|
|
Open dewatering involves simultaneously collecting accruing groundwater water during the excavation process. This process is performed at about 20 in to 40 in (50 cm to 100 cm) ahead of the excavation, and requires stable types of soil (such as rock), coarse gravel or cohesive types of soil and generally low permeable soils to be effective. The groundwater can be directly pumped or allowed to seep to sumps at the boundaries of the trench, where it … |
|
|
(Image: Groundwater lowering using wells) In the groundwater lowering method, vertical wells as well as required piping and pumps are installed around the planned trench or construction pit (in the case of large construction pits also within the pit) prior to the excavation process. Compared to the open water retention method, groundwater lowering by means of wells allows for significantly deeper lowerings. The design type and dimensioning of the well … |
|
|
(Image: Installation of wellpoints for groundwater lowering using gravity drainage) (Image: Groundwater lowering using gravity drainage- mode of operation) (Image: Installation of wellpoints for groundwater lowering using gravity drainage) Basically, we distinguish between gravity drainage and vacuum drainage systems. In the case of gravity drainage, the lowest groundwater level can be found in the well pipe. Consequently, due to gravity, the water … |
|
|
(Image: Example for groundwater lowering using vertical wells (well lowering)) If the subsoil is very impermeable (fine sands and silts (kf = 10-4 – 10-7 m/s)), a vacuum drainage system is used. In contrast to gravity drainage, an additional pump-created vacuum is used to direct the water to the wells. (Image: Groundwater lowering using vacuum drainage (deep well system) – Detail header pipe) (Image: Groundwater lowering using vacuum drainage (deep … |
|
|
(Image: Example for horizontal water collection) Instead of vertical wells, horizontally arranged filters or drainage pipes can also be installed next to the excavation (or even below larger excavations). The so-called horizontal water collection significantly reduces the water quantity to be pumped. However, the additional costs for the installation of this system are only economical for long-term construction measures. |
|
|
|
|
|
Congratulations! You have successfully finished this lesson. Next you will have the opportunity to review the newly acquired knowledge with an interactive questionnaire. You can of course still navigate back to any point in the lessons if you wish to review a specific point or subject. Stay curious! |
|
|
Aug 22, 2016 The construction of sewers is still often carried out in the form of open cut construction. Depending on the design, this results in different pipe-soil systems with different external loads on the sewer. After completing this module, you will have a sound knowledge of:
|
|
|
(Image: Open cut trench working space) The trench width has always been the subject of discussions due to its impact on the economic efficiency and the quality of pipe installation. The trench width should be dimensioned in such a way as to provide sufficient working space around the pipe. The working space is considered to be the area at the base of the trench measuring from the outside edges of the pipe to the inside edge of the shoring or the trench … |
|
|
(Image: Question). What kind of failures or problems are visible in the images? (Image: Inadequate working space at the side of the pipe (no arrow)) (Image: Inadequate working space at the side of the pipe – Proper compaction is impossible) |
|
|
The minimum trench width defines the minimum working space in the trench needed to enable proper compaction of the haunch zone and of the embedment. A definition of the minimum trench width can be found for example in the European standard [EN1610:2015]. The minimum trench width is a function of both the nominal pipe size and the trench depth. (Image: Minimum trench width subject to the nominal pipe size) (Image: Minimum trench width subject to the … |
|
|
The abbreviation for the nominal size of the pipe is DN (Diameter Nominal) or ID (Internal Diameter). It defines the parameter for circular cross sections in millimeters (without specifying the unit mm). The nominal size approximately corresponds to the clear diameter. (Image: Attention!) The minimum trench width is determined solely by the OD = outside diameter of the pipe. Non-circular cross sections are classified into DN groups with the help of … |
|
|
Standards, specifications and installation guidelines used in the United States are specific and unique for each pipe material, therefore, unlike the European standards, there is no general approach documented in one single standard related to minimum trench width calculation. As a result, the most common practice in the US is for the engineers and contractors to follow the specifications imposed by the pipe manufacturer, or the specifications prescribed … |
|
|
|
|
|
Aug 22, 2016 AE-02 Open Cut Method: Embedment Zone and Pipe Installation Minimum Trench Width Calculation in the US for Various Pipe Materials The following formula can be used as a general guide to compute the minimum trench width for circular concrete pipe installation using the open cut method. (Image: Reinforced concrete pipe) (Table: Minimum trench width for circular concrete pipe in the US) Sample calculation: O.D. = 24” ID + 3 in wall thickness x 2 = 30 in Total trench width = O.D. + (O.D./6 x2) = 30 in+ (30/6 x 2) = 30 in + 10 in = 40 in min |
|
|
Jan 04, 2017 AE-02 Open Cut Method: Embedment Zone and Pipe Installation Minimum Trench Width Calculation in the US for Various Pipe Materials The table below presents the method to select the minimum trench width for HDPE pipe installation using the open cut method for stable ground conditions [[Plastic Pipe Institute]] (Image: HDPE pipe) (Table: Minimum trench width for HDPE pipe in stable ground) AASHTO Section 30 requires a minimum trench width of not less than: Wmin = 1.5 x OD + 12 in (300 mm) ASTM D 2321 requires a minimum trench width of the greater of either the pipe OD + 16 in (400 … |
|
|
Jan 04, 2017 AE-02 Open Cut Method: Embedment Zone and Pipe Installation Minimum Trench Width Calculation in the US for Various Pipe Materials The table below presents the method to compute the minimum trench width for polyvinyl chloride (PVC) pipe installation using the open cut method. (Image: PVC pipe) (Table: Minimum trench width for PVC pipe in the US) |
|
|
Jan 09, 2017 AE-02 Open Cut Method: Embedment Zone and Pipe Installation Minimum Trench Width Calculation in the US for Various Pipe Materials The table below presents the minimum trench width as a function of pipe outside diameter for glassfiber reinforced pipe (GRP) installation using the open cut method. (Image: Glass fibre reinforced plastic pipe (GRP pipe)) (Table: Minimum trench width for GRP pipe in the US) |
|
|
Jan 04, 2017 AE-02 Open Cut Method: Embedment Zone and Pipe Installation Minimum Trench Width Calculation in the US for Various Pipe Materials The table below presents the minimum trench width as a function of pipe outside diameter for centrifugally cast glass-fiber reinforced polymer mortar (CCFRPM) pipe installation using the open cut method. (Image: Centrifugally cast fiberglass-reinforced, polymer mortar (CCFRPM) pipe) (Table: Minimum trench width for CCFRPM pipe in the US) |
|
|
Jan 04, 2017 AE-02 Open Cut Method: Embedment Zone and Pipe Installation Minimum Trench Width Calculation in the US for Various Pipe Materials The table below presents the minimum trench width as a function of pipe outside diameter for ductile iron pipe installation using the open cut method. (Image: Ductile iron pipe) (Table: Minimum trench width for ductile iron pipe in the US) |
|
|
Jan 04, 2017 AE-02 Open Cut Method: Embedment Zone and Pipe Installation Minimum Trench Width Calculation in the US for Various Pipe Materials (Image: Vitrified clay pipe) Trenches for Vitrified Clay Pipe (VCP) installation shall be excavated to a width that will provide adequate working space, but not more than the maximum design width, according to [[ASTM C12-07]]. There is no single formula that is applicable for minimum trench width calculation for VCP. Trench width is mainly one factor to compute loads caused by backfilling to determine the supporting strength of VCP. The factors taken … |
|
|
|
|
|
(Image: Pipe haunches for pipes with circular outer contour) Adequate compaction of the haunch area is decisive to achieve a long service life of the sewer pipe. Because of that, European Standards aim to ensure a working space for all pipes and types of installation, which allows sufficient compaction of the haunch and side fill. Therefore the calculation of the minimum trench width is independent of pipe material and installation type and just a … |
|
|
What are the consequences of non-compliance? If the trench width is too narrow, proper compaction of the backfill material (bedding/pipe support) at the pipe haunch zone cannot be achieved. (Image: Pipe haunches for pipes with circular outer contour) (Image: Inadequate working space at the side of the pipe (no arrow)) (Image: Non-compliance with the minimum trench width - Compaction of the haunch zone and side fill not possible) (Image: Non-compliance … |
|
|
(Image: Attention!) What are the consequences of non-compliance? A proper compaction of the side fill is impossible when the required minimum trench width is undercut. Static assumptions cannot be met in such a case. (Image: Inadequate working space at the side of the pipe – Proper compaction is impossible) |
602 search results:
