Analysis of Plastic Zone and Pressure Variance Features of Surrounding Rock of High-Altitude Macker Tunnel: A Case Study in Jiangluling Macker Tunnel in Qinghai

Due to the special mechanical properties of macker rock, problems may be caused easily if the pressure of the surrounding rock calculated from the standard empirical equation is used in the structural design of tunnel support, such as obviously insufficient bearing capacity of the support structure, large deformation, and collapse. Taking the Jiangluling Macker Tunnel in Gonghe-Yushu Highway as an example, the distribution pattern of plastic zone of the surrounding rock and the calculation method and reasonable values of pressure of the surrounding rock are studied in this paper, by means of theoretical analysis, numerical computation, and field measurement data. The results show that the elastic-plastic analysis method is suitable for the pressure of the surrounding rock of macker tunnel. The influence radius of the plastic zone of the surrounding rock can be 32 m, and the lateral pressure of the surrounding rock of the tunnel is equivalent to the vertical pressure. In the absence of test conditions and measured data, the pressure of the surrounding rock can be approximately 0.83 MPa for the purpose of design of tunnel support structure. This conclusion provides technical support for projects in similar conditions.

An Aggregation-Free Local Volume Fraction Formulation for Topological Design of Porous Structure

Cellular structure can possess superior mechanical properties and low density simultaneously. Additive manufacturing has experienced substantial progress in the past decades, which promotes the popularity of such bone-like structure. This paper proposes a methodology on the topological design of porous structure. For the typical technologies such as the p-norm aggregation and implicit porosity control, the violation of the maximum local volume constraint is inevitable. To this end, the primary optimization problem with bounds of local volume constraints is transformed into unconstrained programming by setting up a sequence of minimization sub-problems in terms of the augmented Lagrangian method. The approximation and algorithm using the concept of moving asymptotes is employed as the optimizer. Several numerical tests are provided to illustrate the effectiveness of the proposed approach in comparison with existing approaches. The effects of the global and local volume percentage, influence radius and mesh discretization on the final designs are investigated. In comparison to existing methods, the proposed method is capable of accurately limiting the upper bound of global and local volume fractions, which opens up new possibilities for additive manufacturing.

Ground Subsidence Evolution from 1000 m Deep Mining: A Case Study in Fengfeng Mining Area

The mining of coal resources in eastern China has entered the stage of deep mining, and many mines have reached the depth of 1000 meters. Different from shallow and moderate depth mining, the temporal and spatial evolution regulation of surface movement and deformation under deep mining has its particularity. Combining with the geological and mining conditions of Fengfeng mining area, this paper systematically studies the characteristics of surface movement under the condition of shallow, moderate, and near kilometer mining depth. By means of field measurement, InSAR monitoring, we get the subsidence data under different mining depth and get the relevant subsidence parameters by inversion. Through comparative analysis, the special law of subsidence under the mining depth of 1000 meters is obtained. The results show that under the condition of nearly 1000 meters mining depth, the surface movement and deformation have the characteristics of large displacement angle, small displacement deformation value, and large main influence radius. The regulation of small proportion of active period of maximum subsidence point, gentle shape of surface movement basin, and low mining adequacy are obtained. The research results provide technical references for deep mining under buildings, railways, and water bodies and provide basis and reference for scientific mining and safe recovery of coal pillars in kilometer deep mine.

Stellar hardening of massive black hole binaries: the impact of the host rotation

ABSTRACT Massive black hole binaries (MBHBs) with masses of ∼104 to $\sim 10^{10} \, \mathrm{M}_{\odot {}}$ are one of the main targets for currently operating and forthcoming space-borne gravitational wave observatories. In this paper, we explore the effect of the stellar host rotation on the bound binary hardening efficiency, driven by three-body stellar interactions. As seen in previous studies, we find that the centre of mass (CoM) of a prograde MBHB embedded in a rotating environment starts moving on a nearly circular orbit about the centre of the system shortly after the MBHB binding. In our runs, the oscillation radius is ≈ 0.25 (≈ 0.1) times the binary influence radius for equal mass MBHBs (MBHBs with mass ratio 1:4). Conversely, retrograde binaries remain anchored about the centre of the host. The binary shrinking rate is twice as fast when the binary CoM exhibits a net orbital motion, owing to a more efficient loss cone repopulation even in our spherical stellar systems. We develop a model that captures the CoM oscillations of prograde binaries; we argue that the CoM angular momentum gain per time unit scales with the internal binary angular momentum, so that most of the displacement is induced by stellar interactions occurring around the time of MBHB binding, while the subsequent angular momentum enhancement gets eventually quashed by the effect of dynamical friction. The effect of the background rotation on the MBHB evolution may be relevant for LISA sources, that are expected to form in significantly rotating stellar systems.

Numerical Investigation on Gas Production Performance in Methane Hydrate of Multilateral Well under Depressurization in Krishna-Godavari Basin

Nature gas hydrate is a new kind of clean and potential resources. Depressurization is regarded as the most effective and promising hydrate production technology. One of the key points in improving the gas production effectiveness of depressurization is whether pressure gradient could transmit in strata effectively. Single well method is widely used in hydrate exploit which is circumscribed in expanding the range of hydrate decomposition. Consequently, the well structure and production strategy needs to be optimized for improving the gas recovery efficiency. The multilateral well technology is proposed for increasing the gas productivity of the reservoir greatly by increasing the multilateral branches. In this paper, we established a numerical simulation model based on the geological data NGHP-02-16 site in the KG basin to evaluate the gas production performance of the reservoir by depressurization. It mainly focuses on investigating the gas production performance of multilateral wells with different combinations of geometric parameters of multilateral branches, such as different dip angle, numbers, and spacing of lateral branches. The result shows that the multilateral well method can effectively increase the gas production rate with the water production rate increase slightly. The cumulative gas production volume of a single vertical well is about 2.85 × 10 6 m 3 , while it is of the multilateral well can reach 4.18 × 10 6 m 3 during a one-year production. The well interference, the effective influence radius of each multilateral branch, and the vertical depth of the lateral branch are the main factors which affect the gas production efficiency of the multilateral well. The optimization of the geometric parameters of lateral should consider not only the gas production efficiency but also the well interference between the lateral branches.

Further Discussion on the Influence Radius of a Pumping Well: A Parameter with Little Scientific and Practical Significance That Can Easily Be Misleading

To facilitate understanding and calculation, hydrogeologists have introduced the influence radius. This parameter is now widely used, not only in the theoretical calculation and reasoning of well flow mechanics, but also in guiding production practice, and it has become an essential parameter in hydrogeology. However, the reasonableness of this parameter has always been disputed. This paper discusses the nature of the influence radius and the problems of its practical application based on mathematical reasoning and analogy starting from the Dupuit formula and Thiem formula. It is found that the influence radius is essentially the distance in the time–distance problem in physics; therefore, it is a function of time and velocity and is influenced by hydrogeological conditions and pumping conditions. Additionally, the influence radius is a variable and is essentially different from the hydrogeological parameters reflecting the natural properties of aquifers such as the porosity, specific yield, and hydraulic conductivity. Furthermore, the parameterized influence radius violates the continuity principle of fluids. In reality, there are no infinite horizontal aquifers, and most aquifers are replenished from external sources, which is very different from theory. The stable or seemingly stable groundwater level observed in practice is simply a coincidence that occurs under the influence of various practical factors, which cannot be considered to explain the rationality of applying this parameter in production calculations. Therefore, the influence radius cannot be used to evaluate the sustainable water supply capacity of aquifers, nor can it be used to guide the design of groundwater pollution remediation projects, the division of water source protection areas, and the scheme of riverbank filtration wells. Various ecological and environmental problems caused by groundwater exploitation are related to misleading information from the influence radius theory. Generally, the influence radius does not have scientific or practical significance, but it can easily be misleading, particularly for non-professionals. The influence radius should not be used in the sustainable development and protection of groundwater resources, let alone in theoretical models. From the perspective of regional overall planning, the calculation and evaluation of sustainable development and the utilization of groundwater resources should be investigated in a systematic manner.

Experimental Study on the Adoption of Flushing Technique in Successive Alkalinity-Producing Systems with a Focus on Influence Radius of Orifice

As a successive alkalinity-producing system pond for purifying mine drainage is operated, sediment accumulates in the limestone layer of the pond, and as the amount of accumulated sediment increases, the water permeability and treatment efficiency of the pond decrease. Hence, a flushing system is required, comprising of a network of perforated pipes installed in the limestone layers, to periodically discharge sediment and mine drainage to the outside. The performance of a flushing system depends on four distinct characteristics of the system: the characteristics of the limestone layer, the sediment, the flow, and the flushing device. However, existing studies have evaluated the performance of the entire system without considering these conditions. In this study, a new experimental method for designing a flushing system is proposed. This method is based on an experiment to evaluate the influence radius of orifice, which is the radius of the spherical volume around an orifice that can suck sludge by flushing. The results showed that the flow rate of water through the orifice in the glass bead layer matched well with the Blake–Kozeny formula, and that the greater the diameter of the orifice, the greater the influence radius of orifice. The influence radius of orifice according to the diameter and spacing of the orifice was evaluated, which provides a key criterion for designing a flushing system.

Numerical Simulation of Shallow Geothermal Field in Operating of a Ground Source Heat Pump System—A Case Study in Nan Cha Village, Ping Gu District, Beijing

The inefficient use of single energy and cold accumulation in the shallow geothermal field seriously affect the efficient operation of the ground source heat pump system (GSHPS). The operation of solar-assisted GSHPS can effectively solve the above problems. In this paper, a shallow geothermal utilization project in Nan cha Village, Ping Gu District of Beijing, is chosen as the study area. A three-dimensional numerical model of groundwater flow and heat transfer considering ambient temperature and backfill materials is established, and the level of model integration and validation are novel features of this paper. The thermal response test data in summer and winter conditions are used to validate the model. The results show that increasing hydraulic gradient has a positive impact on the heat exchange. The mixture of sand and barite powder is recognized as a more efficient and economical backfill material. The changes of thermal influence radius, heat balance, and shallow geothermal field are simulated and analyzed by three schemes. It is demonstrated that the thermal influence radius is 5 m, 3.9 m and 3.9 m for Scheme 1, Scheme 2 and Scheme 3, respectively. The ground temperature is always lower than the initial formation temperature in Scheme 1 and Scheme 2; however, under Scheme 3 it is higher than the initial values. The closer the hole wall is, the larger the difference between the initial formation temperature and the ground temperature, and vice versa. The thermal equilibrium of Scheme 1, Scheme 2 and Scheme 3 is −728 × 106 KJ, −269 × 106 KJ and +514 × 106 KJ. Through comprehensive analysis of the above three factors, Scheme 3 is regarded as the most reasonable scheme for a solar system to assist GSHPS.