with reference to fig1 , a light armoured vehicle 1 comprises a cab 2 fixed to a chassis 3 equipped with wheels 4 . the inside of the cab can be accessed by a door 5 and it encloses seats 6 which are suspended from the cab roof by a support frame 7 . such an arrangement is classical and enables the seats to be isolated from the cab floor 8 , thereby protecting the crew from the effects on the floor further to a mine exploding . in accordance with the invention , a floor protection device 9 is provided that comprises an armour plate 10 ( for example , of steel ) that is positioned at a distance from the cab floor 8 . the plate 10 , is fastened to the cab 2 by means of deformable linking means 11 . in accordance with the invention , at least one of the deformable linking means 11 ( and preferably all the linking means 11 ) is constituted by a compartmented caisson . fig1 and 2 a show that the armour plate 10 is fastened by three caissons 11 arranged on each side of the vehicle . as may be seen more particularly in fig2 a , the caissons 11 are arranged under a lateral partition 2 a or 2 b of the cab 2 , such partition being substantially vertical . thus , the loads received by the armour plate 10 will be communicated to the cab , not to the floor 8 , but to the walls 2 a , 2 b that cannot be deformed so much . fig2 b shows a perspective view of a caisson 11 according to this first embodiment of the invention . by compartmented caisson , we mean a substantially parallelepipedic structure that incorporates at least two walls 12 a , 12 b that will be arranged substantially perpendicularly to the armour plate 10 . the walls 12 a , 12 b are integral with a lower wall 14 on which the armour plate 10 presses . the walls 12 a , 12 b are furthermore integral with an upper wall 13 that presses on the cab 2 and enables the device to be fastened to the latter . each caisson 11 delimits an inner space 15 which is open laterally at each end of the caisson . the walls 12 a , 12 b are thus substantially vertical and are furthermore dimensioned such that they buckle as a result of a shock transmitted by the armour plate 10 due to the detonation of an explosive device . this dimensioning will be performed classically by calculation depending on the material of the walls 12 a , 12 b and the expected level of shock . the buckling will be all the greater in that the wall is high with respect to its section . the walls 12 a , 12 b delimit the inner space 15 of the caisson , they are furthermore also substantially perpendicular to the wall 12 a , 12 b in question of the cab 2 . this orientation of the walls leads to their section being reduced thereby improving their deformation by buckling . such a configuration is thus far from that of the longitudinal beams described by de19935573 . indeed , the latter extend over the full length of the vehicle ( thereby increasing the section of the vertical walls of the beams ) and they are reduced in height . such beams absorb little energy by deformation and communicate most of the shock received to the vehicle &# 39 ; s structure . the upper wall 13 will have drill holes enabling the caisson 11 to be fastened to the floor 8 or to the cab 2 . the lower wall 14 will additionally have drill holes enabling the armour plate 10 to be fastened to the caisson 11 . the caissons 11 are made of steel ( depending on the level of protection required , they could also be made of another material , for example aluminium or a composite ). the walls 12 a , 12 b ensure the rigidity of the caisson . when an explosive device or mine explodes under the vehicle 1 , the armour plate 10 is deformed by the blast effect . the free space 16 between the plate 10 and the floor 8 allows such a deformation without the shock being transmitted to the floor 8 . the loads are communicated by the plate to the caissons 11 , which retransmit them to the walls 2 a , 2 b of the cab . however , the walls 12 a , 12 b will also deform by buckling . this deformation will consume part of the energy received but will above all attenuate the violence of the shock . indeed , the energy of the explosion will be transmitted for a less brief duration which will reduce the stresses received by the vehicle and will attenuate the destructive effects on the cab . it is possible for the caissons 11 to be given different shapes . fig3 a and 3 b show another embodiment in which a single caisson 11 is positioned on either side of the vehicle but which has a length that is substantially equal to that of the armour plate 10 . to give the caisson 11 the properties of rigidity / deformability necessary for it to ensure its function of attenuating the shocks , partitions 17 parallel to walls 12 a , 12 b are arranged inside it ( here there are four partitions ). the partitions 17 will , for example , be welded to the upper 13 and lower 14 walls of the caisson . fig4 a and 4 b show another embodiment in which three caissons 11 are implemented , all integral with a same lower wall 18 . it is no longer necessary , in this case , to provide a specific lower wall 14 for each caisson 11 . the lateral walls 12 a , 12 b and upper wall 13 thus form a u - shaped structure which will , for example , be welded to the common wall 18 . when a mine is ignited , the shock received by the armour plate 10 will thus be transmitted to the wall 18 which will ensure the distribution of the shock over the different caissons 11 . with such an embodiment , the caissons 11 will be positioned at a distance from one another . two neighbouring caissons 11 are thus separated by a space 19 . advantage may be taken of these spaces 19 to constitute storage areas to be used by the vehicle &# 39 ; s crew . these spaces 19 may also house the organs of the vehicle , for example an exhaust silencer or batteries . we note that it would also be possible in the embodiment shown in fig3 a , 3 b to use the spaces inside the caisson 11 ( between partitions 17 ) by way of storage areas . fig4 c differs from fig4 b in that the caissons 11 are also fixed to a same lateral plate 20 which here is perpendicular to the lower wall 18 . the caissons 11 , the lateral plate 20 and the lower wall 18 form a chamber 21 . the vehicle thus incorporates a chamber 21 on each side . each chamber constitutes a compact assembly incorporating the caissons 11 to absorb the shock wave transmitted by the armour plate 10 . the lateral plate 20 constitutes another deformable element that completes the caissons 11 . it also enables the chamber to be closed thus insulating the inner spaces 19 from the exterior of the chamber . openings will be advantageously provided in the lateral plate 20 which will carry closing covers to access the internal storage areas 19 . fig5 differs from the previous embodiment in that the caissons 11 , grouped into chambers 21 , incorporate a lateral plate 20 that forms an angle with respect to the armour plate 10 . such an arrangement gives an overall deflector shape to the device 9 , such shape ensuring a deviation of the blast received from a mine when the latter is in the vicinity of one of the rims of the armour plate 10 . furthermore , fig5 shows that each chamber 21 is positioned such that it incorporates a plane upper rim 22 that extends towards the outside of the vehicle beyond the lateral partition 2 a , 2 b . this rim 22 is formed here of part of the upper wall 13 . it constitutes a step to facilitate access to the vehicle . fig6 shows another embodiment of the chambers 21 according to the invention . in accordance with this embodiment , the lateral plate 20 of each chamber is once again inclined with respect to the armour plate 10 . fig6 shows that the lower wall 18 has two rows of holes to enable the armour plate ( not shown in fig6 ) to be fastened . furthermore , the upper walls 13 ( 13 a , 13 b and 13 c ) of the caissons have holes to allow the passage of screws to fasten the device to the cab . we note that in this embodiment , the caissons 11 are not all of the same shape . the end caissons 11 a and 11 c have lateral walls 12 a , 12 b that are not parallel . at least one wall ( 12 a ) is , however , still perpendicular to the lower wall 18 ( and to the armour plate ). the other wall 12 b is slightly inclined with respect to the lower wall 18 . such an arrangement is intended to adapt the external shapes of the front 11 a and rear 11 c caissons ( and thus of the chamber 21 ) to the structure of the vehicle . the walls 12 a and 12 b nevertheless ensure resistance to deformation for the caissons in question . we note also on this figure that the caissons 11 incorporate an opening 24 in certain of their lateral walls 12 . these openings help to lighten the structure of the chambers and furthermore provide an access for the fastening screws enabling the upper faces 13 of the caissons to be joined to the vehicle cab . this figure shows that the lateral plates 20 incorporate openings giving access to the space 19 between the caissons 11 . these openings are block by hatches 22 fitted with hinges and locks ( not shown ). fig6 lastly shows that each chamber 21 here incorporates an upper rim 22 that completes the closing of the spaces 19 . this rim 22 is parallel to the upper walls 13 of the caissons and is located on a plane slightly above the plane of the upper walls 13 . the rim thus forms a step giving access to the vehicle cab . in all of the embodiments previously described , the caissons 11 are empty . it is possible , by way of a variant , to put a deformable material inside one or several caissons able to complete the absorption of the impact energy . for example , deformable foam , for example metallic foam ( such as aluminum foam ) may be placed in the caissons . sand or else a metallic or composite material cell structure , like a honeycomb , may be put in the caissons 11 . it is also possible to install a shock absorbing material between the armour plate 10 and the lower wall 14 and / or between the upper wall 13 and the floor of the cell 8 .