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Ground improvement methods for the construction of the federal road B 176
on a new elevated dump in the brown coal region of MIBRAG
Méthodes d'amélioration de sols pour la construction de la route nationale B 176
traversant un remblai récent d’une mine de lignite de MIBRAG
Kirstein J. F.
BVT DYNIV GmbH; Germany
Ahner C.
Landesamt für Straßenbau und Verkehr; Germany
Uhlemann S.
MIBRAG; Germany
Uhlich P., Röder K.
CDM Smith Consult GmbH; Germany
ABSTRACT: The MIBRAG Company operates two surface mines in the region south of Leipzig in Germany. This is the reason why
the existing B176 road needed to be relocated up to 1 km on a length of more than 5 km. This move will place the new road on
almost 60 m recently placed landfill area. Different ground improvement techniques such as Controlled Modulus Columns (CMC),
Dynamic compaction and Dynamic Replacement were used for the foundation of the bridge and the road depending on the soil
conditions and settlement tolerance of the structure. Because of significant stability problems, 15 m deep “floating” stone columns are
installed in the landfill. The design and the settlements were significantly optimized by the combination of the different soil
improvement techniques. The settlement forecast based on DIN EN 4094-5 Ménard pressuremeter results and finite elements
calculations are validated with the results of inclinometer measurements under the largest 15-m-high and 70-m-wide embankment.
RÉSUMÉ: La société minière MIBRAG exploite deux bassins de lignite dans le sud de Leipzig en Allemagne. Pour continuer
l’extraction de lignite, la route nationale B 176 doit être déplacée sur une longueur de 5 km à une distance de 1 km sur un remblai
récent d’environ 60 m d’épaisseur. Le renforcement du sol de fondation de la route et des ouvrages d’art a nécessité la mise en œuvre
des techniques d’amélioration de sol CMC, consolidation dynamique et colonnes ballastées. Grâce à la combinaison de ces méthodes,
des solutions d’exécution sûres et économiques ont été proposées et réalisées aussi bien pour la fondation principalement flottante de
la route et des ouvrages d’art que pour la zone de transition au terrain naturel. Les déformations sous un remblai de 15 m de haut et 70
m de large ont été estimées grâce au pressiomètre Ménard et aux calculs aux éléments finis ; elles sont validées par les mesures
inclinométriques.
KEYWORDS: Embankment, brown coal mining, Controlled Modulus Columns (CMC), stone columns, Ménard pressuremeter.
MOTS-CLÉS: remblai, mine de lignite, Colonne Module Contrôlé (CMC), colonnes ballastées, Pressiomètre Ménard
1 INTRODUCTION
The area south of Leipzig is characterized by brown coal
mining, and with an area of 500 square kilometer it is one of the
largest landscape construction sites in Europe. The existing
federal road B 176 between Pödelwitz and Neukieritzsch will be
relocated by the MIBRAG for brown coal mining. The first
construction section has an overall length of 8.3 km. The federal
road B 176 will be rebuilt by MIBRAG 5.5 km on the young
elevated dump of the Vereinigtes Schleenhain mine and will be
handed over to the State Agency for Road and Transport.
The young mixed dump fill areas are deep, from at least 60 m
and partially up to 105 m depth down to the natural soil.
Because of the large thickness of this fill deposit, these areas are
usually founded with shallow techniques to remain cost-
effective. The connection to the existing B176 takes place on
the so-called mainland area.
The future road will vary in elevations from existing ground
level to about 15m above the current elevation resulting in
varying settlements profiles across the length of the road.
Without the use of ground improvement methods, differential
settlements of up to one meter across the road would have to be
expected. For areas with more than 3 m of additional fill,
ground improvement was performed using mainly the intensive
dynamic compaction (Dyniv), while for the areas with
embankment of up to 15 m in height and 70 m in width, stone
columns were used. In the transition zones between Dyniv and
stone columns, Dyniv columns were executed as dynamic
replacement. At the bridge abutment, Controlled Modulus
Columns (CMC), full-displacement-columns were used. in
which the soil will be replaced by non-reinforced concrete.
Figure 1. Development of the new B176 (G.U.B. Ingenieur AG 2010).
With the help of various ground improvement methods, the
embankment stability verifications were performed by using the
results of Ménard pressuremeter with enhanced factor of safety.
By adjusting the ground improvement methods to the various
sections and ground conditions, a technical and economical
optimization could be achieved. The improvement of the soil
characteristics as well as the latest results of settlement
measurements confirmed the success of the method.
éthodes d’amélioration de sols pour la construction de la r ute nationale B 176 traversant un
remblai récent d’une mine de lignite de MIBRAG
