|
|
As a result of the walk-over inspection or internal inspection, a direct external inspection of the embedment and/or sewers and structures might become necessary. In the process, either subsurface explorations are carried out or the respective sewer sections or structures are laid open in order to inspect their outer walls and embedment using a trench, test pit or a man-accessible vertical borehole. (Image: Schematic outline of a subsurface exploration) |
|
|
The exposure of damaged sewer sections takes significant time to accomplish, involves traffic obstruction and is very costly, it may not always be carried out. However, one option in this context would be to combine the investigation measure with a repair of the damaged area from outside. [DIN4020:2010] (Image: Repair of a sewer from the outside by means of stainless steel sleeve) (Image: Repair of a sewer from the outside by means of stainless steel … |
|
|
The subsurface explorations are carried out either in-situ from the ground surface or from an excavation, and serve to ... (Image: Purpose of the site investigation - Stratification sequence) Determine the sequence, thickness and spatial position of the individual layers, the network of fissures and disturbances in the embedment and in situ soil; (Image: Purpose of the site investigation - Layers) Determine the type, composition and condition of the … |
|
|
|
|
|
In principle, a distinction is made between direct and indirect subsurface exploration measures. Direct explorations are natural or artificial explorations that provide for an inspection of the soil or rock and its sampling. The direct exploration methods allow for the determination of layer borders, types of soil and rock and rock- or soil-mechanical parameters. Samples can be taken to be classified later on in terms of their appearance and to be … |
|
|
EN ISO 22475-1 sets “the technical basics for soil, rock and groundwater sampling and groundwater surveys in the context of geotechnical explorations and analyses”. The methods used to take soil samples can be distinguished into the following categories:
[ENISO22475:2007] Combinations of the mentioned categories are possible or rather required … |
|
|
Jan 16, 2023 Investigation: Geotechnical Investigations Continuous Extraction of Soil Samples by Means of Boring Methods In EN ISO 22475-1, boring methods with continuous extraction of soil samples are defined as a process in which samples are taken by means of boring devices during boring. [ENISO22475:2007] The target of such boring is to take samples of rock or soil that are as undisturbed as possible to gain representative information on the subsurface conditions (left figure). The boring tool itself serves as sampling device here. Some bore hole probes and small-… |
|
|
Jan 16, 2023 Investigation: Geotechnical Investigations Continuous Extraction of Soil Samples by Means of Boring Methods Exploration borings can also be used to observe the groundwater with regard to the position, quality and quantity of water-bearing layers or as a groundwater measuring point (piezometer). (Image: Groundwater measuring point) (Image: Groundwater conditions in stratified subsoil following [Lauma83]) Groundwater measuring points have also proven their worth as a method of testing the leak tightness of sewers. For sewers below groundwater level, water … |
|
|
Jan 16, 2023 Investigation: Geotechnical Investigations Continuous Extraction of Soil Samples by Means of Boring Methods Furthermore, borings also allow for the extraction of samples for soil air analyses to assess the leak tightness of sewers. There are different options for the analysis, as e.g. the spectral analysis of gas samples in the laboratory by means of a chromatograph or the in-situ inspection using a portable photo-ionisation detector (PID) [AGI94b]. O2, CO2, H2S, CH4 and N2 are useful indicators of leaking sewers. The informative value of the sewer atmosphere … |
|
|
|
|
|
An extraction of samples via sampling devices is ”a process in which samples are extracted by means of sampling devices from trial pits, investigation pits and investigation galleries or from the borehole at chosen depth levels” [ENISO22475:2007]. In the case at hand, samples are mostly taken in a trial pit. (Image: Schematic outline of a subsurface exploration) (Image: Presentation of the results of the extended subsoil investigation) (Image: Exploration) (… |
|
|
The extraction of block samples is done by cutting a sample from the soil or rock using special methods. In the given case of application this type of sampling is unlikely to be relevant. [ENISO22475:2007] |
|
|
|
|
|
Indirect explorations are explorations that allow for conclusions about the subsurface by a given correlation between physical indicators and soil- or rock-mechanical parameters. Indirect explorations include:
Important: The results of measurement gained from this exploration method cannot be attributed directly to the subsurface parameters, but have to be compared … |
|
|
The term sounding defines an indirect subsurface exploration method in soils in which a probe is normally inserted perpendicularly to the soil to determine individual geotechnical parameters. Sounding methods can be subdivided into
(Image: Application of a dynamic probe in situ) (Image: Schematic principle of a rotating wing probe) (Image: Schematic depiction of … |
|
|
Depending on the device that is used, a probe is driven (standard penetration test / dynamic probing) or pushed (cone penetration test) into the subsoil or turned around its longitudinal axis at a specific depth (vane shear test). From the penetration resistance (sounding resistance) - that has to be defined individually - and its change with increasing depth, conclusions can be drawn for example about a layer’s strength or the degree of compaction, … |
|
|
The vane shear test serves to determine the shear strength (cohesion) of a water-saturated, undrained as well as cohesive and organic soil. The resistance against the rotation of a vane wing is measured in situ. The vane shear test is carried out with a rectangular vane consisting of four blades offset by 90° to each other, which is pressed in to the desired depth and then rotated. The higher the shear strength of the soil, the higher the measured … |
|
|
Dynamic probing, also called dynamic cone pentrometer test, is the most applied test method. Differences are made between a light (DPL), medium (DPM), heavy (DPH) and super heavy (DPSH) dynamic probe. Without any borehole, directly from the ground surface the probe is driven into the ground by means of a hammer of a defined weight and a constant drop height. The penetration depth and the number of hammer drops are determined afterwards. Normally, … |
|
|
Basically 4 types of dynamic probing are distinguished. In the table, they are divided into light (DPL), medium (DPM), heavy (DPH) and super-heavy (DPSH) penetration probes depending on their size and other characteristics. (Table: Types of Dynamic Probing) |
|
|
The following points must be taken into account when evaluating number of blows:
|
|
|
The figure shows a comparison between a Dynamic Probing Heavy (DPH) and a Standard Penetration Test (SPT). Compared to the standard probe (SPT), the increase of the penetration resistance due to skin friction is clearly visible in the case of the heavy dynamic probe (DPH). (Image: Comparison of the penetration resistance of Dynamic Probing Heavy (DPH) and Standard Penetration Test (SPT)) Correlation of DPL test results DPL testing results can be correlated … |
|
|
The correlation between the point resistance qcs of the pressure probe CPT-E, the number of blows N10 of the dynamic probes DPL, DPM and DPH (Table) and the consistency of cohesive soils or the density of non-cohesive soils in accordance with Placzek is illustrated in Table 1 and Table 2 [Placz85]. (Table: Correlation between point resistance qc of the pressure probe CPT-E, the number of blows N10 of the dynamic probes DPL, DPM, DPH and the consistency … |
|
|
For reasons of economic efficiency, the composition and the characteristics of the subsoil and the groundwater conditions can only be tested at a number of selected locations, particularly in the case of linear structures (such as supply and drainage pipes). As an example, the geotechnical investigation can be omitted in the case of a pipe replacement using a bursting method via short distances and in artificially backfilled soil. (Image: Bursting … |
|
|
[EN1997-2:2012] |
|
|
If third party pipes (supply and drainage pipes) and other obstacles are suspected in the surrounding area that might put the unhindered rehabilitation process at risk, the preliminary exploration measures and geotechnical analyses will also have to cover results with respect to the type and exact position of those third party pipes. (Image: Preliminary Exploration Measure - Search Slot Bild 1) (Image: Preliminary exploration measure - Search slot … |
11094 search results:
