Study of contact forces in the bearing part of the protective coating of underground pipelines in gravel and cobbles

In the construction and operation of underground pipelines, the feasibility of engineering methods of protecting the insulation coating from external mechanical impacts should be based on the existing loads. When an underground pipeline is laid on coarse gravel and very coarse soil, the analysis of the support forces at the base of the pipeline is a pressing issue. In particular, the difficult conditions for the construction, reconstruction, repair and operation of underground pipelines include cases when the pipeline route passes through sections of rocky soils. Discrete rocky conditions include large grain content in the form of coarse gravel, cobbles, and boulders. The article analyzes the influence of the size of foundation soil components on the magnitude of force arising in the protective coating of the support part of an underground pipeline depending on the unevenness of the soil and its granulometric composition. One of the directions for studying the distribution of contact-mechanical interaction in granular soils is a discrete model. The distinction of the discrete medium model is that individual elements of its structure are viewed as mechanically interacting bodies. Structural elements are particles of bulk material that can be considered as spheres. The results of modeling the contact problem using the discrete (granular) model of the base of the pipeline are presented. It was found that with the same diameter size and depth of burial, the force varies depending on the pipe diameter chosen in the project (for a pipe of 1420 mm, the maximum difference was 23%). In the case of unevenness of the ground, the force in the supporting part can increase by 3-5 times. The conditions of stability and strength of underground pipelines are formulated taking into account the discreteness of the base particles.

Analysis of conservative tracer measurement results inside a planted horizontal subsurface flow constructed wetland filled with coarse gravel using Frechet distribution

We worked out a method in Maple environment to help understand the difficult transport processes in horizontal subsurface flow constructed wetlands filled with coarse gravel (HSFCW-C). With this process, the measured tracer results of the inner points of a HSFCW-C can be fitted more accurately than with the conventionally used distribution functions (Gaussian, Lognormal, Fick (Inverse Gaussian) and Gamma). This research outcome only applies for planted HSFCW-Cs. The outcome of the analysis shows that conventional solutions completely stirred series tank reactor (CSTR) model and convection-dispersion transport (CDT) model do not describe the internal transport processes with sufficient accuracy. This study may help us develop better process descriptions of very complex transport processes in HSFCW-Cs. Our results also revealed that the tracer response curves of planted HSFCW-C conservative inner points can be fitted well with Frechet distribution only if the response curve has one peak.

Exhumation and performance of an Antarctic composite barrier system after 4 years exposure

An Antarctic biopile using a composite liner (high-density polyethylene geomembrane (GMB) over a geosynthetic clay liner (GCL)) was constructed on a coarse granular subgrade to contain hydrocarbon-contaminated soil and leachate. The soil was remediated after 4 years and the biopile was decommissioned. The liner was exhumed to assess the properties and performance of the GMB and GCL. There was no significant change in the GMB index properties. Although cobbles and coarse gravel of the subgrade had left indentations in the GMB, implying tensile strains that could impact long-term performance, there were no holes. There was significant variability in the hydration of the GCL (from 10% to 220%) and in the underlying subgrade soil water content (from 5% to 30%). This reflects the complexity of the subgrade and groundwater flow in the Antarctic environment. The exhumed GCL specimens had low hydraulic conductivity (1 × 10−11 to 7 × 10−11 m/s) at 13 kPa. Soil samples from below the composite liner showed no detectable hydrocarbons and confirmed no migration through the barrier. It is concluded that the composite barrier contained the leachate and biopile soil over the 4 years in service in the extreme Antarctic conditions.

Prediction of ecological impact of two alien gobiids in habitat structures of differing complexity

Rapid expansion of round goby (Neogobius melanostomus) and western tubenose goby (Proterorhinus semilunaris) beyond their native ranges calls for urgent management action, particularly in localities with high introduction possibility of the species. We used a comparative functional response (FR) approach to forecast invader ecological impact. We compared their foraging efficiency in three habitat structures: sand, coarse gravel, and coarse gravel with an artificial plant. Both Neogobius melanostomus and Proterorhinus semilunaris showed type II FR in all habitats. Interspecific comparison showed similar handling times in both the gravel and gravel with artificial plant habitats, suggesting similar per capita impact. Intraspecific comparison showed significantly lower handling times of both predators on gravel substrates. Therefore, their ecological impact in such an environment could be higher. Neogobius melanostomus showed higher attack rates on sandy substrates compared with Proterorhinus semilunaris, while no significant differences were observed on other substrates. Our results highlight the importance of interacting factors in management of ecosystems with multiple invaders, as the elimination of invasive Neogobius melanostomus may lead to utilization of the empty niche by alien Proterorhinus semilunaris with similar ecological impact.

Modifikasi Resipren dan Bitumen Dalam Peningkatan Kekuatan Aspal

Modifikasi Resipren dan Bitumen dalam Peningkatan Kekuatan Aspal telah dilakukan. Aspal modifier dibuat dalam 7 jenis variasi perbandingan aspal, bitumen, dengan resipren yang telah dilarutkan dengan toluene sebesar 75:20:5 ; 70:20:10 ; 65:20:15 ; 60:20:20 ; 55:20:25 (v/v/b) dalam 100 mL, penambahan agregat pasir halus 300 gram dan agregat kasar kerikil 50 gram, dan diproses dalam ekstruder pada suhu 150oC. Sifat mekanik dan sifat termal aspal modifier yang diuji meliputi kuat tekan, daya serap air, morfologi dengan TEM. Hasil karakterisasi menunjukkan bahwa campuran aspal, bitumen, dan resipren dengan perbandingan 55 : 20 : 25 efektif dalam meningkatkan sifat mekanis dari campuran aspal dimana dihasilkan kekuatan tekan maksimum sebesar 0,974 mPa. Sifat fisik menghasilkan penyerapan air sebesar 0,63%. Hasil uji morfologi dengan TEM memperlihatkan adanya perbedaan setelah bitumen ditambahkan kedalam campuran aspal dan resipren. Recipient and bitumen modifications in asphalt strengthening had been carried out. Asphalt modifier was made in 7 types of comparison of asphalt, bitumen variation, with recipient (dissolved with toluene by 75: 20: 5; 70:20:10; 65:20:15; 60:20:20; 55:20:25 (v/v/b) in 100 mL), 300 grams of fine sand aggregate and 50 grams of coarse gravel aggregate; then processed in an extruder at 150oC. The mechanical properties and thermal properties of the modifier test included compressive strength, water absorption, and morphology with TEM. The characterization results showed that asphalt, bitumen and recipient mixtures with a ratio of 55: 20: 25 were effective in increasing the mechanical properties of the asphalt mixture where the maximum compressive strength was 0.974 mPa. Physical properties produced water absorption of 0.63%. The results of morphological tests with TEM showed that there was a difference after bitumen was added to the asphalt and recipient mixture.