Strength and deformation conditions of large deformation-resistant asphalt slabs lying on an elastic base

Introduction

It is known that in our developing country, as in all areas, the President pays special attention to the development of road construction. In the development of the economy of our country, in the development of the new Uzbekistan, along with rail and air transport, the development of road and transport infrastructure also plays an important role in the delivery of household goods. One of the most pressing issues is to improve the quality and long-term durability of roads in the Fergana Valley of Uzbekistan, to increase their resistance to dynamic deformation, freezing, corrosion and hot and cold external environment. That is why our state pays special attention to this issue. One of the ways to improve the quality of highways is to increase the strength and durability of asphalt concrete pavements. Therefore, many foreign and domestic scientists are currently conducting research on this issue. This research was carried out in accordance with the State Scientific and Technical Program for 2017-2021. In order to implement the issues provided for in the program of decrees and resolutions of the President of the Republic of Uzbekistan dated February 7, 2017 PF-4947 "On the Action Strategy for further development of the Republic of Uzbekistan, the program of further development of regional roads in 2017-2020." These studies have been conducted. This study examines the properties of asphalt pavement materials resistant to large deformation in the conditions of Uzbekistan and their application. Today in many developed countries: USA, Germany. In countries such as France and Japan, special attention is paid to the creation of advanced modern technologies to increase the durability and long-term durability of asphalt pavements operated in different natural climatic conditions that meet modern requirements that improve road quality. In this study, the issues of strength and durability of asphalt concrete rough road surfaces made using local materials were analyzed.

We see a study of the stress-strain state of cylindrical bending under the influence of external forces on automobile asphalt concrete pavements lying on an elastic ground. www.extensionjournal.com

The differential equation of bending of multilayer plates in the cylindrical bent position lying at the base of the winch has the following form.

Here for multi-layer plates: D11 -cylindrical thickness of the plate; w is the desired cooling function, q is the intensity of the external propagating force; k is the coefficient of elastic base inclination; For the Kirchhoff hypothesis (flat section hypothesis) to be true, the cylindrical stiffness of a multilayer slab is determined as follows.

-the specific cylindrical virginity of the k-layer; The normal stress in the cross section of the slab is determined as follows.

Where Mx (kH) is the bending moment in a given section. zA is the coordinate of point A, which determines the normal voltage.

The test voltage is determined as follows.

Where Q (kH / m) is the transverse force on the given section of the slab.

(5)the formula "k" represents the law of distribution of transverse stresses in the layer, if k ≥ 2 at k = 1, i.e. for a single-layer slab we have the following 3] .

Where Based on the boundary conditions for the λ-step "i" node by the free edge of the plate, (5) can be written as follows. Boundary conditions are mainly [2,3]  

Here Mi + 1 is equal to the bending moment in the longitudinal direction of the plate. (7) For node "i" is written as follows, the boundary conditions are mainly [2]  

-In addition to the bending moment, there is also a transverse force distributed along the longitudinal edge.

For the edge of the hinged connection * 0 a w  Basically (5) the node "i" also includes the value of the slope of the outer node, which it i w -can be expressed through stiffness. (12) Based on the given boundary conditions, we see the following three-layer asphalt concrete pavement (the structure of the layers is given in Figure 5 and the coefficient of elastic ground).Р=30 кН, q=80 кН/м, λ=1м, Е1 =3,3•10 4 Мпа, Е2 =8•10 2 Мпа, Е3 =100 Мпа, v1=v2=v3=0,3, h1=0,16 м, h2=0,26 м, h3=0,4 м, d1=0,08 м, d2=0,29 м, d3=0,62 м, k=50 МН/м 3 We determine the stiffness of each layer in elongation as follows. 3,3 10 0,16 66 10 1 1 0, 2

Determine the state of the neutral layer affected by the largest tangential stresses:

66 0, 08 2, 6 0, 23 0,5 0, 62 10 0, 092 66 2, 6 0,5 10

In this case, the distance of each layer to the center of gravity is as follows С1=0,012 м, С2=0,198 м, С3=0,528 м.

We calculate the specific cylindrical virginity of each layer    

11,73 66 10 0,012 1, 22 2,6 10 0,198 0,56 0,5 10 0,528 39,81

Determine the coefficient of inclination of the elastic ground;

From the symmetry of the plate calculation form (Fig. 2) we determine the slope for only 3 nodes.

We write for 1 node. Given 1 2/ qP   conditionally equation ( 7)

For 2 nodes we construct equation (8). In this case, we take into account the condition M3 = 0 at q2 = q. In that case, the second equation is as follows.

The third equation is constructed based on the given slope on the third node, which is similar in appearance to (9), that is, under the conditions q3 = 0, a Q3 = P, it follows.  

If we put the values of λ and k * and multiply the second equation by 2, we get the following symmetric form. www.extensionjournal.com

We determine the normal stresses by determining the pressure in the slab floor.

 

We determine the values of the bending moments at each node.

43,62 29,99 10 13,63 10 / 1

The bending moment in the dangerous section of the platemax М we construct a diagram of the stresses extending along the height of the plate for the cut obtained. 3, 3 10 27, 26 10 ( 0, 092) 2,16 1 1 0, 2 39,81

3,3 10 27, 26 10 0, 068 1, 6 1 1 0, 2 39,81

8 10 27, 26 10 0, 068 3,89 10 1 1 0, 2 39,81

800 27, 26 10 0,328 18, 7 10 1 1 0, 2 39,81

100 27, 26 10 0,328 2,34 10 1 1 0, 2 39,81 3,3 10 0, 092 0, 092 30 10 0 0 ; 0 39,81 2 1 2 1 0, 2

Slab contraction joints should intersect at the openings for columns σх normal and xz  -tangential stresses we build the diagrams (Figure 4)

We check the strength of the concrete layer on the top layer of the slab for elongation and shear.. Elasticity module Е1=3,3•10 4 Мпа concrete type V40 corresponds to the accepted, in this case the limit normative strength in elongation at bending is equal to . The calculated tensile strength of concrete is as follows [1,4] () 0,85

Here 0,85 -kи -coefficient taking into account the size of the standard beam-sample due to the coefficient taking into account the increase in strength of concrete over time, () н и R -normative strength of concrete grade to elongation in bending (QMQ II - 47 -80 «Aerodromy») In that case for V40 concrete

We can see that the result of the given calculation fully satisfies the stability conditions. This indicates that multi-layer pavements can be widely used in road construction in the design of rough pavement structures and in the design work of pavements, checking the resistance of concrete to bending and elongation. Special additives have been added to these asphalt concrete pavements. This, in turn, has led to an increase in the strength of coatings, improvement of long-term durability, deformation work and an increase in the level of resistance to the external environment of the Fergana Valley by 20-30%. Several types of special asphalt concrete pavements have been developed, and it turned out that the properties of asphalt pavements resistant to large deformations that we offer have good performance in all physical and mechanical parameters compared to works produced abroad. These parameters were tested experimentally using a new device created [4] . Compared with theoretical studies, the results of the study showed that the relatively high strength of asphalt concrete pavements resistant to large deformations increased the impact on shear deformation by 15-20%.

References

1. Pod red. Varvaka PM, Ryabova Kiev AF, Budivelnik, 1977, 419.
2. Varvak PM, Varvak LP. Method setok v zadachax rascheta stroitelnyx konstruktsii -M. Stroyizdat, 1977, 160.
3. I.X. Xamzaev. Raschet sloistoy plity na uprugom osnovanii plity jestkoy dorojnoy odejdы na temperaturnom vozdeystvii. Fer. PI scientific and technical journal. 2009; 1:41-47.
4. Kasimov II, Kasimov IU, Akhmedov AU. Improvement Of Asphalt Concrete Shear Resistance With The Use Of A Structure-forming Additive and Polymer //International journal of scientific & technology research. ISSN: 2277-8616; Impact Factor: 7.466, IJSTR -2019, Issue-11. 2019; 8:1361-1363. .