Diaphragms

Diaphragms

 

The MARFLUTT technology is particularly performance even for the formation of bulkheads and realization of diaphragms. The vibrofloatation and the use of particular steel shirts suitably shaped with male / female interlocking, allow the realization of continuous baffles with or without removal of soil with the improvement of the mechanical characteristics of the soil in the neighborhood of the panel. The absence of bentonite slurry or polymer simplifies the organization of the site, speeds production and leads to savings in production and sludge management, all in a construction site perfectly clean. The boundary characteristics of the soil are those indicated in the section ”MARFLUTT PILES without removal of soil” and ”MARFLUTT PILES with removal of soil.” The MARFLUTT diaphragms can be:
 

  • Plastic in Granular Bentonite (without removal of soil)

    The performance of which is based on entering compressed air inside the shirt hermetically closed and saturated with granular bentonite, up to reach an internal pressure such as to counter any uplift pressure of the soil during the extraction phase for vibrofloatation of the casing.

  • Self-Hardening Plastic Sludge (with removal of soil)

    Will differ from the previous ones , as well as for the use of an excavation counter-shirt , for making a preliminary mud whose properties are such as to ensure permeability coefficients in the order of k = 10-9

  • Structural Concrete (with removal of soil)

    As well as for the other types described does not require curb guide, they lend themselves to the formation of complex geometries for the particular joint used and for the speed of execution ; are reinforced with metal cage or with steel girders and do not require the removal of heads. The executive process that involves the taking of concrete is synchronized such as to ensure an absolute tightness of joints without the use of water stop; this contributes to the vibration during the ascent phase of the shirt, displacing the concrete, decreases considerably the presence of micro cracks, air voids, honeycombs, increases the mechanical characteristics of the conglomerate and reduces the permeability of the cement matrix.

 

 

Slurry Walls

 
Given the continued demand for execution of waterproof bulkheads, two new types of plastic diaphragms were implemented, with a particular regard to the problems of pollution:
 

  • Slurry walls made of self-hardening mixtures mainly used for waterproofing of canals and waterways with static problems;
  • Bentonite “Marflutt” diaphragm made with dry granular bentonite with high impermeability, for the protection of landfills, waterproofing of reservoirs, made without removal of material;
  • Thin diaphragm in self-hardening mixture, made without removal of material.

 
Are usually used as bulkheads or containment tanks; their peculiarity is the reduced permeability coefficient which varies depending on the type of mixture used and can reach an order of magnitude of 10-10 m / s. The executive procedure can be the traditional one used for the structural diaphragm, but much more used is the one-step procedure in which the mixture is used in place of the bentonite mud. The thickness of these bulkheads is small compared to the structural diaphragm and rarely exceeds 80-100 cm. An alternative, if the terrain allows, is the technology of the MARFLUTT diaphragms. The natural field of application of these works are the reclamation and treatment of polluted sites; applicant is the inclusion of a waterproof membrane inside the diaphragm.
 

 

Structural Diaphragm

 

  • Diaphragms for protection of excavations;
  • Diaphragms to protect excavations with static functions for boxed pipelines;
  • Diaphragms for the construction of wastewater treatment plants;
  • Diaphragms for the construction of hydraulic sealed tanks with static functions;
  • Diaphragms for the construction of river banks, etc…

 
Reinforced concrete structures that are used both as temporary works for sustaining the excavations, and as permanent works for the construction of deep foundations or to service hydraulic works; they are a succession of rectangular panels of variable thickness from 40 to 150 cm, length of 250 or 300 cm, made by means of a hydraulic clamshell bucket mounted on Kelly or free rope. The execution of a panel involves excavation with soil replacement with bentonite mud or polymer that ensure the livelihood of the walls of the excavation ; when target depth is reached the metal armor is inserted and subsequently one or more conveyor hoses through which the casting of the concrete from the bottom of the excavation is made. During the casting phase, the bentonite mud is extracted with the aid of pumps. Processing requires the availability of a sludge preparation plant and of a plant for the desanding of bentonite mud. The bulkhead can be made waterproof by installing water-stop joints between individual panels. This technology, though relatively inexpensive presents some limitations arising from:
 

  • The management and disposal of bentonite and excavated contaminated soil;
  • The need for space in the site, large amount of equipment needed, dirty and noisy construction site;
  • Possibility of damage to adjacent buildings;
  • Realization of geometry based on the individual modules or with throwaway elements.

 
Therefore, this work can be recommended in open areas and not in urban areas.
 

 

CSM Cutter soil mixing

 
Is a technology of soil consolidation that allows the formation of septa with widths between 50 and 120 cm and between 220 and 280 cm in length with a depth of up to 25 meters with guided maneuvering and up to 60 meters with maneuver lowered with ropes. The principle of operation is similar to the Soil Mixing because the soil is treated and simultaneously mixed with a binary or tertiary mix to form a sufficiently compact block with good mechanical characteristics. The substantial difference is that the soil is literally cut and ground by the rotation of two cutters on horizontal axes, and that the maneuver can achieve greater depths. The power of the equipment and the effect of cutting the ground allows operating not only in soft soils, but also in soils that are more consistent. The CSM is currently the replacement to diaphragms solving many of the problems generated by it. In fact the peculiarity of the Cutter Soil Mixing are:
 

  • Avoid vibrations on adjacent buildings and low noise processing; the mere fact that there is no pouring the concrete for the formation of the septum reduces the transit of mixer trucks in the site;
  • The mixing of the soil in-situ does not involve issues of livelihood of the tunnel walls and avoids detensioning of the soil in the neighborhood of the processing ;
  • Reduced bleeding during execution;

 
There are no problems in case of resumption of work; bulkheads are thus made continuous and free from joints; Greater flexibility in the management of geometry and the possibility of carrying out the baffles in close proximity of the buildings.
The CSM bulkhead is made bearing by inserting in the septa steel reinforcement joists