Application of high-pressure water jet technology and the theory of rock burst control in roadway

This paper puts forward using high-pressure water jet technology to control rock burst in roadway, and analyzes the theory of controlling rock burst in roadway by the weak structure zone model. The weak structure zone is formed by using high-pressure water jet to cut the coal wall in a continuous and rotational way. In order to study the influence law of weak structure zone in surrounding rock, this paper numerically analyzed the influence law of weak structure zone, and the disturbance law of coal wall and floor under dynamic and static combined load. The results show that when the distance between high-pressure water jet drillings is 3 m and the diameter of drilling is 300 mm, continuous stress superposition zone can be formed. The weak structure zone can transfer and reduce the concentrated static load in surrounding rock, and then form distressed zone. The longer the high-pressure water jet drilling is, the larger the distressed zone is. The stress change and displacement change of non-distressed zone in coal wall and floor are significantly greater than that of distressed zone under dynamic and static combined load. And it shows that the distressed zone can effectively control rock burst in roadway under dynamic and static combined load. High-pressure water jet technology was applied in the haulage gate of 250203 working face in Yanbei Coal Mine, and had gained good effect. The study conclusions provide theoretical foundation and a new guidance for controlling rock burst in roadway.

In situ experimental study on TBM excavation with high-pressure water-jet-assisted rock breaking

China’s first high-pressure hydraulically coupled rock-breaking tunnel boring machine(TBM) was designed to overcome the rock breaking problems of TBM in super-hard rock geology, where high-pressure water jet system is configured, including high-flow pump sets, high-pressure rotary joint and high-pressure water jet injection device. In order to investigate the rock breaking performance of high-pressure water-jet-assisted TBM, in situ excavation tests were carried out at the Wan’anxi Water Diversion Project in Longyan, Fujian Province, China, under different water jet pressure and rotational speed. The rock-breaking performance of TBM was analyzed including penetration, cutterhead load, advance rate and field penetration index. The test results show that the adoption of high-pressure water-jet-assisted rock breaking technology can improve the boreability of rock mass, where the TBM penetration increases by 64% under the water jet pressure of 270 MPa. In addition, with the increase of the water jet pressure, the TBM penetration increases and the field penetration index decreases. The auxiliary rock-breaking effect of high-pressure water jet decreases with the increase of cutterhead rotational speed. In the case of the in situ tunneling test parameters of this study, the advance rate is the maximum when the pressure of the high-pressure water jet is 270 MPa and the cutterhead rotational speed is 6 r/min. The technical superiority of high-pressure water-jet-assisted rock breaking technology is highlighted and it provides guidance for the excavation parameter selection of high-pressure hydraulically coupled rock-breaking TBM.

Dynamic effects of high-pressure pulsed water jet in low-permeability coal seams

Mine gas extraction in China is difficult due to the characteristics such as micro-porosity,low-permeability and high adsorption of coal seams.The pulsed mechanismof a high-pressure pulsed water jet was studied through theoretical analysis,experimentand field measurement.The results show that high-pressure pulsed water jet has threedynamic properties.What's more,the three dynamic effects can be found in low-permeabilitycoal seams.A new pulsed water jet with 200-1 000 Hz oscillation frequency andpeak pressure 2.5 times than average pressure was introduced.During bubble collapsing,sound vibration and instantaneous high pressures over 100 MPa enhanced the cuttingability of the high-pressure jet.Through high-pressure pulsed water jet drilling and slotting,the exposure area of coal bodies was greatly enlarged and pressure of the coal seamsrapidly decreased.Therefore,the permeability of coal seams was improved and gas absorptionrate also decreased.Application results show that gas adsorption rate decreasedby 30%-40%and the penetrability coefficient increased 100 times.This proves that high-pressurepulsed water is more efficient than other conventional methods.

The Effect of the Propeller Jet on Pile Groups

The objective of this study is to determine the effect of jet propeller on the damage of berthing structures combined of armoured slope with pile groups. For this purpose, scour measurements were performed for four types berthing structures, which were armoured slope with tandem arrangements of piles for two and three piles and with side by side arrangements of piles for two and three piles. The effect of gap between piles on damage was investigated. The damage level induced by propeller jet between piles was determined. The gaps were 1, 2, 3, and 4 times the pile diameter. Three different values of Rpm （690, 820, and 950） were chosen for the tests. The diameter of circular piles is 40 mm. The slope ratio was 1/3 and the diameter of propeller was 10 cm.

The Effect of Jet Grouting on Enhancing the Lateral Behavior of Piled Raft Foundation in Soft Clay(Numerical Investigation)

Soft clay soils cannot usually support large lateral loads,so clay soils must be improved to increase lateral resistance.The jet grouting method is one of the methods used to improve weak soils.In this paper,a series of 3D finite element studies were conducted using Plaxis 3D software to investigate the lateral behavior of piled rafts in improved soft clay utilizing the jet grouting method.Parametric models were analyzed to explore the influence of the width,depth,and location of the grouted clay on the lateral resistance.Additionally,the effect of vertical loads on the lateral behavior of piled rafts in grouted clay was also investigated.The numerical results indicate that the lateral resistance increases by increasing the dimensions of the jet grouting beneath and around the piled raft.Typical increases in lateral resistance are 11.2%,65%,177%,and 35%for applying jet grouting beside the raft,below the raft,below and around the raft,and grouted strips parallel to lateral loads,respectively.It was also found that increasing the depth of grouted clay enhances lateral resistance up to a certain depth,about 6 to 10 times the pile diameter(6 to 10D).In contrast,the improvement ratio is limited beyond 10D.Furthermore,the results demonstrate that the presence of vertical loads has a significant impact on sideward resistance.

N-JET超级旋喷桩在深基坑承压水控制中的应用

承压水控制一直是基坑施工中的重难点,目前隔断深厚层承压水的工艺比较单一,以地下连续墙为主。宁波轨道交通某车站深基坑首次采用地下连续墙和N-JET超级旋喷桩联合隔断双层承压水。结合该应用实践,系统总结了N-JET的施工设备、工艺流程、施工方法、关键技术参数;通过开展原位试桩试验,验证了该工法在深基坑承压水控制中可行性。

大直径超高压喷射注浆N-Jet工法桩技术研究及实施

结合工程实际,对大直径超高压喷射注浆N-Jet工法桩进行了研究,通过对施工流程、材料与浆液制备、预成孔、工程监测等的有效控制,提高了成桩质量和止水效果,可以有效解决地下空间开发所带来的深层地下水控制安全问题,为相关工程项目提供有益借鉴。

基于水平旋喷桩处置优化的地铁隧道施工变形控制分析

为研究富水砂层隧道中水平旋喷桩+超前小导管组合预加固的效果,以青岛地铁某区间段隧道为依托,采用有限元数值模拟方法,对比分析了无预加固、单独使用水平旋喷桩及旋喷桩配合超前小导管组合预加固三种工况的加固效果。结果表明,与无预加固方案相比,单独使用水平旋喷桩预加固可使地表沉降、拱顶沉降、掌子面纵向位移分别相应减少约61%、59%、38%;而水平旋喷桩与超前小导管组合预加固方案可使地表沉降、拱顶沉降、掌子面纵向位移分别相应减少约66%、77.6%、38.9%,典型开挖断面处与拱脚处地下水渗流量分别减少93.4%、96.7%,预加固效果与止水效果显著。

浅埋偏压黄土隧道地表旋喷桩加固工艺参数研究

在黄土隧道修建过程中,其洞口段因浅埋偏压、围岩软弱破碎等通常需要进行加固处理。地表旋喷桩法具有适用范围广、加固效果好等优点,被广泛应用于隧道浅埋偏压段软弱围岩地表加固工程。以浅埋偏压黄土隧道进口段初期支护侵限为研究背景,介绍了现场地表旋喷桩加固的施工过程;建立了侵限段三维加固模型并分析了地表旋喷桩加固前后的变形控制效果,说明了处治措施的合理性;对比分析了现场监控量测结果,验证了数值模拟的准确性;开展了地表旋喷桩的工艺设计参数优化分析。结果表明:由于偏压作用,地表最大沉降值偏离隧道中心线,且拱顶中心线处沉降>右拱肩处沉降>左拱肩处沉降;施加地表旋喷桩对于减小地表沉降十分有效,地表最大沉降值减小了45.5%;采用地表旋喷桩加固处理后,拱顶处加固效果最为显著,较加固前沉降减小了57.9%,同时加固后左、右拱肩沉降差值减小了17.4%;建议隧道浅埋偏压段地表旋喷桩加固工艺设计参数:桩直径为0.4~0.6 m、桩间距为1.2 m、横向加固范围为1.5~2倍洞径、竖向加固范围为洞身两侧旋喷桩与隧道拱底平齐。

嵌岩低桩承台锁口钢管桩围堰设计与施工技术

昌九高铁扬子洲赣江公铁大桥西支主桥为(48+144+320+144+48)m无砟轨道钢箱桁组合梁斜拉桥。桥塔墩位于通航河道内,桥位处河床覆盖层浅,基岩强度高,基础由大直径钻孔桩和矩形嵌岩低桩承台组成,承台采用锁口钢管桩围堰施工方案。G33号主墩围堰平面设计尺寸54.56 m×28.52 m,锁口钢管桩采用Q345B材质∅1020 mm螺旋钢管,长28 m,钢管桩之间采用C-T形锁扣连接;围堰设置4层内支撑,单层内支撑设3道对撑,内支撑四角设型钢斜撑;基底设置混凝土垫层参与围堰结构受力。围堰采用XR360旋挖钻机在岩层中引孔,孔内换填细砂后插打钢管桩,钢管桩壁内、外两侧换填砂采用高压旋喷注浆加固。围堰设置智能化监测系统,对围堰受力、变形等进行实时动态监控。实践证明,该桥围堰结构安全可靠、止水效果良好、施工快捷高效。

带翼排桩式防波堤水动力特性研究

带翼排桩式防波堤能够有效沟通港池内外水体、维护水域环境,是一种环境友好型防波堤结构,在海岸工程领域有广阔的应用前景。采用模型试验与数值模拟方法,开展带翼排桩式防波堤的水动力特性研究。通过实验室水槽模型试验,分析翼板宽度Bw与翼板入水深度Hw对防波堤透反射系数及耗散系数的影响,同时基于大涡模拟(LES)建立数值波浪水槽,讨论规则波与防波堤相互作用过程中的桩周涡流、射流场演化过程。结果表明,不同的翼板宽度、入水深度设置会对防波堤透反射系数产生影响,且不同波长的规则波受翼板影响会呈现出不同的耗散结果;带翼排桩能够有效扰乱规则波的流场,形成不同形态的涡流,耗散波浪能量;当翼板入水深度较大时,翼下射流沿桩底水平发展,且强度大、控制距离远,该射流或成为桩底附近泥沙运动的重要动力。

多维度深水浅层建井方式优选方法研究

深水钻井作业具有海洋环境多变、地质条件复杂、作业风险大和日费率高等特点,深水浅层建井的方式难以选择。针对海底土质强度、建井质量、作业时效、经济性、风险控制等因素,根据现场作业工程数据,分别对不同建井工艺的适应性进行了分析,建立了单维度的适应性分级机制,并借助雷达图进行定量可视化,形成了多维度深水浅层建井方式优选方法。研究结果表明,水深500~1500 m的南海北部海域,单井作业时,喷射法一般为浅层建井最优方法,作业效率相比钻入法可提高50%以上。该方法已在中国南海几十口深水井取得良好应用效果,可为深水复杂地层建井方式选择提供定量评价方法。

临江富水地区深基坑旋喷桩加固效果研究

本文以陇南市东江初级中学综合教学实验楼基坑支护工程为背景,运用PLAXIS对该基坑进行了开挖全过程的数值模拟分析,结合现场实测结果分析了深基坑旋喷桩的加固效果,并与未采用旋喷桩加固的情况进行了对比分析。结果表明:对于长江支流的白龙江II级阶地力学性质差的饱和土地区,采用旋喷桩加固桩间土及坑内土体能够很好地提高桩周土体强度、限制桩顶位移、减小坑外沉降,可使支护桩桩顶水平及竖向位移减小50%,桩身内力减小10%;增加旋喷桩加固长度对限制支护结构变形效果不大,但增加宽度效果明显,可使支护桩桩顶水平位移减小50%以上,但同时存在最优加固宽度;采用旋喷桩的深基坑加固措施安全可靠、经济合理,对该类地区的类似深基坑工程具有参考及借鉴作用。

海上嵌岩钢管桩内卷边切割机器人的设计研究

海上风电桩在基础打桩过程中,容易造成钢管桩下端内卷边,这会增加下插的阻力,须将影响下钻的内卷边切除,提高风电桩插桩效率。现阶段内卷边的处理多是潜水员下水切割,处理过程较为繁琐,难以应对复杂的工况,且有一定的危险性。为解决以上问题,设计了一种用于海上嵌岩式钢管桩内卷边切除的切割机器人。通过对钢管桩内卷边切割现有的施工工艺和施工作业要求进行分析,总结了内卷边切割机器人所需满足的设计要求,提出了适用于切割钢管内卷边的多轴联动机器人系统;确定了总体方案,对内卷边切割机器人的力学性能进行分析,并进行具体结构设计。基于SPH-FEM耦合算法,对磨料水射流切割钢管壁过程进行研究,确定切割工艺参数,对射流反作用进行分析,并结合切割参数进行算例验证。理论分析以及仿真模拟验证表明,所设计的内卷边切割机器人符合施工要求,能改善海上嵌岩式钢管桩内卷边的精确切除问题,有助于完善海上风电桩基础施工工艺的完整性,可为后续内卷边处理技术的发展提供经验。

第三系半成岩富水砂岩隧道水平高压旋喷桩加固机理及参数分析

第三系半成岩具备弱胶结、遇水软化等特征,隧道建设时易诱发涌水突泥和坍塌等地下地质灾害。依托云南临清高速公路王家寨隧道,结合现场地质条件与现有工程案例,采用水平高压旋喷桩对软弱围岩进行超前预加固。结合地基梁理论解析、数值模拟与现场监测方法,研究第三系半成岩水平高压旋喷桩加固机理及不同桩体参数对围岩加固效果的影响,并给出桩体参数建议范围,为类似工程提供参考。研究表明:旋喷桩加固后解析解与数值解的剪力与弯矩分布规律较为一致,在开挖未支护段桩体所受弯矩、剪力最大,最易发生断裂破坏;当围岩水压力在300 kPa时旋喷桩体最大拉应力达598.21 kPa,接近桩体极限抗拉强度,水压力小于300 kPa时水平旋喷桩能有效发挥梁、拱协同作用,拱棚效应与阻水效果显著,能将围岩压力传递给桩体后端及拱肩、边墙处,围岩沉降与地下水压得到有效控制,这与现场监测结果基本吻合;桩径、桩长、咬合厚度及搭接长度变化对桩体应力影响较大,影响程度为咬合厚度>桩长>搭接长度>桩径,建议在第三系半成岩富水砂岩隧道围岩水压力小于300 kPa进行超前预加固时,水平旋喷桩桩体参数范围为桩径65~70 cm、桩长10~13 m、咬合厚度25 cm、搭接长度3~4 m。

三轴搅拌桩组合高压旋喷桩入岩落底式止水帷幕施工技术

某房建深基坑工程支护形式采用排桩+落底式止水帷幕,场地地质条件上部为富水深厚砂层,下部为强风化岩层,止水帷幕需穿透强风化岩0.5 m,以隔断强透水层。通过对地质情况及现有设备条件分析,采用大功率桩机先行施工三轴搅拌桩,养护后进行桩体质量抽芯验证,再针对不同缺陷程度采用高压旋喷桩分别进行补强的组合工艺施工止水帷幕。基坑开挖结果表明,该落底式止水帷幕效果良好,能有效隔断强透水层,与灌注排桩结合形成深基坑支护结构体系具有较高的经济性、适用性。

复杂环境中矩形顶管始发端地层加固方案优化研究与应用

矩形顶管的始发阶段是矩形顶管施工中风险最高的施工阶段,在施工过程中,必须在始发前对始发端地层进行预加固处理。城市核心区域由于受到地面和地下建筑物、管线的影响,经常遇到加固盲区、加固不到位的问题。基于此,本研究总结提出了一种旋喷桩加固结合钢板桩防护的施工方法,在始发基坑洞门处围护结构外侧,密贴围护结构打设钢板桩,结合旋喷加固、洞门凿除等工艺改进措施,有效降低始发端地层施工风险,保证工程自身和周边环境安全。

高层建筑工程中基坑开挖与支护施工技术的运用

本文以某高层住宅为例,探究了基坑开挖技术和高压旋喷桩支护技术的应用。在土方开挖完成后,需要及时支护以防临空面出现滑塌事故,本工程中选用了高压旋喷桩支护技术,将喷射管放入钻孔中,连接高压旋喷桩机后喷射水泥浆液,通过旋转喷嘴的方式让水泥浆液高速冲击、切割土体,形成水泥混合物,干固后既可以取得支护加固的效果,同时又能增强防渗能力,为基坑作业的安全进行以及高层建筑上部结构施工创造了有利条件。

某格形钢板桩码头升级改造方案三维有限元数值分析

某格形钢板桩码头升级改造工程,前沿港池疏浚后改变了格形墙体前板桩埋入深度,影响码头结构稳定性。为了探究改造后格形钢板桩稳定性和破坏形态,利用有限元软件MIDAS GTS,构建适用于格形钢板桩结构稳定性分析的三维有限元数值模型,通过对最不利工况下格形钢板桩改造前后的变形、受力、整体稳定性对比分析,提出复合地基和抗滑桩加固相结合的格形钢板桩码头改造方案。结果表明,码头加固前后的格形钢板桩整体变形、土压力分布、结构内力和地基反力分布基本一致。

第三系半成岩富水砂岩隧道水平高压旋喷桩复合结构超前预加固研究

在诸如第三系半成岩地层等富水软弱均质地层的隧道建设中,常采用水平高压旋喷桩进行洞内超前预加固,但水平旋喷桩往往因自身抗拉强度低在承受较大荷载时容易发生断裂破坏。依托云南临沧至清水河高速公路王家寨隧道工程,提出了一种在桩体内插入小直径钢管的水平高压旋喷复合结构。通过力学理论分析、数值模拟与现场监测,对比分析了水平高压旋喷桩素桩与复合结构的力学机制与对围岩加固作用,并对钢管布置形式及直径进行优化设计。研究表明:在300 kPa水压下,复合结构相比素桩的挠度值降低了34.8%,最大拉应力降低了37.5%,受力模式明显改善,承受的极限水压力荷载大幅提升至700 kPa,对围岩拱顶沉降、应力也有一定削减作用;增加拱顶钢管布置密度可有效降低桩体拉应力,而减少钢管直径则会导致钢管拉应力增大;建议实际工程中拱顶间隔1根桩体布置108 mm钢管,拱肩间隔2~3根布置89 mm钢管,边墙可不设钢管。