Simulation Study on Reinforcing Overburden to Prevent and Cure the Rupture of Shaft Lining

For preventing and curing the rupture disaster of shaft lining effectively, according to the additional force theory of shaft lining fracture, more than forty tests were carried out on the large scale test rig on the basis of simulating theory. The influence of the position of aquifer, the reinforcing scope of aquifer, reinforcing distance and the strength of grouting cemented mixture on the value and variation law of the axial additional force on shaft lining is studied. The relationships between the reinforcing parameters and the axial additional force on shaft lining are obtained, which provides the theoretic foundation and construction design parameters for the method of reinforcing strata by grouting to prevent and cure tbe rupture disaster of shart lining.

Theoretical Investigation on Vertical Additional Force on Shaft Lining in Special Stratum

The model of skaft lining under force is developed on the basis of the special stratum condition led to sbart cracking- The model is broken into 3 sub-questions to solve separately. According to the principle of superposition and strain compatibility, a second kind Fredholm integral equation is generated.A theoretical solution to vertical additional force on shaft lining is obtained by numerical method to the integral equation.

Research on Stress and Strength of High Strength Reinforced Concrete Drilling Shaft Lining in Thick Top Soils

High strength reinforced concrete drilling shaft linings have been adopted to solve the difficult problem of supporting coal drilling shafts penetrating through thick top soils. Through model experiments the stress and strength of such shaft linings are studied. The test results indicate that the load beating capacity of the shaft lining is very high and that the main factors affecting the load bearing capacity are the concrete strength, the ratio of lining thickness to inner radius and the reinforcement ratio. Based on the limit equilibrium conditions and the strength theory of concrete under multi-axial compressive stressed state, a formula for calculating the load-beating capacity of a high strength reinforced concrete shaft lining was obtained. Because the concrete in a shaft lining is in a multi-axial compressive stress state the compressive strength increases to a great extent compared to uni-axial loading. Based on experiment a formula for the gain factor in compressive strength was obtained： it can be used in the structural design of the shaft lining. These results have provided a basis for sound engineering practice when designing this kind of shaft lining structure.

Numerical simulation of the temperature field within new type of monolayer freezing-shaft lining

Numerical simulation was used to estimate the temperature field within a poured concrete,mono-layer freezing-shaft lining.The affects from various factors were investigated.The maximum temperature within the lining increases as the lining thickness increases,decreases as the soil-side wall temperature decreases,decreases as the air temperature inside the shaft decreases and decreases as the air velocity inside the shaft increases.The compression speed of an insulating foam layer affects the maximum temperature difference between the interior and the sidewalls.The maximum temperature difference between the interior and the sidewalls approaches or exceeds the maximum allowable for the curing of poured concrete structures.Attention should be paid to the question of the lining cracking during the curing period.The temperature gradient in the vertical direction may be minimized by preventing air contact against the steel connection board supporting the base of the freshly poured section.

A methodology for lining design of circular mine shafts in different rock masses

In this study, the finite element numerical modelling of 2D shaft sections in a Hoek–Brown medium are carried out in a non-hydrostatic stress state in an attempt to predict pressures developing around mine shafts. An iterative process of applying support pressure until observing no failure zone around the shaft is used to simulate the required lining support pressure for different shaft models. Later, regression analysis is carried out to find a generic shaft pressure equation representing the rock mass and the stress state. Finally, the developed pressure equation which shows a good agreement with a case study is used in elastic ‘‘thick-walled cylinder" equation to calculate the lining thickness required to prevent the development of a failure zone around the shaft. At the end of the study, a user-friendly object-oriented computer program ‘‘Shaft 2D" is developed to simplify the rigorous shaft lining thickness calculation process.

Experimental study on sliding shaft lining mechanical mechanisms under ground subsidence conditions

Aimed at more than 60 shaft linings damaged in Huaibei, Datun, Xuzhou and Yanzhou mine areas, this paper presents a new type of sliding shaft lining with asphalt blocks sliding layer. By model test, it is obtained that the deformation characteristics and the mechanical mechanisms of the sliding shaft lining under the condition of ground subsidence. The research results provide a testing basis for the sliding shaft lining design. By now, this kind of sliding shaft lining had been applied in 9 shafts in China and Bangladesh.

Failure Patterns and Energy Analysis of Shaft Lining Concrete in Simulated Deep Underground Environments

The failure patterns and energy evolution of three types of shaft lining concrete subjected to static and dynamic loading were reported.The energy and damage characteristics of concrete were determined by means of a uniaxial hydraulic servo machine,acoustic emission (AE) equipment,a split Hopkinson pressure bar (SHPB) and an ultrasonic wave analyser.The experimental results indicate that the confluence of multiple cracks forms a penetrating cross section in normal high-strength concrete (NHSC) under the condition of static loading,while the elastic energy that surges out at failure can cause tremendous damage when subjected to dynamic loading.A single crack was split into multiple propagation directions due to the presence of fibres in steel fibre-reinforced concrete (SFRC);adding fibre to concrete should be an effective way to dissipate energy.The non-steam-cured reactive powder concrete (NSC-RPC) designed in this paper can store and dissipate more energy than normal concrete,as NSC-RPC exhibits a strong ability to resist impact.Applying NSC-RPC to the long-service material of a shaft lining structure in deep underground engineering is quite effective.

Forced Axial and Torsional Vibrations of a Shaft Line Using the Transfer Matrix Method Related to Solution Coefficients

This present paper deals with a mathematical description of linear axial and torsional vibrations. The normal and tangential stress tensor components produced by axial-torsional deformations and vibrations in the propeller and intermediate shafts, under the influence of propeller-induced static and variable hydrodynamic excitations are also studied. The transfer matrix method related to the constant coefficients of differential equation solutions is used. The advantage of the latter as compared with a well-known method of transfer matrix associated with state vector is the possibility of reducing the number of multiplied matrices when adjacent shaft segments have the same material properties and diameters. The results show that there is no risk of buckling and confirm that the strength of the shaft line depends on the value of the static tangential stresses which is the most important component of the stress tensor.

MECHANICAL ANALYSIS OF SHAFT LINING WHEN THE STRATUM SETTLEMENT RESULTING FROM WATER DRAINAGE

Based on the stratum settlement resulting from water drainage, this paper establishes the calculating method of stresses and displacements of shaft lining and stratum by using Fourier integration, obtains the calculating formulas of tangiential load which shaft lining is subjected to, and provides theoretical basis for design of shaft lining.

Impact of Underground Mining on Shaft Lining and Aquifer in Eastern China

Serious shaft lining ruptures have often occurred in the eastern part of China since 1987 due to the complicated geological conditions. This paper tries to find out the relationship between mechanisms of shaft lining rupture and the underground mining process. The analysis is based on the existence typical engineering and geological conditions in eastern China;the impact of underground mining on the shaft lining and aquifer layer is analyzed by using numerical method. The impact factors such as different depths, thicknesses, mining widths of coal seam and different distances to the shaft are used in the analysis. The mining area under the aquifer which near the shaft lining has a significant impact on the shaft lining due to mining process, and increases the risk of occurrence of shaft lining rupture.

STUDIES ON VERTICAL SHAFTLINING STRUCTURE ADAPTABLE TO SUBSIDENCE

Subsidence results in a negative force of friction on the outer surface of the shaft lining. This negative force has in recent years led to damage or even destruction of over 20shafts. In the light of this shaft failure mechanism, analytic comparison is conducted on three shaft lining structures as to their respective behaviour under the negative force of friction, by making use of modelling tests. A new shaft lining structure is therefore proposed which is designed to be adaptable to subsidence and found to be rational. Finally designing principles are given.

Analysis and interpretation on the concrete quality of shaft lining by elastic wave technique

The quality problem of the concrete body and backwall grouting of shaft lining must be taken into consideration during the engineering construction of the shaft. Detection and evaluation are needed to determine the parameters such as the location and depth of drilling. The record of elastic wave can be gained through laying the surveying lines of the ring and ver- tical direction in the shaft lining by the elastic wave method. And specifically, through analyzing the different parameters of seismic attribute such as the velocity of high frequency reflection wave, amplitude and frequency, the abnormal range on the wall or under the wall can be forecasted. The concrete quality of shallow layer in the shaft lining can be evaluated through the velocity of surfer wave. Using the evaluating technique of comprehensive frequency and the phase feature of waveform, the basic features such as inner construction, wall back filling and failure depth of shaft lining can be interpreted from qualitatively to half quantitatively, and the interpreting section can be drawn. The results show that the detection effect for the shaft quality is significant by elastic wave technique, and the delineation of abnormal areas is accurate. Its guidance function is better for pro- duction.

CURRENT TECHNOLOGY AND INNOVATIONS IN FREEZE SHAFT SINKING IN CHINA

This paper gives a brief review of the development of shaft sinking by artificial ground freezing since 1949 when new China was founded. Several shaft freezing schemes which have been successfully applied from the economic and safe viewpoints are presented. Current technology and some innovative techniques, especially the shaft lining which have experienced major improvements over the last four decades ,are briefly reviewed. The technique of the in-situ pour concrete incorporating ailica fume with higher early strength under low temperature curing conditions is described. The temperature field in shaft freezing and its finite difference solution are given in this paper. A recently developed method combining freeze wall model test with back analysis technique based on numerical simulation is also described.

融合多尺度特征的YOLOv8裂缝缺陷检测算法

针对井壁裂缝背景复杂,纵横比差异大,导致检测效率低、漏检等问题,提出了一种融合多尺度特征的裂缝缺陷检测模型EDG-YOLO。设计特征提取模块EIRBlock(efficient inverted residual block),并构建C2fEIR增强主干网络对井壁浅层裂缝特征信息的提取能力。在颈部融合CSP_EDRAN(CSP efficient dilated reparam aggregation network)实现对裂缝特征信息的复用,促进浅层与深层语义信息之间的交互。嵌入DAM(dual attention module)注意力机制,增强井壁裂缝特征的表达能力。构建轻量级检测头GDetect,借助GSConv模块进一步轻量化网络。在自制井壁裂缝数据集上的实验结果表明,与YOLOv8相比,EDG-YOLO的平均检测精度达到87.4%,提高了2.3个百分点,模型的参数量和计算量分别降低了33%和47%,单幅图像推理时间为13.2 ms,满足井下场景的实时检测需求。

内层钢板外层高强度混凝土复合井壁受力特性与支护结构参数优化分析

针对内层钢板外层高强度混凝土复合井壁的厚度设计,以受均匀围压的内层钢板外层高强度混凝土复合井壁得出的弹性解析解为基础,对内层钢板采用Mises屈服准则,外层高强度混凝土采用统一强度理论,研究复合井壁的初始屈服临界状态.以内层钢板和外层高强度混凝土均未屈服为条件,提出复合井壁的设计流程.结果表明,当内半径、围压以及材料给定时,存在外半径和分层半径的最佳取值范围,在此范围内选择外半径和对应的分层半径,内层钢板和外层高强度混凝土均不会达到屈服.与模型试验进行对比,发现试验中内半径、外半径、分层半径和材料给定的复合井壁,当围压等于设计围压时,外半径和分层半径处于最佳取值范围;当围压继续增大时,外层高强度混凝土先于内层钢板屈服.弹性解与屈服准则相结合,得到复合井壁设计流程为:通过规范及工程地质条件确定井壁内半径和围压值,选定复合井壁的材料,采用屈服准则求得外半径和分层半径的最佳取值范围.

冻结井壁仿钢纤维混凝土动静态力学性能和微观结构研究

为改善冻结井壁高强混凝土脆性特征,提高其抗裂性和韧性,提出采用仿钢纤维混凝土作为冻结井壁筑壁材料。通过优选材料和正交试验,得到不同配合比的仿钢纤维高性能井壁混凝土,并对其进行静态、动态力学性能及微观结构等试验研究。结果表明,在基准混凝土中掺入15%(质量分数)粉煤灰和0.54%(体积分数)聚丙烯仿钢纤维(PPTF)后,混凝土的抗拉、抗弯强度分别提高了29.46%、26.72%,其脆性特征得以明显提高。相比于基准组,最佳配合比的仿钢纤维混凝土韧性增强显著,在0~0.012应变范围内其韧性指数提高了40.83%,且失效后的破坏形态更完整。掺入PPTF、粉煤灰有效抑制了冻结井壁混凝土内部微裂隙的产生和扩张,混凝土表现出更为致密的微观结构以及更高的宏观力学性能。

超大竖井整体提升式模筑衬砌施工技术

依托天山胜利隧道3号竖井,提出超大竖井整体提升式模筑衬砌施工技术,在井筒初期支护模筑混凝土内侧安装2块独立的半月牙形整体上行式液压金属模板,采用8台稳车同步提升,通过模板周身多个浇筑口连续、均匀、对称地浇筑混凝土,保证超大竖井衬砌快速和高质量施工。对单块模板吊装、模板整体起吊、混凝土浇筑工况下模板变形及强度特征进行分析,并对横肋、纵肋、限位杆等关键构件连接部位建立局部受力分析模型进行计算,保证模板设计的合理性与安全性。研究结果表明,单块模板吊装、模板整体起吊、混凝土浇筑工况下模板、横肋、纵肋、限位杆受力及变形均满足要求;超大竖井整体提升式模筑衬砌施工技术机械化程度高,实现平均200m/月的施工效率,保证浇筑混凝土在模板内有足够的水化反应时间,提高混凝土早期强度,确保施工质量。

圆形超深竖井基坑逆作法施工全过程内外衬协同作用分析

依托上海某超深竖井基坑工程,对超深地下连续墙施工、开挖、内衬逆作等各施工阶段内外衬及地层变形规律进行理论与实测分析,得到主要结论如下:内外衬协同作用显著,随挖深增加,内外衬变形同步增长,而内力呈此消彼长的变化规律;圆形竖井结构的内外衬内力分担比与内外衬墙厚比接近,但与二者的刚度比相差较大,二者弯矩平均分担比趋向40%和60%;内衬对变形的约束作用随开挖深度而增强,其及时施作对超深竖井的变形控制具有关键影响。研究结果可为软土地区圆形超深竖井结构的设计与施工提供参考。

大直径超深圆竖井内衬逆顺结合作法施工过程温度应力研究

珠江三角洲水资源配置工程A2标03号盾构井为外径35.9 m圆形竖井、开挖深度达73.98 m,施工复杂且难度较大,保证施工过程中不出现温度裂缝尤为重要。针对此问题,根据结构、施工特点,将盾构井内衬分为内衬墙、洞门墙和底板3个部分,使用三维有限元程序,采用逆-顺结合施工方法,基于内衬混凝土施工方案,对内衬结构施工过程进行数值模拟,研究内衬墙、洞门墙和底板温度、应力发展情况。数值模拟结果表明:(1)内衬墙、洞门墙和底板降温速率分别为0.28、0.23、0.19℃/d;(2)随着高程的降低,盾构井温控难度逐步下降,内衬墙厚度较小,受地下连续墙约束和气温变化影响较大,在高温季节浇筑的部位开裂风险较大,低温季节浇筑的洞门墙和底板开裂风险较小;(3)洞门墙和底板由于施工工序和间歇期,在结构突变连接处出现较大应力,施工中要加强这些部位的监测。

风电机组主轴轴承在机清洗工艺

主轴轴承传统运维采取定时、定量补脂的方式优化轴承润滑环境,传统运维不能将板结润滑脂或异物排出,当主轴轴承高速运行时,板结润滑脂或异物将使轴承出现高温或振动报警,长时间运行还会引起轴承卡滞、滚子破裂,严重时会发生机组自燃事故。为实现高效、可靠的运维,提出了一种在机清洗工艺,采取在机浸泡清洗和循环清洗对轴承内部润滑脂溶解、过滤排出,检查后注入新润滑脂,从而实现运行状态评估和环境优化。工程应用表明,该工艺可以优化主轴轴承运行环境,做到保养评估,有助于延长风机使用寿命。