We conclude the article devoted to the struggle of shells of the most powerful calibers (420, 380 and 305-mm) with obstacles of various types based on the experience of the struggle of the fortress of Verdun in 1915-1916 (see "Suitcase" against the shelter ").
General observations regarding projectiles of all three calibers
The explosion of the large shells discussed above was extremely powerful.
In contrast to what takes place in the open air, the explosion of these shells in a confined space, for example, in underground galleries of fortifications, formed an air wave propagating over a very long distance.
Indeed, the gases, expanding depending on the resistance of the walls, instantly filled all accessible galleries and paths, and, penetrating into all adjacent rooms, produced various mechanical actions.
So, in one fort, the air wave from the explosion of a 420-mm projectile penetrated into the underground rooms along the staircase, tearing off several doors along the way (one of them was thrown 8 meters away). Having passed about 70 meters, this wave was still felt quite strongly, pushing people apart and squeezing them in the doors - despite the fact that it had 7 successive turns on its way (of which 5 were at right angles) and many open communications with outside air (through windows and doors).
In one gallery, the wave lifted everything that was in the room: beds, earthen bags, tours, etc., made of all this a kind of stuffing at the very end of the gallery, and carried 2 people there.
One telegraph post had an entrance in a long gallery, which was very far from the explosion site. But the air wave ripped out the door, pushing it flat against the wall and crushing the person it had caught along the way.
The tremors that were produced by the impact and explosion of these shells were strongly felt by the defenders, even placed in the underground galleries. Strongly shook the entire mass of the fort; sometimes, in some rooms that had not experienced the impact of shells, rather deep disturbances were made - as was the case in the entrance corridor to the 75-mm tower - a discrepancy between the slabs and the supporting walls and less important cracks.
Occasionally, these delaminations appeared in the retaining walls associated with the slab, slightly below the slab.
The impact of the impact of shells was much less reflected on large masses of concrete than on small ones: delamination and cracks were more noticeable, for example, on the connecting galleries and increased faster there from impacts than on parts of the concreted barracks. Thus, large masses resisted not only because of their great thickness, but also because of their large mass.
To resist this deep shock, the foundations of the structures had to be very well established and sufficiently deep, especially where an explosion under the wall or under the floor of the room could cause serious destruction.
Undoubtedly, such a shock caused collapses in two corridors of underground shelters of one of the forts, which occurred at different times, but in similar conditions. These corridors were pierced 8-9 meters below ground level, in very dense marl mixed with limestone, and had brick retaining walls 0.65 m thick and 2.5 meters high and the same vaults 0.34 meters thick. As a result of the impact and explosion of one 420-mm projectile (which gave craters about 10 meters in diameter and 5 meters deep in similar soil), the corresponding part of the vault was destroyed by "deep compression of the earth": the layer of earth left under the vault with a thickness of about 3 meters was depressed, and the corridor was littered with pieces of marl and stones.
It is understandable, therefore, how important it is that the floors of the deep galleries - even those pierced in the rock - are well filled and have strong supports.
During a short-term bombardment, the garrison did not suffer from the action of the gases of high-explosive bombs, unless the bombs explode in the premises occupied by the troops. A bomb that explodes in a residential building suffocates people with its poisonous gases - especially with poor ventilation.
During prolonged bombardments, ventilation is also necessary for underground shelters organized in mine galleries, since poisonous gases penetrating deep into the soil could penetrate into these shelters, due to their greater density, even through cracks in the rock.
required a sufficiently thick slab against which the projectile would explode, from an interlayer of 1 - 1.5 meters of sand and actually from the overlapping slab, which, depending on the importance of the structure, should be at least 2 meters thick.
was very different.
In 1915, 60 rounds of 420-mm caliber fell on one of the forts and in its immediate vicinity, and by August 1916, he received about 30 more such shells, about a hundred 305-mm bombs and a significant number of smaller-caliber shells.
Another fort from February 26 to July 10, 1916 received 330 bombs of 420 mm caliber and 4940 bombs of other calibers.
Another fort received 15,000 bombs in just one day, and about 33,000 shells of various calibers fell into the second over two months (from April 21 to June 22). The third fort from February 26 to April 11, 1916 received 2,460 shells of various calibers, including 250 bombs of 420 mm caliber.
If the forts were subjected to only medium bombardment (shells of no more than 380-mm caliber), then their elements, which were not directly exposed to the bombs, remained serviceable, as we will note below. The nets were damaged more or less severely, but they were still some obstacle for the enemy.
Escarps and counter-escarps were partly destroyed, but the ditches could be fired fairly easily from coffers and caponiers.
In the event that the bombardment was more intense, and the shells reached 420-mm caliber, then the nets were destroyed in whole or in part. The ditches were more or less littered with debris from escarps and counter-escarps, so flanking could become quite difficult. The earthen embankments were completely destroyed, and the signs of the breastwork bypass disappeared. However, it seemed possible to use the edges of the craters that covered the parapet and parapet to accommodate infantry and machine gunners.
You can no longer count on non-concrete shelters. Some concrete structures were also out of order. The galleries leading to the coffers of the counter-escarp were often overwhelmed, and a very important circumstance for further resistance was the supply of the people in the coffers with sufficient ammunition, hand grenades, provisions and water.
The most important concrete structures, which had a large mass, suffered, in general, little. This fact was established on the example of large concrete barracks, reinforced concrete massifs surrounding towers and other equivalent structures on all forts of the Verdun Fortress. So, in spite of more than 40,000 bombs of various calibers hitting the fort, the old powder magazine (which, after being reinforced, belonged to type No. 2) was still in good condition and was quite suitable for accommodating people.
up to August 1916 they resisted large shells perfectly, and if the functioning of some of the towers was stopped due to the hit of shells, then these towers could always be returned to service in a short time.
Even after the strongest bombing of the Verdun fortifications, the concrete forts retained their value and, in particular, their active qualities.
During the six-month struggle in February-August 1916 between concrete and artillery, long-term fortifications - even the least solid ones - showed great resistance to powerful modern shells.
The effect of very large caliber shells on turrets
According to the testimony of the defenders of Verdun, the armored turrets "resisted well."
Examples.
1) "Towers for 155-mm and 75-mm cannons in the aforementioned fort (which from February 26 to April 11, 1916 received 2460 shells, including 250-420 mm) are fired every day."
2) Although February 26, 1916the enemy focused his fire on them with particular focus, and several times extremely methodically shot them at them - not a single shell hit the domes of the towers, but three 420-mm bombs hit the concrete advance of the 155-mm tower. The concrete mass surrounding the armor cracked, and tangled bunches of iron reinforcement from the concrete were exposed. Despite this, the turret performed well, with slight sticking present in only a few positions.
An earlier fact also supports these indications.
In February 1915, a 420 mm projectile hit the reinforced concrete mass surrounding the 155 mm turret armor and refused. The place of impact is 1.5 meters from the outer circumference of the avankyrasy. The shell bounced off and fell not far - into the courtyard of the fort.
On a circular surface (up to 1.5 meters in diameter) a whole forest of tangled reinforcement rose; the concrete was damaged but not crushed. The tower was jammed, but in general it was not damaged.
It was repaired and put back into operation within 24 hours.
So, forts, fortifications, armored batteries and other strongholds of Verdun, which the defenders had to keep in their hands at all costs, even in a dilapidated state, served as satisfactory shelters for the defenders of the fortress and made it easier to repel German attacks.
The powerful modern artillery was unable to make these structures unsuitable for defense.
Of course, the results of this unparalleled struggle largely depended on the success of the French artillery, which did not allow German guns to smash the fortress with impunity. However, the consequences of the bombing were weakened by the following circumstances.
1) The relative explosive charge in the German bombs was generally small, as can be seen from the attached plate below; even for the 420-mm howitzer, a partition bomb was first adopted, which contained only 11.4% of the explosive. Later, they became convinced of the uselessness of this partition and introduced a new projectile weighing 795 kg, containing 137 kg (17, 2%) of explosive. French sources do not point to a difference in the action of these two types of shells - which were undoubtedly used to bomb Verdun, since the introduction of new shells is marked by documents dating back to this time period.
V. Rdultovsky determines for each projectile the approximate volume of the craters according to the average of the dimensions given in the text and, dividing the volume of the crater by the weight of the explosive, calculates the amount of earth thrown out by the unit of weight of this charge - in cubic meters. meters per 1 kg and cubic meters. feet per 1 Russian pound - as was customary in Russian artillery. To calculate the volumes of the funnels, he uses the following empirical formula
deduced on the basis of measurements of a large number of funnels in various soils, where D1 and D2 are the largest and smallest diameter of the funnel, h is its depth, V is the volume. In this case, D1 = D2.
At the end of the table, information about the projectile for the 370-mm French mortar sist. Filloux, similar in ballistic data to German 305 mm mortars; the relative charge in this bomb was three times higher than in similar German shells.
Judging by the data in this table, it can be considered that the deceleration in the action of the fuse of 420-mm bombs was chosen successfully; their sensitivity was insufficient - since they gave quite a lot of refusals.
380 mm shells, on average, gave satisfactory funnels, but often the volume of the funnels did not exceed 12 cubic meters. meters. These shells had fuses without deceleration and did not act uniformly on earth embankments; and when hitting concrete structures, they exploded almost at the moment of impact; even when hitting civilian houses, they produced destruction only in the upper floors. Therefore, we can assume that their enormous strength (initial speed reached 940 meters per second) and large explosive charge were not used properly.
The explosive charge in 305-mm bombs, in a relatively large number used in shelling French positions, was obviously insufficient.
2) The number of the largest shells hitting the forts turned out to be less significant than could be expected.
3) Noteworthy is the fact noted by the French: during the six-month struggle in the Verdun positions there was not a single hit of large shells in the domes or in the ring armor of the gun turrets, although the Germans repeatedly and methodically conducted the last sighting. It is quite clear that under this condition the towers withstood the bombardment "well".
But carefully organized experiments showed that towers of the same types as those installed in French fortresses suffered greatly from hits in the dome or in the ring armor even with 280-mm shells. Thus, the noted successful resistance of the towers should be largely attributed not to the strength of their structure, but to the difficulty of hitting, in combat conditions, their most vulnerable parts.
It is possible that the results of the bombing would have been different if the 420-mm bombs were used in greater numbers, and the disadvantages noted above were eliminated.
