Each system has been described according to the corresponding station in which the outcrop has been divided

Download (0)

Loading.... (view fulltext now)

Testo completo

(1)

SUMMARY

This degree dissertation is aimed at analizing the stability of Costa delle Calde’s slope, an area who has been the subject of various studies in the past years, as it was characterized by several gravitational movements occurred since the beginning of the 30’s, that coincided with the valley provincial road’s widening. The survey concentrated on the flint-limestone outcrop of Lima’s valley, which extends for about 130 metres along the valley road. The campaign surveyed discontinuities have been grouped into 4 systems, two of which with an appenninic direction and two with an antiappenninic direction, and characterized according to the ISRM recommendations: they result to be persistent-subpersistent, small-spaced, semiopen-open (in some sections up to 40-50 cm), with an incoherent infill, slightly rough and on average altered. Each system has been described according to the corresponding station in which the outcrop has been divided.

As for the value of Resistance to Uniaxial Compressive Strenght, the survey refers to the results obtained by the compressive press, being it a direct test; the instrument registered the following readings: 86 Mpa for station A, 90 Mpa for station B and 51 Mpa for station C.

The values of Resistance to Compressive Strenght obtained by means of indirect tests (sclerometric test and Point Load strenght test) do not diverge in a considerable way, and they range from 50 to 70 Mpa. The possible cinematisms were identified using the software Dips 5.1, analizing the positional relations between the discontinuity systems and the slope (Markland test, 1972; Goodman, 1980).

A slip wedge, given by the intersection of systems S1- S2, was detected within station A and Station B, while a planar slip involving system S1 and a medium wedge between S1-S2 and S3 (this one visible only from Station C) were detected in station C.

Cinematisms referred to station C have been subsequently analized in a more detailed way by means of softwares Rocplane 2.0 and Swedge 5.0 (for the other two stations we make reference to collegue Valentina Gambicorti’s degree dissertation): the results have shown safety factor values below 1, and the situation is rendered even more critical with the addition of seismic activity or forces bound to water pressure inside the fractures.

Similar results have been obtained applying the geomechanical classifications by Bieniawski (1989) and Romana (1985), according to which the greater part of discontinuity systems ranks within class III “moderate” and class II “good” respectively.

As expected, S1 ranks within class V “very low”.

Finally, considering also the stabilization interventions proposed by Romana’s classification itself (1985), it came to be appropriate to study a series of proposable solutions, so that it is possible to guarantee the safety of that part of the slope which stands on the valley’s road.

On the basis of data collections already present in literature, and considering also the limit equilibrium analysis carried out through the software Slide 5.0 by colleague Valentina Gambicorti, some proposable solutions were identified: a riveted wire net support (this intervention should be preceded by a mechanical removal of the most unstable blocks, and, if necessary, by grout injections) or a support wall in the first section of the roadway: this last hypothesis against the risk of seismic or severe meteoric phenomena.

2

figura

Updating...

Riferimenti

Argomenti correlati :