Abstract: A compression body is inserted into the contraction joint between two tunnel lining elements, which body deforms in response to a compressive load caused by the tunnel lining elements moving towards each other. The compression body is composed of a material containing voids, and has a compressive strength of at least 1 MPa and a void fraction of between 10% and 90% of its total volume. The compression body may be composed, for example, of steel foam, or of a mixture which contains cement and blown-glass particles or plastic particles. When a predetermined compressive load is exceeded, the voids within the compression body collapse in a stepwise manner, or are compressed in a stepwise manner.

Abstract: A compression body (7) is inserted into the contraction joint (6) between two tunnel lining elements (2, 3), which body deforms in response to a compressive load caused by the tunnel lining elements' (2, 3) moving towards each other. The compression body (7) is composed of a material containing voids, and has a compressive strength of at least 1 MPa and a void fraction of between 10% and 90% of its total volume. The compression body (7) may be composed, for example, of steel foam, or of a mixture which contains cement and blown-glass particles or plastic particles. When a predetermined compressive load is exceeded, the voids within the compression body (7) collapse in a stepwise manner, or are compressed in a stepwise manner.

Abstract: A measuring instrument includes first and second rigid, elongate measuring elements which are interconnected by a flexible element. The measuring elements are supported in a measuring tube inserted in the foundation soil. Whenever a displacement occurs in the foundation soil or construction, the measuring tube is deformed and the second measuring element is pivoted with respect to the first measuring element. The curvature or bending which thereby occurs in the flexible element of suitable dimensioning or configuration is preferably determined by at least one wire strain gage fitted to the flexible element in the plane of deformation, the elongations being converted, for example by use of a Wheatstone bridge circuit, into proportional electrical current or voltage signals. Preferably, wire strain gages are disposed on all four mutually perpendicular outer sides of the flexible element, in order to allow for the detection of displacements in mutually perpendicular planes.

Abstract: The tubing system comprises a number of measuring stops or surfaces arranged in a predetermined mutual spaced relationship. The spacing is utilized for determining the displacements in the material enclosing the tubing. This displacement is ascertained by a measuring probe introduced into the tubing from the outside. The measuring stops are provided on measuring tube unions or coupling sleeves in order to ensure that displacements in the material can also be transmitted to the measuring stops even in relatively soft material without a stiffening effect of the tubing. The connection between the measuring tube unions or coupling sleeves takes place exclusively through a telescope-type protecting tube insert. A rigid anchoring of the measuring tube unions or coupling sleeves to the inner wall of an accommodating hole or bore hole provided in the material to be investigated takes place through filling collars fastened to the outside of the measuring tube unions or coupling sleeves.

Abstract: A measuring tube is inserted into a bore hole for measuring underground fluid pressure and is sealed against the bore hole wall for limiting the areas or regions in which the pressure measurement is to occur. A measuring cell is inserted into the measuring tube wall in each of these areas or regions and includes a mobile pressure sensing element against which acts the pressure of the medium surrounding the measuring tube. An end of the pressure sensing element projects into the inner space of the measuring tube and, for measurement, a measuring wheel of a measuring probe is brought into position underneath the end of the pressure sensing element such that the latter is moved radially outwards against the pressure exerted on it. The force which thus acts on the measuring wheel is determined by a measuring device for measuring the pressure. The medium to be measured does not enter or leak into the measuring tube since the measuring cell is sealingly inserted into the measuring tube.

Abstract: In the medium to be examined there is embedded a measuring tube which possesses at its inner surface essentially equidistantly spaced measuring markers. These measuring markers are in the form of mechanical stops or impact members having an impact surface forming part of a right circular cone. To determine the spacing between neighboring measuring markers there is provided a measuring probe or sensor having two measuring heads connected with one another, by means of a connection tube, such that they are relatively shiftable in the lengthwise axis of the measuring probe. Each measuring head is constructed as a mechanical counter stop having an impact or stop surface forming part of a spherical surface. Internally of the connection tube there is arranged an inductive length transmitter producing an output signal characteristic of the spacing between the measuring heads.