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(Image: Attention!) It is important to note that the materials used in the construction process should not negatively affect the structural components or the groundwater and soil. |
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Aug 22, 2016 There has to be a contractual settlement between the client and the contractor with respect to the following items on the agenda:
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Aug 22, 2016 (Image: Open cut method of construction – Built-up area in the zone of influence of the building pit) Prior to the start of the civil engineering works, the exact position of the structures (buildings, piping, cables etc.) within the construction area of the excavation is to be crosschecked by the contractor. The trench construction process should never result in deformations or settlements of the surrounding structures. It is important to ensure that … |
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Aug 22, 2016 Depending on the individual requirements, the open cut method of construction allows for different cross sections of utility trenches, ranging from the sloped trench to trenches with vertical faces [Stein88d]. Combinations, such as stepped trenches with vertical, sloped or partly sloped trench walls, can also be found. (Image: Cross sections of utility trenches for the installation of sewers by means of the open cut method of contruction in accordance … |
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Aug 22, 2016 (Image: Attention!) Excavations and trenches are to be sloped, lined or secured in any other way in order to ensure that they remain stable during all individual states of construction. All conditions and influences that could have a negative effect on the stability of the excavation walls or trench walls are to be taken into account, particularly the differences in the behavior of non-cohesive and cohesive types of soil. (Image: Unshored trench with … |
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Dec 02, 2016 OSHA defines cohesive soil as "clay (fine grained soil), or soil with a high clay content, which has a cohesive strength. Cohesive soil does not crumble, can be excavated with vertical sideslopes, and is plastic when moist. Cohesive soil is hard to break up when dry, and exhibits significant cohesion when submerged. Cohesive soils include clayey silt, sandy clay, silty clay, clay and organic clay." [[OSHA 29 CFR 1926 Subpart P App A]] Non-cohesive … |
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Aug 22, 2016 (Image: Attention!) (Image: Trench excavation úsing a crawler excavator) During the excavation process, it is necessary to inspect the in-situ soil in order to ensure that it’s properties match the assumptions that have been made in the structural calculations (e.g. by means of soil identification). In case of deviations, it is imperative to inform the construction supervisor or structural engineer. |
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Aug 22, 2016 Existing piping and cables need to be taken into consideration when working in urban locations. In case of doubt, it is recommended to excavate the area in question using hand tools or hydro or vacuum excavation in order to determine the exact position of other services, as their actual position very often deviates from the planning drawings. Located services need be properly secured through suspending, supporting, rerouting etc. measures as specified … |
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Aug 22, 2016 To ensure the stability of the excavation, the trench construction must comply with national construction safety standards, and excavation safety regulation, by providing sloped walls in unlined trenches, and shored walls in vertical trenches. The type and extent of the required trench safety measures is dependant on the in-situ soil type, groundwater conditions, and the depth of the trench. (Image: Unlined trench – sloped trench walls) (Image: Shored … |
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Aug 22, 2016 In order to assess the stability of the trench, the following information is generally required:
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Aug 22, 2016 (Image: Overview of possible measures used to secure open cut trench walls) |
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Dec 05, 2016 The Occupational Safety and Health Administration (OSHA) Excavation and Trenching standard, Title 29 of the Code of Federal Regulation (CFR), Part 1926.650, covers requirements for excavation and trenching operations. A trench is defined as a narrow underground excavation that is deeper than it is wide, and no wider than 15 ft (4.5 m) [[OSHA CFR 29, Part 1926.650]] (Image: Cross sections of utility trenches for the installation of sewers by means of … |
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Dec 05, 2016 OSHA requires that all excavations in which employees could potentially be exposed to cave-ins be protected by:
Additionally, temporary soil must be placed no closer than 2 ft (0.61 m) from the surface edge of the excavation, measured from the nearest base of the spoil to the cut. The … |
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Dec 05, 2016 According to [[OSHA CFR 29, Part 1926.650]], the excavation does not require a protective system when it is:
Some European countries have stricter limits. Here only excavations and trenches up to a depth of 4 ft (1.25 m) may be constructed without additional shoring. Further information can be found … |
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Dec 05, 2016 |
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Aug 22, 2016 AE-02 Open Cut Method: Utility Trench Construction Trench Without Support System as per International Standards Excavations and trenches up to a depth of 4 ft (1.25 m) may be constructed without additional shoring of the vertical walls if the adjacent ground surface
(Image: Securing of unlined trenches and shafts at depths of ≤ 1.25 m/4 ft in accordance with [DIN4124c] – Vertically sloped trench walls) (Image: Lack of shoring, although … |
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Aug 22, 2016 AE-02 Open Cut Method: Utility Trench Construction Trench Without Support System as per International Standards Excavations and trenches up to 6 ft (1.75 m) in depth may be excavated, if the portion of the trench wall above 4 ft (1.25 m) from the trench base is sloped at the angle β ≤ 45° and …
(Image: Securing of unshored trenches and shafts at depths of > 1.25 m/4 ft and ≤ 1.75 m/6 ft in accordance with [DIN4124c] – vertically sloped trench walls with sloped edges (… |
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Aug 22, 2016 AE-02 Open Cut Method: Utility Trench Construction Trench Without Support System as per International Standards The securing of trenches up to a depth of 6 ft (1.75 m) using only a timber plank is no longer permissible. This case requires a partial shoring of the trench walls above 4 ft (1.25 m) from the trench base. Right Wrong (Image: Cosmetic, respectively non-functional … |
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Dec 06, 2016 |
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Aug 22, 2016 (Image: Shored trench – Use of an edge-supported trench lining system) For trench depths of more than 6 ft (1.75 m), either a full shoring or sloping at a proper angle of the trench walls is required. It has to be taken into account that the headwalls of the trenches have to be secured by sloping or shoring as well. This step is not necessary in trenches with firm cohesive soil and a depth of 6 ft (1.75 m), and a width of up to 4 ft (1.25 m). (Image: … |
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Aug 22, 2016 The slope angle depends on the subsoil (physical characteristics of the in situ types of soil, water conditions), the use of adjacent surfaces (traffic ways, built-up areas), the stress to be expected due to construction equipment, the height of the slope and its anticipated stability time. (Image: Slope angle and working space width according to DWA-A 139) (Image: Trench without support system with a slope angle of ß = 45° and minimum distance to … |
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Dec 05, 2016 The table below presents the maximum allowable slopes for excavations that are less than 20 ft (6.1 m) deep. The soil classification, according to [[OSHA 29 CFR 1926 Subpart P App A]], are based on the definitions in whole or in part, the following; American Society for Testing Materials (ASTM) Standards D653-85 and D2488; The Unified Soils Classification System; The U.S. Department of Agriculture (USDA) Textural Classification Scheme; and The National … |
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Dec 05, 2016 Trench benching is a method of protecting workers from cave-ins by excavating the sides of an excavation to form one or a series of horizontal levels or steps, usually with vertical or near-vertical surfaces between levels. (Image: Benching with allowable slopes and step hight for type A soil according to OSHA) (Image: Benching with allowable slopes and step hight for type B soil according to OSHA) It is not safe to cut steps into a slope of type C … |
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