaphragm wall in the ground, in which a diaphragm wall cutter with rotating cutting wheels is lowered into the ground, whereby soil material is cleared away and shredded. The cleared soil material is mixed with a setting liquid within the milling slot, forming a so-called soil mortar. Before the soil mortar hardens, the trench wall cutter is withdrawn from the milling slot filled with soil mortar. Furthermore, it is possible to insert support beams into the floor mortar using a crane before the floor mortar has hardened to form the supporting wall.

Such a retaining wall can serve, for example, as a construction pit enclosure.

Such a method of creating a retaining wall in the ground from a soil mortar is also called the CSM ^™ method.

In principle, it is also known to similarly form a supporting or drilling wall in the ground from a soil mortar by means of a drilling and mixing screw and in particular an arrangement of parallel drilling and mixing screws arranged next to one another. The soil material removed during drilling is mixed with a setting liquid in the hole to form a soil mortar. To achieve the desired load-bearing capacity of the wall, support beams are inserted vertically into the floor mortar.

A major advantage of the process for creating a retaining wall with a soil mortar is that there is little or ideally no waste of removed soil material that needs to be disposed of. This reduces transportation and landfill costs for removed soil material. In addition, the consumption of gravel and sand and the associated costs are reduced accordingly or, ideally, even avoided entirely.

However, when using soil mortar, which is created in situ in a milling slot or a borehole, no defined strength value can be assigned with regard to the transverse force load that a retaining wall in the ground is exposed to. For this load, when creating retaining walls with floor mortar, it is common practice to design support beams and arrange them in the retaining wall in such a way that the required target wall stiffness is given and ensured solely by the overall beam stiffness of the set support beams. The sum of the stiffness/strength of the support beams used is therefore greater than the required target wall stiffness or overall strength of the supporting wall to be created.

The invention is based on the object of specifying a method and a supporting wall with which particularly good safety and economic efficiency can be achieved with a supporting wall in the ground.

The object is achieved on the one hand by a method with the features of claim 1 and on the other hand by a supporting wall with the features of claim 10.

Preferred embodiments of the invention are specified in the dependent claims.

The method according to the invention is characterized in that the support beams are arranged in such a way that the designed overall beam stiffness is smaller than the required target wall stiffness, and that when designing and arranging the support beams, an additional stiffness component is included, which results from at least one adjacent wall section Floor mortar results.

A basic idea of the invention is to design the necessary support beams in terms of their size, number and arrangement when forming a supporting wall from a soil mortar in such a way that their total total beam stiffness is smaller than a designed and required target wall stiffness of the supporting wall. In this way, material for support beams can be saved and the effort required to adjust support beams can be reduced. This reduces the work and time required and therefore the costs of creating the retaining wall. The target wall stiffness can be specified in particular by a building approval authority or by static specifications for a building to be built.

The invention is based on the finding that in the case of a retaining wall made of soil mortar, the surrounding soil mortar demonstrably contributes to the wall rigidity of the retaining wall. In particular, the total beam stiffness of the set support beams can be at least 10%, preferably at least 20%, below the required value for the target wall stiffness of the supporting wall to be formed.

The invention is based on intensive tests and calculations by the applicant that, depending on its design, the floor mortar contributes a reliable portion of the stiffness and also the strength of the supporting wall.

A preferred embodiment of the invention is that, apart from the support beams, no additional reinforcing elements are introduced into the floor mortar. As a test, only the essentially vertically directed support beams are inserted into the hole in the floor with the floor mortar before the floor mortar has hardened. Additional cross beams or cross plates on the support beams can be omitted.

For the purposes of the invention, support beams are longitudinal or support profiles produced by rolling or casting with a substantially uniform cross-sectional profile. According to one embodiment of the invention, it is particularly preferred that steel beams, in particular with the C-profile, an H-profile or an I-profile, are used as support beams. Such steel support beams are available relatively inexpensively and reliably as standard profiles with a specified stiffness and strength.

A further preferred embodiment variant of the invention is that the support beams are kept free of composite elements to the floor mortar. In particular, the elongated steel supports can be kept free of screws, hooks or other projections, which would otherwise have to be attached to the elongated support supports in a complex manner before being introduced into the floor mortar.

• wobei: D_c,d = A_c,x x 0,85 x f_cd mit: f_c,d = a_c × f_m,k : γm und
• wobei:
  • D_c,d die Design-Druckkraft des Bodenmörtels ist;
  • der Index c (concrete) eine Größe kennzeichnet, die dem Bodenmörtel zuzuordnen ist; der Index d (design) eine Bemessungsgröße kennzeichnet, d.h. bei der Bestimmung wurden entsprechende Teilsicherheiten berücksichtigt; und
  • der Index x sich auf die Beton-Druckzone bezieht, also hier im auf die Druckzone des Bodenmörtels.

Another expedient method variant is that the additional stiffness component M _c,d on a support beam is determined by the at least one adjacent wall section made of floor mortar according to the formula: $${\mathrm{M}}_{\mathrm{c},\mathrm{d}}={\mathrm{D}}_{\mathrm{c},\mathrm{d}}\times {\mathrm{e}}_{\mathrm{c},\mathrm{d},}$$

• where: D _c,d = A _c,x x 0.85 xf _cd with: f _c,d = a _c × f _m,k : γm and
• where:
  • D _c,d is the design compressive force of the floor mortar;
  • the index c (concrete) indicates a size that can be assigned to the floor mortar; the index d (design) indicates a design variable, ie corresponding partial safety factors were taken into account during the determination; and
  • the index x refers to the concrete pressure zone, i.e. here in the pressure zone of the floor mortar.

Furthermore, ym ("Gamma m") is the partial safety factor for the material with a magnitude of preferably between 1.5 - 1.8 [-].

fcd is the reduced value of the compressive strength of the building material with a magnitude of preferably between 0.5 - 30 [MPa].

fmk is the unreduced value of the compressive strength of the building material with a magnitude of preferably between 0.5 - 50 [MPa].

Acx is the area of the pressure area in cross section with a magnitude of preferably between 0.5 - 3 [m ² ].

Dcd is the compressive force. The order of magnitude results from the calculation of the values given above [MN].

ecd is an inner lever arm of Dcd with a magnitude of preferably between 0.1 -0.5 [m].

wobei M_R,d ≥ M_E,d und

• der Index eine Größe bezeichnet, die dem Stützträger-Teilquerschnitt zuzuordnen ist; der Index R für resistance, also Widerstände steht;
• der Indes E für Einwirkungen steht;
• M Momente bezeichnet;
• D Druckkräfte und Z Zugkräfte bezeichnen; und
• e der innere Hebelarm ist.

According to a further development, it is also preferred that the total support strength M _R,d results from the formula: $${\mathrm{M}}_{\mathrm{R},\mathrm{d}}={\displaystyle \sum {\mathrm{D}}_{\mathrm{i},\mathrm{d}}}\times {\mathrm{e}}_{\mathrm{i},\mathrm{e.g}}={\mathrm{D}}_{\mathrm{c},\mathrm{d}}\times {\mathrm{e}}_{\mathrm{c},\mathrm{d}}+{\mathrm{D}}_{\mathrm{s},\mathrm{d}}\times {\mathrm{e}}_{\mathrm{s},\mathrm{d}}+{\mathrm{Z}}_{\mathrm{s},\mathrm{d}}\times {\mathrm{e}}_{\mathrm{s},\mathrm{e.g}},$$

where M _R,d ≥ M _E,d and

• the index denotes a size that is to be assigned to the support beam partial cross-section; the index R stands for resistance;
• where E stands for influences;
• M denotes moments;
• D denote compressive forces and Z tensile forces; and
• e is the inner lever arm.

In principle, the retaining wall in the ground can be made using the ground mortar in any suitable way. According to one embodiment of the invention, it is particularly expedient that a milling slot is formed in the ground by milling, with removed soil material in the milling slot being processed into the ground mortar by feeding and mixing it with a cement suspension. The soil mortar is thus formed in situ within the milling slot by mixing the milled soil material with the supplied cement suspension. The cement suspension can be fed directly into the area of the cutting wheels on a trench wall cutter. The milling wheels can take on a multiple function, namely milling off the soil material and at the same time mixing the milled soil material with the supplied cement suspension. In this way, a floor mortar can be created directly in the milling slot in a particularly expedient manner.

A further preferred embodiment variant of the invention is that a borehole is formed in the ground by drilling, with removed soil material in the borehole being processed to feed and mix with a cement suspension to form the ground mortar. The borehole can in particular be created by an earth drilling device with an elongated drilling tool, which has a removal device on its underside for removing soil material. The removed soil material can be conveyed into a rear area of the borehole via a screw conveyor. In this area, mixing elements protruding radially on a drill string can be arranged, through which the drilled and crushed soil material is mixed with supplied cement suspension to form the floor mortar. The cement suspension can preferably be supplied via a hollow drill string of the drilling tool and exit into the borehole at the lower end of the drill string and/or through outlet openings along the drill string.

A particularly efficient method variant results from the fact that, to form the supporting wall, several boreholes are formed next to each other in the ground by drilling. The drilling tools can be arranged and designed parallel to one another in such a way that they create overlapping drill holes so that elongated slot elements can be created in the ground.

The invention further comprises a support wall in the ground, which is characterized in that the support beams are arranged such that the designed total beam stiffness is smaller than the required target wall stiffness, and that the support beams are designed and arranged with an additional stiffness component, which results from at least one adjacent wall section made of floor mortar. The supporting wall can in particular be formed by the method according to the invention described above. This can result in the advantages described above.

Basically, the retaining wall can form a linear or curved wall in the ground. A particularly preferred embodiment of the supporting wall according to the invention is that it is designed in a ring shape to form an excavation pit enclosure.

Claims (11)

Method for designing and forming a retaining wall in the ground with a required target wall stiffness a floor mortar, which is produced in the ground by mixing soil material and a cement suspension and vertically directed support beams, which are set into the floor mortar and arranged therein, the arrangement of the support beams being designed with an overall beam stiffness, characterized, that the support beams are arranged in such a way that the designed overall beam stiffness is smaller than the required target wall stiffness, and that when designing and arranging the support beams, an additional stiffness component is added, which results from at least one adjacent wall section made of floor mortar. Method according to claim 1
characterized,
that apart from the support beams, no additional reinforcing elements are inserted into the floor mortar. Method according to claim 1 or 2,
characterized,
that steel beams, in particular with a C-profile, an H-profile or an I-profile, are set as support beams. Method according to one of claims 1 to 3,
characterized,
that the support beams are kept free of composite elements to the floor mortar. Method according to one of claims 1 to 4, characterized, that the additional stiffness component M _c,d on a support beam is determined by the at least one adjacent wall section made of floor mortar according to the formula: $${\mathrm{M}}_{\mathrm{c},\mathrm{d}}={\mathrm{D}}_{\mathrm{c},\mathrm{d}}\times {\mathrm{e}}_{\mathrm{c},\mathrm{d},}$$

where: D _c,d = A _c,x × 0.85 × f _cd with: f _c,d = a _c × f _m,k : Y _M and where: D _c,d is the design compressive force of the floor mortar; the index c (concrete) indicates a size that can be assigned to the floor mortar; the index d (design) indicates a design variable, ie corresponding partial safety factors were taken into account during the determination; and the index x refers to the concrete pressure zone, i.e. here in the pressure zone of the floor mortar. Method according to one of claims 1 to 5, characterized, that the total beam strength M _R,d results from the formula: $${\mathrm{M}}_{\mathrm{R},\mathrm{d}}={\displaystyle \sum {\mathrm{D}}_{\mathrm{i},\mathrm{d}}}\times {\mathrm{e}}_{\mathrm{i},\mathrm{e.g}}={\mathrm{D}}_{\mathrm{c},\mathrm{d}}\times {\mathrm{e}}_{\mathrm{c},\mathrm{d}}+{\mathrm{D}}_{\mathrm{s},\mathrm{d}}\times {\mathrm{e}}_{\mathrm{s},\mathrm{d}}+{\mathrm{Z}}_{\mathrm{s},\mathrm{d}}\times {\mathrm{e}}_{\mathrm{s},\mathrm{e.g}},$$

where M _R,d ≥ M _E,d and the index denotes a size that is to be assigned to the support beam partial cross-section; the index R stands for resistance; where E stands for influences; M denotes moments; D denote compressive forces and Z tensile forces; and e is the inner lever arm. Method according to one of claims 1 to 6,
characterized,
that a milling slot is formed in the ground by milling, with removed soil material in the milling slot being processed into the ground mortar by feeding and mixing with a cement suspension. Method according to one of claims 1 to 6,
characterized,
that a borehole is formed in the ground by drilling, with removed soil material in the borehole being processed into the ground mortar by feeding and mixing it with a cement suspension. Method according to claim 8,
characterized,
that in order to form the supporting wall, several boreholes are formed next to each other in the ground by drilling. Supporting wall in the ground, which is formed in particular according to a method according to one of claims 1 to 9, with a required target wall stiffness from a soil mortar, which is produced in the ground by mixing soil material and a cement suspension, and vertically directed support beams, which are used to form the Supporting wall is set in the floor mortar and arranged therein, the arrangement of the support beams being designed with an overall beam stiffness, characterized, that the support beams are arranged in such a way that the designed overall beam stiffness is smaller than the required target wall stiffness, and that the support beams are designed and arranged with an additional stiffness component, which results from at least one adjacent wall section made of floor mortar. Supporting wall according to claim 10,
characterized,
that the supporting wall is designed in a ring shape to form an excavation pit enclosure.