THE REACTIVE CAPACITY OF THE SOIL BASES OF GRAVITY-TYPE QUAY WALL

The results of studies of the reactive capacity of the soil base of a gravitytype quay-wall on the basis of the method developed for calculating the “structure soil base” system are considered. The method proposed allows determining the reactive capacity of the soil base in conditions of mixed stress state model (limit and sublimit stress state of the soil base) under and around of the base of the foundation structure in a wide range of loads of lateral earth pressure. The transformation of limit and sublimit stress state zones of the soil base on the basis of numerical modeling is presented which shows an increase of the sizes of limit stress state and a decrease of the sizes of sublimit stress state. KEYWORDS

Introduction. Gravity-type quay-walls are the most common type of walls used for harbor berths. Reliability of the soil bases is one of the main factors in the design and the reconstruction of gravity-type quay-walls. Maritime transport development considerate the task of cargo complexes modernization and change their specialization including change of their operating condition. Thus, the studies of the reactive capacity of the soil base of a gravity-type quay-wall are importance and up-to-date.
The limit loads produced an effect on gravity-type quay-walls are of interest in the design or reconstruction of mentioned structures. It should be noted that the increase limit loads cause the loss of the reactive capacity of the soil base under the base of the foundation structure. Most often disturbance of stability of the soil base leads to a large settlement, to the rise from under the foundation and to the displacement of the structure. Significant displacement is dangerous for most of the aforementioned structures. Therefore, it is important to determine the maximum possible load on the soil base that won't disturb its stability.
Purpose of the study: to present the study's results of the reactive capacity of the soil base of gravity-type quay-wall on the basis of developed calculation method "structure -soil base" system [1] taking into consideration features work of the structure and soil backfill. The method proposed determines the reactive capacity of the soil base in the conditions of mixed stress state model. The model considers limit and sublimit stress state of the soil base under and around the foundation structure.
Research results. Calculation model of the "structure -soil base" system has been developed and numerical modeling has been performed in a wide range of loads of soil backfill pressure for studying of the system considered.
Occurrence issues of limit state zones of the soil base, determination of limit load causing their formation under the base of the foundation structure and influence of considered factors on the work 17 of the "structure -soil base" system have been discussed earlier by authors: M.V. Malyshev [2], P.I. Yakovlev [3], S.G. Kushner [4].

ARCHITECTURE AND CONSTRUCTION
Currently, methods of calculation of the soil bases which are used in the design of berth structures don't take into consideration the presence and the transformation of the limit and sublimit stress state zones. Experimental studies conducted by Y.K. Zaretsky [5] have shown that the reactive capacity of the soil base depends not only on the strength properties of the soil base but also on the parameters which describe its behavior in sublimit stress state.
The calculation method of the reactive capacity of the soil base has been developed. It is based on the theory of the limit stress state. The method is different from other methods by the presence of two zones of soil stress state (limit and sublimit) in the soil base of the structure and by considering of the friction on the contact of rigid foundation structure and the soil base. The scheme of calculation of the reactive capacity of the soil base is shown in Fig. 1.
The model proposed of the interaction of a gravity-type quay wall with the soil base is based on the following presupposition: 1. The soil base interacting with the base of the foundation structure includes zones of limit and sublimit stress state.
2. The boundary of limit and sublimit stress state zones of the soil base (the width bе of the contact zone of the soil base which is in limit stress state) is determined according to recommendations [1] and can be got from the expression 5 .
0  Some results of numerical modeling of the "structure -soil base" system are considered. It should be emphasized that there are two phases of the interaction of gravity-type quay wall and the soil backfill: the phase of structure construction which includes the process of formation of the soil backfill; the phase of operation when an uniformly distributed load q effects on the structure. The paper studies the second phase of the interaction of gravity-type quay wall and the soil backfill. In this case, soil backfill lateral pressure will increase depending on the loading and the increase of an uniformly distributed load q.
The increase load q leads to the growth of the reactive capacity of the soil base (due to the appearance and development of limit stress zones in the soil base). This process can be continued while limit reactive capacity in the soil base won't be reached. Further increase of the external load may lead to loss of the structure stability due to the exhaustion of the bearing capacity of soil base.
The growth of an uniformly distributed load q leads to the increase of active earth pressure of the soil backfill and to the transformation of the areas of limit and sublimit stress states of the soil base. The transformation leads to the increase of the area of limit stress state and to the decrease of the area of sublimit stress state. An example of the transformation of considered zones as a result of the increase of the load q is given in fig. 2. The boundaries of sublimit stress state 1', 2', 3' and 4' in the area located behind the foundation structure change the slope to the horizon from angle 45°-φ1'/2 to 45°-φ2'/2; 45°-φ3'/2; 45°-φ4'/2 in accordance with considered range of active pressure. The boundaries of sublimit stress state 1', 2', 3' and 4' in the intermediate area change the angle from θ1 ' to θ2 ' , θ3 ' , θ4 ' . Pointed boundaries are drowned by a logarithmic spiral as shown in fig. 2.
It should be noted that the growth of an uniformly distributed load q at the time of the formation of sublimit stress state zones reduces the sizes of sublimit stress state and changes the boundaries outline of the sliding surfaces. This process continues until the width of limit stress state zone won't reach of the value B.
Conclusions. The most important factor affecting on the assessment of the reactive capacity of the soil bases of gravity-type quay walls and on the determination of work of the "structure-soil base" system is lateral soil pressure. Thus, the study of the reactive capacity of the soil base on the basis of the calculation model proposed of the "structure-soil base" system is an important task. The findings of studies can be used in the design and the construction of considered structures and so for the analysis of the technical condition of the operation structures including rigid retaining walls.