Behavior of Confined Concrete using Prestressing Skew Bars

This paper presents the results of an experimental study on the biaxial compression behavior of concrete prism confined using pre-stressed bars. The pre-stressed bars could provide passive confinement stress, that preventing the lateral strain of the prism from increasing leading to an increase in both the initial modulus of elasticity and prism compressive strength. The confined concrete had a higher compressive strength that was directly proportional to the confinement bar pressing force and lower ductility than the plain prisms. The concrete initial modulus of elasticity is directly proportioned to the confinement lateral pressure of the prestressing bar and inversely proportion with the spacing between prestressing bars. It was simple to find out that the best pre-stressing stress was 10 N/mm2, also the compressive strength of the confined concrete with pre-stressed skew bars was greater than the compressive strength of the unconfined concrete by more 3.3 times.

ANALYSIS OF THE TRAFFIC LOAD–INDUCED STRESSES OF EMBANKMENT

This article represents traffic loads on the road structure distribution and evaluation of the vertical and horizontal stresses formation in the soil embankment. This evaluation allows to predict the depth and intensity of the propagation of additional stresses resulting from traffic loads. The calculations were performed in accordance with four normative documents applied in Lithuania, which define the loads on the road structure. The obtained results showed that the area to which the load is distributed has the greatest influence on the intensity of stresses and the distance of propagation. The maximum horizontal stress in the embankment was found to be no more than 70 kPa and the maximum stress propagation depth did not exceed 0.9 m. The results can be applied to a triaxial test apparatus to restore horizontal stresses in the embankment. It is recommended to select a lateral pressure from 20 kPa to 70 kPa for tests provided with triaxial test device. The mechanical properties of the soil determined with triaxial test device and recommended lateral pressure would be representative of the test results obtained in the field of embankment.

Modified Lateral Pressure Formula of Shallow and Circular Silo Considering the Elasticities of Silo Wall and Storage Materials

For the shallow and circular silo(SCS), when the aspect ratio is between 1.0 and 1.5, the lateral pressure especially dynamic pressure may cause destruction if the size of the silo is large. In general, the lateral pressures should be calculated simultaneously according to the shallow silo and the deep silo calculation formulas based on Rankine’s earth pressure theory and Janssen’s theory, respectively, and the larger value of them should be adopted. However, whether the two formulas are reasonable needs to be verified. This paper proposed a modified calculation method of lateral pressure on the silo wall of SCS, considering the elasticities of silo wall and storage materials. The availability of shallow silo and deep silo methods, and the modified method were compared with the experiment and simulation. The results show that the Rankine’s formula is too conservative for the static lateral pressure, and the results of the modified method and Janssen formula are close to that of the experimental and simulation. For the dynamic lateral pressure calculation, Rankine theory is unsafe for the discharging load. The relative error of the dynamic lateral pressure based on Janssen theory is between 20% and 30%, which is too large. The dynamic lateral pressure calculated by the modified method is in good agreement with that of the experimental and simulation, and the relative error is less than 10%. Therefore, the modified method of lateral pressure formula is reasonable, which can provide guidance for the safety design of silo structure.

Lipid Membrane State Change by Catalytic Protonation and the Implications for Synaptic Transmission

In cholinergic synapses, the neurotransmitter acetylcholine (ACh) is rapidly hydrolyzed by esterases to choline and acetic acid (AH). It is believed that this reaction serves the purpose of deactivating ACh once it has exerted its effect on a receptor protein (AChR). The protons liberated in this reaction, however, may by themselves excite the postsynaptic membrane. Herein, we investigated the response of cell membrane models made from phosphatidylcholine (PC), phosphatidylserine (PS) and phosphatidic acid (PA) to ACh in the presence and absence of acetylcholinesterase (AChE). Without a catalyst, there were no significant effects of ACh on the membrane state (lateral pressure change ≤0.5 mN/m). In contrast, strong responses were observed in membranes made from PS and PA when ACh was applied in presence of AChE (>5 mN/m). Control experiments demonstrated that this effect was due to the protonation of lipid headgroups, which is maximal at the pK (for PS: pKCOOH≈5.0; for PA: pKHPO4−≈8.5). These findings are physiologically relevant, because both of these lipids are present in postsynaptic membranes. Furthermore, we discussed evidence which suggests that AChR assembles a lipid-protein interface that is proton-sensitive in the vicinity of pH 7.5. Such a membrane could be excited by hydrolysis of micromolar amounts of ACh. Based on these results, we proposed that cholinergic transmission is due to postsynaptic membrane protonation. Our model will be falsified if cholinergic membranes do not respond to acidification.

CALCULATION OF THE BEARING CAPACITY OF A TWO-SLOT STRIP FOUNDATION

The results of computer modeling of the process of formation and development of areas of plastic deformations in the connected base of a double-slit ribbon foundation are presented. All calculations are performed using computer programs developed with the participation of the author. These programs allow you to take into account all the variety of physical and mechanical properties of the foundation soil (volume weight, internal friction angle, specific adhesion, lateral pressure coefficient and deformation modulus) and the foundation material (elastic modulus and Poisson's ratio). In the calculations, it is assumed that the value of the lateral pressure coefficient of the soil is 0.75, as is typical for cohesive clay soils, and the same value for the foundation material is assumed to be 0.43 (converted through the Poisson's ratio). Based on the results of calculations, it was possible to determine the features of the stress state of the base of the double-slit foundation and the process of development of plastic areas in the core of the foundation. First of all, the part of the bearing capacity of the base of the double-slit foundation that contacts its side surface is realized, and the inclusion of the side surface of the slit foundation in the work occurs from the bottom up. Then the part of the base that is located directly under the soles of the walls in the ground (cracks) is included in the work. It is established that the smaller the distance between the slits, the greater the bearing capacity of the base and the greater its part falls on the side surface. The bearing capacity of the base of a double-slit foundation is directly proportional to the depth of its foundation (the height of the cracks). The part of the load-bearing capacity realized on the side surface of the foundation can reach 60 % or more of its full value. An engineering method for calculating the load-bearing capacity of the base of a double-slit foundation, including simple formulas and graphs, is proposed. The method is formalized in a calculator program. The verification calculations showed a high degree of accuracy in approximating the results of the numerical experiment.

Stability analysis of rock slope and calculation of rock lateral pressure in foundation pit with structural plane and cave development

In this study, numerical simulations were carried out to analyze the influence of caves in different positions and shapes, in combination with structural planes, on the stability of the slope and the failure characteristics of a rock slope in a deep foundation pit with high inclination structural planes and cave development. The schemes for substituting a single karst cave for karst caves were constructed. Based on the penetration failure characteristics of karst caves between parallel structural planes, methods for calculating the safety factor of the rock foundation pit and the upper bound of the lateral pressure of the supporting structure under the combined influence of the caves and structural planes were developed, which can be used to assess the safety factor of a rock mass and to calculate the lateral pressure under complex geological conditions.

Initial data from monitoring of a landslide process affecting Emine Cape, Bulgaria

In October 2019, a 3D extensometer was installed to monitor slow landslide movements, affecting the slope of Cape Emine north of the lighthouse. For almost 2 years of observations, a tendency of shrinkage of the zone as a result of lateral pressure from the southern landslide was established. The movements are divided into two stages: the first – until December 2020, and the second – after that date. In the months from April to June the movements in direction X are more intensive due to the rainy situation at this time of the year.